From 3484a760f45e89a586514e2d4078938aac36c244 Mon Sep 17 00:00:00 2001 From: Glenn Randers-Pehrson Date: Tue, 21 Feb 2012 14:09:23 -0600 Subject: [master] Bump version to 1.5.10beta01 --- LICENSE | 4 +- README | 2 +- contrib/pngminim/decoder/gather.sh | 10 - contrib/pngminim/encoder/gather.sh | 11 - contrib/pngminim/preader/gather.sh | 11 - libpng-1.4.9beta01.txt | 3367 ----------------------- libpng-manual.txt | 6 +- libpng.3 | 14 +- libpngpf.3 | 2 +- png.5 | 2 +- png.c | 4 +- png.h | 10 +- pngconf.h | 2 +- pngrutil.c | 2 +- projects/visualc6/README.txt | 57 - projects/visualc6/libpng.dsp | 328 --- projects/visualc6/pngtest.dsp | 178 -- projects/vstudio/readme.txt | 2 +- projects/vstudio/zlib.props | 2 +- projects/xcode/README.txt | 3 - projects/xcode/libpng.xcodeproj/.gitignore | 2 - projects/xcode/libpng.xcodeproj/project.pbxproj | 805 ------ scripts/README.txt | 2 +- scripts/makefile.cygwin | 291 -- scripts/makefile.mingw | 282 -- scripts/makefile.os2 | 72 - scripts/makefile.watcom | 112 - scripts/png32ce.def | 262 -- scripts/pnglibconf.h.prebuilt | 2 +- scripts/pngos2.def | 256 -- scripts/pngwin.def | 219 -- 31 files changed, 28 insertions(+), 6294 deletions(-) delete mode 100755 contrib/pngminim/decoder/gather.sh delete mode 100755 contrib/pngminim/encoder/gather.sh delete mode 100755 contrib/pngminim/preader/gather.sh delete mode 100644 libpng-1.4.9beta01.txt delete mode 100644 projects/visualc6/README.txt delete mode 100644 projects/visualc6/libpng.dsp delete mode 100644 projects/visualc6/pngtest.dsp delete mode 100644 projects/xcode/README.txt delete mode 100644 projects/xcode/libpng.xcodeproj/.gitignore delete mode 100644 projects/xcode/libpng.xcodeproj/project.pbxproj delete mode 100644 scripts/makefile.cygwin delete mode 100644 scripts/makefile.mingw delete mode 100644 scripts/makefile.os2 delete mode 100644 scripts/makefile.watcom delete mode 100644 scripts/png32ce.def delete mode 100644 scripts/pngos2.def delete mode 100644 scripts/pngwin.def diff --git a/LICENSE b/LICENSE index 78d836c1c..ade027218 100644 --- a/LICENSE +++ b/LICENSE @@ -10,7 +10,7 @@ this sentence. This code is released under the libpng license. -libpng versions 1.2.6, August 15, 2004, through 1.5.10beta01, February 19, 2012, are +libpng versions 1.2.6, August 15, 2004, through 1.5.10beta01, February 21, 2012, are Copyright (c) 2004, 2006-2011 Glenn Randers-Pehrson, and are distributed according to the same disclaimer and license as libpng-1.2.5 with the following individual added to the list of Contributing Authors @@ -108,4 +108,4 @@ certification mark of the Open Source Initiative. Glenn Randers-Pehrson glennrp at users.sourceforge.net -February 19, 2012 +February 21, 2012 diff --git a/README b/README index 5cb8ee147..36b4cc81d 100644 --- a/README +++ b/README @@ -1,4 +1,4 @@ -README for libpng version 1.5.10beta01 - February 19, 2012 (shared library 15.0) +README for libpng version 1.5.10beta01 - February 21, 2012 (shared library 15.0) See the note about version numbers near the top of png.h See INSTALL for instructions on how to install libpng. diff --git a/contrib/pngminim/decoder/gather.sh b/contrib/pngminim/decoder/gather.sh deleted file mode 100755 index 4eb1d677d..000000000 --- a/contrib/pngminim/decoder/gather.sh +++ /dev/null @@ -1,10 +0,0 @@ -#!/bin/sh - -cp ../../pngminus/png2pnm.c pngm2pnm.c -cp ../../../*.h . -cp ../../../*.c . -rm example.c pngtest.c pngpread.c pngw*.c -# change the following 2 lines if zlib is somewhere else -cp ../../../../zlib/*.h . -cp ../../../../zlib/*.c . -rm minigzip.c example.c compress.c deflate.c gz* diff --git a/contrib/pngminim/encoder/gather.sh b/contrib/pngminim/encoder/gather.sh deleted file mode 100755 index e9ccffc77..000000000 --- a/contrib/pngminim/encoder/gather.sh +++ /dev/null @@ -1,11 +0,0 @@ -#!/bin/sh - -cp ../../pngminus/pnm2png.c pnm2pngm.c -cp ../../../*.h . -cp ../../../*.c . -rm example.c pngtest.c pngr*.c pngpread.c -# Change the next 2 lines if zlib is somewhere else. -cp ../../../../zlib/*.h . -cp ../../../../zlib/*.c . -rm inf*.[ch] -rm uncompr.c minigzip.c example.c gz* diff --git a/contrib/pngminim/preader/gather.sh b/contrib/pngminim/preader/gather.sh deleted file mode 100755 index 4207af7b8..000000000 --- a/contrib/pngminim/preader/gather.sh +++ /dev/null @@ -1,11 +0,0 @@ -#!/bin/sh - -cp ../../gregbook/rpng2-x.c ../../gregbook/readpng2.[ch] . -cp ../../gregbook/COPYING ../../gregbook/LICENSE . -cp ../../../*.h . -cp ../../../*.c . -rm example.c pngtest.c pngw*.c -# change the following 2 lines if zlib is somewhere else -cp ../../../../zlib/*.h . -cp ../../../../zlib/*.c . -rm minigzip.c example.c compress.c deflate.c gz* diff --git a/libpng-1.4.9beta01.txt b/libpng-1.4.9beta01.txt deleted file mode 100644 index 80e22ad16..000000000 --- a/libpng-1.4.9beta01.txt +++ /dev/null @@ -1,3367 +0,0 @@ -libpng.txt - A description on how to use and modify libpng - - libpng version 1.4.9beta01 - July 13, 2011 - Updated and distributed by Glenn Randers-Pehrson - - Copyright (c) 1998-2010 Glenn Randers-Pehrson - - This document is released under the libpng license. - For conditions of distribution and use, see the disclaimer - and license in png.h - - Based on: - - libpng versions 0.97, January 1998, through 1.4.9beta01 - July 13, 2011 - Updated and distributed by Glenn Randers-Pehrson - Copyright (c) 1998-2010 Glenn Randers-Pehrson - - libpng 1.0 beta 6 version 0.96 May 28, 1997 - Updated and distributed by Andreas Dilger - Copyright (c) 1996, 1997 Andreas Dilger - - libpng 1.0 beta 2 - version 0.88 January 26, 1996 - For conditions of distribution and use, see copyright - notice in png.h. Copyright (c) 1995, 1996 Guy Eric - Schalnat, Group 42, Inc. - - Updated/rewritten per request in the libpng FAQ - Copyright (c) 1995, 1996 Frank J. T. Wojcik - December 18, 1995 & January 20, 1996 - -I. Introduction - -This file describes how to use and modify the PNG reference library -(known as libpng) for your own use. There are five sections to this -file: introduction, structures, reading, writing, and modification and -configuration notes for various special platforms. In addition to this -file, example.c is a good starting point for using the library, as -it is heavily commented and should include everything most people -will need. We assume that libpng is already installed; see the -INSTALL file for instructions on how to install libpng. - -For examples of libpng usage, see the files "example.c", "pngtest.c", -and the files in the "contrib" directory, all of which are included in -the libpng distribution. - -Libpng was written as a companion to the PNG specification, as a way -of reducing the amount of time and effort it takes to support the PNG -file format in application programs. - -The PNG specification (second edition), November 2003, is available as -a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2003 (E)) at -. It is technically equivalent -to the PNG specification (second edition) but has some additional material. - -The PNG-1.0 specification is available -as RFC 2083 and as a -W3C Recommendation . - -Some additional chunks are described in the special-purpose public chunks -documents at . - -Other information -about PNG, and the latest version of libpng, can be found at the PNG home -page, . - -Most users will not have to modify the library significantly; advanced -users may want to modify it more. All attempts were made to make it as -complete as possible, while keeping the code easy to understand. -Currently, this library only supports C. Support for other languages -is being considered. - -Libpng has been designed to handle multiple sessions at one time, -to be easily modifiable, to be portable to the vast majority of -machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy -to use. The ultimate goal of libpng is to promote the acceptance of -the PNG file format in whatever way possible. While there is still -work to be done (see the TODO file), libpng should cover the -majority of the needs of its users. - -Libpng uses zlib for its compression and decompression of PNG files. -Further information about zlib, and the latest version of zlib, can -be found at the zlib home page, . -The zlib compression utility is a general purpose utility that is -useful for more than PNG files, and can be used without libpng. -See the documentation delivered with zlib for more details. -You can usually find the source files for the zlib utility wherever you -find the libpng source files. - -Libpng is thread safe, provided the threads are using different -instances of the structures. Each thread should have its own -png_struct and png_info instances, and thus its own image. -Libpng does not protect itself against two threads using the -same instance of a structure. - -II. Structures - -There are two main structures that are important to libpng, png_struct -and png_info. The first, png_struct, is an internal structure that -will not, for the most part, be used by a user except as the first -variable passed to every libpng function call. - -The png_info structure is designed to provide information about the -PNG file. At one time, the fields of png_info were intended to be -directly accessible to the user. However, this tended to cause problems -with applications using dynamically loaded libraries, and as a result -a set of interface functions for png_info (the png_get_*() and png_set_*() -functions) was developed. The fields of png_info are still available for -older applications, but it is suggested that applications use the new -interfaces if at all possible. - -Applications that do make direct access to the members of png_struct (except -for png_ptr->jmpbuf) must be recompiled whenever the library is updated, -and applications that make direct access to the members of png_info must -be recompiled if they were compiled or loaded with libpng version 1.0.6, -in which the members were in a different order. In version 1.0.7, the -members of the png_info structure reverted to the old order, as they were -in versions 0.97c through 1.0.5. Starting with version 2.0.0, both -structures are going to be hidden, and the contents of the structures will -only be accessible through the png_get/png_set functions. - -The png.h header file is an invaluable reference for programming with libpng. -And while I'm on the topic, make sure you include the libpng header file: - -#include - -III. Reading - -We'll now walk you through the possible functions to call when reading -in a PNG file sequentially, briefly explaining the syntax and purpose -of each one. See example.c and png.h for more detail. While -progressive reading is covered in the next section, you will still -need some of the functions discussed in this section to read a PNG -file. - -Setup - -You will want to do the I/O initialization(*) before you get into libpng, -so if it doesn't work, you don't have much to undo. Of course, you -will also want to insure that you are, in fact, dealing with a PNG -file. Libpng provides a simple check to see if a file is a PNG file. -To use it, pass in the first 1 to 8 bytes of the file to the function -png_sig_cmp(), and it will return 0 (false) if the bytes match the -corresponding bytes of the PNG signature, or nonzero (true) otherwise. -Of course, the more bytes you pass in, the greater the accuracy of the -prediction. - -If you are intending to keep the file pointer open for use in libpng, -you must ensure you don't read more than 8 bytes from the beginning -of the file, and you also have to make a call to png_set_sig_bytes_read() -with the number of bytes you read from the beginning. Libpng will -then only check the bytes (if any) that your program didn't read. - -(*): If you are not using the standard I/O functions, you will need -to replace them with custom functions. See the discussion under -Customizing libpng. - - - FILE *fp = fopen(file_name, "rb"); - if (!fp) - { - return (ERROR); - } - fread(header, 1, number, fp); - is_png = !png_sig_cmp(header, 0, number); - if (!is_png) - { - return (NOT_PNG); - } - - -Next, png_struct and png_info need to be allocated and initialized. In -order to ensure that the size of these structures is correct even with a -dynamically linked libpng, there are functions to initialize and -allocate the structures. We also pass the library version, optional -pointers to error handling functions, and a pointer to a data struct for -use by the error functions, if necessary (the pointer and functions can -be NULL if the default error handlers are to be used). See the section -on Changes to Libpng below regarding the old initialization functions. -The structure allocation functions quietly return NULL if they fail to -create the structure, so your application should check for that. - - png_structp png_ptr = png_create_read_struct - (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, - user_error_fn, user_warning_fn); - if (!png_ptr) - return (ERROR); - - png_infop info_ptr = png_create_info_struct(png_ptr); - if (!info_ptr) - { - png_destroy_read_struct(&png_ptr, - (png_infopp)NULL, (png_infopp)NULL); - return (ERROR); - } - - png_infop end_info = png_create_info_struct(png_ptr); - if (!end_info) - { - png_destroy_read_struct(&png_ptr, &info_ptr, - (png_infopp)NULL); - return (ERROR); - } - -If you want to use your own memory allocation routines, -define PNG_USER_MEM_SUPPORTED and use -png_create_read_struct_2() instead of png_create_read_struct(): - - png_structp png_ptr = png_create_read_struct_2 - (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, - user_error_fn, user_warning_fn, (png_voidp) - user_mem_ptr, user_malloc_fn, user_free_fn); - -The error handling routines passed to png_create_read_struct() -and the memory alloc/free routines passed to png_create_struct_2() -are only necessary if you are not using the libpng supplied error -handling and memory alloc/free functions. - -When libpng encounters an error, it expects to longjmp back -to your routine. Therefore, you will need to call setjmp and pass -your png_jmpbuf(png_ptr). If you read the file from different -routines, you will need to update the jmpbuf field every time you enter -a new routine that will call a png_*() function. - -See your documentation of setjmp/longjmp for your compiler for more -information on setjmp/longjmp. See the discussion on libpng error -handling in the Customizing Libpng section below for more information -on the libpng error handling. If an error occurs, and libpng longjmp's -back to your setjmp, you will want to call png_destroy_read_struct() to -free any memory. - - if (setjmp(png_jmpbuf(png_ptr))) - { - png_destroy_read_struct(&png_ptr, &info_ptr, - &end_info); - fclose(fp); - return (ERROR); - } - -If you would rather avoid the complexity of setjmp/longjmp issues, -you can compile libpng with PNG_NO_SETJMP, in which case -errors will result in a call to PNG_ABORT() which defaults to abort(). - -You can #define PNG_ABORT() to a function that does something -more useful than abort(), as long as your function does not -return. - -Now you need to set up the input code. The default for libpng is to -use the C function fread(). If you use this, you will need to pass a -valid FILE * in the function png_init_io(). Be sure that the file is -opened in binary mode. If you wish to handle reading data in another -way, you need not call the png_init_io() function, but you must then -implement the libpng I/O methods discussed in the Customizing Libpng -section below. - - png_init_io(png_ptr, fp); - -If you had previously opened the file and read any of the signature from -the beginning in order to see if this was a PNG file, you need to let -libpng know that there are some bytes missing from the start of the file. - - png_set_sig_bytes(png_ptr, number); - -You can change the zlib compression buffer size to be used while -reading compressed data with - - png_set_compression_buffer_size(png_ptr, buffer_size); - -where the default size is 8192 bytes. Note that the buffer size -is changed immediately and the buffer is reallocated immediately, -instead of setting a flag to be acted upon later. - -Setting up callback code - -You can set up a callback function to handle any unknown chunks in the -input stream. You must supply the function - - read_chunk_callback(png_structp png_ptr, - png_unknown_chunkp chunk); - { - /* The unknown chunk structure contains your - chunk data, along with similar data for any other - unknown chunks: */ - - png_byte name[5]; - png_byte *data; - png_size_t size; - - /* Note that libpng has already taken care of - the CRC handling */ - - /* put your code here. Search for your chunk in the - unknown chunk structure, process it, and return one - of the following: */ - - return (-n); /* chunk had an error */ - return (0); /* did not recognize */ - return (n); /* success */ - } - -(You can give your function another name that you like instead of -"read_chunk_callback") - -To inform libpng about your function, use - - png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr, - read_chunk_callback); - -This names not only the callback function, but also a user pointer that -you can retrieve with - - png_get_user_chunk_ptr(png_ptr); - -If you call the png_set_read_user_chunk_fn() function, then all unknown -chunks will be saved when read, in case your callback function will need -one or more of them. This behavior can be changed with the -png_set_keep_unknown_chunks() function, described below. - -At this point, you can set up a callback function that will be -called after each row has been read, which you can use to control -a progress meter or the like. It's demonstrated in pngtest.c. -You must supply a function - - void read_row_callback(png_structp png_ptr, - png_uint_32 row, int pass); - { - /* put your code here */ - } - -(You can give it another name that you like instead of "read_row_callback") - -To inform libpng about your function, use - - png_set_read_status_fn(png_ptr, read_row_callback); - -Unknown-chunk handling - -Now you get to set the way the library processes unknown chunks in the -input PNG stream. Both known and unknown chunks will be read. Normal -behavior is that known chunks will be parsed into information in -various info_ptr members while unknown chunks will be discarded. This -behavior can be wasteful if your application will never use some known -chunk types. To change this, you can call: - - png_set_keep_unknown_chunks(png_ptr, keep, - chunk_list, num_chunks); - keep - 0: default unknown chunk handling - 1: ignore; do not keep - 2: keep only if safe-to-copy - 3: keep even if unsafe-to-copy - You can use these definitions: - PNG_HANDLE_CHUNK_AS_DEFAULT 0 - PNG_HANDLE_CHUNK_NEVER 1 - PNG_HANDLE_CHUNK_IF_SAFE 2 - PNG_HANDLE_CHUNK_ALWAYS 3 - chunk_list - list of chunks affected (a byte string, - five bytes per chunk, NULL or '\0' if - num_chunks is 0) - num_chunks - number of chunks affected; if 0, all - unknown chunks are affected. If nonzero, - only the chunks in the list are affected - -Unknown chunks declared in this way will be saved as raw data onto a -list of png_unknown_chunk structures. If a chunk that is normally -known to libpng is named in the list, it will be handled as unknown, -according to the "keep" directive. If a chunk is named in successive -instances of png_set_keep_unknown_chunks(), the final instance will -take precedence. The IHDR and IEND chunks should not be named in -chunk_list; if they are, libpng will process them normally anyway. - -Here is an example of the usage of png_set_keep_unknown_chunks(), -where the private "vpAg" chunk will later be processed by a user chunk -callback function: - - png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'}; - - #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) - png_byte unused_chunks[]= - { - 104, 73, 83, 84, (png_byte) '\0', /* hIST */ - 105, 84, 88, 116, (png_byte) '\0', /* iTXt */ - 112, 67, 65, 76, (png_byte) '\0', /* pCAL */ - 115, 67, 65, 76, (png_byte) '\0', /* sCAL */ - 115, 80, 76, 84, (png_byte) '\0', /* sPLT */ - 116, 73, 77, 69, (png_byte) '\0', /* tIME */ - }; - #endif - - ... - - #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) - /* ignore all unknown chunks: */ - png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0); - /* except for vpAg: */ - png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1); - /* also ignore unused known chunks: */ - png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks, - (int)sizeof(unused_chunks)/5); - #endif - -User limits - -The PNG specification allows the width and height of an image to be as -large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns. -Since very few applications really need to process such large images, -we have imposed an arbitrary 1-million limit on rows and columns. -Larger images will be rejected immediately with a png_error() call. If -you wish to override this limit, you can use - - png_set_user_limits(png_ptr, width_max, height_max); - -to set your own limits, or use width_max = height_max = 0x7fffffffL -to allow all valid dimensions (libpng may reject some very large images -anyway because of potential buffer overflow conditions). - -You should put this statement after you create the PNG structure and -before calling png_read_info(), png_read_png(), or png_process_data(). -If you need to retrieve the limits that are being applied, use - - width_max = png_get_user_width_max(png_ptr); - height_max = png_get_user_height_max(png_ptr); - -The PNG specification sets no limit on the number of ancillary chunks -allowed in a PNG datastream. You can impose a limit on the total number -of sPLT, tEXt, iTXt, zTXt, and unknown chunks that will be stored, with - - png_set_chunk_cache_max(png_ptr, user_chunk_cache_max); - -where 0x7fffffffL means unlimited. You can retrieve this limit with - - chunk_cache_max = png_get_chunk_cache_max(png_ptr); - -This limit also applies to the number of buffers that can be allocated -by png_decompress_chunk() while decompressing iTXt, zTXt, and iCCP chunks. - -You can also set a limit on the amount of memory that a compressed chunk -other than IDAT can occupy, with - - png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max); - -and you can retrieve the limit with - - chunk_malloc_max = png_get_chunk_malloc_max(png_ptr); - -Any chunks that would cause either of these limits to be exceeded will -be ignored. - -The high-level read interface - -At this point there are two ways to proceed; through the high-level -read interface, or through a sequence of low-level read operations. -You can use the high-level interface if (a) you are willing to read -the entire image into memory, and (b) the input transformations -you want to do are limited to the following set: - - PNG_TRANSFORM_IDENTITY No transformation - PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to - 8 bits - PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel - PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit - samples to bytes - PNG_TRANSFORM_PACKSWAP Change order of packed - pixels to LSB first - PNG_TRANSFORM_EXPAND Perform set_expand() - PNG_TRANSFORM_INVERT_MONO Invert monochrome images - PNG_TRANSFORM_SHIFT Normalize pixels to the - sBIT depth - PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA - to BGRA - PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA - to AG - PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity - to transparency - PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples - PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples - to RGB (or GA to RGBA) - -(This excludes setting a background color, doing gamma transformation, -quantizing, and setting filler.) If this is the case, simply do this: - - png_read_png(png_ptr, info_ptr, png_transforms, NULL) - -where png_transforms is an integer containing the bitwise OR of some -set of transformation flags. This call is equivalent to png_read_info(), -followed the set of transformations indicated by the transform mask, -then png_read_image(), and finally png_read_end(). - -(The final parameter of this call is not yet used. Someday it might point -to transformation parameters required by some future input transform.) - -You must use png_transforms and not call any png_set_transform() functions -when you use png_read_png(). - -After you have called png_read_png(), you can retrieve the image data -with - - row_pointers = png_get_rows(png_ptr, info_ptr); - -where row_pointers is an array of pointers to the pixel data for each row: - - png_bytep row_pointers[height]; - -If you know your image size and pixel size ahead of time, you can allocate -row_pointers prior to calling png_read_png() with - - if (height > PNG_UINT_32_MAX/png_sizeof(png_byte)) - png_error (png_ptr, - "Image is too tall to process in memory"); - if (width > PNG_UINT_32_MAX/pixel_size) - png_error (png_ptr, - "Image is too wide to process in memory"); - row_pointers = png_malloc(png_ptr, - height*png_sizeof(png_bytep)); - for (int i=0; i) and -png_get_(png_ptr, info_ptr, ...) functions return non-zero if the -data has been read, or zero if it is missing. The parameters to the -png_get_ are set directly if they are simple data types, or a -pointer into the info_ptr is returned for any complex types. - - png_get_PLTE(png_ptr, info_ptr, &palette, - &num_palette); - palette - the palette for the file - (array of png_color) - num_palette - number of entries in the palette - - png_get_gAMA(png_ptr, info_ptr, &gamma); - gamma - the gamma the file is written - at (PNG_INFO_gAMA) - - png_get_sRGB(png_ptr, info_ptr, &srgb_intent); - srgb_intent - the rendering intent (PNG_INFO_sRGB) - The presence of the sRGB chunk - means that the pixel data is in the - sRGB color space. This chunk also - implies specific values of gAMA and - cHRM. - - png_get_iCCP(png_ptr, info_ptr, &name, - &compression_type, &profile, &proflen); - name - The profile name. - compression_type - The compression type; always - PNG_COMPRESSION_TYPE_BASE for PNG 1.0. - You may give NULL to this argument to - ignore it. - profile - International Color Consortium color - profile data. May contain NULs. - proflen - length of profile data in bytes. - - png_get_sBIT(png_ptr, info_ptr, &sig_bit); - sig_bit - the number of significant bits for - (PNG_INFO_sBIT) each of the gray, - red, green, and blue channels, - whichever are appropriate for the - given color type (png_color_16) - - png_get_tRNS(png_ptr, info_ptr, &trans_alpha, - &num_trans, &trans_color); - trans_alpha - array of alpha (transparency) - entries for palette (PNG_INFO_tRNS) - num_trans - number of transparent entries - (PNG_INFO_tRNS) - trans_color - graylevel or color sample values of - the single transparent color for - non-paletted images (PNG_INFO_tRNS) - - png_get_hIST(png_ptr, info_ptr, &hist); - (PNG_INFO_hIST) - hist - histogram of palette (array of - png_uint_16) - - png_get_tIME(png_ptr, info_ptr, &mod_time); - mod_time - time image was last modified - (PNG_VALID_tIME) - - png_get_bKGD(png_ptr, info_ptr, &background); - background - background color (of type - png_color_16p) (PNG_VALID_bKGD) - valid 16-bit red, green and blue - values, regardless of color_type - - num_comments = png_get_text(png_ptr, info_ptr, - &text_ptr, &num_text); - num_comments - number of comments - text_ptr - array of png_text holding image - comments - text_ptr[i].compression - type of compression used - on "text" PNG_TEXT_COMPRESSION_NONE - PNG_TEXT_COMPRESSION_zTXt - PNG_ITXT_COMPRESSION_NONE - PNG_ITXT_COMPRESSION_zTXt - text_ptr[i].key - keyword for comment. Must contain - 1-79 characters. - text_ptr[i].text - text comments for current - keyword. Can be empty. - text_ptr[i].text_length - length of text string, - after decompression, 0 for iTXt - text_ptr[i].itxt_length - length of itxt string, - after decompression, 0 for tEXt/zTXt - text_ptr[i].lang - language of comment (empty - string for unknown). - text_ptr[i].lang_key - keyword in UTF-8 - (empty string for unknown). - Note that the itxt_length, lang, and lang_key - members of the text_ptr structure only exist - when the library is built with iTXt chunk support. - - num_text - number of comments (same as - num_comments; you can put NULL here - to avoid the duplication) - Note while png_set_text() will accept text, language, - and translated keywords that can be NULL pointers, the - structure returned by png_get_text will always contain - regular zero-terminated C strings. They might be - empty strings but they will never be NULL pointers. - - num_spalettes = png_get_sPLT(png_ptr, info_ptr, - &palette_ptr); - palette_ptr - array of palette structures holding - contents of one or more sPLT chunks - read. - num_spalettes - number of sPLT chunks read. - - png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y, - &unit_type); - offset_x - positive offset from the left edge - of the screen - offset_y - positive offset from the top edge - of the screen - unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER - - png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y, - &unit_type); - res_x - pixels/unit physical resolution in - x direction - res_y - pixels/unit physical resolution in - x direction - unit_type - PNG_RESOLUTION_UNKNOWN, - PNG_RESOLUTION_METER - - png_get_sCAL(png_ptr, info_ptr, &unit, &width, - &height) - unit - physical scale units (an integer) - width - width of a pixel in physical scale units - height - height of a pixel in physical scale units - (width and height are doubles) - - png_get_sCAL_s(png_ptr, info_ptr, &unit, &width, - &height) - unit - physical scale units (an integer) - width - width of a pixel in physical scale units - height - height of a pixel in physical scale units - (width and height are strings like "2.54") - - num_unknown_chunks = png_get_unknown_chunks(png_ptr, - info_ptr, &unknowns) - unknowns - array of png_unknown_chunk - structures holding unknown chunks - unknowns[i].name - name of unknown chunk - unknowns[i].data - data of unknown chunk - unknowns[i].size - size of unknown chunk's data - unknowns[i].location - position of chunk in file - - The value of "i" corresponds to the order in which the - chunks were read from the PNG file or inserted with the - png_set_unknown_chunks() function. - -The data from the pHYs chunk can be retrieved in several convenient -forms: - - res_x = png_get_x_pixels_per_meter(png_ptr, - info_ptr) - res_y = png_get_y_pixels_per_meter(png_ptr, - info_ptr) - res_x_and_y = png_get_pixels_per_meter(png_ptr, - info_ptr) - res_x = png_get_x_pixels_per_inch(png_ptr, - info_ptr) - res_y = png_get_y_pixels_per_inch(png_ptr, - info_ptr) - res_x_and_y = png_get_pixels_per_inch(png_ptr, - info_ptr) - aspect_ratio = png_get_pixel_aspect_ratio(png_ptr, - info_ptr) - - (Each of these returns 0 [signifying "unknown"] if - the data is not present or if res_x is 0; - res_x_and_y is 0 if res_x != res_y) - -The data from the oFFs chunk can be retrieved in several convenient -forms: - - x_offset = png_get_x_offset_microns(png_ptr, info_ptr); - y_offset = png_get_y_offset_microns(png_ptr, info_ptr); - x_offset = png_get_x_offset_inches(png_ptr, info_ptr); - y_offset = png_get_y_offset_inches(png_ptr, info_ptr); - - (Each of these returns 0 [signifying "unknown" if both - x and y are 0] if the data is not present or if the - chunk is present but the unit is the pixel) - -For more information, see the png_info definition in png.h and the -PNG specification for chunk contents. Be careful with trusting -rowbytes, as some of the transformations could increase the space -needed to hold a row (expand, filler, gray_to_rgb, etc.). -See png_read_update_info(), below. - -A quick word about text_ptr and num_text. PNG stores comments in -keyword/text pairs, one pair per chunk, with no limit on the number -of text chunks, and a 2^31 byte limit on their size. While there are -suggested keywords, there is no requirement to restrict the use to these -strings. It is strongly suggested that keywords and text be sensible -to humans (that's the point), so don't use abbreviations. Non-printing -symbols are not allowed. See the PNG specification for more details. -There is also no requirement to have text after the keyword. - -Keywords should be limited to 79 Latin-1 characters without leading or -trailing spaces, but non-consecutive spaces are allowed within the -keyword. It is possible to have the same keyword any number of times. -The text_ptr is an array of png_text structures, each holding a -pointer to a language string, a pointer to a keyword and a pointer to -a text string. The text string, language code, and translated -keyword may be empty or NULL pointers. The keyword/text -pairs are put into the array in the order that they are received. -However, some or all of the text chunks may be after the image, so, to -make sure you have read all the text chunks, don't mess with these -until after you read the stuff after the image. This will be -mentioned again below in the discussion that goes with png_read_end(). - -Input transformations - -After you've read the header information, you can set up the library -to handle any special transformations of the image data. The various -ways to transform the data will be described in the order that they -should occur. This is important, as some of these change the color -type and/or bit depth of the data, and some others only work on -certain color types and bit depths. Even though each transformation -checks to see if it has data that it can do something with, you should -make sure to only enable a transformation if it will be valid for the -data. For example, don't swap red and blue on grayscale data. - -The colors used for the background and transparency values should be -supplied in the same format/depth as the current image data. They -are stored in the same format/depth as the image data in a bKGD or tRNS -chunk, so this is what libpng expects for this data. The colors are -transformed to keep in sync with the image data when an application -calls the png_read_update_info() routine (see below). - -Data will be decoded into the supplied row buffers packed into bytes -unless the library has been told to transform it into another format. -For example, 4 bit/pixel paletted or grayscale data will be returned -2 pixels/byte with the leftmost pixel in the high-order bits of the -byte, unless png_set_packing() is called. 8-bit RGB data will be stored -in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha() -is called to insert filler bytes, either before or after each RGB triplet. -16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant -byte of the color value first, unless png_set_strip_16() is called to -transform it to regular RGB RGB triplets, or png_set_filler() or -png_set_add alpha() is called to insert filler bytes, either before or -after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can -be modified with -png_set_filler(), png_set_add_alpha(), or png_set_strip_16(). - -The following code transforms grayscale images of less than 8 to 8 bits, -changes paletted images to RGB, and adds a full alpha channel if there is -transparency information in a tRNS chunk. This is most useful on -grayscale images with bit depths of 2 or 4 or if there is a multiple-image -viewing application that wishes to treat all images in the same way. - - if (color_type == PNG_COLOR_TYPE_PALETTE) - png_set_palette_to_rgb(png_ptr); - - if (color_type == PNG_COLOR_TYPE_GRAY && - bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr); - - if (png_get_valid(png_ptr, info_ptr, - PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr); - -These three functions are actually aliases for png_set_expand(), added -in libpng version 1.0.4, with the function names expanded to improve code -readability. In some future version they may actually do different -things. - -As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was -added. It expands the sample depth without changing tRNS to alpha. - -As of libpng version 1.4.9beta01, not all possible expansions are supported. - -In the following table, the 01 means grayscale with depth<8, 31 means -indexed with depth<8, other numerals represent the color type, "T" means -the tRNS chunk is present, A means an alpha channel is present, and O -means tRNS or alpha is present but all pixels in the image are opaque. - - FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O - TO - 01 - - 31 - - 0 1 - - 0T - - 0O - - 2 GX - - 2T - - 2O - - 3 1 - - 3T - - 3O - - 4A T - - 4O - - 6A GX TX TX - - 6O GX TX - - -Within the matrix, - "-" means the transformation is not supported. - "X" means the transformation is obtained by png_set_expand(). - "1" means the transformation is obtained by - png_set_expand_gray_1_2_4_to_8 - "G" means the transformation is obtained by - png_set_gray_to_rgb(). - "P" means the transformation is obtained by - png_set_expand_palette_to_rgb(). - "T" means the transformation is obtained by - png_set_tRNS_to_alpha(). - -PNG can have files with 16 bits per channel. If you only can handle -8 bits per channel, this will strip the pixels down to 8 bit. - - if (bit_depth == 16) - png_set_strip_16(png_ptr); - -If, for some reason, you don't need the alpha channel on an image, -and you want to remove it rather than combining it with the background -(but the image author certainly had in mind that you *would* combine -it with the background, so that's what you should probably do): - - if (color_type & PNG_COLOR_MASK_ALPHA) - png_set_strip_alpha(png_ptr); - -In PNG files, the alpha channel in an image -is the level of opacity. If you need the alpha channel in an image to -be the level of transparency instead of opacity, you can invert the -alpha channel (or the tRNS chunk data) after it's read, so that 0 is -fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit -images) is fully transparent, with - - png_set_invert_alpha(png_ptr); - -PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as -they can, resulting in, for example, 8 pixels per byte for 1 bit -files. This code expands to 1 pixel per byte without changing the -values of the pixels: - - if (bit_depth < 8) - png_set_packing(png_ptr); - -PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels -stored in a PNG image have been "scaled" or "shifted" up to the next -higher possible bit depth (e.g. from 5 bits/sample in the range [0,31] -to 8 bits/sample in the range [0, 255]). However, it is also possible -to convert the PNG pixel data back to the original bit depth of the -image. This call reduces the pixels back down to the original bit depth: - - png_color_8p sig_bit; - - if (png_get_sBIT(png_ptr, info_ptr, &sig_bit)) - png_set_shift(png_ptr, sig_bit); - -PNG files store 3-color pixels in red, green, blue order. This code -changes the storage of the pixels to blue, green, red: - - if (color_type == PNG_COLOR_TYPE_RGB || - color_type == PNG_COLOR_TYPE_RGB_ALPHA) - png_set_bgr(png_ptr); - -PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them -into 4 or 8 bytes for windowing systems that need them in this format: - - if (color_type == PNG_COLOR_TYPE_RGB) - png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE); - -where "filler" is the 8 or 16-bit number to fill with, and the location is -either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether -you want the filler before the RGB or after. This transformation -does not affect images that already have full alpha channels. To add an -opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which -will generate RGBA pixels. - -Note that png_set_filler() does not change the color type. If you want -to do that, you can add a true alpha channel with - - if (color_type == PNG_COLOR_TYPE_RGB || - color_type == PNG_COLOR_TYPE_GRAY) - png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER); - -where "filler" contains the alpha value to assign to each pixel. -This function was added in libpng-1.2.7. - -If you are reading an image with an alpha channel, and you need the -data as ARGB instead of the normal PNG format RGBA: - - if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) - png_set_swap_alpha(png_ptr); - -For some uses, you may want a grayscale image to be represented as -RGB. This code will do that conversion: - - if (color_type == PNG_COLOR_TYPE_GRAY || - color_type == PNG_COLOR_TYPE_GRAY_ALPHA) - png_set_gray_to_rgb(png_ptr); - -Conversely, you can convert an RGB or RGBA image to grayscale or grayscale -with alpha. - - if (color_type == PNG_COLOR_TYPE_RGB || - color_type == PNG_COLOR_TYPE_RGB_ALPHA) - png_set_rgb_to_gray_fixed(png_ptr, error_action, - int red_weight, int green_weight); - - error_action = 1: silently do the conversion - error_action = 2: issue a warning if the original - image has any pixel where - red != green or red != blue - error_action = 3: issue an error and abort the - conversion if the original - image has any pixel where - red != green or red != blue - - red_weight: weight of red component times 100000 - green_weight: weight of green component times 100000 - If either weight is negative, default - weights (21268, 71514) are used. - -If you have set error_action = 1 or 2, you can -later check whether the image really was gray, after processing -the image rows, with the png_get_rgb_to_gray_status(png_ptr) function. -It will return a png_byte that is zero if the image was gray or -1 if there were any non-gray pixels. bKGD and sBIT data -will be silently converted to grayscale, using the green channel -data, regardless of the error_action setting. - -With red_weight+green_weight<=100000, -the normalized graylevel is computed: - - int rw = red_weight * 65536; - int gw = green_weight * 65536; - int bw = 65536 - (rw + gw); - gray = (rw*red + gw*green + bw*blue)/65536; - -The default values approximate those recommended in the Charles -Poynton's Color FAQ, -Copyright (c) 1998-01-04 Charles Poynton - - Y = 0.212671 * R + 0.715160 * G + 0.072169 * B - -Libpng approximates this with - - Y = 0.21268 * R + 0.7151 * G + 0.07217 * B - -which can be expressed with integers as - - Y = (6969 * R + 23434 * G + 2365 * B)/32768 - -The calculation is done in a linear colorspace, if the image gamma -is known. - -If you have a grayscale and you are using png_set_expand_depth(), -png_set_expand(), or png_set_gray_to_rgb to change to truecolor or to -a higher bit-depth, you must either supply the background color as a gray -value at the original file bit-depth (need_expand = 1) or else supply the -background color as an RGB triplet at the final, expanded bit depth -(need_expand = 0). Similarly, if you are reading a paletted image, you -must either supply the background color as a palette index (need_expand = 1) -or as an RGB triplet that may or may not be in the palette (need_expand = 0). - - png_color_16 my_background; - png_color_16p image_background; - - if (png_get_bKGD(png_ptr, info_ptr, &image_background)) - png_set_background(png_ptr, image_background, - PNG_BACKGROUND_GAMMA_FILE, 1, 1.0); - else - png_set_background(png_ptr, &my_background, - PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0); - -The png_set_background() function tells libpng to composite images -with alpha or simple transparency against the supplied background -color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid), -you may use this color, or supply another color more suitable for -the current display (e.g., the background color from a web page). You -need to tell libpng whether the color is in the gamma space of the -display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file -(PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one -that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't -know why anyone would use this, but it's here). - -To properly display PNG images on any kind of system, the application needs -to know what the display gamma is. Ideally, the user will know this, and -the application will allow them to set it. One method of allowing the user -to set the display gamma separately for each system is to check for a -SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be -correctly set. - -Note that display_gamma is the overall gamma correction required to produce -pleasing results, which depends on the lighting conditions in the surrounding -environment. In a dim or brightly lit room, no compensation other than -the physical gamma exponent of the monitor is needed, while in a dark room -a slightly smaller exponent is better. - - double gamma, screen_gamma; - - if (/* We have a user-defined screen - gamma value */) - { - screen_gamma = user_defined_screen_gamma; - } - /* One way that applications can share the same - screen gamma value */ - else if ((gamma_str = getenv("SCREEN_GAMMA")) - != NULL) - { - screen_gamma = (double)atof(gamma_str); - } - /* If we don't have another value */ - else - { - screen_gamma = 2.2; /* A good guess for a - PC monitor in a bright office or a dim room */ - screen_gamma = 2.0; /* A good guess for a - PC monitor in a dark room */ - screen_gamma = 1.7 or 1.0; /* A good - guess for Mac systems */ - } - -The png_set_gamma() function handles gamma transformations of the data. -Pass both the file gamma and the current screen_gamma. If the file does -not have a gamma value, you can pass one anyway if you have an idea what -it is (usually 0.45455 is a good guess for GIF images on PCs). Note -that file gammas are inverted from screen gammas. See the discussions -on gamma in the PNG specification for an excellent description of what -gamma is, and why all applications should support it. It is strongly -recommended that PNG viewers support gamma correction. - - if (png_get_gAMA(png_ptr, info_ptr, &gamma)) - png_set_gamma(png_ptr, screen_gamma, gamma); - else - png_set_gamma(png_ptr, screen_gamma, 0.45455); - -If you need to reduce an RGB file to a paletted file, or if a paletted -file has more entries then will fit on your screen, png_set_quantize() -will do that. Note that this is a simple match dither that merely -finds the closest color available. This should work fairly well with -optimized palettes, and fairly badly with linear color cubes. If you -pass a palette that is larger then maximum_colors, the file will -reduce the number of colors in the palette so it will fit into -maximum_colors. If there is a histogram, it will use it to make -more intelligent choices when reducing the palette. If there is no -histogram, it may not do as good a job. - - if (color_type & PNG_COLOR_MASK_COLOR) - { - if (png_get_valid(png_ptr, info_ptr, - PNG_INFO_PLTE)) - { - png_uint_16p histogram = NULL; - png_get_hIST(png_ptr, info_ptr, - &histogram); - png_set_quantize(png_ptr, palette, num_palette, - max_screen_colors, histogram, 1); - } - else - { - png_color std_color_cube[MAX_SCREEN_COLORS] = - { ... colors ... }; - - png_set_quantize(png_ptr, std_color_cube, - MAX_SCREEN_COLORS, MAX_SCREEN_COLORS, - NULL,0); - } - } - -PNG files describe monochrome as black being zero and white being one. -The following code will reverse this (make black be one and white be -zero): - - if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY) - png_set_invert_mono(png_ptr); - -This function can also be used to invert grayscale and gray-alpha images: - - if (color_type == PNG_COLOR_TYPE_GRAY || - color_type == PNG_COLOR_TYPE_GRAY_ALPHA) - png_set_invert_mono(png_ptr); - -PNG files store 16 bit pixels in network byte order (big-endian, -ie. most significant bits first). This code changes the storage to the -other way (little-endian, i.e. least significant bits first, the -way PCs store them): - - if (bit_depth == 16) - png_set_swap(png_ptr); - -If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you -need to change the order the pixels are packed into bytes, you can use: - - if (bit_depth < 8) - png_set_packswap(png_ptr); - -Finally, you can write your own transformation function if none of -the existing ones meets your needs. This is done by setting a callback -with - - png_set_read_user_transform_fn(png_ptr, - read_transform_fn); - -You must supply the function - - void read_transform_fn(png_structp png_ptr, png_row_infop - row_info, png_bytep data) - -See pngtest.c for a working example. Your function will be called -after all of the other transformations have been processed. - -You can also set up a pointer to a user structure for use by your -callback function, and you can inform libpng that your transform -function will change the number of channels or bit depth with the -function - - png_set_user_transform_info(png_ptr, user_ptr, - user_depth, user_channels); - -The user's application, not libpng, is responsible for allocating and -freeing any memory required for the user structure. - -You can retrieve the pointer via the function -png_get_user_transform_ptr(). For example: - - voidp read_user_transform_ptr = - png_get_user_transform_ptr(png_ptr); - -The last thing to handle is interlacing; this is covered in detail below, -but you must call the function here if you want libpng to handle expansion -of the interlaced image. - - number_of_passes = png_set_interlace_handling(png_ptr); - -After setting the transformations, libpng can update your png_info -structure to reflect any transformations you've requested with this -call. This is most useful to update the info structure's rowbytes -field so you can use it to allocate your image memory. This function -will also update your palette with the correct screen_gamma and -background if these have been given with the calls above. - - png_read_update_info(png_ptr, info_ptr); - -After you call png_read_update_info(), you can allocate any -memory you need to hold the image. The row data is simply -raw byte data for all forms of images. As the actual allocation -varies among applications, no example will be given. If you -are allocating one large chunk, you will need to build an -array of pointers to each row, as it will be needed for some -of the functions below. - -Reading image data - -After you've allocated memory, you can read the image data. -The simplest way to do this is in one function call. If you are -allocating enough memory to hold the whole image, you can just -call png_read_image() and libpng will read in all the image data -and put it in the memory area supplied. You will need to pass in -an array of pointers to each row. - -This function automatically handles interlacing, so you don't need -to call png_set_interlace_handling() or call this function multiple -times, or any of that other stuff necessary with png_read_rows(). - - png_read_image(png_ptr, row_pointers); - -where row_pointers is: - - png_bytep row_pointers[height]; - -You can point to void or char or whatever you use for pixels. - -If you don't want to read in the whole image at once, you can -use png_read_rows() instead. If there is no interlacing (check -interlace_type == PNG_INTERLACE_NONE), this is simple: - - png_read_rows(png_ptr, row_pointers, NULL, - number_of_rows); - -where row_pointers is the same as in the png_read_image() call. - -If you are doing this just one row at a time, you can do this with -a single row_pointer instead of an array of row_pointers: - - png_bytep row_pointer = row; - png_read_row(png_ptr, row_pointer, NULL); - -If the file is interlaced (interlace_type != 0 in the IHDR chunk), things -get somewhat harder. The only current (PNG Specification version 1.2) -interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7) -is a somewhat complicated 2D interlace scheme, known as Adam7, that -breaks down an image into seven smaller images of varying size, based -on an 8x8 grid. - -libpng can fill out those images or it can give them to you "as is". -If you want them filled out, there are two ways to do that. The one -mentioned in the PNG specification is to expand each pixel to cover -those pixels that have not been read yet (the "rectangle" method). -This results in a blocky image for the first pass, which gradually -smooths out as more pixels are read. The other method is the "sparkle" -method, where pixels are drawn only in their final locations, with the -rest of the image remaining whatever colors they were initialized to -before the start of the read. The first method usually looks better, -but tends to be slower, as there are more pixels to put in the rows. - -If you don't want libpng to handle the interlacing details, just call -png_read_rows() seven times to read in all seven images. Each of the -images is a valid image by itself, or they can all be combined on an -8x8 grid to form a single image (although if you intend to combine them -you would be far better off using the libpng interlace handling). - -The first pass will return an image 1/8 as wide as the entire image -(every 8th column starting in column 0) and 1/8 as high as the original -(every 8th row starting in row 0), the second will be 1/8 as wide -(starting in column 4) and 1/8 as high (also starting in row 0). The -third pass will be 1/4 as wide (every 4th pixel starting in column 0) and -1/8 as high (every 8th row starting in row 4), and the fourth pass will -be 1/4 as wide and 1/4 as high (every 4th column starting in column 2, -and every 4th row starting in row 0). The fifth pass will return an -image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2), -while the sixth pass will be 1/2 as wide and 1/2 as high as the original -(starting in column 1 and row 0). The seventh and final pass will be as -wide as the original, and 1/2 as high, containing all of the odd -numbered scanlines. Phew! - -If you want libpng to expand the images, call this before calling -png_start_read_image() or png_read_update_info(): - - if (interlace_type == PNG_INTERLACE_ADAM7) - number_of_passes - = png_set_interlace_handling(png_ptr); - -This will return the number of passes needed. Currently, this -is seven, but may change if another interlace type is added. -This function can be called even if the file is not interlaced, -where it will return one pass. - -If you are not going to display the image after each pass, but are -going to wait until the entire image is read in, use the sparkle -effect. This effect is faster and the end result of either method -is exactly the same. If you are planning on displaying the image -after each pass, the "rectangle" effect is generally considered the -better looking one. - -If you only want the "sparkle" effect, just call png_read_rows() as -normal, with the third parameter NULL. Make sure you make pass over -the image number_of_passes times, and you don't change the data in the -rows between calls. You can change the locations of the data, just -not the data. Each pass only writes the pixels appropriate for that -pass, and assumes the data from previous passes is still valid. - - png_read_rows(png_ptr, row_pointers, NULL, - number_of_rows); - -If you only want the first effect (the rectangles), do the same as -before except pass the row buffer in the third parameter, and leave -the second parameter NULL. - - png_read_rows(png_ptr, NULL, row_pointers, - number_of_rows); - -Finishing a sequential read - -After you are finished reading the image through the -low-level interface, you can finish reading the file. If you are -interested in comments or time, which may be stored either before or -after the image data, you should pass the separate png_info struct if -you want to keep the comments from before and after the image -separate. If you are not interested, you can pass NULL. - - png_read_end(png_ptr, end_info); - -When you are done, you can free all memory allocated by libpng like this: - - png_destroy_read_struct(&png_ptr, &info_ptr, - &end_info); - -It is also possible to individually free the info_ptr members that -point to libpng-allocated storage with the following function: - - png_free_data(png_ptr, info_ptr, mask, seq) - mask - identifies data to be freed, a mask - containing the bitwise OR of one or - more of - PNG_FREE_PLTE, PNG_FREE_TRNS, - PNG_FREE_HIST, PNG_FREE_ICCP, - PNG_FREE_PCAL, PNG_FREE_ROWS, - PNG_FREE_SCAL, PNG_FREE_SPLT, - PNG_FREE_TEXT, PNG_FREE_UNKN, - or simply PNG_FREE_ALL - seq - sequence number of item to be freed - (-1 for all items) - -This function may be safely called when the relevant storage has -already been freed, or has not yet been allocated, or was allocated -by the user and not by libpng, and will in those cases do nothing. -The "seq" parameter is ignored if only one item of the selected data -type, such as PLTE, is allowed. If "seq" is not -1, and multiple items -are allowed for the data type identified in the mask, such as text or -sPLT, only the n'th item in the structure is freed, where n is "seq". - -The default behavior is only to free data that was allocated internally -by libpng. This can be changed, so that libpng will not free the data, -or so that it will free data that was allocated by the user with png_malloc() -or png_zalloc() and passed in via a png_set_*() function, with - - png_data_freer(png_ptr, info_ptr, freer, mask) - mask - which data elements are affected - same choices as in png_free_data() - freer - one of - PNG_DESTROY_WILL_FREE_DATA - PNG_SET_WILL_FREE_DATA - PNG_USER_WILL_FREE_DATA - -This function only affects data that has already been allocated. -You can call this function after reading the PNG data but before calling -any png_set_*() functions, to control whether the user or the png_set_*() -function is responsible for freeing any existing data that might be present, -and again after the png_set_*() functions to control whether the user -or png_destroy_*() is supposed to free the data. When the user assumes -responsibility for libpng-allocated data, the application must use -png_free() to free it, and when the user transfers responsibility to libpng -for data that the user has allocated, the user must have used png_malloc() -or png_zalloc() to allocate it. - -If you allocated your row_pointers in a single block, as suggested above in -the description of the high level read interface, you must not transfer -responsibility for freeing it to the png_set_rows or png_read_destroy function, -because they would also try to free the individual row_pointers[i]. - -If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword -separately, do not transfer responsibility for freeing text_ptr to libpng, -because when libpng fills a png_text structure it combines these members with -the key member, and png_free_data() will free only text_ptr.key. Similarly, -if you transfer responsibility for free'ing text_ptr from libpng to your -application, your application must not separately free those members. - -The png_free_data() function will turn off the "valid" flag for anything -it frees. If you need to turn the flag off for a chunk that was freed by -your application instead of by libpng, you can use - - png_set_invalid(png_ptr, info_ptr, mask); - mask - identifies the chunks to be made invalid, - containing the bitwise OR of one or - more of - PNG_INFO_gAMA, PNG_INFO_sBIT, - PNG_INFO_cHRM, PNG_INFO_PLTE, - PNG_INFO_tRNS, PNG_INFO_bKGD, - PNG_INFO_hIST, PNG_INFO_pHYs, - PNG_INFO_oFFs, PNG_INFO_tIME, - PNG_INFO_pCAL, PNG_INFO_sRGB, - PNG_INFO_iCCP, PNG_INFO_sPLT, - PNG_INFO_sCAL, PNG_INFO_IDAT - -For a more compact example of reading a PNG image, see the file example.c. - -Reading PNG files progressively - -The progressive reader is slightly different then the non-progressive -reader. Instead of calling png_read_info(), png_read_rows(), and -png_read_end(), you make one call to png_process_data(), which calls -callbacks when it has the info, a row, or the end of the image. You -set up these callbacks with png_set_progressive_read_fn(). You don't -have to worry about the input/output functions of libpng, as you are -giving the library the data directly in png_process_data(). I will -assume that you have read the section on reading PNG files above, -so I will only highlight the differences (although I will show -all of the code). - -png_structp png_ptr; -png_infop info_ptr; - - /* An example code fragment of how you would - initialize the progressive reader in your - application. */ - int - initialize_png_reader() - { - png_ptr = png_create_read_struct - (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, - user_error_fn, user_warning_fn); - if (!png_ptr) - return (ERROR); - info_ptr = png_create_info_struct(png_ptr); - if (!info_ptr) - { - png_destroy_read_struct(&png_ptr, (png_infopp)NULL, - (png_infopp)NULL); - return (ERROR); - } - - if (setjmp(png_jmpbuf(png_ptr))) - { - png_destroy_read_struct(&png_ptr, &info_ptr, - (png_infopp)NULL); - return (ERROR); - } - - /* This one's new. You can provide functions - to be called when the header info is valid, - when each row is completed, and when the image - is finished. If you aren't using all functions, - you can specify NULL parameters. Even when all - three functions are NULL, you need to call - png_set_progressive_read_fn(). You can use - any struct as the user_ptr (cast to a void pointer - for the function call), and retrieve the pointer - from inside the callbacks using the function - - png_get_progressive_ptr(png_ptr); - - which will return a void pointer, which you have - to cast appropriately. - */ - png_set_progressive_read_fn(png_ptr, (void *)user_ptr, - info_callback, row_callback, end_callback); - - return 0; - } - - /* A code fragment that you call as you receive blocks - of data */ - int - process_data(png_bytep buffer, png_uint_32 length) - { - if (setjmp(png_jmpbuf(png_ptr))) - { - png_destroy_read_struct(&png_ptr, &info_ptr, - (png_infopp)NULL); - return (ERROR); - } - - /* This one's new also. Simply give it a chunk - of data from the file stream (in order, of - course). On machines with segmented memory - models machines, don't give it any more than - 64K. The library seems to run fine with sizes - of 4K. Although you can give it much less if - necessary (I assume you can give it chunks of - 1 byte, I haven't tried less then 256 bytes - yet). When this function returns, you may - want to display any rows that were generated - in the row callback if you don't already do - so there. - */ - png_process_data(png_ptr, info_ptr, buffer, length); - return 0; - } - - /* This function is called (as set by - png_set_progressive_read_fn() above) when enough data - has been supplied so all of the header has been - read. - */ - void - info_callback(png_structp png_ptr, png_infop info) - { - /* Do any setup here, including setting any of - the transformations mentioned in the Reading - PNG files section. For now, you _must_ call - either png_start_read_image() or - png_read_update_info() after all the - transformations are set (even if you don't set - any). You may start getting rows before - png_process_data() returns, so this is your - last chance to prepare for that. - */ - } - - /* This function is called when each row of image - data is complete */ - void - row_callback(png_structp png_ptr, png_bytep new_row, - png_uint_32 row_num, int pass) - { - /* If the image is interlaced, and you turned - on the interlace handler, this function will - be called for every row in every pass. Some - of these rows will not be changed from the - previous pass. When the row is not changed, - the new_row variable will be NULL. The rows - and passes are called in order, so you don't - really need the row_num and pass, but I'm - supplying them because it may make your life - easier. - - For the non-NULL rows of interlaced images, - you must call png_progressive_combine_row() - passing in the row and the old row. You can - call this function for NULL rows (it will just - return) and for non-interlaced images (it just - does the memcpy for you) if it will make the - code easier. Thus, you can just do this for - all cases: - */ - - png_progressive_combine_row(png_ptr, old_row, - new_row); - - /* where old_row is what was displayed for - previously for the row. Note that the first - pass (pass == 0, really) will completely cover - the old row, so the rows do not have to be - initialized. After the first pass (and only - for interlaced images), you will have to pass - the current row, and the function will combine - the old row and the new row. - */ - } - - void - end_callback(png_structp png_ptr, png_infop info) - { - /* This function is called after the whole image - has been read, including any chunks after the - image (up to and including the IEND). You - will usually have the same info chunk as you - had in the header, although some data may have - been added to the comments and time fields. - - Most people won't do much here, perhaps setting - a flag that marks the image as finished. - */ - } - - - -IV. Writing - -Much of this is very similar to reading. However, everything of -importance is repeated here, so you won't have to constantly look -back up in the reading section to understand writing. - -Setup - -You will want to do the I/O initialization before you get into libpng, -so if it doesn't work, you don't have anything to undo. If you are not -using the standard I/O functions, you will need to replace them with -custom writing functions. See the discussion under Customizing libpng. - - FILE *fp = fopen(file_name, "wb"); - if (!fp) - { - return (ERROR); - } - -Next, png_struct and png_info need to be allocated and initialized. -As these can be both relatively large, you may not want to store these -on the stack, unless you have stack space to spare. Of course, you -will want to check if they return NULL. If you are also reading, -you won't want to name your read structure and your write structure -both "png_ptr"; you can call them anything you like, such as -"read_ptr" and "write_ptr". Look at pngtest.c, for example. - - png_structp png_ptr = png_create_write_struct - (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, - user_error_fn, user_warning_fn); - if (!png_ptr) - return (ERROR); - - png_infop info_ptr = png_create_info_struct(png_ptr); - if (!info_ptr) - { - png_destroy_write_struct(&png_ptr, - (png_infopp)NULL); - return (ERROR); - } - -If you want to use your own memory allocation routines, -define PNG_USER_MEM_SUPPORTED and use -png_create_write_struct_2() instead of png_create_write_struct(): - - png_structp png_ptr = png_create_write_struct_2 - (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, - user_error_fn, user_warning_fn, (png_voidp) - user_mem_ptr, user_malloc_fn, user_free_fn); - -After you have these structures, you will need to set up the -error handling. When libpng encounters an error, it expects to -longjmp() back to your routine. Therefore, you will need to call -setjmp() and pass the png_jmpbuf(png_ptr). If you -write the file from different routines, you will need to update -the png_jmpbuf(png_ptr) every time you enter a new routine that will -call a png_*() function. See your documentation of setjmp/longjmp -for your compiler for more information on setjmp/longjmp. See -the discussion on libpng error handling in the Customizing Libpng -section below for more information on the libpng error handling. - - if (setjmp(png_jmpbuf(png_ptr))) - { - png_destroy_write_struct(&png_ptr, &info_ptr); - fclose(fp); - return (ERROR); - } - ... - return; - -If you would rather avoid the complexity of setjmp/longjmp issues, -you can compile libpng with PNG_NO_SETJMP, in which case -errors will result in a call to PNG_ABORT() which defaults to abort(). - -You can #define PNG_ABORT() to a function that does something -more useful than abort(), as long as your function does not -return. - -Now you need to set up the output code. The default for libpng is to -use the C function fwrite(). If you use this, you will need to pass a -valid FILE * in the function png_init_io(). Be sure that the file is -opened in binary mode. Again, if you wish to handle writing data in -another way, see the discussion on libpng I/O handling in the Customizing -Libpng section below. - - png_init_io(png_ptr, fp); - -If you are embedding your PNG into a datastream such as MNG, and don't -want libpng to write the 8-byte signature, or if you have already -written the signature in your application, use - - png_set_sig_bytes(png_ptr, 8); - -to inform libpng that it should not write a signature. - -Write callbacks - -At this point, you can set up a callback function that will be -called after each row has been written, which you can use to control -a progress meter or the like. It's demonstrated in pngtest.c. -You must supply a function - - void write_row_callback(png_structp png_ptr, png_uint_32 row, - int pass); - { - /* put your code here */ - } - -(You can give it another name that you like instead of "write_row_callback") - -To inform libpng about your function, use - - png_set_write_status_fn(png_ptr, write_row_callback); - -You now have the option of modifying how the compression library will -run. The following functions are mainly for testing, but may be useful -in some cases, like if you need to write PNG files extremely fast and -are willing to give up some compression, or if you want to get the -maximum possible compression at the expense of slower writing. If you -have no special needs in this area, let the library do what it wants by -not calling this function at all, as it has been tuned to deliver a good -speed/compression ratio. The second parameter to png_set_filter() is -the filter method, for which the only valid values are 0 (as of the -July 1999 PNG specification, version 1.2) or 64 (if you are writing -a PNG datastream that is to be embedded in a MNG datastream). The third -parameter is a flag that indicates which filter type(s) are to be tested -for each scanline. See the PNG specification for details on the specific -filter types. - - - /* turn on or off filtering, and/or choose - specific filters. You can use either a single - PNG_FILTER_VALUE_NAME or the bitwise OR of one - or more PNG_FILTER_NAME masks. */ - png_set_filter(png_ptr, 0, - PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE | - PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB | - PNG_FILTER_UP | PNG_FILTER_VALUE_UP | - PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG | - PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH| - PNG_ALL_FILTERS); - -If an application -wants to start and stop using particular filters during compression, -it should start out with all of the filters (to ensure that the previous -row of pixels will be stored in case it's needed later), and then add -and remove them after the start of compression. - -If you are writing a PNG datastream that is to be embedded in a MNG -datastream, the second parameter can be either 0 or 64. - -The png_set_compression_*() functions interface to the zlib compression -library, and should mostly be ignored unless you really know what you are -doing. The only generally useful call is png_set_compression_level() -which changes how much time zlib spends on trying to compress the image -data. See the Compression Library (zlib.h and algorithm.txt, distributed -with zlib) for details on the compression levels. - - /* set the zlib compression level */ - png_set_compression_level(png_ptr, - Z_BEST_COMPRESSION); - - /* set other zlib parameters */ - png_set_compression_mem_level(png_ptr, 8); - png_set_compression_strategy(png_ptr, - Z_DEFAULT_STRATEGY); - png_set_compression_window_bits(png_ptr, 15); - png_set_compression_method(png_ptr, 8); - png_set_compression_buffer_size(png_ptr, 8192) - -extern PNG_EXPORT(void,png_set_zbuf_size) - -Setting the contents of info for output - -You now need to fill in the png_info structure with all the data you -wish to write before the actual image. Note that the only thing you -are allowed to write after the image is the text chunks and the time -chunk (as of PNG Specification 1.2, anyway). See png_write_end() and -the latest PNG specification for more information on that. If you -wish to write them before the image, fill them in now, and flag that -data as being valid. If you want to wait until after the data, don't -fill them until png_write_end(). For all the fields in png_info and -their data types, see png.h. For explanations of what the fields -contain, see the PNG specification. - -Some of the more important parts of the png_info are: - - png_set_IHDR(png_ptr, info_ptr, width, height, - bit_depth, color_type, interlace_type, - compression_type, filter_method) - width - holds the width of the image - in pixels (up to 2^31). - height - holds the height of the image - in pixels (up to 2^31). - bit_depth - holds the bit depth of one of the - image channels. - (valid values are 1, 2, 4, 8, 16 - and depend also on the - color_type. See also significant - bits (sBIT) below). - color_type - describes which color/alpha - channels are present. - PNG_COLOR_TYPE_GRAY - (bit depths 1, 2, 4, 8, 16) - PNG_COLOR_TYPE_GRAY_ALPHA - (bit depths 8, 16) - PNG_COLOR_TYPE_PALETTE - (bit depths 1, 2, 4, 8) - PNG_COLOR_TYPE_RGB - (bit_depths 8, 16) - PNG_COLOR_TYPE_RGB_ALPHA - (bit_depths 8, 16) - - PNG_COLOR_MASK_PALETTE - PNG_COLOR_MASK_COLOR - PNG_COLOR_MASK_ALPHA - - interlace_type - PNG_INTERLACE_NONE or - PNG_INTERLACE_ADAM7 - compression_type - (must be - PNG_COMPRESSION_TYPE_DEFAULT) - filter_method - (must be PNG_FILTER_TYPE_DEFAULT - or, if you are writing a PNG to - be embedded in a MNG datastream, - can also be - PNG_INTRAPIXEL_DIFFERENCING) - -If you call png_set_IHDR(), the call must appear before any of the -other png_set_*() functions, because they might require access to some of -the IHDR settings. The remaining png_set_*() functions can be called -in any order. - -If you wish, you can reset the compression_type, interlace_type, or -filter_method later by calling png_set_IHDR() again; if you do this, the -width, height, bit_depth, and color_type must be the same in each call. - - png_set_PLTE(png_ptr, info_ptr, palette, - num_palette); - palette - the palette for the file - (array of png_color) - num_palette - number of entries in the palette - - png_set_gAMA(png_ptr, info_ptr, gamma); - gamma - the gamma the image was created - at (PNG_INFO_gAMA) - - png_set_sRGB(png_ptr, info_ptr, srgb_intent); - srgb_intent - the rendering intent - (PNG_INFO_sRGB) The presence of - the sRGB chunk means that the pixel - data is in the sRGB color space. - This chunk also implies specific - values of gAMA and cHRM. Rendering - intent is the CSS-1 property that - has been defined by the International - Color Consortium - (http://www.color.org). - It can be one of - PNG_sRGB_INTENT_SATURATION, - PNG_sRGB_INTENT_PERCEPTUAL, - PNG_sRGB_INTENT_ABSOLUTE, or - PNG_sRGB_INTENT_RELATIVE. - - - png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, - srgb_intent); - srgb_intent - the rendering intent - (PNG_INFO_sRGB) The presence of the - sRGB chunk means that the pixel - data is in the sRGB color space. - This function also causes gAMA and - cHRM chunks with the specific values - that are consistent with sRGB to be - written. - - png_set_iCCP(png_ptr, info_ptr, name, compression_type, - profile, proflen); - name - The profile name. - compression_type - The compression type; always - PNG_COMPRESSION_TYPE_BASE for PNG 1.0. - You may give NULL to this argument to - ignore it. - profile - International Color Consortium color - profile data. May contain NULs. - proflen - length of profile data in bytes. - - png_set_sBIT(png_ptr, info_ptr, sig_bit); - sig_bit - the number of significant bits for - (PNG_INFO_sBIT) each of the gray, red, - green, and blue channels, whichever are - appropriate for the given color type - (png_color_16) - - png_set_tRNS(png_ptr, info_ptr, trans_alpha, - num_trans, trans_color); - trans_alpha - array of alpha (transparency) - entries for palette (PNG_INFO_tRNS) - trans_color - graylevel or color sample values - (in order red, green, blue) of the - single transparent color for - non-paletted images (PNG_INFO_tRNS) - num_trans - number of transparent entries - (PNG_INFO_tRNS) - - png_set_hIST(png_ptr, info_ptr, hist); - (PNG_INFO_hIST) - hist - histogram of palette (array of - png_uint_16) - - png_set_tIME(png_ptr, info_ptr, mod_time); - mod_time - time image was last modified - (PNG_VALID_tIME) - - png_set_bKGD(png_ptr, info_ptr, background); - background - background color (of type - png_color_16p) (PNG_VALID_bKGD) - - png_set_text(png_ptr, info_ptr, text_ptr, num_text); - text_ptr - array of png_text holding image - comments - text_ptr[i].compression - type of compression used - on "text" PNG_TEXT_COMPRESSION_NONE - PNG_TEXT_COMPRESSION_zTXt - PNG_ITXT_COMPRESSION_NONE - PNG_ITXT_COMPRESSION_zTXt - text_ptr[i].key - keyword for comment. Must contain - 1-79 characters. - text_ptr[i].text - text comments for current - keyword. Can be NULL or empty. - text_ptr[i].text_length - length of text string, - after decompression, 0 for iTXt - text_ptr[i].itxt_length - length of itxt string, - after decompression, 0 for tEXt/zTXt - text_ptr[i].lang - language of comment (NULL or - empty for unknown). - text_ptr[i].translated_keyword - keyword in UTF-8 (NULL - or empty for unknown). - Note that the itxt_length, lang, and lang_key - members of the text_ptr structure only exist - when the library is built with iTXt chunk support. - - num_text - number of comments - - png_set_sPLT(png_ptr, info_ptr, &palette_ptr, - num_spalettes); - palette_ptr - array of png_sPLT_struct structures - to be added to the list of palettes - in the info structure. - num_spalettes - number of palette structures to be - added. - - png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, - unit_type); - offset_x - positive offset from the left - edge of the screen - offset_y - positive offset from the top - edge of the screen - unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER - - png_set_pHYs(png_ptr, info_ptr, res_x, res_y, - unit_type); - res_x - pixels/unit physical resolution - in x direction - res_y - pixels/unit physical resolution - in y direction - unit_type - PNG_RESOLUTION_UNKNOWN, - PNG_RESOLUTION_METER - - png_set_sCAL(png_ptr, info_ptr, unit, width, height) - unit - physical scale units (an integer) - width - width of a pixel in physical scale units - height - height of a pixel in physical scale units - (width and height are doubles) - - png_set_sCAL_s(png_ptr, info_ptr, unit, width, height) - unit - physical scale units (an integer) - width - width of a pixel in physical scale units - height - height of a pixel in physical scale units - (width and height are strings like "2.54") - - png_set_unknown_chunks(png_ptr, info_ptr, &unknowns, - num_unknowns) - unknowns - array of png_unknown_chunk - structures holding unknown chunks - unknowns[i].name - name of unknown chunk - unknowns[i].data - data of unknown chunk - unknowns[i].size - size of unknown chunk's data - unknowns[i].location - position to write chunk in file - 0: do not write chunk - PNG_HAVE_IHDR: before PLTE - PNG_HAVE_PLTE: before IDAT - PNG_AFTER_IDAT: after IDAT - -The "location" member is set automatically according to -what part of the output file has already been written. -You can change its value after calling png_set_unknown_chunks() -as demonstrated in pngtest.c. Within each of the "locations", -the chunks are sequenced according to their position in the -structure (that is, the value of "i", which is the order in which -the chunk was either read from the input file or defined with -png_set_unknown_chunks). - -A quick word about text and num_text. text is an array of png_text -structures. num_text is the number of valid structures in the array. -Each png_text structure holds a language code, a keyword, a text value, -and a compression type. - -The compression types have the same valid numbers as the compression -types of the image data. Currently, the only valid number is zero. -However, you can store text either compressed or uncompressed, unlike -images, which always have to be compressed. So if you don't want the -text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE. -Because tEXt and zTXt chunks don't have a language field, if you -specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt -any language code or translated keyword will not be written out. - -Until text gets around 1000 bytes, it is not worth compressing it. -After the text has been written out to the file, the compression type -is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR, -so that it isn't written out again at the end (in case you are calling -png_write_end() with the same struct. - -The keywords that are given in the PNG Specification are: - - Title Short (one line) title or - caption for image - Author Name of image's creator - Description Description of image (possibly long) - Copyright Copyright notice - Creation Time Time of original image creation - (usually RFC 1123 format, see below) - Software Software used to create the image - Disclaimer Legal disclaimer - Warning Warning of nature of content - Source Device used to create the image - Comment Miscellaneous comment; conversion - from other image format - -The keyword-text pairs work like this. Keywords should be short -simple descriptions of what the comment is about. Some typical -keywords are found in the PNG specification, as is some recommendations -on keywords. You can repeat keywords in a file. You can even write -some text before the image and some after. For example, you may want -to put a description of the image before the image, but leave the -disclaimer until after, so viewers working over modem connections -don't have to wait for the disclaimer to go over the modem before -they start seeing the image. Finally, keywords should be full -words, not abbreviations. Keywords and text are in the ISO 8859-1 -(Latin-1) character set (a superset of regular ASCII) and can not -contain NUL characters, and should not contain control or other -unprintable characters. To make the comments widely readable, stick -with basic ASCII, and avoid machine specific character set extensions -like the IBM-PC character set. The keyword must be present, but -you can leave off the text string on non-compressed pairs. -Compressed pairs must have a text string, as only the text string -is compressed anyway, so the compression would be meaningless. - -PNG supports modification time via the png_time structure. Two -conversion routines are provided, png_convert_from_time_t() for -time_t and png_convert_from_struct_tm() for struct tm. The -time_t routine uses gmtime(). You don't have to use either of -these, but if you wish to fill in the png_time structure directly, -you should provide the time in universal time (GMT) if possible -instead of your local time. Note that the year number is the full -year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and -that months start with 1. - -If you want to store the time of the original image creation, you should -use a plain tEXt chunk with the "Creation Time" keyword. This is -necessary because the "creation time" of a PNG image is somewhat vague, -depending on whether you mean the PNG file, the time the image was -created in a non-PNG format, a still photo from which the image was -scanned, or possibly the subject matter itself. In order to facilitate -machine-readable dates, it is recommended that the "Creation Time" -tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"), -although this isn't a requirement. Unlike the tIME chunk, the -"Creation Time" tEXt chunk is not expected to be automatically changed -by the software. To facilitate the use of RFC 1123 dates, a function -png_convert_to_rfc1123(png_timep) is provided to convert from PNG -time to an RFC 1123 format string. - -Writing unknown chunks - -You can use the png_set_unknown_chunks function to queue up chunks -for writing. You give it a chunk name, raw data, and a size; that's -all there is to it. The chunks will be written by the next following -png_write_info_before_PLTE, png_write_info, or png_write_end function. -Any chunks previously read into the info structure's unknown-chunk -list will also be written out in a sequence that satisfies the PNG -specification's ordering rules. - -The high-level write interface - -At this point there are two ways to proceed; through the high-level -write interface, or through a sequence of low-level write operations. -You can use the high-level interface if your image data is present -in the info structure. All defined output -transformations are permitted, enabled by the following masks. - - PNG_TRANSFORM_IDENTITY No transformation - PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples - PNG_TRANSFORM_PACKSWAP Change order of packed - pixels to LSB first - PNG_TRANSFORM_INVERT_MONO Invert monochrome images - PNG_TRANSFORM_SHIFT Normalize pixels to the - sBIT depth - PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA - to BGRA - PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA - to AG - PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity - to transparency - PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples - PNG_TRANSFORM_STRIP_FILLER Strip out filler - bytes (deprecated). - PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading - filler bytes - PNG_TRANSFORM_STRIP_FILLER_AFTER Strip out trailing - filler bytes - -If you have valid image data in the info structure (you can use -png_set_rows() to put image data in the info structure), simply do this: - - png_write_png(png_ptr, info_ptr, png_transforms, NULL) - -where png_transforms is an integer containing the bitwise OR of some set of -transformation flags. This call is equivalent to png_write_info(), -followed the set of transformations indicated by the transform mask, -then png_write_image(), and finally png_write_end(). - -(The final parameter of this call is not yet used. Someday it might point -to transformation parameters required by some future output transform.) - -You must use png_transforms and not call any png_set_transform() functions -when you use png_write_png(). - -The low-level write interface - -If you are going the low-level route instead, you are now ready to -write all the file information up to the actual image data. You do -this with a call to png_write_info(). - - png_write_info(png_ptr, info_ptr); - -Note that there is one transformation you may need to do before -png_write_info(). In PNG files, the alpha channel in an image is the -level of opacity. If your data is supplied as a level of transparency, -you can invert the alpha channel before you write it, so that 0 is -fully transparent and 255 (in 8-bit or paletted images) or 65535 -(in 16-bit images) is fully opaque, with - - png_set_invert_alpha(png_ptr); - -This must appear before png_write_info() instead of later with the -other transformations because in the case of paletted images the tRNS -chunk data has to be inverted before the tRNS chunk is written. If -your image is not a paletted image, the tRNS data (which in such cases -represents a single color to be rendered as transparent) won't need to -be changed, and you can safely do this transformation after your -png_write_info() call. - -If you need to write a private chunk that you want to appear before -the PLTE chunk when PLTE is present, you can write the PNG info in -two steps, and insert code to write your own chunk between them: - - png_write_info_before_PLTE(png_ptr, info_ptr); - png_set_unknown_chunks(png_ptr, info_ptr, ...); - png_write_info(png_ptr, info_ptr); - -After you've written the file information, you can set up the library -to handle any special transformations of the image data. The various -ways to transform the data will be described in the order that they -should occur. This is important, as some of these change the color -type and/or bit depth of the data, and some others only work on -certain color types and bit depths. Even though each transformation -checks to see if it has data that it can do something with, you should -make sure to only enable a transformation if it will be valid for the -data. For example, don't swap red and blue on grayscale data. - -PNG files store RGB pixels packed into 3 or 6 bytes. This code tells -the library to strip input data that has 4 or 8 bytes per pixel down -to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2 -bytes per pixel). - - png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); - -where the 0 is unused, and the location is either PNG_FILLER_BEFORE or -PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel -is stored XRGB or RGBX. - -PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as -they can, resulting in, for example, 8 pixels per byte for 1 bit files. -If the data is supplied at 1 pixel per byte, use this code, which will -correctly pack the pixels into a single byte: - - png_set_packing(png_ptr); - -PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your -data is of another bit depth, you can write an sBIT chunk into the -file so that decoders can recover the original data if desired. - - /* Set the true bit depth of the image data */ - if (color_type & PNG_COLOR_MASK_COLOR) - { - sig_bit.red = true_bit_depth; - sig_bit.green = true_bit_depth; - sig_bit.blue = true_bit_depth; - } - else - { - sig_bit.gray = true_bit_depth; - } - if (color_type & PNG_COLOR_MASK_ALPHA) - { - sig_bit.alpha = true_bit_depth; - } - - png_set_sBIT(png_ptr, info_ptr, &sig_bit); - -If the data is stored in the row buffer in a bit depth other than -one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG), -this will scale the values to appear to be the correct bit depth as -is required by PNG. - - png_set_shift(png_ptr, &sig_bit); - -PNG files store 16 bit pixels in network byte order (big-endian, -ie. most significant bits first). This code would be used if they are -supplied the other way (little-endian, i.e. least significant bits -first, the way PCs store them): - - if (bit_depth > 8) - png_set_swap(png_ptr); - -If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you -need to change the order the pixels are packed into bytes, you can use: - - if (bit_depth < 8) - png_set_packswap(png_ptr); - -PNG files store 3 color pixels in red, green, blue order. This code -would be used if they are supplied as blue, green, red: - - png_set_bgr(png_ptr); - -PNG files describe monochrome as black being zero and white being -one. This code would be used if the pixels are supplied with this reversed -(black being one and white being zero): - - png_set_invert_mono(png_ptr); - -Finally, you can write your own transformation function if none of -the existing ones meets your needs. This is done by setting a callback -with - - png_set_write_user_transform_fn(png_ptr, - write_transform_fn); - -You must supply the function - - void write_transform_fn(png_structp png_ptr, png_row_infop - row_info, png_bytep data) - -See pngtest.c for a working example. Your function will be called -before any of the other transformations are processed. - -You can also set up a pointer to a user structure for use by your -callback function. - - png_set_user_transform_info(png_ptr, user_ptr, 0, 0); - -The user_channels and user_depth parameters of this function are ignored -when writing; you can set them to zero as shown. - -You can retrieve the pointer via the function png_get_user_transform_ptr(). -For example: - - voidp write_user_transform_ptr = - png_get_user_transform_ptr(png_ptr); - -It is possible to have libpng flush any pending output, either manually, -or automatically after a certain number of lines have been written. To -flush the output stream a single time call: - - png_write_flush(png_ptr); - -and to have libpng flush the output stream periodically after a certain -number of scanlines have been written, call: - - png_set_flush(png_ptr, nrows); - -Note that the distance between rows is from the last time png_write_flush() -was called, or the first row of the image if it has never been called. -So if you write 50 lines, and then png_set_flush 25, it will flush the -output on the next scanline, and every 25 lines thereafter, unless -png_write_flush() is called before 25 more lines have been written. -If nrows is too small (less than about 10 lines for a 640 pixel wide -RGB image) the image compression may decrease noticeably (although this -may be acceptable for real-time applications). Infrequent flushing will -only degrade the compression performance by a few percent over images -that do not use flushing. - -Writing the image data - -That's it for the transformations. Now you can write the image data. -The simplest way to do this is in one function call. If you have the -whole image in memory, you can just call png_write_image() and libpng -will write the image. You will need to pass in an array of pointers to -each row. This function automatically handles interlacing, so you don't -need to call png_set_interlace_handling() or call this function multiple -times, or any of that other stuff necessary with png_write_rows(). - - png_write_image(png_ptr, row_pointers); - -where row_pointers is: - - png_byte *row_pointers[height]; - -You can point to void or char or whatever you use for pixels. - -If you don't want to write the whole image at once, you can -use png_write_rows() instead. If the file is not interlaced, -this is simple: - - png_write_rows(png_ptr, row_pointers, - number_of_rows); - -row_pointers is the same as in the png_write_image() call. - -If you are just writing one row at a time, you can do this with -a single row_pointer instead of an array of row_pointers: - - png_bytep row_pointer = row; - - png_write_row(png_ptr, row_pointer); - -When the file is interlaced, things can get a good deal more complicated. -The only currently (as of the PNG Specification version 1.2, dated July -1999) defined interlacing scheme for PNG files is the "Adam7" interlace -scheme, that breaks down an image into seven smaller images of varying -size. libpng will build these images for you, or you can do them -yourself. If you want to build them yourself, see the PNG specification -for details of which pixels to write when. - -If you don't want libpng to handle the interlacing details, just -use png_set_interlace_handling() and call png_write_rows() the -correct number of times to write all seven sub-images. - -If you want libpng to build the sub-images, call this before you start -writing any rows: - - number_of_passes = - png_set_interlace_handling(png_ptr); - -This will return the number of passes needed. Currently, this is seven, -but may change if another interlace type is added. - -Then write the complete image number_of_passes times. - - png_write_rows(png_ptr, row_pointers, - number_of_rows); - -As some of these rows are not used, and thus return immediately, you may -want to read about interlacing in the PNG specification, and only update -the rows that are actually used. - -Finishing a sequential write - -After you are finished writing the image, you should finish writing -the file. If you are interested in writing comments or time, you should -pass an appropriately filled png_info pointer. If you are not interested, -you can pass NULL. - - png_write_end(png_ptr, info_ptr); - -When you are done, you can free all memory used by libpng like this: - - png_destroy_write_struct(&png_ptr, &info_ptr); - -It is also possible to individually free the info_ptr members that -point to libpng-allocated storage with the following function: - - png_free_data(png_ptr, info_ptr, mask, seq) - mask - identifies data to be freed, a mask - containing the bitwise OR of one or - more of - PNG_FREE_PLTE, PNG_FREE_TRNS, - PNG_FREE_HIST, PNG_FREE_ICCP, - PNG_FREE_PCAL, PNG_FREE_ROWS, - PNG_FREE_SCAL, PNG_FREE_SPLT, - PNG_FREE_TEXT, PNG_FREE_UNKN, - or simply PNG_FREE_ALL - seq - sequence number of item to be freed - (-1 for all items) - -This function may be safely called when the relevant storage has -already been freed, or has not yet been allocated, or was allocated -by the user and not by libpng, and will in those cases do nothing. -The "seq" parameter is ignored if only one item of the selected data -type, such as PLTE, is allowed. If "seq" is not -1, and multiple items -are allowed for the data type identified in the mask, such as text or -sPLT, only the n'th item in the structure is freed, where n is "seq". - -If you allocated data such as a palette that you passed in to libpng -with png_set_*, you must not free it until just before the call to -png_destroy_write_struct(). - -The default behavior is only to free data that was allocated internally -by libpng. This can be changed, so that libpng will not free the data, -or so that it will free data that was allocated by the user with png_malloc() -or png_zalloc() and passed in via a png_set_*() function, with - - png_data_freer(png_ptr, info_ptr, freer, mask) - mask - which data elements are affected - same choices as in png_free_data() - freer - one of - PNG_DESTROY_WILL_FREE_DATA - PNG_SET_WILL_FREE_DATA - PNG_USER_WILL_FREE_DATA - -For example, to transfer responsibility for some data from a read structure -to a write structure, you could use - - png_data_freer(read_ptr, read_info_ptr, - PNG_USER_WILL_FREE_DATA, - PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) - png_data_freer(write_ptr, write_info_ptr, - PNG_DESTROY_WILL_FREE_DATA, - PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) - -thereby briefly reassigning responsibility for freeing to the user but -immediately afterwards reassigning it once more to the write_destroy -function. Having done this, it would then be safe to destroy the read -structure and continue to use the PLTE, tRNS, and hIST data in the write -structure. - -This function only affects data that has already been allocated. -You can call this function before calling after the png_set_*() functions -to control whether the user or png_destroy_*() is supposed to free the data. -When the user assumes responsibility for libpng-allocated data, the -application must use -png_free() to free it, and when the user transfers responsibility to libpng -for data that the user has allocated, the user must have used png_malloc() -or png_zalloc() to allocate it. - -If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword -separately, do not transfer responsibility for freeing text_ptr to libpng, -because when libpng fills a png_text structure it combines these members with -the key member, and png_free_data() will free only text_ptr.key. Similarly, -if you transfer responsibility for free'ing text_ptr from libpng to your -application, your application must not separately free those members. -For a more compact example of writing a PNG image, see the file example.c. - -V. Modifying/Customizing libpng: - -There are two issues here. The first is changing how libpng does -standard things like memory allocation, input/output, and error handling. -The second deals with more complicated things like adding new chunks, -adding new transformations, and generally changing how libpng works. -Both of those are compile-time issues; that is, they are generally -determined at the time the code is written, and there is rarely a need -to provide the user with a means of changing them. - -Memory allocation, input/output, and error handling - -All of the memory allocation, input/output, and error handling in libpng -goes through callbacks that are user-settable. The default routines are -in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change -these functions, call the appropriate png_set_*_fn() function. - -Memory allocation is done through the functions png_malloc(), png_calloc(), -and png_free(). These currently just call the standard C functions. -png_calloc() calls png_malloc() and then png_memset() to clear the newly -allocated memory to zero. If your pointers can't access more then 64K -at a time, you will want to set MAXSEG_64K in zlib.h. Since it is -unlikely that the method of handling memory allocation on a platform -will change between applications, these functions must be modified in -the library at compile time. If you prefer to use a different method -of allocating and freeing data, you can use png_create_read_struct_2() or -png_create_write_struct_2() to register your own functions as described -above. These functions also provide a void pointer that can be retrieved -via - - mem_ptr=png_get_mem_ptr(png_ptr); - -Your replacement memory functions must have prototypes as follows: - - png_voidp malloc_fn(png_structp png_ptr, - png_alloc_size_t size); - void free_fn(png_structp png_ptr, png_voidp ptr); - -Your malloc_fn() must return NULL in case of failure. The png_malloc() -function will normally call png_error() if it receives a NULL from the -system memory allocator or from your replacement malloc_fn(). - -Your free_fn() will never be called with a NULL ptr, since libpng's -png_free() checks for NULL before calling free_fn(). - -Input/Output in libpng is done through png_read() and png_write(), -which currently just call fread() and fwrite(). The FILE * is stored in -png_struct and is initialized via png_init_io(). If you wish to change -the method of I/O, the library supplies callbacks that you can set -through the function png_set_read_fn() and png_set_write_fn() at run -time, instead of calling the png_init_io() function. These functions -also provide a void pointer that can be retrieved via the function -png_get_io_ptr(). For example: - - png_set_read_fn(png_structp read_ptr, - voidp read_io_ptr, png_rw_ptr read_data_fn) - - png_set_write_fn(png_structp write_ptr, - voidp write_io_ptr, png_rw_ptr write_data_fn, - png_flush_ptr output_flush_fn); - - voidp read_io_ptr = png_get_io_ptr(read_ptr); - voidp write_io_ptr = png_get_io_ptr(write_ptr); - -The replacement I/O functions must have prototypes as follows: - - void user_read_data(png_structp png_ptr, - png_bytep data, png_size_t length); - void user_write_data(png_structp png_ptr, - png_bytep data, png_size_t length); - void user_flush_data(png_structp png_ptr); - -The user_read_data() function is responsible for detecting and -handling end-of-data errors. - -Supplying NULL for the read, write, or flush functions sets them back -to using the default C stream functions, which expect the io_ptr to -point to a standard *FILE structure. It is probably a mistake -to use NULL for one of write_data_fn and output_flush_fn but not both -of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined. -It is an error to read from a write stream, and vice versa. - -Error handling in libpng is done through png_error() and png_warning(). -Errors handled through png_error() are fatal, meaning that png_error() -should never return to its caller. Currently, this is handled via -setjmp() and longjmp() (unless you have compiled libpng with -PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()), -but you could change this to do things like exit() if you should wish, -as long as your function does not return. - -On non-fatal errors, png_warning() is called -to print a warning message, and then control returns to the calling code. -By default png_error() and png_warning() print a message on stderr via -fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined -(because you don't want the messages) or PNG_NO_STDIO defined (because -fprintf() isn't available). If you wish to change the behavior of the error -functions, you will need to set up your own message callbacks. These -functions are normally supplied at the time that the png_struct is created. -It is also possible to redirect errors and warnings to your own replacement -functions after png_create_*_struct() has been called by calling: - - png_set_error_fn(png_structp png_ptr, - png_voidp error_ptr, png_error_ptr error_fn, - png_error_ptr warning_fn); - - png_voidp error_ptr = png_get_error_ptr(png_ptr); - -If NULL is supplied for either error_fn or warning_fn, then the libpng -default function will be used, calling fprintf() and/or longjmp() if a -problem is encountered. The replacement error functions should have -parameters as follows: - - void user_error_fn(png_structp png_ptr, - png_const_charp error_msg); - void user_warning_fn(png_structp png_ptr, - png_const_charp warning_msg); - -The motivation behind using setjmp() and longjmp() is the C++ throw and -catch exception handling methods. This makes the code much easier to write, -as there is no need to check every return code of every function call. -However, there are some uncertainties about the status of local variables -after a longjmp, so the user may want to be careful about doing anything -after setjmp returns non-zero besides returning itself. Consult your -compiler documentation for more details. For an alternative approach, you -may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net), -which is illustrated in pngvalid.c and in contrib/visupng. - -Custom chunks - -If you need to read or write custom chunks, you may need to get deeper -into the libpng code. The library now has mechanisms for storing -and writing chunks of unknown type; you can even declare callbacks -for custom chunks. However, this may not be good enough if the -library code itself needs to know about interactions between your -chunk and existing `intrinsic' chunks. - -If you need to write a new intrinsic chunk, first read the PNG -specification. Acquire a first level of understanding of how it works. -Pay particular attention to the sections that describe chunk names, -and look at how other chunks were designed, so you can do things -similarly. Second, check out the sections of libpng that read and -write chunks. Try to find a chunk that is similar to yours and use -it as a template. More details can be found in the comments inside -the code. It is best to handle private or unknown chunks in a generic method, -via callback functions, instead of by modifying libpng functions. This -is illustrated in pngtest.c, which uses a callback function to handle a -private "vpAg" chunk and the new "sTER" chunk, which are both unknown to -libpng. - -If you wish to write your own transformation for the data, look through -the part of the code that does the transformations, and check out some of -the simpler ones to get an idea of how they work. Try to find a similar -transformation to the one you want to add and copy off of it. More details -can be found in the comments inside the code itself. - -Configuring for 16 bit platforms - -You will want to look into zconf.h to tell zlib (and thus libpng) that -it cannot allocate more then 64K at a time. Even if you can, the memory -won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K. - -Configuring for DOS - -For DOS users who only have access to the lower 640K, you will -have to limit zlib's memory usage via a png_set_compression_mem_level() -call. See zlib.h or zconf.h in the zlib library for more information. - -Configuring for Medium Model - -Libpng's support for medium model has been tested on most of the popular -compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets -defined, and FAR gets defined to far in pngconf.h, and you should be -all set. Everything in the library (except for zlib's structure) is -expecting far data. You must use the typedefs with the p or pp on -the end for pointers (or at least look at them and be careful). Make -note that the rows of data are defined as png_bytepp, which is an -unsigned char far * far *. - -Configuring for gui/windowing platforms: - -You will need to write new error and warning functions that use the GUI -interface, as described previously, and set them to be the error and -warning functions at the time that png_create_*_struct() is called, -in order to have them available during the structure initialization. -They can be changed later via png_set_error_fn(). On some compilers, -you may also have to change the memory allocators (png_malloc, etc.). - -Configuring for compiler xxx: - -All includes for libpng are in pngconf.h. If you need to add, change -or delete an include, this is the place to do it. -The includes that are not needed outside libpng are placed in pngpriv.h, -which is only used by the routines inside libpng itself. -The files in libpng proper only include pngpriv.h and png.h, which -in turn includes pngconf.h. - -Configuring zlib: - -There are special functions to configure the compression. Perhaps the -most useful one changes the compression level, which currently uses -input compression values in the range 0 - 9. The library normally -uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests -have shown that for a large majority of images, compression values in -the range 3-6 compress nearly as well as higher levels, and do so much -faster. For online applications it may be desirable to have maximum speed -(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also -specify no compression (Z_NO_COMPRESSION = 0), but this would create -files larger than just storing the raw bitmap. You can specify the -compression level by calling: - - png_set_compression_level(png_ptr, level); - -Another useful one is to reduce the memory level used by the library. -The memory level defaults to 8, but it can be lowered if you are -short on memory (running DOS, for example, where you only have 640K). -Note that the memory level does have an effect on compression; among -other things, lower levels will result in sections of incompressible -data being emitted in smaller stored blocks, with a correspondingly -larger relative overhead of up to 15% in the worst case. - - png_set_compression_mem_level(png_ptr, level); - -The other functions are for configuring zlib. They are not recommended -for normal use and may result in writing an invalid PNG file. See -zlib.h for more information on what these mean. - - png_set_compression_strategy(png_ptr, - strategy); - png_set_compression_window_bits(png_ptr, - window_bits); - png_set_compression_method(png_ptr, method); - png_set_compression_buffer_size(png_ptr, size); - -Controlling row filtering - -If you want to control whether libpng uses filtering or not, which -filters are used, and how it goes about picking row filters, you -can call one of these functions. The selection and configuration -of row filters can have a significant impact on the size and -encoding speed and a somewhat lesser impact on the decoding speed -of an image. Filtering is enabled by default for RGB and grayscale -images (with and without alpha), but not for paletted images nor -for any images with bit depths less than 8 bits/pixel. - -The 'method' parameter sets the main filtering method, which is -currently only '0' in the PNG 1.2 specification. The 'filters' -parameter sets which filter(s), if any, should be used for each -scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS -to turn filtering on and off, respectively. - -Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB, -PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise -ORed together with '|' to specify one or more filters to use. -These filters are described in more detail in the PNG specification. -If you intend to change the filter type during the course of writing -the image, you should start with flags set for all of the filters -you intend to use so that libpng can initialize its internal -structures appropriately for all of the filter types. (Note that this -means the first row must always be adaptively filtered, because libpng -currently does not allocate the filter buffers until png_write_row() -is called for the first time.) - - filters = PNG_FILTER_NONE | PNG_FILTER_SUB - PNG_FILTER_UP | PNG_FILTER_AVG | - PNG_FILTER_PAETH | PNG_ALL_FILTERS; - - png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, - filters); - The second parameter can also be - PNG_INTRAPIXEL_DIFFERENCING if you are - writing a PNG to be embedded in a MNG - datastream. This parameter must be the - same as the value of filter_method used - in png_set_IHDR(). - -It is also possible to influence how libpng chooses from among the -available filters. This is done in one or both of two ways - by -telling it how important it is to keep the same filter for successive -rows, and by telling it the relative computational costs of the filters. - - double weights[3] = {1.5, 1.3, 1.1}, - costs[PNG_FILTER_VALUE_LAST] = - {1.0, 1.3, 1.3, 1.5, 1.7}; - - png_set_filter_heuristics(png_ptr, - PNG_FILTER_HEURISTIC_WEIGHTED, 3, - weights, costs); - -The weights are multiplying factors that indicate to libpng that the -row filter should be the same for successive rows unless another row filter -is that many times better than the previous filter. In the above example, -if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a -"sum of absolute differences" 1.5 x 1.3 times higher than other filters -and still be chosen, while the NONE filter could have a sum 1.1 times -higher than other filters and still be chosen. Unspecified weights are -taken to be 1.0, and the specified weights should probably be declining -like those above in order to emphasize recent filters over older filters. - -The filter costs specify for each filter type a relative decoding cost -to be considered when selecting row filters. This means that filters -with higher costs are less likely to be chosen over filters with lower -costs, unless their "sum of absolute differences" is that much smaller. -The costs do not necessarily reflect the exact computational speeds of -the various filters, since this would unduly influence the final image -size. - -Note that the numbers above were invented purely for this example and -are given only to help explain the function usage. Little testing has -been done to find optimum values for either the costs or the weights. - -Removing unwanted object code - -There are a bunch of #define's in pngconf.h that control what parts of -libpng are compiled. All the defines end in _SUPPORTED. If you are -never going to use a capability, you can change the #define to #undef -before recompiling libpng and save yourself code and data space, or -you can turn off individual capabilities with defines that begin with -PNG_NO_. - -You can also turn all of the transforms and ancillary chunk capabilities -off en masse with compiler directives that define -PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS, -or all four, -along with directives to turn on any of the capabilities that you do -want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable the extra -transformations but still leave the library fully capable of reading -and writing PNG files with all known public chunks. Use of the -PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive produces a library -that is incapable of reading or writing ancillary chunks. If you are -not using the progressive reading capability, you can turn that off -with PNG_NO_PROGRESSIVE_READ (don't confuse this with the INTERLACING -capability, which you'll still have). - -All the reading and writing specific code are in separate files, so the -linker should only grab the files it needs. However, if you want to -make sure, or if you are building a stand alone library, all the -reading files start with "pngr" and all the writing files start with "pngw". -The files that don't match either (like png.c, pngtrans.c, etc.) -are used for both reading and writing, and always need to be included. -The progressive reader is in pngpread.c - -If you are creating or distributing a dynamically linked library (a .so -or DLL file), you should not remove or disable any parts of the library, -as this will cause applications linked with different versions of the -library to fail if they call functions not available in your library. -The size of the library itself should not be an issue, because only -those sections that are actually used will be loaded into memory. - -Requesting debug printout - -The macro definition PNG_DEBUG can be used to request debugging -printout. Set it to an integer value in the range 0 to 3. Higher -numbers result in increasing amounts of debugging information. The -information is printed to the "stderr" file, unless another file -name is specified in the PNG_DEBUG_FILE macro definition. - -When PNG_DEBUG > 0, the following functions (macros) become available: - - png_debug(level, message) - png_debug1(level, message, p1) - png_debug2(level, message, p1, p2) - -in which "level" is compared to PNG_DEBUG to decide whether to print -the message, "message" is the formatted string to be printed, -and p1 and p2 are parameters that are to be embedded in the string -according to printf-style formatting directives. For example, - - png_debug1(2, "foo=%d\n", foo); - -is expanded to - - if(PNG_DEBUG > 2) - fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo); - -When PNG_DEBUG is defined but is zero, the macros aren't defined, but you -can still use PNG_DEBUG to control your own debugging: - - #ifdef PNG_DEBUG - fprintf(stderr, ... - #endif - -When PNG_DEBUG = 1, the macros are defined, but only png_debug statements -having level = 0 will be printed. There aren't any such statements in -this version of libpng, but if you insert some they will be printed. - -VI. MNG support - -The MNG specification (available at http://www.libpng.org/pub/mng) allows -certain extensions to PNG for PNG images that are embedded in MNG datastreams. -Libpng can support some of these extensions. To enable them, use the -png_permit_mng_features() function: - - feature_set = png_permit_mng_features(png_ptr, mask) - mask is a png_uint_32 containing the bitwise OR of the - features you want to enable. These include - PNG_FLAG_MNG_EMPTY_PLTE - PNG_FLAG_MNG_FILTER_64 - PNG_ALL_MNG_FEATURES - feature_set is a png_uint_32 that is the bitwise AND of - your mask with the set of MNG features that is - supported by the version of libpng that you are using. - -It is an error to use this function when reading or writing a standalone -PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped -in a MNG datastream. As a minimum, it must have the MNG 8-byte signature -and the MHDR and MEND chunks. Libpng does not provide support for these -or any other MNG chunks; your application must provide its own support for -them. You may wish to consider using libmng (available at -http://www.libmng.com) instead. - -VII. Changes to Libpng from version 0.88 - -It should be noted that versions of libpng later than 0.96 are not -distributed by the original libpng author, Guy Schalnat, nor by -Andreas Dilger, who had taken over from Guy during 1996 and 1997, and -distributed versions 0.89 through 0.96, but rather by another member -of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are -still alive and well, but they have moved on to other things. - -The old libpng functions png_read_init(), png_write_init(), -png_info_init(), png_read_destroy(), and png_write_destroy() have been -moved to PNG_INTERNAL in version 0.95 to discourage their use. These -functions will be removed from libpng version 2.0.0. - -The preferred method of creating and initializing the libpng structures is -via the png_create_read_struct(), png_create_write_struct(), and -png_create_info_struct() because they isolate the size of the structures -from the application, allow version error checking, and also allow the -use of custom error handling routines during the initialization, which -the old functions do not. The functions png_read_destroy() and -png_write_destroy() do not actually free the memory that libpng -allocated for these structs, but just reset the data structures, so they -can be used instead of png_destroy_read_struct() and -png_destroy_write_struct() if you feel there is too much system overhead -allocating and freeing the png_struct for each image read. - -Setting the error callbacks via png_set_message_fn() before -png_read_init() as was suggested in libpng-0.88 is no longer supported -because this caused applications that do not use custom error functions -to fail if the png_ptr was not initialized to zero. It is still possible -to set the error callbacks AFTER png_read_init(), or to change them with -png_set_error_fn(), which is essentially the same function, but with a new -name to force compilation errors with applications that try to use the old -method. - -Starting with version 1.0.7, you can find out which version of the library -you are using at run-time: - - png_uint_32 libpng_vn = png_access_version_number(); - -The number libpng_vn is constructed from the major version, minor -version with leading zero, and release number with leading zero, -(e.g., libpng_vn for version 1.0.7 is 10007). - -You can also check which version of png.h you used when compiling your -application: - - png_uint_32 application_vn = PNG_LIBPNG_VER; - -VIII. Changes to Libpng from version 1.0.x to 1.2.x - -Support for user memory management was enabled by default. To -accomplish this, the functions png_create_read_struct_2(), -png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(), -png_malloc_default(), and png_free_default() were added. - -Support for the iTXt chunk has been enabled by default as of -version 1.2.41. - -Support for certain MNG features was enabled. - -Support for numbered error messages was added. However, we never got -around to actually numbering the error messages. The function -png_set_strip_error_numbers() was added (Note: the prototype for this -function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE -builds of libpng-1.2.15. It was restored in libpng-1.2.36). - -The png_malloc_warn() function was added at libpng-1.2.3. This issues -a png_warning and returns NULL instead of aborting when it fails to -acquire the requested memory allocation. - -Support for setting user limits on image width and height was enabled -by default. The functions png_set_user_limits(), png_get_user_width_max(), -and png_get_user_height_max() were added at libpng-1.2.6. - -The png_set_add_alpha() function was added at libpng-1.2.7. - -The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9. -Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the -tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is -deprecated. - -A number of macro definitions in support of runtime selection of -assembler code features (especially Intel MMX code support) were -added at libpng-1.2.0: - - PNG_ASM_FLAG_MMX_SUPPORT_COMPILED - PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU - PNG_ASM_FLAG_MMX_READ_COMBINE_ROW - PNG_ASM_FLAG_MMX_READ_INTERLACE - PNG_ASM_FLAG_MMX_READ_FILTER_SUB - PNG_ASM_FLAG_MMX_READ_FILTER_UP - PNG_ASM_FLAG_MMX_READ_FILTER_AVG - PNG_ASM_FLAG_MMX_READ_FILTER_PAETH - PNG_ASM_FLAGS_INITIALIZED - PNG_MMX_READ_FLAGS - PNG_MMX_FLAGS - PNG_MMX_WRITE_FLAGS - PNG_MMX_FLAGS - -We added the following functions in support of runtime -selection of assembler code features: - - png_get_mmx_flagmask() - png_set_mmx_thresholds() - png_get_asm_flags() - png_get_mmx_bitdepth_threshold() - png_get_mmx_rowbytes_threshold() - png_set_asm_flags() - -We replaced all of these functions with simple stubs in libpng-1.2.20, -when the Intel assembler code was removed due to a licensing issue. - -These macros are deprecated: - - PNG_READ_TRANSFORMS_NOT_SUPPORTED - PNG_PROGRESSIVE_READ_NOT_SUPPORTED - PNG_NO_SEQUENTIAL_READ_SUPPORTED - PNG_WRITE_TRANSFORMS_NOT_SUPPORTED - PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED - PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED - -They have been replaced, respectively, by: - - PNG_NO_READ_TRANSFORMS - PNG_NO_PROGRESSIVE_READ - PNG_NO_SEQUENTIAL_READ - PNG_NO_WRITE_TRANSFORMS - PNG_NO_READ_ANCILLARY_CHUNKS - PNG_NO_WRITE_ANCILLARY_CHUNKS - -PNG_MAX_UINT was replaced with PNG_UINT_31_MAX. It has been -deprecated since libpng-1.0.16 and libpng-1.2.6. - -The function - png_check_sig(sig, num) -was replaced with - !png_sig_cmp(sig, 0, num) -It has been deprecated since libpng-0.90. - -The function - png_set_gray_1_2_4_to_8() -which also expands tRNS to alpha was replaced with - png_set_expand_gray_1_2_4_to_8() -which does not. It has been deprecated since libpng-1.0.18 and 1.2.9. - -IX. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x - -Private libpng prototypes and macro definitions were moved from -png.h and pngconf.h into a new pngpriv.h header file. - -Functions png_set_benign_errors(), png_benign_error(), and -png_chunk_benign_error() were added. - -Support for setting the maximum amount of memory that the application -will allocate for reading chunks was added, as a security measure. -The functions png_set_chunk_cache_max() and png_get_chunk_cache_max() -were added to the library. - -We implemented support for I/O states by adding png_ptr member io_state -and functions png_get_io_chunk_name() and png_get_io_state() in pngget.c - -We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level -input transforms. - -Checking for and reporting of errors in the IHDR chunk is more thorough. - -Support for global arrays was removed, to improve thread safety. - -Some obsolete/deprecated macros and functions have been removed. - -Typecasted NULL definitions such as - #define png_voidp_NULL (png_voidp)NULL -were eliminated. If you used these in your application, just use -NULL instead. - -The png_struct and info_struct members "trans" and "trans_values" were -changed to "trans_alpha" and "trans_color", respectively. - -The obsolete, unused pnggccrd.c and pngvcrd.c files and related makefiles -were removed. - -The PNG_1_0_X and PNG_1_2_X macros were eliminated. - -The PNG_LEGACY_SUPPORTED macro was eliminated. - -Many WIN32_WCE #ifdefs were removed. - -The functions png_read_init(info_ptr), png_write_init(info_ptr), -png_info_init(info_ptr), png_read_destroy(), and png_write_destroy() -have been removed. They have been deprecated since libpng-0.95. - -The png_permit_empty_plte() was removed. It has been deprecated -since libpng-1.0.9. Use png_permit_mng_features() instead. - -We removed the obsolete stub functions png_get_mmx_flagmask(), -png_set_mmx_thresholds(), png_get_asm_flags(), -png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(), -png_set_asm_flags(), and png_mmx_supported() - -We removed the obsolete png_check_sig(), png_memcpy_check(), and -png_memset_check() functions. Instead use !png_sig_cmp(), png_memcpy(), -and png_memset(), respectively. - -The function png_set_gray_1_2_4_to_8() was removed. It has been -deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with -png_set_expand_gray_1_2_4_to_8() because the former function also -expanded palette images. - -Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32 -were added and are used by default instead of the corresponding -functions. Unfortunately, -from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the -function) incorrectly returned a value of type png_uint_32. - -We changed the prototype for png_malloc() from - png_malloc(png_structp png_ptr, png_uint_32 size) -to - png_malloc(png_structp png_ptr, png_alloc_size_t size) - -This also applies to the prototype for the user replacement malloc_fn(). - -The png_calloc() function was added and is used in place of -of "png_malloc(); png_memset();" except in the case in png_read_png() -where the array consists of pointers; in this case a "for" loop is used -after the png_malloc() to set the pointers to NULL, to give robust. -behavior in case the application runs out of memory part-way through -the process. - -We changed the prototypes of png_get_compression_buffer_size() and -png_set_compression_buffer_size() to work with png_size_t instead of -png_uint_32. - -Support for numbered error messages was removed by default, since we -never got around to actually numbering the error messages. The function -png_set_strip_error_numbers() was removed from the library by default. - -The png_zalloc() and png_zfree() functions are no longer exported. -The png_zalloc() function no longer zeroes out the memory that it -allocates. - -Support for dithering was disabled by default in libpng-1.4.0, because -it has not been well tested and doesn't actually "dither". -The code was not -removed, however, and could be enabled by building libpng with -PNG_READ_DITHER_SUPPORTED defined. In libpng-1.4.2, this support -was reenabled, but the function was renamed png_set_quantize() to -reflect more accurately what it actually does. At the same time, -the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to -PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS. - -We removed the trailing '.' from the warning and error messages. - -X. Detecting libpng - -The png_get_io_ptr() function has been present since libpng-0.88, has never -changed, and is unaffected by conditional compilation macros. It is the -best choice for use in configure scripts for detecting the presence of any -libpng version since 0.88. In an autoconf "configure.in" you could use - - AC_CHECK_LIB(png, png_get_io_ptr, ... - -XI. Source code repository - -Since about February 2009, version 1.2.34, libpng has been under "git" source -control. The git repository was built from old libpng-x.y.z.tar.gz files -going back to version 0.70. You can access the git repository (read only) -at - - git://libpng.git.sourceforge.net/gitroot/libpng - -or you can browse it via "gitweb" at - - http://libpng.git.sourceforge.net/git/gitweb.cgi?p=libpng - -Patches can be sent to glennrp at users.sourceforge.net or to -png-mng-implement at lists.sourceforge.net or you can upload them to -the libpng bug tracker at - - http://libpng.sourceforge.net - -XII. Coding style - -Our coding style is similar to the "Allman" style, with curly -braces on separate lines: - - if (condition) - { - action; - } - - else if (another condition) - { - another action; - } - -The braces can be omitted from simple one-line actions: - - if (condition) - return (0); - -We use 3-space indentation, except for continued statements which -are usually indented the same as the first line of the statement -plus four more spaces. - -For macro definitions we use 2-space indentation, always leaving the "#" -in the first column. - - #ifndef PNG_NO_FEATURE - # ifndef PNG_FEATURE_SUPPORTED - # define PNG_FEATURE_SUPPORTED - # endif - #endif - -Comments appear with the leading "/*" at the same indentation as -the statement that follows the comment: - - /* Single-line comment */ - statement; - - /* This is a multiple-line - * comment. - */ - statement; - -Very short comments can be placed after the end of the statement -to which they pertain: - - statement; /* comment */ - -We don't use C++ style ("//") comments. We have, however, -used them in the past in some now-abandoned MMX assembler -code. - -Functions and their curly braces are not indented, and -exported functions are marked with PNGAPI: - - /* This is a public function that is visible to - * application programers. It does thus-and-so. - */ - void PNGAPI - png_exported_function(png_ptr, png_info, foo) - { - body; - } - -The prototypes for all exported functions appear in png.h, -above the comment that says - - /* Maintainer: Put new public prototypes here ... */ - -We mark all non-exported functions with "/* PRIVATE */"": - - void /* PRIVATE */ - png_non_exported_function(png_ptr, png_info, foo) - { - body; - } - -The prototypes for non-exported functions (except for those in -pngtest) appear in -pngpriv.h -above the comment that says - - /* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */ - -To avoid polluting the global namespace, the names of all exported -functions and variables begin with "png_", and all publicly visible C -preprocessor macros begin with "PNG_". We request that applications that -use libpng *not* begin any of their own symbols with either of these strings. - -We put a space after each comma and after each semicolon -in "for" statments, and we put spaces before and after each -C binary operator and after "for" or "while", and before -"?". We don't put a space between a typecast and the expression -being cast, nor do we put one between a function name and the -left parenthesis that follows it: - - for (i = 2; i > 0; --i) - y[i] = a(x) + (int)b; - -We prefer #ifdef and #ifndef to #if defined() and if !defined() -when there is only one macro being tested. - -We do not use the TAB character for indentation in the C sources. - -Lines do not exceed 80 characters. - -Other rules can be inferred by inspecting the libpng source. - -XIII. Y2K Compliance in libpng - -July 13, 2011 - -Since the PNG Development group is an ad-hoc body, we can't make -an official declaration. - -This is your unofficial assurance that libpng from version 0.71 and -upward through 1.4.9beta01 are Y2K compliant. It is my belief that earlier -versions were also Y2K compliant. - -Libpng only has three year fields. One is a 2-byte unsigned integer that -will hold years up to 65535. The other two hold the date in text -format, and will hold years up to 9999. - -The integer is - "png_uint_16 year" in png_time_struct. - -The strings are - "png_charp time_buffer" in png_struct and - "near_time_buffer", which is a local character string in png.c. - -There are seven time-related functions: - - png_convert_to_rfc_1123() in png.c - (formerly png_convert_to_rfc_1152() in error) - png_convert_from_struct_tm() in pngwrite.c, called - in pngwrite.c - png_convert_from_time_t() in pngwrite.c - png_get_tIME() in pngget.c - png_handle_tIME() in pngrutil.c, called in pngread.c - png_set_tIME() in pngset.c - png_write_tIME() in pngwutil.c, called in pngwrite.c - -All appear to handle dates properly in a Y2K environment. The -png_convert_from_time_t() function calls gmtime() to convert from system -clock time, which returns (year - 1900), which we properly convert to -the full 4-digit year. There is a possibility that applications using -libpng are not passing 4-digit years into the png_convert_to_rfc_1123() -function, or that they are incorrectly passing only a 2-digit year -instead of "year - 1900" into the png_convert_from_struct_tm() function, -but this is not under our control. The libpng documentation has always -stated that it works with 4-digit years, and the APIs have been -documented as such. - -The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned -integer to hold the year, and can hold years as large as 65535. - -zlib, upon which libpng depends, is also Y2K compliant. It contains -no date-related code. - - - Glenn Randers-Pehrson - libpng maintainer - PNG Development Group diff --git a/libpng-manual.txt b/libpng-manual.txt index 771522501..1163cb075 100644 --- a/libpng-manual.txt +++ b/libpng-manual.txt @@ -1,6 +1,6 @@ libpng-manual.txt - A description on how to use and modify libpng - libpng version 1.5.10beta01 - February 19, 2012 + libpng version 1.5.10beta01 - February 21, 2012 Updated and distributed by Glenn Randers-Pehrson Copyright (c) 1998-2011 Glenn Randers-Pehrson @@ -11,7 +11,7 @@ libpng-manual.txt - A description on how to use and modify libpng Based on: - libpng versions 0.97, January 1998, through 1.5.10beta01 - February 19, 2012 + libpng versions 0.97, January 1998, through 1.5.10beta01 - February 21, 2012 Updated and distributed by Glenn Randers-Pehrson Copyright (c) 1998-2011 Glenn Randers-Pehrson @@ -4573,7 +4573,7 @@ Other rules can be inferred by inspecting the libpng source. XIV. Y2K Compliance in libpng -February 19, 2012 +February 21, 2012 Since the PNG Development group is an ad-hoc body, we can't make an official declaration. diff --git a/libpng.3 b/libpng.3 index 7faba8a3a..5fd34921c 100644 --- a/libpng.3 +++ b/libpng.3 @@ -1,4 +1,4 @@ -.TH LIBPNG 3 "February 19, 2012" +.TH LIBPNG 3 "February 21, 2012" .SH NAME libpng \- Portable Network Graphics (PNG) Reference Library 1.5.10beta01 .SH SYNOPSIS @@ -977,7 +977,7 @@ Following is a copy of the libpng-manual.txt file that accompanies libpng. .SH LIBPNG.TXT libpng-manual.txt - A description on how to use and modify libpng - libpng version 1.5.10beta01 - February 19, 2012 + libpng version 1.5.10beta01 - February 21, 2012 Updated and distributed by Glenn Randers-Pehrson Copyright (c) 1998-2011 Glenn Randers-Pehrson @@ -988,7 +988,7 @@ libpng-manual.txt - A description on how to use and modify libpng Based on: - libpng versions 0.97, January 1998, through 1.5.10beta01 - February 19, 2012 + libpng versions 0.97, January 1998, through 1.5.10beta01 - February 21, 2012 Updated and distributed by Glenn Randers-Pehrson Copyright (c) 1998-2011 Glenn Randers-Pehrson @@ -5551,7 +5551,7 @@ Other rules can be inferred by inspecting the libpng source. .SH XIV. Y2K Compliance in libpng -February 19, 2012 +February 21, 2012 Since the PNG Development group is an ad-hoc body, we can't make an official declaration. @@ -5825,7 +5825,7 @@ possible without all of you. Thanks to Frank J. T. Wojcik for helping with the documentation. -Libpng version 1.5.10beta01 - February 19, 2012: +Libpng version 1.5.10beta01 - February 21, 2012: Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc. Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net). @@ -5848,7 +5848,7 @@ this sentence. This code is released under the libpng license. -libpng versions 1.2.6, August 15, 2004, through 1.5.10beta01, February 19, 2012, are +libpng versions 1.2.6, August 15, 2004, through 1.5.10beta01, February 21, 2012, are Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are distributed according to the same disclaimer and license as libpng-1.2.5 with the following individual added to the list of Contributing Authors @@ -5947,7 +5947,7 @@ certification mark of the Open Source Initiative. Glenn Randers-Pehrson glennrp at users.sourceforge.net -February 19, 2012 +February 21, 2012 .\" end of man page diff --git a/libpngpf.3 b/libpngpf.3 index bcd649645..7722c281a 100644 --- a/libpngpf.3 +++ b/libpngpf.3 @@ -1,4 +1,4 @@ -.TH LIBPNGPF 3 "February 19, 2012" +.TH LIBPNGPF 3 "February 21, 2012" .SH NAME libpng \- Portable Network Graphics (PNG) Reference Library 1.5.10beta01 (private functions) diff --git a/png.5 b/png.5 index ec587cd23..b96ddd493 100644 --- a/png.5 +++ b/png.5 @@ -1,4 +1,4 @@ -.TH PNG 5 "February 19, 2012" +.TH PNG 5 "February 21, 2012" .SH NAME png \- Portable Network Graphics (PNG) format .SH DESCRIPTION diff --git a/png.c b/png.c index 4cdbad9ca..488a3da7c 100644 --- a/png.c +++ b/png.c @@ -655,13 +655,13 @@ png_get_copyright(png_const_structp png_ptr) #else # ifdef __STDC__ return PNG_STRING_NEWLINE \ - "libpng version 1.5.10beta01 - February 19, 2012" PNG_STRING_NEWLINE \ + "libpng version 1.5.10beta01 - February 21, 2012" PNG_STRING_NEWLINE \ "Copyright (c) 1998-2011 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \ "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \ "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \ PNG_STRING_NEWLINE; # else - return "libpng version 1.5.10beta01 - February 19, 2012\ + return "libpng version 1.5.10beta01 - February 21, 2012\ Copyright (c) 1998-2011 Glenn Randers-Pehrson\ Copyright (c) 1996-1997 Andreas Dilger\ Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc."; diff --git a/png.h b/png.h index aaf615196..e4ad279af 100644 --- a/png.h +++ b/png.h @@ -1,7 +1,7 @@ /* png.h - header file for PNG reference library * - * libpng version 1.5.10beta01 - February 19, 2012 + * libpng version 1.5.10beta01 - February 21, 2012 * Copyright (c) 1998-2012 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) @@ -11,7 +11,7 @@ * Authors and maintainers: * libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat * libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger - * libpng versions 0.97, January 1998, through 1.5.10beta01 - February 19, 2012: Glenn + * libpng versions 0.97, January 1998, through 1.5.10beta01 - February 21, 2012: Glenn * See also "Contributing Authors", below. * * Note about libpng version numbers: @@ -204,7 +204,7 @@ * * This code is released under the libpng license. * - * libpng versions 1.2.6, August 15, 2004, through 1.5.10beta01, February 19, 2012, are + * libpng versions 1.2.6, August 15, 2004, through 1.5.10beta01, February 21, 2012, are * Copyright (c) 2004, 2006-2012 Glenn Randers-Pehrson, and are * distributed according to the same disclaimer and license as libpng-1.2.5 * with the following individual added to the list of Contributing Authors: @@ -316,7 +316,7 @@ * Y2K compliance in libpng: * ========================= * - * February 19, 2012 + * February 21, 2012 * * Since the PNG Development group is an ad-hoc body, we can't make * an official declaration. @@ -382,7 +382,7 @@ /* Version information for png.h - this should match the version in png.c */ #define PNG_LIBPNG_VER_STRING "1.5.10beta01" #define PNG_HEADER_VERSION_STRING \ - " libpng version 1.5.10beta01 - February 19, 2012\n" + " libpng version 1.5.10beta01 - February 21, 2012\n" #define PNG_LIBPNG_VER_SONUM 15 #define PNG_LIBPNG_VER_DLLNUM 15 diff --git a/pngconf.h b/pngconf.h index 70c9b84e7..e68c7b04c 100644 --- a/pngconf.h +++ b/pngconf.h @@ -1,7 +1,7 @@ /* pngconf.h - machine configurable file for libpng * - * libpng version 1.5.10beta01 - February 19, 2012 + * libpng version 1.5.10beta01 - February 21, 2012 * * Copyright (c) 1998-2012 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) diff --git a/pngrutil.c b/pngrutil.c index 74822a92b..629c33ad0 100644 --- a/pngrutil.c +++ b/pngrutil.c @@ -1,7 +1,7 @@ /* pngrutil.c - utilities to read a PNG file * - * Last changed in libpng 1.5.10 [(PENDING RELEASE)] + * Last changed in libpng 1.5.9 [(PENDING RELEASE)] * Copyright (c) 1998-2012 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) diff --git a/projects/visualc6/README.txt b/projects/visualc6/README.txt deleted file mode 100644 index 578af6c72..000000000 --- a/projects/visualc6/README.txt +++ /dev/null @@ -1,57 +0,0 @@ -Microsoft Developer Studio Project File, Format Version 6.00 for libpng. - -Copyright (C) 2000-2004 Simon-Pierre Cadieux. -Copyright (C) 2004 Cosmin Truta. - -This code is released under the libpng license. -For conditions of distribution and use, see copyright notice in png.h - -NOTE: This project will be removed from libpng-1.5.0. It has -been replaced with the "vstudio" project. - -Assumptions: -* The libpng source files are in ..\.. -* The zlib source files are in ..\..\..\zlib -* The zlib project files are in ..\..\..\zlib\projects\visualc6 - - -To use: - -1) On the main menu, select "File | Open Workspace". - Open "libpng.dsw". - -2) Select "Build | Set Active Configuration". - Choose the configuration you wish to build. - (Choose libpng or pngtest; zlib will be built automatically.) - -3) Select "Build | Clean". - -4) Select "Build | Build ... (F7)". Ignore warning messages about - not being able to find certain include files (e.g. alloc.h). - -5) If you built the sample program (pngtest), - select "Build | Execute ... (Ctrl+F5)". - - -This project builds the libpng binaries as follows: - -* Win32_DLL_Release\libpng14.dll DLL build -* Win32_DLL_Debug\libpng14d.dll DLL build (debug version) -* Win32_DLL_VB\libpng14vb.dll DLL build for Visual Basic, using stdcall -* Win32_LIB_Release\libpng.lib static build -* Win32_LIB_Debug\libpngd.lib static build (debug version) - - -Notes: - -If you change anything in the source files, or select different compiler -settings, please change the DLL name to something different than any of -the above names. Also, make sure that in your "pngusr.h" you define -PNG_USER_PRIVATEBUILD and PNG_USER_DLLFNAME_POSTFIX according to the -instructions provided in "pngconf.h". - -All DLLs built by this project use the Microsoft dynamic C runtime library -MSVCRT.DLL (MSVCRTD.DLL for debug versions). If you distribute any of the -above mentioned libraries you should also include this DLL in your package. -For a list of files that are redistributable in Visual C++ 6.0, see -Common\Redist\Redist.txt on Disc 1 of the Visual C++ 6.0 product CDs. diff --git a/projects/visualc6/libpng.dsp b/projects/visualc6/libpng.dsp deleted file mode 100644 index 6704255ab..000000000 --- a/projects/visualc6/libpng.dsp +++ /dev/null @@ -1,328 +0,0 @@ -# Microsoft Developer Studio Project File - Name="libpng" - Package Owner=<4> -# Microsoft Developer Studio Generated Build File, Format Version 6.00 -# ** DO NOT EDIT ** - -# TARGTYPE "Win32 (x86) Dynamic-Link Library" 0x0102 -# TARGTYPE "Win32 (x86) Static Library" 0x0104 - -CFG=libpng - Win32 DLL Release -!MESSAGE This is not a valid makefile. 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-SOURCE=..\..\scripts\pngwin.rc - -!IF "$(CFG)" == "libpng - Win32 DLL Release" - -!ELSEIF "$(CFG)" == "libpng - Win32 DLL Debug" - -!ELSEIF "$(CFG)" == "libpng - Win32 DLL VB" - -!ELSEIF "$(CFG)" == "libpng - Win32 LIB Release" - -# PROP Exclude_From_Build 1 - -!ELSEIF "$(CFG)" == "libpng - Win32 LIB Debug" - -# PROP Exclude_From_Build 1 - -!ENDIF - -# End Source File -# End Group -# Begin Source File - -SOURCE=.\README.txt -# End Source File -# End Target -# End Project diff --git a/projects/visualc6/pngtest.dsp b/projects/visualc6/pngtest.dsp deleted file mode 100644 index d3cb0682c..000000000 --- a/projects/visualc6/pngtest.dsp +++ /dev/null @@ -1,178 +0,0 @@ -# Microsoft Developer Studio Project File - Name="pngtest" - Package Owner=<4> -# Microsoft Developer Studio Generated Build File, Format Version 6.00 -# ** DO NOT EDIT ** - -# TARGTYPE "Win32 (x86) Console Application" 0x0103 - -CFG=pngtest - Win32 DLL Release -!MESSAGE This is not a valid makefile. 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For example: -!MESSAGE -!MESSAGE NMAKE /f "pngtest.mak" CFG="pngtest - Win32 DLL Release" -!MESSAGE -!MESSAGE Possible choices for configuration are: -!MESSAGE -!MESSAGE "pngtest - Win32 DLL Release" (based on "Win32 (x86) Console Application") -!MESSAGE "pngtest - Win32 DLL Debug" (based on "Win32 (x86) Console Application") -!MESSAGE "pngtest - Win32 LIB Release" (based on "Win32 (x86) Console Application") -!MESSAGE "pngtest - Win32 LIB Debug" (based on "Win32 (x86) Console Application") -!MESSAGE - -# Begin Project -# PROP AllowPerConfigDependencies 0 -# PROP Scc_ProjName "" -# PROP Scc_LocalPath "" -CPP=cl.exe -RSC=rc.exe - -!IF "$(CFG)" == "pngtest - Win32 DLL Release" - -# PROP BASE Use_MFC 0 -# PROP BASE Use_Debug_Libraries 0 -# PROP BASE Output_Dir "pngtest___Win32_DLL_Release" -# PROP BASE Intermediate_Dir "pngtest___Win32_DLL_Release" -# PROP BASE Target_Dir "" -# PROP Use_MFC 0 -# PROP Use_Debug_Libraries 0 -# PROP Output_Dir "Win32_DLL_Release" -# PROP Intermediate_Dir "Win32_DLL_Release" -# PROP Ignore_Export_Lib 0 -# PROP Target_Dir "" -# ADD BASE CPP /nologo /W3 /O2 /D "WIN32" /D "NDEBUG" /FD /c -# SUBTRACT BASE CPP /YX -# ADD CPP /nologo /MD /W3 /O2 /I "..\..\..\zlib" /D "WIN32" /D "NDEBUG" /D "PNG_DLL" /D "PNG_NO_STDIO" /FD /c -# SUBTRACT CPP /YX -# ADD BASE RSC /l 0x409 /d "NDEBUG" -# ADD RSC /l 0x409 /d "NDEBUG" -BSC32=bscmake.exe -# ADD BASE BSC32 /nologo -# ADD BSC32 /nologo -LINK32=link.exe -# ADD BASE LINK32 /nologo /subsystem:console /machine:I386 -# ADD LINK32 Win32_DLL_Release\libpng14.lib ..\..\..\zlib\projects\visualc6\Win32_DLL_Release\zlib1.lib /nologo /subsystem:console /machine:I386 -# Begin Special Build Tool -OutDir=.\Win32_DLL_Release -SOURCE="$(InputPath)" -PostBuild_Desc=[Run Test] -PostBuild_Cmds=set path=$(outdir);..\..\..\zlib\projects\visualc6\Win32_DLL_Release; $(outdir)\pngtest.exe ..\..\pngtest.png -# End Special Build Tool - -!ELSEIF "$(CFG)" == "pngtest - Win32 DLL Debug" - -# PROP BASE Use_MFC 0 -# PROP BASE Use_Debug_Libraries 1 -# PROP BASE Output_Dir "pngtest___Win32_DLL_Debug" -# PROP BASE Intermediate_Dir "pngtest___Win32_DLL_Debug" -# PROP BASE Target_Dir "" -# PROP Use_MFC 0 -# PROP Use_Debug_Libraries 1 -# PROP Output_Dir "Win32_DLL_Debug" -# PROP Intermediate_Dir "Win32_DLL_Debug" -# PROP Ignore_Export_Lib 0 -# PROP Target_Dir "" -# ADD BASE CPP /nologo /W3 /Gm /ZI /Od /D "WIN32" /D "_DEBUG" /FD /GZ /c -# SUBTRACT BASE CPP /YX -# ADD CPP /nologo /MDd /W3 /Gm /ZI /Od /I "..\..\..\zlib" /D "WIN32" /D "_DEBUG" /D "PNG_DLL" /D "PNG_NO_STDIO" /FD /GZ /c -# SUBTRACT CPP /YX -# ADD BASE RSC /l 0x409 /d "_DEBUG" -# ADD RSC /l 0x409 /d "_DEBUG" -BSC32=bscmake.exe -# ADD BASE BSC32 /nologo -# ADD BSC32 /nologo -LINK32=link.exe -# ADD BASE LINK32 /nologo /subsystem:console /debug /machine:I386 /pdbtype:sept -# ADD LINK32 Win32_DLL_Debug\libpng14d.lib ..\..\..\zlib\projects\visualc6\Win32_DLL_Debug\zlib1d.lib /nologo /subsystem:console /debug /machine:I386 /pdbtype:sept -# Begin Special Build Tool -OutDir=.\Win32_DLL_Debug -SOURCE="$(InputPath)" -PostBuild_Desc=[Run Test] -PostBuild_Cmds=set path=$(outdir);..\..\..\zlib\projects\visualc6\Win32_DLL_Debug; $(outdir)\pngtest.exe ..\..\pngtest.png -# End Special Build Tool - -!ELSEIF "$(CFG)" == "pngtest - Win32 LIB Release" - -# PROP BASE Use_MFC 0 -# PROP BASE Use_Debug_Libraries 0 -# PROP BASE Output_Dir "pngtest___Win32_LIB_Release" -# PROP BASE Intermediate_Dir "pngtest___Win32_LIB_Release" -# PROP BASE Target_Dir "" -# PROP Use_MFC 0 -# PROP Use_Debug_Libraries 0 -# PROP Output_Dir "Win32_LIB_Release" -# PROP Intermediate_Dir "Win32_LIB_Release" -# PROP Ignore_Export_Lib 0 -# PROP Target_Dir "" -# ADD BASE CPP /nologo /W3 /O2 /D "WIN32" /D "NDEBUG" /FD /c -# SUBTRACT BASE CPP /YX -# ADD CPP /nologo /MD /W3 /O2 /I "..\..\..\zlib" /D "WIN32" /D "NDEBUG" /FD /c -# SUBTRACT CPP /YX -# ADD BASE RSC /l 0x409 /d "NDEBUG" -# ADD RSC /l 0x409 /d "NDEBUG" -BSC32=bscmake.exe -# ADD BASE BSC32 /nologo -# ADD BSC32 /nologo -LINK32=link.exe -# ADD BASE LINK32 /nologo /subsystem:console /machine:I386 -# ADD LINK32 Win32_LIB_Release\libpng.lib ..\..\..\zlib\projects\visualc6\Win32_LIB_Release\zlib.lib /nologo /subsystem:console /machine:I386 -# Begin Special Build Tool -OutDir=.\Win32_LIB_Release -SOURCE="$(InputPath)" -PostBuild_Desc=[Run Test] -PostBuild_Cmds=$(outdir)\pngtest.exe ..\..\pngtest.png -# End Special Build Tool - -!ELSEIF "$(CFG)" == "pngtest - Win32 LIB Debug" - -# PROP BASE Use_MFC 0 -# PROP BASE Use_Debug_Libraries 1 -# PROP BASE Output_Dir "pngtest___Win32_LIB_Debug" -# PROP BASE Intermediate_Dir "pngtest___Win32_LIB_Debug" -# PROP BASE Target_Dir "" -# PROP Use_MFC 0 -# PROP Use_Debug_Libraries 1 -# PROP Output_Dir "Win32_LIB_Debug" -# PROP Intermediate_Dir "Win32_LIB_Debug" -# PROP Ignore_Export_Lib 0 -# PROP Target_Dir "" -# ADD BASE CPP /nologo /W3 /Gm /ZI /Od /D "WIN32" /D "_DEBUG" /FD /GZ /c -# SUBTRACT BASE CPP /YX -# ADD CPP /nologo /MDd /W3 /Gm /ZI /Od /I "..\..\..\zlib" /D "WIN32" /D "_DEBUG" /FD /GZ /c -# SUBTRACT CPP /YX -# ADD BASE RSC /l 0x409 /d "_DEBUG" -# ADD RSC /l 0x409 /d "_DEBUG" -BSC32=bscmake.exe -# ADD BASE BSC32 /nologo -# ADD BSC32 /nologo -LINK32=link.exe -# ADD BASE LINK32 /nologo /subsystem:console /debug /machine:I386 /pdbtype:sept -# ADD LINK32 Win32_LIB_Debug\libpngd.lib ..\..\..\zlib\projects\visualc6\Win32_LIB_Debug\zlibd.lib /nologo /subsystem:console /debug /machine:I386 /pdbtype:sept -# Begin Special Build Tool -OutDir=.\Win32_LIB_Debug -SOURCE="$(InputPath)" -PostBuild_Desc=[Run Test] -PostBuild_Cmds=$(outdir)\pngtest.exe ..\..\pngtest.png -# End Special Build Tool - -!ENDIF - -# Begin Target - -# Name "pngtest - Win32 DLL Release" -# Name "pngtest - Win32 DLL Debug" -# Name "pngtest - Win32 LIB Release" -# Name "pngtest - Win32 LIB Debug" -# Begin Group "Source Files" - -# PROP Default_Filter "cpp;c;cxx;rc;def;r;odl;idl;hpj;bat" -# Begin Source File - -SOURCE=..\..\pngtest.c -# End Source File -# End Group -# End Target -# End Project diff --git a/projects/vstudio/readme.txt b/projects/vstudio/readme.txt index 1d8b99e0e..abbbafa35 100644 --- a/projects/vstudio/readme.txt +++ b/projects/vstudio/readme.txt @@ -1,7 +1,7 @@ VisualStudio instructions -libpng version 1.5.10beta01 - February 19, 2012 +libpng version 1.5.10beta01 - February 21, 2012 Copyright (c) 1998-2010 Glenn Randers-Pehrson diff --git a/projects/vstudio/zlib.props b/projects/vstudio/zlib.props index 8e02f8dc9..0456bda0f 100644 --- a/projects/vstudio/zlib.props +++ b/projects/vstudio/zlib.props @@ -2,7 +2,7 @@