Imported from libpng-0.98.tarv0.98

26 files changed, 687 insertions, 240 deletions

diff --git a/CHANGES b/CHANGES
index c067808be..94eb8dd7c 100644
--- a/CHANGES
+++ b/CHANGES
@@ -170,20 +170,33 @@ version 0.96 [May, 1997]
 version 0.97 [January, 1998]
    removed PNG_USE_OWN_CRC capability
    relocated png_set_crc_action from pngrutil.c to pngrtran.c
-   fixed typecasts of "new_key", etc.
-   added RFC 1152 date support
+   fixed typecasts of "new_key", etc. (Andreas Dilger)
+   added RFC 1152 [sic] date support
    fixed bug in gamma handling of 4-bit grayscale
-   added more typecasts. 65536L becomes (png_uint_32)65536L, etc.
+   added 2-bit grayscale gamma handling (Glenn R-P)
+   added more typecasts. 65536L becomes (png_uint_32)65536L, etc. (Glenn R-P)
    minor corrections in libpng.txt
-   added simple sRGB support
-   make it simpler to do conditional compiling: PNG_READ_NOT_FULLY_SUPPORTED
-   fixed memory leak in pngwrite.c (free info_ptr->text)
+   added simple sRGB support (Glenn R-P)
+   easier conditional compiling, e.g. define PNG_READ/WRITE_NOT_FULLY_SUPPORTED;
+      all configurable options can be selected from command-line instead
+      of having to edit pngconf.h (Glenn R-P)
+   fixed memory leak in pngwrite.c (free info_ptr->text) (Glenn R-P)
    added more conditions for png_do_background, to avoid changing
       black pixels to background when a background is supplied and
       no pixels are transparent
    repaired PNG_NO_STDIO behaviour
-   tested NODIV support and made it default behaviour
-   added "-m" option to pngtest
-   [anything else?  2-bit grayscale gamma bug?]
+   tested NODIV support and made it default behaviour (Greg Roelofs)
+   added "-m" option and PNGTEST_DEBUG_MEMORY to pngtest (John Bowler)
    regularized version numbering scheme and bumped shared-library major
-      version number to 2 to avoid potential problems with libpng 0.89 apps
+      version number to 2 to avoid problems with libpng 0.89 apps (Greg Roelofs)
+version 0.98 [January, 1998]
+   cleaned up some typos in libpng.txt and in code documentation
+   fixed memory leaks in pCAL chunk processing (Glenn R-P and John Bowler)
+   cosmetic change "display_gamma" to "screen_gamma" in pngrtran.c
+   changed recommendation about file_gamma for PC images to .51 from .45,
+      in example.c and libpng.txt, added comments to distinguish between
+      screen_gamma, viewing_gamma, and display_gamma.
+   changed all references to RFC1152 to read RFC1123 and changed the
+      PNG_TIME_RFC1152_SUPPORTED macro to PNG_TIME_RFC1123_SUPPORTED
+   added png_invert_alpha capability (Glenn R-P -- suggestion by Jon Vincent)
+   changed srgb_intent from png_byte to int to avoid compiler bugs
diff --git a/README b/README
index 5fe912040..949e4ebb6 100644
--- a/README
+++ b/README
@@ -1,4 +1,4 @@
-[NOTE:  this is still beta version 0.97c; the text below has already
+[NOTE:  this is still beta version 0.97d; the text below has already
  been updated in anticipation of the imminent 1.0 release.]
 
 
@@ -6,7 +6,7 @@ README for libpng 1.0
 
 This is the first official release of libpng.  Don't let the fact that
 it's the first release fool you.  The libpng library has been in
-extensive use and testing for about two years.  However, it's
+extensive use and testing for about two and a half years.  However, it's
 finally gotten to the stage where there haven't been significant
 changes to the API in some time, and people have a bad feeling about
 libraries with versions < 1.0.
@@ -77,7 +77,7 @@ If not, it should be at ftp.uu.net in /graphics/png
 Eventually, it will be at ftp.uu.net in /pub/archiving/zip/zlib
 
 You may also want a copy of the PNG specification.  It is available
-as an Internet Draft, and RFC, and a W3C Recommendation.  Failing
+as an RFC and a W3C Recommendation.  Failing
 these resources you can try ftp.uu.net in the /graphics/png directory.
 
 This code is currently being archived at ftp.uu.net in the
@@ -97,19 +97,19 @@ Finally, if you get any warning messages when compiling libpng
 fix.  Please mention "libpng" somewhere in the subject line.  Thanks.
 
 This release was created and will be supported by myself (of course
-based in a large way on Guy's earlier work), and the PNG group.
+based in a large way on Guy's and Andreas' earlier work), and the PNG group.
 
 adilger@enel.ucalgary.ca
 png-implement@dworkin.wustl.edu
 
-You can reach Guy, the original libpng author, at (internet preferred):
-
-internet: schalnat@group42.com
-CompuServe: 75501,1625
+You can't reach Guy, the original libpng author, at the addresses
+given in previous versions of this document.  He will read mail
+addressed to the png-implement list, however.
 
 Please do not send general questions about PNG.  Send them to
-the address in the specification.  At the same time, please do
-not send libpng questions to that address, send them to me.  I'll
+the address in the specification (png-group@w3.org).  At the same
+time, please do not send libpng questions to that address, send them to me
+or to png-implement@dworkin.wustl.edu.  I'll
 get them in the end anyway.  If you have a question about something
 in the PNG specification that is related to using libpng, send it
 to me.  Send me any questions that start with "I was using libpng,
@@ -132,18 +132,20 @@ Files in this distribution:
       descrip.mms   =>  VMS project file
       example.c     =>  Example code for using libpng functions
       libpng.txt    =>  Description of libpng and its functions
-      makefile      =>  Default Unixish makefile
       makefile.aco  =>  ACORN makefile
       makefile.ama  =>  Amiga makefile
       makefile.atr  =>  Atari makefile
       makefile.bor  =>  Borland makefile
+      makefile.dec  =>  DEC makefile
       makefile.dj2  =>  DJGPP 2 makefile
       makefile.elf  =>  Unix ELF makefile
       makefile.knr  =>  Makefile which calls ansi2knr to convert files
       makefile.mip  =>  MIPS makefile
       makefile.msc  =>  Microsoft C makefile
+      makefile.sgi  =>  Silicon Graphics Irix makefile
       makefile.std  =>  Standard Unix makefile
-      makefile.tc   =>  Turbo C makefile
+      makefile.sun  =>  SUN makefile
+      makefile.tc3  =>  Turbo C 3.0 makefile
       makevms.com   =>  VMS make program
       png.c         =>  Basic interface functions common to library
       png.h         =>  Library function and interface declarations
@@ -166,13 +168,15 @@ Files in this distribution:
 
 Good luck, and happy coding.
 
+-Glenn Randers-Pehrson
+ Internet: randeg@alumni.rpi.edu
+ Web: http://www.rpi.edu/~randeg/index.html
+
 -Andreas Eric Dilger
  Internet: adilger@enel.ucalgary.ca
  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
 
 -Guy Eric Schalnat
- Group 42, Inc.
- Internet: schalnat@group42.com
- CompuServe: 75501,1625
+ (formerly of Group 42, Inc)
  Web: http://www.group42.com/
 
diff --git a/TODO b/TODO
index e8c95ea62..8df30ccb2 100644
--- a/TODO
+++ b/TODO
@@ -5,7 +5,7 @@ improved dithering
 multi-lingual error and warning message support
 sPLT chunk handling
 cHRM transformation
-complete sRGB transformation (presently it simply uses gamma=0.5)
+complete sRGB transformation (presently it simply uses gamma=0.51)
 man pages for function calls
 high-level API for reading images
 final bug fixes
diff --git a/example.c b/example.c
index 90cbb8adb..6bd338285 100644
--- a/example.c
+++ b/example.c
@@ -190,19 +190,22 @@ void read_png(FILE *fp, unsigned int sig_read)  /* file is already open */
                          PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
 
    /* Some suggestions as to how to get a screen gamma value */
+
+   /* Note that screen gamma is (display_gamma/viewing_gamma)
    if (/* We have a user-defined screen gamma value */)
    {
       screen_gamma = user-defined screen_gamma;
    }
    /* This is one way that applications share the same screen gamma value */
-   else if ((gamma_str = getenv("DISPLAY_GAMMA")) != NULL)
+   else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL)
    {
       screen_gamma = atof(gamma_str);
    }
    /* If we don't have another value */
    else
    {
-      screen_gamma = 2.2;  /* A good guess for PC monitors */
+      screen_gamma = 2.2;  /* A good guess for a PC monitors in a brightly
+                              lit room */
       screen_gamma = 1.7 or 1.0;  /* A good guess for Mac systems */
    }
 
@@ -211,13 +214,16 @@ void read_png(FILE *fp, unsigned int sig_read)  /* file is already open */
     * by the user at run time by the user.  It is strongly suggested that
     * your application support gamma correction.
     */
-   if (png_get_sRGB(png_ptr, info_ptr, &srgb_intent)
-      png_set_sRGB(png_ptr, srgb_intent, 0);
+
+   int intent;
+
+   if (png_get_sRGB(png_ptr, info_ptr, &intent)
+      png_set_sRGB(png_ptr, intent, 0);
    else 
       if (png_get_gAMA(png_ptr, info_ptr, &image_gamma)
          png_set_gamma(png_ptr, screen_gamma, image_gamma);
       else
-         png_set_gamma(png_ptr, screen_gamma, 0.45);
+         png_set_gamma(png_ptr, screen_gamma, 0.51);
 
    /* Dither RGB files down to 8 bit palette or reduce palettes
     * to the number of colors available on your screen.
diff --git a/libpng.txt b/libpng.txt
index 76c2d6fb4..1fe172ec7 100644
--- a/libpng.txt
+++ b/libpng.txt
@@ -1,10 +1,13 @@
 libpng.txt - a description on how to use and modify libpng
 
-   libpng version 1.00 version 0.97
+   libpng version 0.98
+   Updated and distributed by Glenn Randers-Pehrson <randeg@alumni.rpi.edu>
+   Copyright (c) 1998, Glenn Randers-Pehrson
+   January 16, 1998
 
       based on:
 
-   libpng version 1.00 version 0.96
+   libpng 1.0 beta 6  version 0.96
    Updated and distributed by Andreas Dilger <adilger@enel.ucalgary.ca>,
    Copyright (c) 1996, 1997 Andreas Dilger
    May 28, 1997
@@ -29,7 +32,7 @@ it is heavily commented and should include everything most people
 will need.
 
 Libpng was written as a companion to the PNG specification, as a way
-to reduce the amount of time and effort it takes to support the PNG
+of reducing the amount of time and effort it takes to support the PNG
 file format in application programs.  The PNG specification is available
 as RFC 2083 <ftp://ftp.uu.net/graphics/png/documents/> and as a
 W3C Recommendation <http://www.w3.org/pub/WWW/TR/REC.png.html>. Some
@@ -49,12 +52,14 @@ 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 it's users.
+majority of the needs of its users.
 
 Libpng uses zlib for its compression and decompression of PNG files.
 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
@@ -69,13 +74,15 @@ 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.
+variable passed to every libpng function call.  It is not actually
+used in many of the functions; do not be alarmed about compiler
+warnings that say something to the effect that "png_ptr is not used."
 
 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 were delevoped.  The fields
+a set of interface functions for png_info 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.
 
@@ -193,6 +200,19 @@ libpng know that there are some bytes missing from the start of the file.
 
     png_set_sig_bytes(png_ptr, number);
 
+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);
+
+This has to appear here rather than later with the other transformations
+because the tRNS chunk data must be modified in the case of paletted images.
+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 be changed.
+
 You are now ready to read all the file information up to the actual
 image data.  You do this with a call to png_read_info().
 
@@ -252,6 +272,12 @@ into the info_ptr is returned for any complex types.
     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_sBIT(png_ptr, info_ptr, &sig_bit);
     sig_bit        - the number of significant bits for (PNG_INFO_sBIT)
                      the gray, red, green, and blue channels, whichever
@@ -301,9 +327,9 @@ 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 or non-printing
-symbols.  See the PNG specification for more details.  There is also
-no requirement to have text after the keyword.
+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
@@ -381,7 +407,7 @@ values of the pixels:
         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 whave been "scaled" or "shifted" up to the next
+stored in a PNG image have been "scaled" or "shifted" up to the next
 higher possible bit depth (eg 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.
@@ -429,7 +455,7 @@ 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
-dispay (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file
+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).
@@ -457,28 +483,39 @@ 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 the
-DISPLAY_GAMMA environment variable, which will hopefully be correctly set.
+DISPLAY_GAMMA and VIEWING_GAMMA environment variables or for a SCREEN_GAMMA
+environment variable, which will hopefully be correctly set.
+
+Note that display_gamma is the gamma of your display, while screen_gamma is
+the overall gamma correction required to produce pleasing results,
+which depends on the lighting conditions in the surrounding environment.
+Screen_gamma is display_gamma/viewing_gamma, where viewing_gamma is
+the amount of additional gamma correction needed to compensate for
+a dim (viewing_gamma=1.125) or dark (viewing_gamma=1.25) environment.
+In a brightly lit room, no compensation other than the display_gamma
+is needed (viewing_gamma=1.0).
 
    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("DISPLAY_GAMMA")) != NULL)
+   else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL)
    {
       screen_gamma = atof(gamma_str);
    }
    /* If we don't have another value */
    else
    {
-      screen_gamma = 2.2;  /* A good guess for PC monitors */
+      screen_gamma = 2.2; /* A good guess for a PC monitor in a bright office */
+      screen_gamma = 1.956; /* A good guess for a PC monitor in a dim 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 0.45 is a good guess for GIF images on PCs).  Note
+it is (usually 0.51 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
@@ -487,7 +524,7 @@ 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, 0.45);
+      png_set_gamma(png_ptr, screen_gamma, 0.51);
 
 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_dither()
@@ -544,7 +581,7 @@ need to change the order the pixels are packed into bytes, you can use:
 The last thing to handle is interlacing; this is covered in detail below,
 but you must call the function here.
 
-    number_passes = png_set_interlace_handling(png_ptr);
+    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
@@ -582,7 +619,7 @@ where row_pointers is:
 
 You can point to void or char or whatever you use for pixels.
 
-If you don't want to read int the whole image at once, you can
+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_TYPE_NONE), this is simple:
 
@@ -599,24 +636,24 @@ row_pointers:
 If the file is interlaced (info_ptr->interlace_type != 0), things get
 somewhat harder.  The only current (PNG Specification version 1.0)
 interlacing type for PNG is (interlace_type == PNG_INTERLACE_TYPE_ADAM7)
-is a someewhat complicated 2D interlace scheme, known as Adam7, that
+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.  This results in a blocky
-image for the first pass, which gradually smoothes out as more pixels
-are read.  The other method is the "sparkle" method, where pixels are
-draw 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.
+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 are valid images by themselves, or they can be combined on an
+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).
 
@@ -638,7 +675,7 @@ 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_TYPE_ADAM7)
-        number_passes = png_set_interlace_handling(png_ptr);
+        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.
@@ -649,12 +686,12 @@ 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
+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_passes times, and you don't change the data in the
+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.
@@ -963,6 +1000,19 @@ Some of the more important parts of the png_info are:
     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.
+
+    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 chunk also
+                     causes gAMA and cHRM chunks with the specific values
+                     that are consistent with sRGB to be written.
+
     png_set_sBIT(png_ptr, info_ptr, sig_bit);
     sig_bit        - the number of significant bits for (PNG_INFO_sBIT)
                      the gray, red, green, and blue channels, whichever
@@ -996,11 +1046,25 @@ Some of the more important parts of the png_info are:
     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);
+    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 x direction
     unit_type      - PNG_RESOLUTION_UNKOWN, PNG_RESOLUTION_METER
 
+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 here 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 be changed.
+
 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.
 If you want, you can use max_text to hold the size of the array, but
@@ -1072,8 +1136,8 @@ tEXt chunk use RFC 1123 format dates (eg 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_rfc1152(png_timep) is provided to convert from PNG
-time to an RFC 1152 format string.
+png_convert_to_rfc1123(png_timep) is provided to convert from PNG
+time to an RFC 1123 format string.
 
 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().
@@ -1229,12 +1293,12 @@ 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_passes = png_set_interlace_handling(png_ptr);
+    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_passes times.
+Then write the complete image number_of_passes times.
 
     png_write_rows(png_ptr, row_pointers, number_of_rows);
 
@@ -1280,7 +1344,7 @@ 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.
 
-Input/Output in libpng is done throught png_read() and png_write(),
+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
@@ -1378,7 +1442,7 @@ 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
-complers.  Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
+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
@@ -1410,8 +1474,8 @@ 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 as well as higher levels, and do so much faster.
-For online applications it may be desirable to have maximum speed
+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
@@ -1495,8 +1559,13 @@ 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 an ability, you can change the #define to #undef
-before recompiling libpng and save yourself code and data space.  All
-the reading and writing specific code are in seperate files, so the
+before recompiling libpng and save yourself code and data space.
+You can also turn them off en masse with a compiler directive to
+define PNG_READ_NOT_FULLY_SUPPORTED or PNG_WRITE_NOT_FULLY_SUPPORTED,
+along with directives to turn on any of the capabilities that you do
+want.
+
+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
@@ -1514,10 +1583,12 @@ those sections which are actually used will be loaded into memory.
 
 Changes to Libpng from version 0.88
 
-It should be noted that versions of libpng later than 0.88 are not
-distributed by the original libpng author, Guy Schalnat, but rather
-another member of the original PNG Group, Andreas Dilger.  Guy is still
-alive and well, but he has moved on to other things.
+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_destory() have been
diff --git a/makefile.elf b/makefile.elf
index 1a8737883..2040b2c08 100644
--- a/makefile.elf
+++ b/makefile.elf
@@ -1,6 +1,6 @@
 # makefile for libpng on Linux ELF with gcc
 # Copyright (C) 1996, 1997 Andreas Dilger
-# Copyright (C) 1998 Glenn Randers-Pehrson
+# Copyright (C) 1998 Greg Roelofs
 # For conditions of distribution and use, see copyright notice in png.h
 
 CC=gcc
@@ -22,7 +22,7 @@ RANLIB=ranlib
 #RANLIB=echo
 
 PNGMAJ = 2
-PNGMIN = 0.97
+PNGMIN = 0.98
 PNGVER = $(PNGMAJ).$(PNGMIN)
 
 # where make install puts libpng.a, libpng.so*, and png.h
diff --git a/makefile.sgi b/makefile.sgi
new file mode 100644
index 000000000..cd980cdbb
--- /dev/null
+++ b/makefile.sgi
@@ -0,0 +1,69 @@
+# makefile for libpng
+# Copyright (C) 1995 Guy Eric Schalnat, Group 42, Inc.
+# For conditions of distribution and use, see copyright notice in png.h
+
+# Where the zlib library and include files are located
+#ZLIBLIB=/usr/local/lib
+#ZLIBINC=/usr/local/include
+ZLIBLIB=../zlib
+ZLIBINC=../zlib
+
+CC=cc
+
+CFLAGS=-I$(ZLIBINC) -O -fullwarn # -g -DPNG_DEBUG=1
+LDFLAGS=-L. -L$(ZLIBLIB) -lpng -lz -lm
+
+RANLIB=echo
+#RANLIB=ranlib
+
+# where make install puts libpng.a and png.h
+prefix=/usr/local
+
+OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
+	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
+	pngwtran.o pngmem.o pngerror.o pngpread.o
+
+all: libpng.a pngtest
+
+libpng.a: $(OBJS)
+	ar rc $@  $(OBJS)
+	$(RANLIB) $@
+
+pngtest: pngtest.o libpng.a
+	$(CC) -o pngtest $(CCFLAGS) pngtest.o $(LDFLAGS)
+
+test: pngtest
+	./pngtest
+
+install: libpng.a
+	-@mkdir $(prefix)/include
+	-@mkdir $(prefix)/lib
+	cp png.h $(prefix)/include
+	cp pngconf.h $(prefix)/include
+	chmod 644 $(prefix)/include/png.h
+	chmod 644 $(prefix)/include/pngconf.h
+	cp libpng.a $(prefix)/lib
+	chmod 644 $(prefix)/lib/libpng.a
+
+clean:
+	rm -f *.o libpng.a pngtest pngout.png
+
+# DO NOT DELETE THIS LINE -- make depend depends on it.
+
+png.o: png.h pngconf.h
+pngerror.o: png.h pngconf.h
+pngrio.o: png.h pngconf.h
+pngwio.o: png.h pngconf.h
+pngmem.o: png.h pngconf.h
+pngset.o: png.h pngconf.h
+pngget.o: png.h pngconf.h
+pngread.o: png.h pngconf.h
+pngrtran.o: png.h pngconf.h
+pngrutil.o: png.h pngconf.h
+pngtest.o: png.h pngconf.h
+pngtrans.o: png.h pngconf.h
+pngwrite.o: png.h pngconf.h
+pngwtran.o: png.h pngconf.h
+pngwutil.o: png.h pngconf.h
+pngpread.o: png.h pngconf.h
+
diff --git a/makefile.tc b/makefile.tc3
index 7e1fc91ea..050c822ec 100644
--- a/makefile.tc
+++ b/makefile.tc3
@@ -1,7 +1,7 @@
 # Makefile for libpng
 # TurboC++ 3.0 (Note: All modules are compiled in C mode)
 
-# To use, do "make -fmakefile.tc"
+# To use, do "make -fmakefile.tc3"
 
 # ------------- Turbo C++ 3.0 -------------
 MODEL=-ml
diff --git a/png.c b/png.c
index 1fd3713a3..d9abb2ffd 100644
--- a/png.c
+++ b/png.c
@@ -1,12 +1,12 @@
 
 /* png.c - location for general purpose libpng functions
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  */
 
 #define PNG_INTERNAL
@@ -16,7 +16,7 @@
 /* Version information for C files.  This had better match the version
  * string defined in png.h.
  */
-char png_libpng_ver[] = "0.97";
+char png_libpng_ver[] = "0.98";
 
 /* Place to hold the signiture string for a PNG file. */
 png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
diff --git a/png.h b/png.h
index e3eaeba4d..bc09c7ebf 100644
--- a/png.h
+++ b/png.h
@@ -1,12 +1,37 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng 0.97 beta
+ * libpng 0.98 beta
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998 Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
+ *
+ * Note about libpng version numbers:
+ *
+ *    Due to various miscommunications, unforeseen code incompatibilities
+ *    and occasional factors outside the authors' control, version numbering
+ *    on the library has not always been consistent and straightforward.
+ *    The following table summarizes matters since version 0.89c, which was
+ *    the first widely used release:
+ *
+ *      source                    png.h     shared-lib
+ *      version                   string    version
+ *      -------                   ------    ----------
+ *      0.89c ("1.0 beta 3")      0.89      1.0.89
+ *      0.90  ("1.0 beta 4")      0.90      0.90  [should have been 2.0.90]
+ *      0.95  ("1.0 beta 5")      0.95      0.95  [should have been 2.0.95]
+ *      0.96  ("1.0 beta 6")      0.96      0.96  [should have been 2.0.96]
+ *      0.97b ("1.00.97 beta 7")  1.00.97   1.0.0 [should have been 2.0.97]
+ *      0.97c                     0.97      2.0.97
+ *      0.98                      0.98      2.0.98
+ *      0.99                      0.99      2.0.99
+ *      1.0                       1.00      2.1.0
+ *
+ *    Henceforth the source version will match the shared-library minor
+ *    and patch numbers; the shared-library major version number will be
+ *    used for changes in backward compatibility, as it is intended.
  *
  * BETA NOTICE:
  *    This is a beta version.  It reads and writes valid files on the
@@ -94,12 +119,12 @@ extern "C" {
  */
 
 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "0.97"
+#define PNG_LIBPNG_VER_STRING "0.98"
 
 /* careful here.  At one time, I wanted to use 082, but that would be octal.
  * Version 1.0 will be 100 here, etc.
  */
-#define PNG_LIBPNG_VER  97
+#define PNG_LIBPNG_VER  98
 
 /* variables declared in png.c - only it needs to define PNG_NO_EXTERN */
 #ifndef PNG_NO_EXTERN
@@ -108,33 +133,6 @@ extern "C" {
  */
 extern char png_libpng_ver[];
 
-/*
- * Note about libpng version numbers:
- *
- *    Due to various miscommunications, unforeseen code incompatibilities
- *    and occasional factors outside the authors' control, version numbering
- *    on the library has not always been consistent and straightforward.
- *    The following table summarizes matters since version 0.89c, which was
- *    the first widely used release:
- *
- *      source                    png.h     shared-lib
- *      version                   string    version
- *      -------                   ------    ----------
- *      0.89c ("1.0 beta 3")      0.89      1.0.89
- *      0.90  ("1.0 beta 4")      0.90      0.90  [should have been 2.0.90]
- *      0.95  ("1.0 beta 5")      0.95      0.95  [should have been 2.0.95]
- *      0.96  ("1.0 beta 6")      0.96      0.96  [should have been 2.0.96]
- *      0.97b ("1.00.97 beta 7")  1.00.97   1.0.0 [should have been 2.0.97]
- *      0.97c                     0.97      2.0.97
- *      0.98                      0.98      2.0.98
- *      0.99                      0.99      2.0.99
- *      1.0                       1.00      2.1.0
- *
- *    Henceforth the source version will match the shared-library minor
- *    and patch numbers; the shared-library major version number will be
- *    used for changes in backward compatibility, as it is intended.
- */
- 
 /* Structures to facilitate easy interlacing.  See png.c for more details */
 extern int FARDATA png_pass_start[];
 extern int FARDATA png_pass_inc[];
@@ -582,9 +580,9 @@ struct png_struct_def
    png_uint_32 flush_rows;    /* number of rows written since last flush */
 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
 #if defined(PNG_READ_GAMMA_SUPPORTED)
-   int gamma_shift;           /* number of "insignificant" bits 16-bit gamma */
-   float gamma;               /* file gamma value */
-   float display_gamma;       /* display gamma value */
+   int gamma_shift;      /* number of "insignificant" bits 16-bit gamma */
+   float gamma;          /* file gamma value */
+   float screen_gamma;   /* screen gamma value (display_gamma/viewing_gamma */
 #endif /* PNG_READ_GAMMA_SUPPORTED */
 #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
    png_bytep gamma_table;     /* gamma table for 8 bit depth files */
@@ -626,6 +624,7 @@ struct png_struct_def
    png_charp current_text;           /* current text chunk buffer */
    png_charp current_text_ptr;       /* current location in current_text */
 #endif /* PNG_PROGRESSIVE_READ_SUPPORTED && PNG_READ_tEXt/zTXt_SUPPORTED */
+#endif /* PNG_PROGRESSIVE_READ_SUPPORTED */
 #if defined(__TURBOC__) && !defined(_Windows) && !defined(__FLAT__)
 /* for the Borland special 64K segment handler */
    png_bytepp offset_table_ptr;
@@ -633,8 +632,7 @@ struct png_struct_def
    png_uint_16 offset_table_number;
    png_uint_16 offset_table_count;
    png_uint_16 offset_table_count_free;
-#endif /* PNG_PROGRESSIVE_READ_SUPPORTED&&__TURBOC__&&!_Windows&&!__FLAT__ */
-#endif /* PNG_PROGRESSIVE_READ_SUPPORTED */
+#endif /* __TURBOC__&&!_Windows&&!__FLAT__ */
 #if defined(PNG_READ_DITHER_SUPPORTED)
    png_bytep palette_lookup;         /* lookup table for dithering */
    png_bytep dither_index;           /* index translation for palette files */
@@ -649,9 +647,9 @@ struct png_struct_def
    png_uint_16p filter_costs;        /* relative filter calculation cost */
    png_uint_16p inv_filter_costs;    /* 1/relative filter calculation cost */
 #endif /* PNG_WRITE_WEIGHTED_FILTER_SUPPORTED */
-#if defined(PNG_TIME_RFC1152_SUPPORTED)
-   png_charp time_buffer;            /* String to hold RFC 1152 time text */
-#endif /* PNG_TIME_RFC1152_SUPPORTED */
+#if defined(PNG_TIME_RFC1123_SUPPORTED)
+   png_charp time_buffer;            /* String to hold RFC 1123 time text */
+#endif /* PNG_TIME_RFC1123_SUPPORTED */
 };
 
 typedef png_struct FAR * FAR * png_structpp;
@@ -706,10 +704,10 @@ extern PNG_EXPORT(void,png_write_info) PNGARG((png_structp png_ptr,
 extern PNG_EXPORT(void,png_read_info) PNGARG((png_structp png_ptr,
    png_infop info_ptr));
 
-#if defined(PNG_TIME_RFC1152_SUPPORTED)
-extern PNG_EXPORT(png_charp,png_convert_to_rfc1152)
+#if defined(PNG_TIME_RFC1123_SUPPORTED)
+extern PNG_EXPORT(png_charp,png_convert_to_rfc1123)
    PNGARG((png_structp png_ptr, png_timep ptime));
-#endif /* PNG_TIME_RFC1152_SUPPORTED */
+#endif /* PNG_TIME_RFC1123_SUPPORTED */
 
 #if defined(PNG_WRITE_tIME_SUPPORTED)
 /* convert from a struct tm to png_time */
@@ -753,6 +751,11 @@ extern PNG_EXPORT(void,png_set_strip_alpha) PNGARG((png_structp png_ptr));
 extern PNG_EXPORT(void,png_set_swap_alpha) PNGARG((png_structp png_ptr));
 #endif /* PNG_READ_SWAP_ALPHA_SUPPORTED || PNG_WRITE_SWAP_ALPHA_SUPPORTED */
 
+#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
+    defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
+extern PNG_EXPORT(void,png_set_invert_alpha) PNGARG((png_structp png_ptr));
+#endif /* PNG_READ_INVERT_ALPHA_SUPPORTED || PNG_WRITE_INVERT_ALPHA_SUPPORTED */
+
 #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
 /* Add a filler byte to 24-bit RGB images. */
 extern PNG_EXPORT(void,png_set_filler) PNGARG((png_structp png_ptr,
@@ -819,7 +822,7 @@ extern PNG_EXPORT(void,png_set_dither) PNGARG((png_structp png_ptr,
 #endif /* PNG_READ_DITHER_SUPPORTED */
 
 #if defined(PNG_READ_GAMMA_SUPPORTED)
-/* Handle gamma correction. */
+/* Handle gamma correction. Screen_gamma=(display_gamma/viewing_gamma) */
 extern PNG_EXPORT(void,png_set_gamma) PNGARG((png_structp png_ptr,
    double screen_gamma, double default_file_gamma));
 #endif /* PNG_READ_GAMMA_SUPPORTED */
@@ -1240,14 +1243,14 @@ extern PNG_EXPORT(void,png_set_sBIT) PNGARG((png_structp png_ptr,
 
 #if defined(PNG_READ_sRGB_SUPPORTED)
 extern PNG_EXPORT(png_uint_32,png_get_sRGB) PNGARG((png_structp png_ptr,
-   png_infop info_ptr, png_bytep srgb_intent));
+   png_infop info_ptr, int *intent));
 #endif /* PNG_READ_sRGB_SUPPORTED */
 
 #if defined(PNG_READ_sRGB_SUPPORTED) || defined(PNG_WRITE_sRGB_SUPPORTED)
 extern PNG_EXPORT(void,png_set_sRGB) PNGARG((png_structp png_ptr,
-   png_infop info_ptr, png_byte srgb_intent));
+   png_infop info_ptr, int intent));
 extern PNG_EXPORT(void,png_set_sRGB_gAMA_and_cHRM) PNGARG((png_structp png_ptr,
-   png_infop info_ptr, png_byte srgb_intent));
+   png_infop info_ptr, int intent));
 #endif /* PNG_READ_sRGB_SUPPORTED || PNG_WRITE_sRGB_SUPPORTED */
 
 #if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_READ_zTXt_SUPPORTED)
@@ -1361,6 +1364,7 @@ extern PNG_EXPORT(void,png_set_tRNS) PNGARG((png_structp png_ptr,
 #define PNG_PACKSWAP          0x10000
 #define PNG_SWAP_ALPHA        0x20000
 #define PNG_STRIP_ALPHA       0x40000
+#define PNG_INVERT_ALPHA      0x80000
 
 /* flags for png_create_struct */
 #define PNG_STRUCT_PNG   0x0001
@@ -1585,7 +1589,7 @@ PNG_EXTERN void png_write_cHRM PNGARG((png_structp png_ptr,
 
 #if defined(PNG_WRITE_sRGB_SUPPORTED)
 PNG_EXTERN void png_write_sRGB PNGARG((png_structp png_ptr,
-   png_byte srgb_intent));
+   int intent));
 #endif
 
 #if defined(PNG_WRITE_tRNS_SUPPORTED)
@@ -1702,6 +1706,16 @@ PNG_EXTERN void png_do_write_swap_alpha PNGARG((png_row_infop row_info,
    png_bytep row));
 #endif
 
+#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
+PNG_EXTERN void png_do_read_invert_alpha PNGARG((png_row_infop row_info,
+   png_bytep row));
+#endif
+
+#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
+PNG_EXTERN void png_do_write_invert_alpha PNGARG((png_row_infop row_info,
+   png_bytep row));
+#endif
+
 #if defined(PNG_WRITE_FILLER_SUPPORTED) || \
     defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
 PNG_EXTERN void png_do_strip_filler PNGARG((png_row_infop row_info,
diff --git a/pngconf.h b/pngconf.h
index 56df55632..283c46250 100644
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,12 +1,12 @@
 
 /* pngconf.c - machine configurable file for libpng
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  */
 
 /* Any machine specific code is near the front of this file, so if you
@@ -191,24 +191,25 @@ __dont__ include it again
  * less then 8, and even that may not work (I haven't tested it).
  */
 
+#ifndef PNG_MAX_GAMMA_8
 #define PNG_MAX_GAMMA_8 11
+#endif
 
 /* This controls how much a difference in gamma we can tolerate before
  * we actually start doing gamma conversion.
  */
+#ifndef PNG_GAMMA_THRESHOLD
 #define PNG_GAMMA_THRESHOLD 0.05
+#endif
 
 #endif /* PNG_INTERNAL */
 
 /* The following uses const char * instead of char * for error
  * and warning message functions, so some compilers won't complain.
- * If you want to use const, define PNG_USE_CONST here.  It is not
- * normally defined to make configuration easier, as it is not a
- * critical part of the code.
+ * If you do not want to use const, define PNG_NO_CONST here.
  */
-#define PNG_USE_CONST
 
-#ifdef PNG_USE_CONST
+#ifndef PNG_NO_CONST
 #  define PNG_CONST const
 #else
 #  define PNG_CONST
@@ -259,6 +260,7 @@ __dont__ include it again
 #define PNG_READ_GAMMA_SUPPORTED
 #define PNG_READ_GRAY_TO_RGB_SUPPORTED
 #define PNG_READ_SWAP_ALPHA_SUPPORTED
+#define PNG_READ_INVERT_ALPHA_SUPPORTED
 #define PNG_READ_STRIP_ALPHA_SUPPORTED
 #define PNG_READ_COMPOSITE_NODIV_SUPPORTED        /* well tested on Intel */
 #endif /* PNG_READ_FULLY_SUPPORTED */
@@ -275,22 +277,32 @@ __dont__ include it again
 #define PNG_WRITE_FILLER_SUPPORTED  /* This is the same as WRITE_STRIP_ALPHA */
 #define PNG_WRITE_FLUSH_SUPPORTED
 #define PNG_WRITE_SWAP_ALPHA_SUPPORTED
+#define PNG_WRITE_INVERT_ALPHA_SUPPORTED
 #define PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
 #endif /* PNG_WRITE_FULLY_SUPPORTED */
 
 #if !defined(PNG_NO_STDIO)
-#define PNG_TIME_RFC1152_SUPPORTED
+#define PNG_TIME_RFC1123_SUPPORTED
 #endif
 
-/* These are currently experimental features */
-#undef PNG_READ_16_TO_8_ACCURATE_SHIFT_SUPPORTED /* very little testing */
+/* These are currently experimental features, define them if you want */
+
+/* very little testing */
+/*
+#define PNG_READ_16_TO_8_ACCURATE_SHIFT_SUPPORTED
+*/
 
 /* This is only for PowerPC big-endian and 680x0 systems */
-#undef PNG_READ_BIG_ENDIAN_SUPPORTED             /* some testing */
+/* some testing */
+/*
+#define PNG_READ_BIG_ENDIAN_SUPPORTED
+*/
 
 /* These functions are turned off by default, as they will be phased out. */
-#undef  PNG_USELESS_TESTS_SUPPORTED
-#undef  PNG_CORRECT_PALETTE_SUPPORTED
+/*
+#define  PNG_USELESS_TESTS_SUPPORTED
+#define  PNG_CORRECT_PALETTE_SUPPORTED
+*/
 
 /* Any chunks you are not interested in, you can undef here.  The
  * ones that allocate memory may be expecially important (hIST,
diff --git a/pngerror.c b/pngerror.c
index 305762832..61a91f0c5 100644
--- a/pngerror.c
+++ b/pngerror.c
@@ -1,12 +1,12 @@
 
 /* pngerror.c - stub functions for i/o and memory allocation
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  *
  * This file provides a location for all error handling.  Users which
  * need special error handling are expected to write replacement functions
diff --git a/pngget.c b/pngget.c
index 5ff2be647..618161609 100644
--- a/pngget.c
+++ b/pngget.c
@@ -1,12 +1,12 @@
 
 /* pngget.c - retrieval of values from info struct
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  */
 
 #define PNG_INTERNAL
@@ -112,14 +112,13 @@ png_get_gAMA(png_structp png_ptr, png_infop info_ptr, double *file_gamma)
 
 #if defined(PNG_READ_sRGB_SUPPORTED)
 png_uint_32
-png_get_sRGB(png_structp png_ptr, png_infop info_ptr, png_bytep
-    file_srgb_intent)
+png_get_sRGB(png_structp png_ptr, png_infop info_ptr, int *file_srgb_intent)
 {
    if (info_ptr != NULL && info_ptr->valid & PNG_INFO_sRGB &&
       file_srgb_intent != NULL)
    {
       png_debug1(1, "in %s retrieval function\n", "sRGB");
-      *file_srgb_intent = info_ptr->srgb_intent;
+      *file_srgb_intent = (int)info_ptr->srgb_intent;
       return (PNG_INFO_sRGB);
    }
    return (0);
@@ -272,7 +271,8 @@ png_get_text(png_structp png_ptr, png_infop info_ptr, png_textp *text_ptr,
    if ((info_ptr != NULL) || (info_ptr->num_text > 0))
    {
       png_debug1(1, "in %s retrieval function\n",
-         (png_ptr->chunk_name[0] == '\0' ? "text" : png_ptr->chunk_name));
+         (png_ptr->chunk_name[0] == '\0' ? "text"
+             : (png_const_charp)png_ptr->chunk_name));
       if (text_ptr != NULL)
          *text_ptr = info_ptr->text;
       if (num_text != NULL)
diff --git a/pngmem.c b/pngmem.c
index 88a6319c7..a79c78b10 100644
--- a/pngmem.c
+++ b/pngmem.c
@@ -1,12 +1,11 @@
-
 /* pngmem.c - stub functions for memory allocation
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  *
  * This file provides a location for all memory allocation.  Users which
  * need special memory handling are expected to modify the code in this file
@@ -16,6 +15,16 @@
 #define PNG_INTERNAL
 #include "png.h"
 
+/* The following "hides" PNG_MALLOC and PNG_FREE thus allowing the pngtest
+   application to put a wrapper on top of them. */
+#ifdef PNGTEST_MEMORY_DEBUG
+   #define PNG_MALLOC png_debug_malloc
+   #define PNG_FREE   png_debug_free
+#else
+   #define PNG_MALLOC png_malloc
+   #define PNG_FREE   png_free
+#endif
+
 /* Borland DOS special memory handler */
 #if defined(__TURBOC__) && !defined(_Windows) && !defined(__FLAT__)
 /* if you change this, be sure to change the one in png.h also */
@@ -72,7 +81,7 @@ png_destroy_struct(png_voidp struct_ptr)
  * (which should cause a fatal error) and introducing major problems.
  */
 png_voidp
-png_malloc(png_structp png_ptr, png_uint_32 size)
+PNG_MALLOC(png_structp png_ptr, png_uint_32 size)
 {
    png_voidp ret;
    if (png_ptr == NULL || size == 0)
@@ -166,11 +175,11 @@ png_malloc(png_structp png_ptr, png_uint_32 size)
    return ret;
 }
 
-/* free a pointer allocated by png_malloc().  In the default
+/* free a pointer allocated by PNG_MALLOC().  In the default
    configuration, png_ptr is not used, but is passed in case it
    is needed.  If ptr is NULL, return without taking any action. */
 void
-png_free(png_structp png_ptr, png_voidp ptr)
+PNG_FREE(png_structp png_ptr, png_voidp ptr)
 {
    if (png_ptr == NULL || ptr == NULL)
       return;
@@ -260,7 +269,7 @@ png_destroy_struct(png_voidp struct_ptr)
    have the ability to do that. */
 
 png_voidp
-png_malloc(png_structp png_ptr, png_uint_32 size)
+PNG_MALLOC(png_structp png_ptr, png_uint_32 size)
 {
    png_voidp ret;
    if (png_ptr == NULL || size == 0)
@@ -289,11 +298,11 @@ png_malloc(png_structp png_ptr, png_uint_32 size)
    return ret;
 }
 
-/* Free a pointer allocated by png_malloc().  In the default
+/* Free a pointer allocated by PNG_MALLOC().  In the default
   configuration, png_ptr is not used, but is passed in case it
   is needed.  If ptr is NULL, return without taking any action. */
 void
-png_free(png_structp png_ptr, png_voidp ptr)
+PNG_FREE(png_structp png_ptr, png_voidp ptr)
 {
    if (png_ptr == NULL || ptr == NULL)
       return;
diff --git a/pngpread.c b/pngpread.c
index b721f9197..f56291ce8 100644
--- a/pngpread.c
+++ b/pngpread.c
@@ -1,12 +1,12 @@
 
 /* pngpread.c - read a png file in push mode
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  */
 
 #define PNG_INTERNAL
diff --git a/pngread.c b/pngread.c
index d116fd6a6..454601e5e 100644
--- a/pngread.c
+++ b/pngread.c
@@ -1,12 +1,12 @@
 
 /* pngread.c - read a PNG file
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  *
  * This file contains routines that an application calls directly to
  * read a PNG file or stream.
@@ -655,12 +655,18 @@ png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
 
    if (info_ptr != NULL)
    {
+#if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_READ_zTXt_SUPPORTED)
+      png_free(png_ptr, info_ptr->text);
+#endif
       png_destroy_struct((png_voidp)info_ptr);
       *info_ptr_ptr = (png_infop)NULL;
    }
 
    if (end_info_ptr != NULL)
    {
+#if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_READ_zTXt_SUPPORTED)
+      png_free(png_ptr, info_ptr->text);
+#endif
       png_destroy_struct((png_voidp)end_info_ptr);
       *end_info_ptr_ptr = (png_infop)NULL;
    }
diff --git a/pngrio.c b/pngrio.c
index d45a71bd3..525e89887 100644
--- a/pngrio.c
+++ b/pngrio.c
@@ -1,12 +1,12 @@
 
 /* pngrio.c - functions for data input
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  *
  * This file provides a location for all input.  Users which need
  * special handling are expected to write a function which has the same
diff --git a/pngrtran.c b/pngrtran.c
index fd1800ece..8d0ad77f1 100644
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -1,12 +1,12 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  *
  * This file contains functions optionally called by an application 
  * in order to tell libpng how to handle data when reading a PNG.
@@ -549,13 +549,13 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
  * also needlessly introduces small errors.
  */
 void
-png_set_gamma(png_structp png_ptr, double screen_gamma, double file_gamma)
+png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
 {
    png_debug(1, "in png_set_gamma\n");
-   if (fabs(screen_gamma * file_gamma - 1.0) > PNG_GAMMA_THRESHOLD)
+   if (fabs(scrn_gamma * file_gamma - 1.0) > PNG_GAMMA_THRESHOLD)
       png_ptr->transformations |= PNG_GAMMA;
    png_ptr->gamma = (float)file_gamma;
-   png_ptr->display_gamma = (float)screen_gamma;
+   png_ptr->screen_gamma = (float)scrn_gamma;
 }
 #endif
 
@@ -592,6 +592,7 @@ png_set_rgb_to_gray(png_structp png_ptr, int gray_bits)
    png_debug(1, "in png_set_rgb_to_gray\n");
    png_ptr->transformations |= PNG_RGB_TO_GRAY;
    /* Need to do something with gray_bits here. */
+   png_warning(png_ptr, "RGB to GRAY transformation is not yet implemented.");
 }
 #endif
 
@@ -644,6 +645,23 @@ png_init_read_transformations(png_structp png_ptr)
             png_ptr->palette[png_ptr->background.index].green;
          png_ptr->background.blue  =
             png_ptr->palette[png_ptr->background.index].blue;
+
+#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
+        if (png_ptr->transformations & PNG_INVERT_ALPHA)
+        {
+#if defined(PNG_READ_EXPAND_SUPPORTED)
+           if (png_ptr->transformations & !PNG_EXPAND)
+#endif
+           {
+           /* invert the alpha channel (in tRNS) unless the pixels are 
+              going to be expanded, in which case leave it for later */
+              int i;
+              for (i=0; i<png_ptr->num_trans; i++)
+                 png_ptr->trans[i] = 255 - png_ptr->trans[i];
+           }
+        }
+#endif
+
       }
    }
 #endif
@@ -681,7 +699,7 @@ png_init_read_transformations(png_structp png_ptr)
             {
                double g;
 
-               g = 1.0 / (png_ptr->background_gamma * png_ptr->display_gamma);
+               g = 1.0 / (png_ptr->background_gamma * png_ptr->screen_gamma);
 
                if (png_ptr->background_gamma_type==PNG_BACKGROUND_GAMMA_SCREEN||
                    fabs(g - 1.0) < PNG_GAMMA_THRESHOLD)
@@ -761,17 +779,17 @@ png_init_read_transformations(png_structp png_ptr)
             switch (png_ptr->background_gamma_type)
             {
                case PNG_BACKGROUND_GAMMA_SCREEN:
-                  g = (png_ptr->display_gamma);
+                  g = (png_ptr->screen_gamma);
                   gs = 1.0;
                   break;
                case PNG_BACKGROUND_GAMMA_FILE:
                   g = 1.0 / (png_ptr->gamma);
-                  gs = 1.0 / (png_ptr->gamma * png_ptr->display_gamma);
+                  gs = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
                   break;
                case PNG_BACKGROUND_GAMMA_UNIQUE:
                   g = 1.0 / (png_ptr->background_gamma);
                   gs = 1.0 / (png_ptr->background_gamma *
-                     png_ptr->display_gamma);
+                     png_ptr->screen_gamma);
                   break;
             }
 
@@ -954,7 +972,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
    else
       info_ptr->channels = 1;
 
-#if defined(PNG_STRIP_ALPHA_SUPPORTED)
+#if defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
    if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
        info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
    {
@@ -1112,6 +1130,11 @@ png_do_read_transformations(png_structp png_ptr)
       png_do_read_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
+#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
+   if (png_ptr->transformations & PNG_INVERT_ALPHA)
+      png_do_read_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+#endif
+
 #if defined(PNG_READ_SWAP_SUPPORTED)
    if (png_ptr->transformations & PNG_SWAP_BYTES)
       png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
@@ -1468,6 +1491,87 @@ png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
 }
 #endif
 
+#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
+void
+png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
+{
+   png_debug(1, "in png_do_read_invert_alpha\n");
+#if defined(PNG_USELESS_TESTS_SUPPORTED)
+   if (row != NULL && row_info != NULL)
+#endif
+   {
+      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+      {
+         /* This inverts the alpha channel in RGBA */
+         if (row_info->bit_depth == 8)
+         {
+            png_bytep sp, dp;
+            png_uint_32 i;
+
+            for (i = 0, sp = dp = row + row_info->rowbytes;
+               i < row_info->width; i++)
+            {
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = 255 - *(--sp);
+            }
+         }
+         /* This inverts the alpha channel in RRGGBBAA */
+         else
+         {
+            png_bytep sp, dp;
+            png_uint_32 i;
+
+            for (i = 0, sp = dp = row + row_info->rowbytes;
+               i < row_info->width; i++)
+            {
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = 255 - *(--sp);
+               *(--dp) = 255 - *(--sp);
+            }
+         }
+      }
+      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+      {
+         /* This inverts the alpha channel in AG */
+         if (row_info->bit_depth == 8)
+         {
+            png_bytep sp, dp;
+            png_uint_32 i;
+
+            for (i = 0, sp = dp = row + row_info->rowbytes;
+               i < row_info->width; i++)
+            {
+               *(--dp) = *(--sp);
+               *(--dp) = 255 - *(--sp);
+            }
+         }
+         /* This inverts the alpha channel in AAGG */
+         else
+         {
+            png_bytep sp, dp;
+            png_uint_32 i;
+
+            for (i = 0, sp = dp = row + row_info->rowbytes;
+               i < row_info->width; i++)
+            {
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = 255 - *(--sp);
+               *(--dp) = 255 - *(--sp);
+            }
+         }
+      }
+   }
+}
+#endif
+
 #if defined(PNG_READ_FILLER_SUPPORTED)
 /* Add filler channel if we have RGB color */
 void
@@ -1693,7 +1797,7 @@ png_correct_palette(png_structp png_ptr, png_colorp palette,
       {
          double g;
 
-         g = 1.0 / (png_ptr->background_gamma * png_ptr->display_gamma);
+         g = 1.0 / (png_ptr->background_gamma * png_ptr->screen_gamma);
 
          if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_SCREEN ||
              fabs(g - 1.0) < PNG_GAMMA_THRESHOLD)
@@ -3082,7 +3186,7 @@ png_build_gamma_table(png_structp png_ptr)
       int i;
       double g;
 
-      g = 1.0 / (png_ptr->gamma * png_ptr->display_gamma);
+      g = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
 
       png_ptr->gamma_table = (png_bytep)png_malloc(png_ptr,
          (png_uint_32)256);
@@ -3107,7 +3211,7 @@ png_build_gamma_table(png_structp png_ptr)
                g) * 255.0 + .5);
          }
 
-         g = 1.0 / (png_ptr->display_gamma);
+         g = 1.0 / (png_ptr->screen_gamma);
 
          png_ptr->gamma_from_1 = (png_bytep)png_malloc(png_ptr,
             (png_uint_32)256);
@@ -3160,7 +3264,7 @@ png_build_gamma_table(png_structp png_ptr)
 
       num = (1 << (8 - shift));
 
-      g = 1.0 / (png_ptr->gamma * png_ptr->display_gamma);
+      g = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
 
       png_ptr->gamma_16_table = (png_uint_16pp)png_malloc(png_ptr,
          num * sizeof (png_uint_16p));
@@ -3238,7 +3342,7 @@ png_build_gamma_table(png_structp png_ptr)
                      65535.0, g) * 65535.0 + .5);
             }
          }
-         g = 1.0 / (png_ptr->display_gamma);
+         g = 1.0 / (png_ptr->screen_gamma);
 
          png_ptr->gamma_16_from_1 = (png_uint_16pp)png_malloc(png_ptr,
             num * sizeof (png_uint_16p));
diff --git a/pngrutil.c b/pngrutil.c
index 7c86fb022..2b81de916 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -1,12 +1,12 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  *
  * This file contains routines which are only called from within
  * libpng itself during the course of reading an image.
@@ -106,7 +106,7 @@ png_crc_finish(png_structp png_ptr, png_uint_32 skip)
    return 0;
 }
 
-/* Compare the CRC stored in the PNG file with that calulated by libpng from
+/* Compare the CRC stored in the PNG file with that calculated by libpng from
    the data it has read thus far. */
 int
 png_crc_error(png_structp png_ptr)
@@ -281,7 +281,7 @@ png_handle_PLTE(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    num = (int)length / 3;
-   palette = (png_colorp)png_zalloc(png_ptr, num, sizeof (png_color));
+   palette = (png_colorp)png_zalloc(png_ptr, (uInt)num, sizeof (png_color));
    png_ptr->flags |= PNG_FLAG_FREE_PALETTE;
    for (i = 0; i < num; i++)
    {
@@ -318,7 +318,7 @@ png_handle_PLTE(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
          {
             png_chunk_warning(png_ptr, "CRC error");
             png_ptr->flags &= ~PNG_FLAG_FREE_PALETTE;
-            png_free(png_ptr, palette);
+            png_zfree(png_ptr, palette);
             return;
          }
       }
@@ -404,7 +404,7 @@ png_handle_gAMA(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
 #if defined(PNG_READ_sRGB_SUPPORTED)
    if (info_ptr->valid & PNG_INFO_sRGB)
-      if(igamma != (png_uint_32)45000L)
+      if(igamma != (png_uint_32)51000L)
       {
          png_warning(png_ptr,
            "Ignoring incorrect gAMA value when sRGB is also present");
@@ -626,7 +626,7 @@ png_handle_cHRM(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 void
 png_handle_sRGB(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
-   png_byte intent;
+   int intent;
    png_byte buf[1];
 
    png_debug(1, "in png_handle_sRGB\n");
@@ -671,7 +671,7 @@ png_handle_sRGB(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
 #ifdef PNG_READ_gAMA_SUPPORTED
    if ((info_ptr->valid & PNG_INFO_gAMA))
-      if((png_uint_32)(png_ptr->gamma*(float)100000.+.5) != (png_uint_32)45000L)
+      if((png_uint_32)(png_ptr->gamma*(float)100000.+.5) != (png_uint_32)51000L)
       {
          png_warning(png_ptr,
            "Ignoring incorrect gAMA value when sRGB is also present");
diff --git a/pngset.c b/pngset.c
index ea38d6136..dd8b2f0e7 100644
--- a/pngset.c
+++ b/pngset.c
@@ -1,12 +1,12 @@
 
 /* pngset.c - storage of image information into info struct
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  *
  * The functions here are used during reads to store data from the file
  * into the info struct, and during writes to store application data
@@ -213,18 +213,18 @@ png_set_sBIT(png_structp png_ptr, png_infop info_ptr,
 
 #if defined(PNG_READ_sRGB_SUPPORTED) || defined(PNG_WRITE_sRGB_SUPPORTED)
 void
-png_set_sRGB(png_structp png_ptr, png_infop info_ptr, png_byte intent)
+png_set_sRGB(png_structp png_ptr, png_infop info_ptr, int intent)
 {
    png_debug1(1, "in %s storage function\n", "sRGB");
    if (info_ptr == NULL)
       return;
 
-   info_ptr->srgb_intent = intent;
+   info_ptr->srgb_intent = (png_byte)intent;
    info_ptr->valid |= PNG_INFO_sRGB;
 }
 void
 png_set_sRGB_gAMA_and_cHRM(png_structp png_ptr, png_infop info_ptr,
-   png_byte intent)
+   int intent)
 {
 #if defined(PNG_READ_gAMA_SUPPORTED) || defined(PNG_WRITE_gAMA_SUPPORTED)
    float file_gamma;
@@ -239,7 +239,7 @@ png_set_sRGB_gAMA_and_cHRM(png_structp png_ptr, png_infop info_ptr,
    png_set_sRGB(png_ptr, info_ptr, intent);
 
 #if defined(PNG_READ_gAMA_SUPPORTED) || defined(PNG_WRITE_gAMA_SUPPORTED)
-   file_gamma = (float).45;
+   file_gamma = (float).51;
    png_set_gAMA(png_ptr, info_ptr, file_gamma);
 #endif
 
@@ -269,7 +269,7 @@ png_set_text(png_structp png_ptr, png_infop info_ptr, png_textp text_ptr,
    int i;
 
    png_debug1(1, "in %s storage function\n", (png_ptr->chunk_name[0] == '\0' ?
-      "text" : png_ptr->chunk_name));
+      "text" : (png_const_charp)png_ptr->chunk_name));
 
    if (info_ptr == NULL || num_text == 0)
       return;
@@ -308,7 +308,7 @@ png_set_text(png_structp png_ptr, png_infop info_ptr, png_textp text_ptr,
       png_textp textp = &(info_ptr->text[info_ptr->num_text]);
 
       if (text_ptr[i].text == NULL)
-         text_ptr[i].text = "";
+         text_ptr[i].text = (png_charp)"";
 
       if (text_ptr[i].text[0] == '\0')
       {
diff --git a/pngtest.c b/pngtest.c
index c23df9dac..9e302dc89 100644
--- a/pngtest.c
+++ b/pngtest.c
@@ -1,12 +1,12 @@
 
 /* pngtest.c - a simple test program to test libpng
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  *
  * This program reads in a PNG image, writes it out again, and then
  * compares the two files.  If the files are identical, this shows that
@@ -37,6 +37,8 @@
 
 #include "png.h"
 
+int test_one_file(PNG_CONST char *inname, PNG_CONST char *outname);
+
 #ifdef __TURBOC__
 #include <mem.h>
 #endif
@@ -45,10 +47,10 @@
 /*  #define STDERR stderr  */
 #define STDERR stdout   /* for DOS */
 
+#if defined(PNG_NO_STDIO)
 /* START of code to validate stdio-free compilation */
 /* These copies of the default read/write functions come from pngrio.c and */
 /* pngwio.c.  They allow "don't include stdio" testing of the library. */
-#if defined(PNG_NO_STDIO)
 /* This is the function which does the actual reading of data.  If you are
    not reading from a standard C stream, you should create a replacement
    read_data function and use it at run time with png_set_read_fn(), rather
@@ -118,7 +120,7 @@ png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
       png_error(png_ptr, "read Error");
    }
 }
-#endif
+#endif /* USE_FAR_KEYWORD */
 
 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 static void
@@ -196,7 +198,7 @@ png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
    }
 }
 
-#endif
+#endif /* USE_FAR_KEYWORD */
 
 /* This function is called when there is a warning, but the library thinks
  * it can continue anyway.  Replacement functions don't have to do anything
@@ -224,13 +226,13 @@ png_default_error(png_structp png_ptr, png_const_charp message)
    /* We can return because png_error calls the default handler which is
     * actually ok in this case. */
 }
-#endif
+#endif /* PNG_NO_STDIO */
 /* END of code to validate stdio-free compilation */
 
 /* Test one file */
-int test(PNG_CONST char *inname, PNG_CONST char *outname)
+int test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
 {
-   FILE *fpin, *fpout;
+   static FILE *fpin, *fpout;  /* "static" prevents setjmp corruption */
    png_structp read_ptr, write_ptr;
    png_infop read_info_ptr, write_info_ptr, end_info_ptr;
    png_bytep row_buf;
@@ -263,16 +265,18 @@ int test(PNG_CONST char *inname, PNG_CONST char *outname)
    read_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (png_voidp)NULL,
       (png_error_ptr)NULL, (png_error_ptr)NULL);
 #if defined(PNG_NO_STDIO)
-   png_set_error_fn(read_ptr, (png_voidp)inname, png_default_error, png_default_warning);
+   png_set_error_fn(read_ptr, (png_voidp)inname, png_default_error,
+       png_default_warning);
 #endif
    write_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, (png_voidp)NULL,
       (png_error_ptr)NULL, (png_error_ptr)NULL);
 #if defined(PNG_NO_STDIO)
-   png_set_error_fn(write_ptr, (png_voidp)inname, png_default_error, png_default_warning);
+   png_set_error_fn(write_ptr, (png_voidp)inname, png_default_error,
+       png_default_warning);
 #endif
    png_debug(0, "Allocating read_info, write_info and end_info structures\n");
    read_info_ptr = png_create_info_struct(read_ptr);
-   write_info_ptr = png_create_info_struct(read_ptr);
+   write_info_ptr = png_create_info_struct(write_ptr);
    end_info_ptr = png_create_info_struct(read_ptr);
 
    png_debug(0, "Setting jmpbuf for read struct\n");
@@ -371,7 +375,7 @@ int test(PNG_CONST char *inname, PNG_CONST char *outname)
 #endif
 #if defined(PNG_READ_sRGB_SUPPORTED) && defined(PNG_WRITE_sRGB_SUPPORTED)
    {
-      png_byte intent;
+      int intent;
 
       if (png_get_sRGB(read_ptr, read_info_ptr, &intent))
       {
@@ -515,14 +519,13 @@ int test(PNG_CONST char *inname, PNG_CONST char *outname)
    png_write_end(write_ptr, end_info_ptr);
 
    png_debug(0, "Destroying data structs\n");
+   png_free(read_ptr, row_buf);
    png_destroy_read_struct(&read_ptr, &read_info_ptr, &end_info_ptr);
    png_destroy_write_struct(&write_ptr, &write_info_ptr);
 
    fclose(fpin);
    fclose(fpout);
 
-   png_free(read_ptr, row_buf);
-
    png_debug(0, "Opening files for comparison\n");
    if ((fpin = fopen(inname, "rb")) == NULL)
    {
@@ -576,8 +579,8 @@ int test(PNG_CONST char *inname, PNG_CONST char *outname)
 PNG_CONST char *inname = "pngtest_png";
 PNG_CONST char *outname = "pngout_png";
 #else
-PNG_CONST char *inname = "pngtest.png";
-PNG_CONST char *outname = "pngout.png";
+static char *inname = "pngtest.png";
+static char *outname = "pngout.png";
 #endif
 
 int
@@ -608,12 +611,15 @@ main(int argc, char *argv[])
    if (!multiple && argc == 3)
      outname = argv[2];
 
-   if (!multiple && argc > 3 || multiple && argc < 2)
+   if ((!multiple && argc > 3) || (multiple && argc < 2))
    {
-     fprintf(STDERR, "usage: %s [infile.png] [outfile.png]\n\t%s -m {infile.png}\n",
+     fprintf(STDERR,
+       "usage: %s [infile.png] [outfile.png]\n\t%s -m {infile.png}\n",
         argv[0], argv[0]);
-     fprintf(STDERR, "  reads/writes one PNG file (without -m) or multiple files (-m)\n");
-     fprintf(STDERR, "  with -m %s is used as a temporary file\n", outname);
+     fprintf(STDERR,
+       "  reads/writes one PNG file (without -m) or multiple files (-m)\n");
+     fprintf(STDERR,
+       "  with -m %s is used as a temporary file\n", outname);
      exit(1);
    }
 
@@ -622,13 +628,29 @@ main(int argc, char *argv[])
       int i;
       for (i=2; i<argc; ++i)
          {
-         fprintf(STDERR, "Testing %s:\n",argv[i]);
-         ierror += test(argv[i], outname);
+         int kerror;
+         fprintf(STDERR, "Testing %s:",argv[i]);
+         kerror = test_one_file(argv[i], outname);
+         if (kerror == 0) fprintf(STDERR, " PASS\n");
+         else {
+            fprintf(STDERR, " FAIL\n");
+            ierror += kerror;
+            }
          }
    }
    else
    {
-      ierror += test(inname, outname);
+      int i;
+      for (i=0; i<3; ++i) {
+         int kerror;
+         fprintf(STDERR, "Testing %s:",inname);
+         kerror = test_one_file(inname, outname);
+         if (kerror == 0) fprintf(STDERR, " PASS\n");
+         else {
+            fprintf(STDERR, " FAIL\n");
+            ierror += kerror;
+            }
+       }
    }
 
    if (ierror == 0)
diff --git a/pngtrans.c b/pngtrans.c
index dbfe2d53b..acda26cfa 100644
--- a/pngtrans.c
+++ b/pngtrans.c
@@ -1,12 +1,12 @@
 
 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  */
 
 #define PNG_INTERNAL
@@ -118,6 +118,16 @@ png_set_swap_alpha(png_structp png_ptr)
 }
 #endif
 
+#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
+    defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
+void
+png_set_invert_alpha(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_invert_alpha\n");
+   png_ptr->transformations |= PNG_INVERT_ALPHA;
+}
+#endif
+
 #if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
 void
 png_set_invert_mono(png_structp png_ptr)
diff --git a/pngwio.c b/pngwio.c
index dfb406faa..64cb4c23e 100644
--- a/pngwio.c
+++ b/pngwio.c
@@ -1,12 +1,12 @@
 
 /* pngwio.c - functions for data output
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  *
  * This file provides a location for all output.  Users which need
  * special handling are expected to write functions which have the same
diff --git a/pngwrite.c b/pngwrite.c
index 5896e3446..4bcadc2a1 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1,12 +1,12 @@
    
 /* pngwrite.c - general routines to write a PNG file
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  */
 
 /* get internal access to png.h */
@@ -43,7 +43,7 @@ png_write_info(png_structp png_ptr, png_infop info_ptr)
 #endif
 #if defined(PNG_WRITE_sRGB_SUPPORTED)
    if (info_ptr->valid & PNG_INFO_sRGB)
-      png_write_sRGB(png_ptr, info_ptr->srgb_intent);
+      png_write_sRGB(png_ptr, (int)info_ptr->srgb_intent);
 #endif
 #if defined(PNG_WRITE_sBIT_SUPPORTED)
    if (info_ptr->valid & PNG_INFO_sBIT)
@@ -62,10 +62,23 @@ png_write_info(png_structp png_ptr, png_infop info_ptr)
          (png_uint_32)info_ptr->num_palette);
    else if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       png_error(png_ptr, "Valid palette required for paletted images\n");
+
 #if defined(PNG_WRITE_tRNS_SUPPORTED)
    if (info_ptr->valid & PNG_INFO_tRNS)
+      {
+#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
+         /* invert the alpha channel (in tRNS) */
+         if (png_ptr->transformations & PNG_INVERT_ALPHA &&
+            info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+         {
+            int i;
+            for (i=0; i<info_ptr->num_trans; i++)
+               info_ptr->trans[i] = 255 - info_ptr->trans[i];
+         }
+#endif
       png_write_tRNS(png_ptr, info_ptr->trans, &(info_ptr->trans_values),
          info_ptr->num_trans, info_ptr->color_type);
+      }
 #endif
 #if defined(PNG_WRITE_bKGD_SUPPORTED)
    if (info_ptr->valid & PNG_INFO_bKGD)
@@ -200,12 +213,12 @@ png_write_end(png_structp png_ptr, png_infop info_ptr)
    png_write_IEND(png_ptr);
 }
 
-#if defined(PNG_TIME_RFC1152_SUPPORTED)
-/* Convert the supplied time into an RFC 1152 string suitable for use in
+#if defined(PNG_TIME_RFC1123_SUPPORTED)
+/* Convert the supplied time into an RFC 1123 string suitable for use in
  * a "Creation Time" or other text-based time string.
  */
 png_charp
-png_convert_to_rfc1152(png_structp png_ptr, png_timep ptime)
+png_convert_to_rfc1123(png_structp png_ptr, png_timep ptime)
 {
    const char *short_months[12] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
                                    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
@@ -233,7 +246,7 @@ png_convert_to_rfc1152(png_structp png_ptr, png_timep ptime)
 #endif
    return png_ptr->time_buffer;
 }
-#endif /* PNG_TIME_RFC1152_SUPPORTED */
+#endif /* PNG_TIME_RFC1123_SUPPORTED */
 
 #if defined(PNG_WRITE_tIME_SUPPORTED)
 void
@@ -583,6 +596,19 @@ png_destroy_write_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr)
 #ifdef PNG_WRITE_tEXt_SUPPORTED
       png_free(png_ptr, info_ptr->text);
 #endif
+#if defined(PNG_READ_pCAL_SUPPORTED)
+      png_free(png_ptr, info_ptr->pcal_purpose);
+      png_free(png_ptr, info_ptr->pcal_units);
+      if (info_ptr->pcal_params != NULL)
+      {
+         int i;
+         for (i = 0; i < info_ptr->pcal_nparams; i++)
+         {
+            png_free(png_ptr, info_ptr->pcal_params[i]);
+         }
+         png_free(png_ptr, info_ptr->pcal_params);
+      }
+#endif
       png_destroy_struct((png_voidp)info_ptr);
       *info_ptr_ptr = (png_infop)NULL;
    }
@@ -617,9 +643,9 @@ png_write_destroy(png_structp png_ptr)
    png_free(png_ptr, png_ptr->up_row);
    png_free(png_ptr, png_ptr->avg_row);
    png_free(png_ptr, png_ptr->paeth_row);
-#if defined(PNG_TIME_RFC1152_SUPPORTED)
+#if defined(PNG_TIME_RFC1123_SUPPORTED)
    png_free(png_ptr, png_ptr->time_buffer);
-#endif /* PNG_TIME_RFC1152_SUPPORTED */
+#endif /* PNG_TIME_RFC1123_SUPPORTED */
 #if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
    png_free(png_ptr, png_ptr->prev_filters);
    png_free(png_ptr, png_ptr->filter_weights);
diff --git a/pngwtran.c b/pngwtran.c
index dab4d5ae6..fc7d56c12 100644
--- a/pngwtran.c
+++ b/pngwtran.c
@@ -1,12 +1,12 @@
 
 /* pngwtran.c - transforms the data in a row for PNG writers
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  */
 
 #define PNG_INTERNAL
@@ -42,6 +42,10 @@ png_do_write_transformations(png_structp png_ptr)
    if (png_ptr->transformations & PNG_SWAP_ALPHA)
       png_do_write_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
+#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
+   if (png_ptr->transformations & PNG_INVERT_ALPHA)
+      png_do_write_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+#endif
 #if defined(PNG_WRITE_BGR_SUPPORTED)
    if (png_ptr->transformations & PNG_BGR)
       png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
@@ -394,3 +398,79 @@ png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
 }
 #endif
 
+#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
+void
+png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
+{
+   png_debug(1, "in png_do_write_invert_alpha\n");
+#if defined(PNG_USELESS_TESTS_SUPPORTED)
+   if (row != NULL && row_info != NULL)
+#endif
+   {
+      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+      {
+         /* This inverts the alpha channel in RGBA */
+         if (row_info->bit_depth == 8)
+         {
+            png_bytep sp, dp;
+            png_uint_32 i;
+
+            for (i = 0, sp = dp = row; i < row_info->width; i++)
+            {
+               *(dp++) = *(sp++);
+               *(dp++) = *(sp++);
+               *(dp++) = *(sp++);
+               *(dp++) = 255 - *(sp++);
+            }
+         }
+         /* This inverts the alpha channel in RRGGBBAA */
+         else
+         {
+            png_bytep sp, dp;
+            png_uint_32 i;
+
+            for (i = 0, sp = dp = row; i < row_info->width; i++)
+            {
+               *(dp++) = *(sp++);
+               *(dp++) = *(sp++);
+               *(dp++) = *(sp++);
+               *(dp++) = *(sp++);
+               *(dp++) = *(sp++);
+               *(dp++) = *(sp++);
+               *(dp++) = 255 - *(sp++);
+               *(dp++) = 255 - *(sp++);
+            }
+         }
+      }
+      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+      {
+         /* This inverts the alpha channel in GA */
+         if (row_info->bit_depth == 8)
+         {
+            png_bytep sp, dp;
+            png_uint_32 i;
+
+            for (i = 0, sp = dp = row; i < row_info->width; i++)
+            {
+               *(dp++) = *(sp++);
+               *(dp++) = 255 - *(sp++);
+            }
+         }
+         /* This inverts the alpha channel in GGAA */
+         else
+         {
+            png_bytep sp, dp;
+            png_uint_32 i;
+
+            for (i = 0, sp = dp = row; i < row_info->width; i++)
+            {
+               *(dp++) = *(sp++);
+               *(dp++) = *(sp++);
+               *(dp++) = 255 - *(sp++);
+               *(dp++) = 255 - *(sp++);
+            }
+         }
+      }
+   }
+}
+#endif
diff --git a/pngwutil.c b/pngwutil.c
index fccd7b68d..0a06935f3 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1,12 +1,12 @@
 
 /* pngwutil.c - utilities to write a PNG file
  *
- * libpng 0.97
+ * libpng 0.98
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 7, 1998
+ * January 16, 1998
  */
 
 #define PNG_INTERNAL
@@ -346,7 +346,7 @@ png_write_gAMA(png_structp png_ptr, double file_gamma)
 #if defined(PNG_WRITE_sRGB_SUPPORTED)
 /* write a sRGB chunk */
 void
-png_write_sRGB(png_structp png_ptr, png_byte srgb_intent)
+png_write_sRGB(png_structp png_ptr, int srgb_intent)
 {
    png_byte buf[1];
 
@@ -354,7 +354,7 @@ png_write_sRGB(png_structp png_ptr, png_byte srgb_intent)
    if(srgb_intent > 3)
          png_warning(png_ptr,
             "Invalid sRGB rendering intent specified");
-   buf[0]=srgb_intent;
+   buf[0]=(png_byte)srgb_intent;
    png_write_chunk(png_ptr, png_sRGB, buf, (png_size_t)1);
 }
 #endif
@@ -506,7 +506,7 @@ png_write_tRNS(png_structp png_ptr, png_bytep trans, png_color_16p tran,
    }
    else
    {
-      png_warning(png_ptr, "Can't write tRNS with and alpha channel");
+      png_warning(png_ptr, "Can't write tRNS with an alpha channel");
    }
 }
 #endif
@@ -992,6 +992,7 @@ png_write_pCAL(png_structp png_ptr, png_charp purpose, png_int_32 X0,
          (png_size_t)params_len[i]);
    }
 
+   png_free(png_ptr, params_len);
    png_write_chunk_end(png_ptr);
 }
 #endif
@@ -1395,7 +1396,7 @@ png_write_find_filter(png_structp png_ptr, png_row_infop row_info)
     * smallest value when summing the absolute values of the distances
     * from zero using anything >= 128 as negative numbers.  This is known
     * as the "minimum sum of absolute differences" heuristic.  Other
-    * heruistics are the "weighted minumum sum of absolute differences"
+    * heuristics are the "weighted minumum sum of absolute differences"
     * (experimental and can in theory improve compression), and the "zlib
     * predictive" method (not implemented in libpng 0.95), which does test
     * compressions of lines using different filter methods, and then chooses