[devel] Minor documentation editing.

2 files changed, 179 insertions, 72 deletions

diff --git a/libpng-manual.txt b/libpng-manual.txt
index 5e157a9d3..d758ea554 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 1.5.5beta03 - July 14, 2011
+ libpng version 1.5.5beta03 - July 26, 2011
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  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 1.5.5beta03 - July 14, 2011
+ libpng versions 0.97, January 1998, through 1.5.5beta03 - July 26, 2011
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
 
@@ -107,7 +107,8 @@ 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.
+functions) was developed, and direct access to the png_info fields was
+deprecated..
 
 The png_struct structure is the object used by the library to decode a
 single image.  As of 1.5.0 this structure is also not exposed.
@@ -146,9 +147,9 @@ the value by multiplying by 100,000.  As of libpng 1.5.0 a convenience
 macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point)
 which is simply (png_int_32).
 
-All APIs that take (double) arguments also have an matching API that
+All APIs that take (double) arguments also have a matching API that
 takes the corresponding fixed point integer arguments.  The fixed point
-API has the same name as the floating point one with _fixed appended.
+API has the same name as the floating point one with "_fixed" appended.
 The actual range of values permitted in the APIs is frequently less than
 the full range of (png_fixed_point) (-21474 to +21474).  When APIs require
 a non-negative argument the type is recorded as png_uint_32 above.  Consult
@@ -166,6 +167,10 @@ preprocessing directives of the form:
     #ifdef PNG_feature_SUPPORTED
     declare-function
     #endif
+    ...
+    #ifdef PNG_feature_SUPPORTED
+    use-function
+    #endif
 
 The library can be built without support for these APIs, although a
 standard build will have all implemented APIs.  Application programs
@@ -206,24 +211,25 @@ A variety of methods exist to build libpng.  Not all of these support
 reconfiguration of pnglibconf.h.  To reconfigure pnglibconf.h it must either be
 rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
 
-Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing
-the lines defining the supported features, paying very close attention to
-the 'option' information in scripts/pnglibconf.dfa that describes those
-features and their requirements.  This is easy to get wrong.
+Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt to
+pnglibconf.h and changing the lines defining the supported features, paying
+very close attention to the 'option' information in scripts/pnglibconf.dfa
+that describes those features and their requirements.  This is easy to get
+wrong.
 
 B. Configuration using DFA_XTRA
 
 Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later
 variant such as 'nawk' or 'gawk', is available.  The configure build will
 automatically find an appropriate awk and build pnglibconf.h.
-scripts/pnglibconf.mak contains a set of make rules for doing the same thing if
-configure is not used, and many of the makefiles in the scripts directory use
-this approach.
+The scripts/pnglibconf.mak file contains a set of make rules for doing the
+same thing if configure is not used, and many of the makefiles in the scripts
+directory use this approach.
 
-When rebuilding simply write new file containing changed options and set
+When rebuilding simply write a new file containing changed options and set
 DFA_XTRA to the name of this file.  This causes the build to append the new file
-to the end of scripts/pnglibconf.dfa.  pngusr.dfa should contain lines of the
-following forms:
+to the end of scripts/pnglibconf.dfa.  The pngusr.dfa file should contain lines
+of the following forms:
 
 everything = off
 
@@ -255,8 +261,8 @@ C. Configuration using PNG_USR_CONFIG
 
 If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file
 pngusr.h will automatically be included before the options in
-scripts/pnglibconf.dfa are processed.  pngusr.h should contain only macro
-definitions turning features on or off or setting settings.
+scripts/pnglibconf.dfa are processed.  Your pngusr.h file should contain only
+macro definitions turning features on or off or setting settings.
 
 Apart from the global setting "everything = off" all the options listed above
 can be set using macros in pngusr.h:
@@ -573,6 +579,8 @@ 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.
+If you know that your application will never make use of some particular
+chunks, use PNG_HANDLE_CHUNK_NEVER (or 1) as demonstrated below.
 
 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
@@ -669,7 +677,8 @@ called before the PNG file header had been read and png_set_alpha_mode() did not
 exist.
 
 If you need to support versions prior to libpng-1.5.4 test the version number
-and follow the procedures described in the appropriate manual page.
+as illustrated below using "PNG_LIBPNG_VER >= 10504" and follow the procedures
+described in the appropriate manual page.
 
 You give libpng the encoding expected by your system expressed as a 'gamma'
 value.  You can also specify a default encoding for the PNG file in
@@ -714,7 +723,9 @@ Libpng only supports composing onto a single color (using png_set_background;
 see below.)  Otherwise you must do the composition yourself and, in this case,
 you may need to call png_set_alpha_mode:
 
+#if PNG_LIBPNG_VER >= 10504
    png_set_alpha_mode(png_ptr, mode, screen_gamma);
+#endif
 
 The screen_gamma value is the same as the argument to png_set_gamma, however how
 it affects the output depends on the mode.  png_set_alpha_mode() sets the file
@@ -1229,6 +1240,8 @@ pointer into the info_ptr is returned for any complex types.
     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.
+    Prior to libpng-1.4.0, the default build was
+    was without iTXt chunk support.
 
     num_text       - number of comments (same as
                      num_comments; you can put NULL here
@@ -1253,10 +1266,10 @@ pointer into the info_ptr is returned for any complex types.
        &unit_type);
 
     offset_x       - positive offset from the left edge
-                     of the screen
+                     of the screen (can be negative)
 
     offset_y       - positive offset from the top edge
-                     of the screen
+                     of the screen (can be negative)
 
     unit_type      - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
 
@@ -1288,6 +1301,7 @@ pointer into the info_ptr is returned for any complex types.
     unit        - physical scale units (an integer)
 
     width       - width of a pixel in physical scale units
+                  (expressed as a string)
 
     height      - height of a pixel in physical scale units
                  (width and height are strings like "2.54")
@@ -1310,6 +1324,12 @@ pointer into the info_ptr is returned for any complex types.
     chunks were read from the PNG file or inserted with the
     png_set_unknown_chunks() function.
 
+    The value of "location" is a bitwise "or" of
+
+         PNG_HAVE_IHDR  (0x01)
+         PNG_HAVE_PLTE  (0x02)
+         PNG_AFTER_IDAT (0x08)
+
 The data from the pHYs chunk can be retrieved in several convenient
 forms:
 
@@ -1454,7 +1474,7 @@ 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 1.5.2, png_set_expand_16() was added.  It behaves as
-png_set_expand(), however, the resultant channels have 16 bits rather than 8.
+png_set_expand(); however, the resultant channels have 16 bits rather than 8.
 Use this when the output color or gray channels are made linear to avoid fairly
 severe accuracy loss.
 
@@ -1465,7 +1485,14 @@ 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)
+#if PNG_LIBPNG_VER >= 10504
        png_set_scale_16(png_ptr);
+#else
+       png_set_strip_16(png_ptr);
+#endif
+
+(The more accurate "png_set_scale_16()" API became available in libpng version
+1.5.4).
 
 If you need to process the alpha channel on the image separately from the image
 data (for example if you convert it to a bitmap mask) it is possible to have
@@ -1643,7 +1670,7 @@ It will return a png_byte that is zero if the image was gray or
 will be silently converted to grayscale, using the green channel
 data for sBIT, regardless of the error_action setting.
 
-The default values come from the PNG file cHRM chunk if present, otherwise the
+The default values come from the PNG file cHRM chunk if present; otherwise, the
 defaults correspond to the ITU-R recommendation 709, and also the sRGB color
 space, as recommended in the Charles Poynton's Colour FAQ,
 <http://www.poynton.com/>, in section 9:
@@ -1655,7 +1682,7 @@ space, as recommended in the Charles Poynton's Colour FAQ,
 The calculation is done in a linear colorspace, if the image gamma
 can be determined.
 
-The png_set_background() function has been described already, it tells libpng to
+The png_set_background() function has been described already; it tells libpng to
 composite images with alpha or simple transparency against the supplied
 background color.  For compatibility with versions of libpng earlier than
 libpng-1.5.4 it is recommended that you call the function after reading the file
@@ -1718,9 +1745,9 @@ file has more entries then will fit on your screen, png_set_quantize()
 will do that.  Note that this is a simple match quantization that merely
 finds the closest color available.  This should work fairly well with
 optimized palettes, but fairly badly with linear color cubes.  If you
-pass a palette that is larger then maximum_colors, the file will
+pass a palette that is larger than 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
+maximum_colors.  If there is a histogram, libpng 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.
 
@@ -1792,7 +1819,7 @@ after all of the other transformations have been processed.  Take care with
 interlaced images if you do the interlace yourself - the width of the row is the
 width in 'row_info', not the overall image width.
 
-If supported libpng provides two information routines that you can use to find
+If supported, libpng provides two information routines that you can use to find
 where you are in processing the image:
 
    png_get_current_pass_number(png_structp png_ptr);
@@ -2716,14 +2743,14 @@ width, height, bit_depth, and color_type must be the same in each call.
     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
                      (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);
 
     hist           - histogram of palette (array of
@@ -2764,6 +2791,8 @@ width, height, bit_depth, and color_type must be the same in each call.
     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.
+    Prior to libpng-1.4.0 the library was built by default
+    without iTXt support.
 
     num_text       - number of comments
 
@@ -2813,6 +2842,7 @@ width, height, bit_depth, and color_type must be the same in each call.
     unit        - physical scale units (an integer)
 
     width       - width of a pixel in physical scale units
+                  expressed as a string
 
     height      - height of a pixel in physical scale units
                  (width and height are strings like "2.54")
@@ -2854,7 +2884,7 @@ 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.
+Until text gets around a few hundred 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
@@ -3515,8 +3545,8 @@ 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 *.
+note that the rows of data are defined as png_bytepp, which is
+an "unsigned char far * far *".
 
 Configuring for gui/windowing platforms:
 
@@ -3534,7 +3564,10 @@ 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.
+in turn includes pngconf.h and, as of libpng-1.5.0, pnglibconf.h.
+As of libpng-1.5.0, pngpriv.h also includes three other private header
+files, pngstruct.h, pnginfo.h, and pngdebug.h, which contain material
+that previously appeared in the public headers.
 
 Configuring zlib:
 
@@ -3576,8 +3609,28 @@ zlib.h for more information on what these mean.
         window_bits);
 
     png_set_compression_method(png_ptr, method);
+
     png_set_compression_buffer_size(png_ptr, size);
 
+As of libpng version 1.5.4, additional APIs became
+available to set these separately for non-IDAT
+compressed chunks such as zTXt, iTXt, and iCCP:
+
+    #include zlib.h
+    #if PNG_LIBPNG_VER <= 10504
+    png_set_text_compression_level(png_ptr, level);
+
+    png_set_text_compression_mem_level(png_ptr, level);
+
+    png_set_text_compression_strategy(png_ptr,
+        strategy);
+
+    png_set_text_compression_window_bits(png_ptr,
+        window_bits);
+
+    png_set_text_compression_method(png_ptr, method);
+    #endif
+
 Controlling row filtering
 
 If you want to control whether libpng uses filtering or not, which
@@ -4447,7 +4500,7 @@ Other rules can be inferred by inspecting the libpng source.
 
 XIV. Y2K Compliance in libpng
 
-July 14, 2011
+July 26, 2011
 
 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 83cf11eb0..dab4e9313 100644
--- a/libpng.3
+++ b/libpng.3
@@ -1,4 +1,4 @@
-.TH LIBPNG 3 "July 14, 2011"
+.TH LIBPNG 3 "July 26, 2011"
 .SH NAME
 libpng \- Portable Network Graphics (PNG) Reference Library 1.5.5beta03
 .SH SYNOPSIS
@@ -955,7 +955,7 @@ 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 1.5.5beta03 - July 14, 2011
+ libpng version 1.5.5beta03 - July 26, 2011
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
@@ -966,7 +966,7 @@ libpng-manual.txt - A description on how to use and modify libpng
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.5.5beta03 - July 14, 2011
+ libpng versions 0.97, January 1998, through 1.5.5beta03 - July 26, 2011
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
 
@@ -1062,7 +1062,8 @@ 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.
+functions) was developed, and direct access to the png_info fields was
+deprecated..
 
 The png_struct structure is the object used by the library to decode a
 single image.  As of 1.5.0 this structure is also not exposed.
@@ -1101,9 +1102,9 @@ the value by multiplying by 100,000.  As of libpng 1.5.0 a convenience
 macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point)
 which is simply (png_int_32).
 
-All APIs that take (double) arguments also have an matching API that
+All APIs that take (double) arguments also have a matching API that
 takes the corresponding fixed point integer arguments.  The fixed point
-API has the same name as the floating point one with _fixed appended.
+API has the same name as the floating point one with "_fixed" appended.
 The actual range of values permitted in the APIs is frequently less than
 the full range of (png_fixed_point) (-21474 to +21474).  When APIs require
 a non-negative argument the type is recorded as png_uint_32 above.  Consult
@@ -1121,6 +1122,10 @@ preprocessing directives of the form:
     #ifdef PNG_feature_SUPPORTED
     declare-function
     #endif
+    ...
+    #ifdef PNG_feature_SUPPORTED
+    use-function
+    #endif
 
 The library can be built without support for these APIs, although a
 standard build will have all implemented APIs.  Application programs
@@ -1161,24 +1166,25 @@ A variety of methods exist to build libpng.  Not all of these support
 reconfiguration of pnglibconf.h.  To reconfigure pnglibconf.h it must either be
 rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
 
-Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing
-the lines defining the supported features, paying very close attention to
-the 'option' information in scripts/pnglibconf.dfa that describes those
-features and their requirements.  This is easy to get wrong.
+Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt to
+pnglibconf.h and changing the lines defining the supported features, paying
+very close attention to the 'option' information in scripts/pnglibconf.dfa
+that describes those features and their requirements.  This is easy to get
+wrong.
 
 B. Configuration using DFA_XTRA
 
 Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later
 variant such as 'nawk' or 'gawk', is available.  The configure build will
 automatically find an appropriate awk and build pnglibconf.h.
-scripts/pnglibconf.mak contains a set of make rules for doing the same thing if
-configure is not used, and many of the makefiles in the scripts directory use
-this approach.
+The scripts/pnglibconf.mak file contains a set of make rules for doing the
+same thing if configure is not used, and many of the makefiles in the scripts
+directory use this approach.
 
-When rebuilding simply write new file containing changed options and set
+When rebuilding simply write a new file containing changed options and set
 DFA_XTRA to the name of this file.  This causes the build to append the new file
-to the end of scripts/pnglibconf.dfa.  pngusr.dfa should contain lines of the
-following forms:
+to the end of scripts/pnglibconf.dfa.  The pngusr.dfa file should contain lines
+of the following forms:
 
 everything = off
 
@@ -1210,8 +1216,8 @@ C. Configuration using PNG_USR_CONFIG
 
 If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file
 pngusr.h will automatically be included before the options in
-scripts/pnglibconf.dfa are processed.  pngusr.h should contain only macro
-definitions turning features on or off or setting settings.
+scripts/pnglibconf.dfa are processed.  Your pngusr.h file should contain only
+macro definitions turning features on or off or setting settings.
 
 Apart from the global setting "everything = off" all the options listed above
 can be set using macros in pngusr.h:
@@ -1528,6 +1534,8 @@ 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.
+If you know that your application will never make use of some particular
+chunks, use PNG_HANDLE_CHUNK_NEVER (or 1) as demonstrated below.
 
 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
@@ -1624,7 +1632,8 @@ called before the PNG file header had been read and png_set_alpha_mode() did not
 exist.
 
 If you need to support versions prior to libpng-1.5.4 test the version number
-and follow the procedures described in the appropriate manual page.
+as illustrated below using "PNG_LIBPNG_VER >= 10504" and follow the procedures
+described in the appropriate manual page.
 
 You give libpng the encoding expected by your system expressed as a 'gamma'
 value.  You can also specify a default encoding for the PNG file in
@@ -1669,7 +1678,9 @@ Libpng only supports composing onto a single color (using png_set_background;
 see below.)  Otherwise you must do the composition yourself and, in this case,
 you may need to call png_set_alpha_mode:
 
+#if PNG_LIBPNG_VER >= 10504
    png_set_alpha_mode(png_ptr, mode, screen_gamma);
+#endif
 
 The screen_gamma value is the same as the argument to png_set_gamma, however how
 it affects the output depends on the mode.  png_set_alpha_mode() sets the file
@@ -2184,6 +2195,8 @@ pointer into the info_ptr is returned for any complex types.
     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.
+    Prior to libpng-1.4.0, the default build was
+    was without iTXt chunk support.
 
     num_text       - number of comments (same as
                      num_comments; you can put NULL here
@@ -2208,10 +2221,10 @@ pointer into the info_ptr is returned for any complex types.
        &unit_type);
 
     offset_x       - positive offset from the left edge
-                     of the screen
+                     of the screen (can be negative)
 
     offset_y       - positive offset from the top edge
-                     of the screen
+                     of the screen (can be negative)
 
     unit_type      - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
 
@@ -2243,6 +2256,7 @@ pointer into the info_ptr is returned for any complex types.
     unit        - physical scale units (an integer)
 
     width       - width of a pixel in physical scale units
+                  (expressed as a string)
 
     height      - height of a pixel in physical scale units
                  (width and height are strings like "2.54")
@@ -2265,6 +2279,12 @@ pointer into the info_ptr is returned for any complex types.
     chunks were read from the PNG file or inserted with the
     png_set_unknown_chunks() function.
 
+    The value of "location" is a bitwise "or" of
+
+         PNG_HAVE_IHDR  (0x01)
+         PNG_HAVE_PLTE  (0x02)
+         PNG_AFTER_IDAT (0x08)
+
 The data from the pHYs chunk can be retrieved in several convenient
 forms:
 
@@ -2409,7 +2429,7 @@ 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 1.5.2, png_set_expand_16() was added.  It behaves as
-png_set_expand(), however, the resultant channels have 16 bits rather than 8.
+png_set_expand(); however, the resultant channels have 16 bits rather than 8.
 Use this when the output color or gray channels are made linear to avoid fairly
 severe accuracy loss.
 
@@ -2420,7 +2440,14 @@ 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)
+#if PNG_LIBPNG_VER >= 10504
        png_set_scale_16(png_ptr);
+#else
+       png_set_strip_16(png_ptr);
+#endif
+
+(The more accurate "png_set_scale_16()" API became available in libpng version
+1.5.4).
 
 If you need to process the alpha channel on the image separately from the image
 data (for example if you convert it to a bitmap mask) it is possible to have
@@ -2598,7 +2625,7 @@ It will return a png_byte that is zero if the image was gray or
 will be silently converted to grayscale, using the green channel
 data for sBIT, regardless of the error_action setting.
 
-The default values come from the PNG file cHRM chunk if present, otherwise the
+The default values come from the PNG file cHRM chunk if present; otherwise, the
 defaults correspond to the ITU-R recommendation 709, and also the sRGB color
 space, as recommended in the Charles Poynton's Colour FAQ,
 <http://www.poynton.com/>, in section 9:
@@ -2610,7 +2637,7 @@ space, as recommended in the Charles Poynton's Colour FAQ,
 The calculation is done in a linear colorspace, if the image gamma
 can be determined.
 
-The png_set_background() function has been described already, it tells libpng to
+The png_set_background() function has been described already; it tells libpng to
 composite images with alpha or simple transparency against the supplied
 background color.  For compatibility with versions of libpng earlier than
 libpng-1.5.4 it is recommended that you call the function after reading the file
@@ -2673,9 +2700,9 @@ file has more entries then will fit on your screen, png_set_quantize()
 will do that.  Note that this is a simple match quantization that merely
 finds the closest color available.  This should work fairly well with
 optimized palettes, but fairly badly with linear color cubes.  If you
-pass a palette that is larger then maximum_colors, the file will
+pass a palette that is larger than 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
+maximum_colors.  If there is a histogram, libpng 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.
 
@@ -2747,7 +2774,7 @@ after all of the other transformations have been processed.  Take care with
 interlaced images if you do the interlace yourself - the width of the row is the
 width in 'row_info', not the overall image width.
 
-If supported libpng provides two information routines that you can use to find
+If supported, libpng provides two information routines that you can use to find
 where you are in processing the image:
 
    png_get_current_pass_number(png_structp png_ptr);
@@ -3671,14 +3698,14 @@ width, height, bit_depth, and color_type must be the same in each call.
     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
                      (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);
 
     hist           - histogram of palette (array of
@@ -3719,6 +3746,8 @@ width, height, bit_depth, and color_type must be the same in each call.
     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.
+    Prior to libpng-1.4.0 the library was built by default
+    without iTXt support.
 
     num_text       - number of comments
 
@@ -3768,6 +3797,7 @@ width, height, bit_depth, and color_type must be the same in each call.
     unit        - physical scale units (an integer)
 
     width       - width of a pixel in physical scale units
+                  expressed as a string
 
     height      - height of a pixel in physical scale units
                  (width and height are strings like "2.54")
@@ -3809,7 +3839,7 @@ 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.
+Until text gets around a few hundred 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
@@ -4470,8 +4500,8 @@ 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 *.
+note that the rows of data are defined as png_bytepp, which is
+an "unsigned char far * far *".
 
 .SS Configuring for gui/windowing platforms:
 
@@ -4489,7 +4519,11 @@ 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.
+%14%in turn includes pngconf.h.
+in turn includes pngconf.h and, as of libpng-1.5.0, pnglibconf.h.
+As of libpng-1.5.0, pngpriv.h also includes three other private header
+files, pngstruct.h, pnginfo.h, and pngdebug.h, which contain material
+that previously appeared in the public headers.
 
 .SS Configuring zlib:
 
@@ -4531,8 +4565,28 @@ zlib.h for more information on what these mean.
         window_bits);
 
     png_set_compression_method(png_ptr, method);
+
     png_set_compression_buffer_size(png_ptr, size);
 
+As of libpng version 1.5.4, additional APIs became
+available to set these separately for non-IDAT
+compressed chunks such as zTXt, iTXt, and iCCP:
+
+    #include zlib.h
+    #if PNG_LIBPNG_VER <= 10504
+    png_set_text_compression_level(png_ptr, level);
+
+    png_set_text_compression_mem_level(png_ptr, level);
+
+    png_set_text_compression_strategy(png_ptr,
+        strategy);
+
+    png_set_text_compression_window_bits(png_ptr,
+        window_bits);
+
+    png_set_text_compression_method(png_ptr, method);
+    #endif
+
 .SS Controlling row filtering
 
 If you want to control whether libpng uses filtering or not, which
@@ -5402,7 +5456,7 @@ Other rules can be inferred by inspecting the libpng source.
 
 .SH XIV. Y2K Compliance in libpng
 
-July 14, 2011
+July 26, 2011
 
 Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.
@@ -5661,7 +5715,7 @@ possible without all of you.
 
 Thanks to Frank J. T. Wojcik for helping with the documentation.
 
-Libpng version 1.5.5beta03 - July 14, 2011:
+Libpng version 1.5.5beta03 - July 26, 2011:
 Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
 Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
 
@@ -5684,7 +5738,7 @@ this sentence.
 
 This code is released under the libpng license.
 
-libpng versions 1.2.6, August 15, 2004, through 1.5.5beta03, July 14, 2011, are
+libpng versions 1.2.6, August 15, 2004, through 1.5.5beta03, July 26, 2011, 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
@@ -5783,7 +5837,7 @@ certification mark of the Open Source Initiative.
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-July 14, 2011
+July 26, 2011
 
 .\" end of man page