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[libpng15] Added demo of how to deal with unknown chunk location
to the man page.
This commit is contained in:
Glenn Randers-Pehrson
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033a157a65
@ -1,6 +1,6 @@
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Libpng-manual.txt - A description on how to use and modify libpng
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libpng version 1.5.16beta04 - April 26, 2013
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libpng version 1.5.16beta04 - April 29, 2013
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Updated and distributed by Glenn Randers-Pehrson
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<glennrp at users.sourceforge.net>
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Copyright (c) 1998-2013 Glenn Randers-Pehrson
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@ -11,7 +11,7 @@ Libpng-manual.txt - A description on how to use and modify libpng
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Based on:
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libpng versions 0.97, January 1998, through 1.5.16beta04 - April 26, 2013
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libpng versions 0.97, January 1998, through 1.5.16beta04 - April 29, 2013
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Updated and distributed by Glenn Randers-Pehrson
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Copyright (c) 1998-2013 Glenn Randers-Pehrson
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@ -31,9 +31,7 @@ Libpng-manual.txt - A description on how to use and modify libpng
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I. Introduction
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This file describes how to use and modify the PNG reference library
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(known as libpng) for your own use. There are five sections to this
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file: introduction, structures, reading, writing, and modification and
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configuration notes for various special platforms. In addition to this
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(known as libpng) for your own use. In addition to this
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file, example.c is a good starting point for using the library, as
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it is heavily commented and should include everything most people
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will need. We assume that libpng is already installed; see the
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@ -3037,13 +3035,45 @@ from PNG time to an RFC 1123 format string.
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Writing unknown chunks
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You can use the png_set_unknown_chunks function to queue up chunks
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for writing. You give it a chunk name, raw data, and a size; that's
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all there is to it. The chunks will be written by the next following
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png_write_info_before_PLTE, png_write_info, or png_write_end function.
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Any chunks previously read into the info structure's unknown-chunk
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list will also be written out in a sequence that satisfies the PNG
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specification's ordering rules.
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You can use the png_set_unknown_chunks function to queue up private chunks
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for writing. You give it a chunk name, location, raw data, and a size. You
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also must use png_set_keep_unknown_chunks() to ensure that libpng will
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handle them. That's all there is to it. The chunks will be written by the
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next following png_write_info_before_PLTE, png_write_info, or png_write_end
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function, depending upon the specified location. Any chunks previously
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read into the info structure's unknown-chunk list will also be written out
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in a sequence that satisfies the PNG specification's ordering rules.
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Here is an example of writing two private chunks, prVt and miNE:
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#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
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/* Set unknown chunk data */
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png_unknown_chunk unk_chunk[2];
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strcpy((char *) unk_chunk[0].name, "prVt";
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unk_chunk[0].data = (unsigned char *) "PRIVATE DATA";
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unk_chunk[0].size = strlen(unk_chunk[0].data)+1;
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unk_chunk[0].location = PNG_HAVE_IHDR;
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strcpy((char *) unk_chunk[1].name, "miNE";
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unk_chunk[1].data = (unsigned char *) "MY CHUNK DATA";
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unk_chunk[1].size = strlen(unk_chunk[0].data)+1;
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unk_chunk[1].location = PNG_AFTER_IDAT;
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png_set_unknown_chunks(write_ptr, write_info_ptr,
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unk_chunk, 2);
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/* Needed because miNE is not safe-to-copy */
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png_set_keep_unknown_chunks(png, PNG_HANDLE_CHUNK_ALWAYS,
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(png_bytep) "miNE", 1);
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/* Deal with unknown chunk location bug in 1.5.x and earlier */
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png_set_unknown_chunk_location(png, info, 0, PNG_HAVE_IHDR);
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png_set_unknown_chunk_location(png, info, 1, PNG_AFTER_IDAT);
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# if PNG_LIBPNG_VER < 10500
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/* PNG_AFTER_IDAT writes two copies of the chunk prior to libpng-1.5.0,
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* one before IDAT and another after IDAT, so don't use it; only use
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* PNG_HAVE_IHDR location. This call resets the location previously
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* set by assignment and png_set_unknown_chunk_location() for chunk 1.
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*/
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png_set_unknown_chunk_location(png, info, 1, PNG_HAVE_IHDR);
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# endif
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#endif
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The high-level write interface
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@ -4625,7 +4655,7 @@ Other rules can be inferred by inspecting the libpng source.
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XIV. Y2K Compliance in libpng
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April 26, 2013
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April 29, 2013
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Since the PNG Development group is an ad-hoc body, we can't make
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an official declaration.
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64
libpng.3
64
libpng.3
@ -1,4 +1,4 @@
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.TH LIBPNG 3 "April 26, 2013"
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.TH LIBPNG 3 "April 29, 2013"
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.SH NAME
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libpng \- Portable Network Graphics (PNG) Reference Library 1.5.16beta04
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.SH SYNOPSIS
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@ -492,7 +492,7 @@ Following is a copy of the libpng-manual.txt file that accompanies libpng.
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.SH LIBPNG.TXT
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Libpng-manual.txt - A description on how to use and modify libpng
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libpng version 1.5.16beta04 - April 26, 2013
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libpng version 1.5.16beta04 - April 29, 2013
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Updated and distributed by Glenn Randers-Pehrson
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<glennrp at users.sourceforge.net>
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Copyright (c) 1998-2013 Glenn Randers-Pehrson
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@ -503,7 +503,7 @@ Libpng-manual.txt - A description on how to use and modify libpng
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Based on:
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libpng versions 0.97, January 1998, through 1.5.16beta04 - April 26, 2013
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libpng versions 0.97, January 1998, through 1.5.16beta04 - April 29, 2013
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Updated and distributed by Glenn Randers-Pehrson
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Copyright (c) 1998-2013 Glenn Randers-Pehrson
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@ -523,9 +523,7 @@ Libpng-manual.txt - A description on how to use and modify libpng
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.SH I. Introduction
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This file describes how to use and modify the PNG reference library
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(known as libpng) for your own use. There are five sections to this
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file: introduction, structures, reading, writing, and modification and
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configuration notes for various special platforms. In addition to this
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(known as libpng) for your own use. In addition to this
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file, example.c is a good starting point for using the library, as
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it is heavily commented and should include everything most people
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will need. We assume that libpng is already installed; see the
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@ -3529,13 +3527,45 @@ from PNG time to an RFC 1123 format string.
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.SS Writing unknown chunks
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You can use the png_set_unknown_chunks function to queue up chunks
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for writing. You give it a chunk name, raw data, and a size; that's
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all there is to it. The chunks will be written by the next following
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png_write_info_before_PLTE, png_write_info, or png_write_end function.
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Any chunks previously read into the info structure's unknown-chunk
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list will also be written out in a sequence that satisfies the PNG
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specification's ordering rules.
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You can use the png_set_unknown_chunks function to queue up private chunks
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for writing. You give it a chunk name, location, raw data, and a size. You
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also must use png_set_keep_unknown_chunks() to ensure that libpng will
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handle them. That's all there is to it. The chunks will be written by the
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next following png_write_info_before_PLTE, png_write_info, or png_write_end
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function, depending upon the specified location. Any chunks previously
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read into the info structure's unknown-chunk list will also be written out
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in a sequence that satisfies the PNG specification's ordering rules.
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Here is an example of writing two private chunks, prVt and miNE:
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#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
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/* Set unknown chunk data */
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png_unknown_chunk unk_chunk[2];
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strcpy((char *) unk_chunk[0].name, "prVt";
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unk_chunk[0].data = (unsigned char *) "PRIVATE DATA";
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unk_chunk[0].size = strlen(unk_chunk[0].data)+1;
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unk_chunk[0].location = PNG_HAVE_IHDR;
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strcpy((char *) unk_chunk[1].name, "miNE";
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unk_chunk[1].data = (unsigned char *) "MY CHUNK DATA";
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unk_chunk[1].size = strlen(unk_chunk[0].data)+1;
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unk_chunk[1].location = PNG_AFTER_IDAT;
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png_set_unknown_chunks(write_ptr, write_info_ptr,
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unk_chunk, 2);
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/* Needed because miNE is not safe-to-copy */
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png_set_keep_unknown_chunks(png, PNG_HANDLE_CHUNK_ALWAYS,
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(png_bytep) "miNE", 1);
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/* Deal with unknown chunk location bug in 1.5.x and earlier */
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png_set_unknown_chunk_location(png, info, 0, PNG_HAVE_IHDR);
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png_set_unknown_chunk_location(png, info, 1, PNG_AFTER_IDAT);
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# if PNG_LIBPNG_VER < 10500
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/* PNG_AFTER_IDAT writes two copies of the chunk prior to libpng-1.5.0,
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* one before IDAT and another after IDAT, so don't use it; only use
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* PNG_HAVE_IHDR location. This call resets the location previously
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* set by assignment and png_set_unknown_chunk_location() for chunk 1.
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*/
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png_set_unknown_chunk_location(png, info, 1, PNG_HAVE_IHDR);
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# endif
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#endif
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.SS The high-level write interface
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@ -5118,7 +5148,7 @@ Other rules can be inferred by inspecting the libpng source.
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.SH XIV. Y2K Compliance in libpng
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April 26, 2013
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April 29, 2013
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Since the PNG Development group is an ad-hoc body, we can't make
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an official declaration.
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@ -5407,7 +5437,7 @@ possible without all of you.
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Thanks to Frank J. T. Wojcik for helping with the documentation.
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Libpng version 1.5.16beta04 - April 26, 2013:
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Libpng version 1.5.16beta04 - April 29, 2013:
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Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
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Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
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@ -5430,7 +5460,7 @@ this sentence.
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This code is released under the libpng license.
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libpng versions 1.2.6, August 15, 2004, through 1.5.16beta04, April 26, 2013, are
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libpng versions 1.2.6, August 15, 2004, through 1.5.16beta04, April 29, 2013, are
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Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
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distributed according to the same disclaimer and license as libpng-1.2.5
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with the following individual added to the list of Contributing Authors
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@ -5529,7 +5559,7 @@ certification mark of the Open Source Initiative.
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Glenn Randers-Pehrson
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glennrp at users.sourceforge.net
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April 26, 2013
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April 29, 2013
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.\" end of man page
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