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Imported from libpng-1.4.0beta33.tar
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Glenn Randers-Pehrson
89
libpng.3
89
libpng.3
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.TH LIBPNG 3 "August 19, 2008"
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.TH LIBPNG 3 "August 20, 2008"
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.SH NAME
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libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0beta32
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libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0beta33
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.SH SYNOPSIS
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\fI\fB
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@@ -128,10 +128,18 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0beta32
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\fI\fB
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\fBpng_uint_32 png_get_chunk_cache_max (png_structp \fIpng_ptr\fP\fB);\fP
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\fI\fB
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\fBpng_byte png_get_color_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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\fI\fB
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\fBpng_uint_32 png_get_compression_buffer_size (png_structp \fIpng_ptr\fP\fB);\fP
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\fI\fB
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\fBpng_byte png_get_compression_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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\fI\fB
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@@ -338,10 +346,6 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0beta32
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\fI\fB
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\fBpng_uint_32 png_get_compression_buffer_size (png_structp \fIpng_ptr\fP\fB);\fP
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\fI\fB
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\fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP
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\fI\fB
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@@ -446,6 +450,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0beta32
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\fI\fB
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\fBvoid png_set_chunk_cache_max (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIuser_chunk_cache_max\fP\fB);\fP
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\fI\fB
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\fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
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\fI\fB
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@@ -801,7 +809,7 @@ Following is a copy of the libpng.txt file that accompanies libpng.
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.SH LIBPNG.TXT
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libpng.txt - A description on how to use and modify libpng
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libpng version 1.4.0beta32 - August 19, 2008
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libpng version 1.4.0beta33 - August 20, 2008
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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) 1998-2005 Glenn Randers-Pehrson
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@@ -1103,29 +1111,6 @@ You must supply a function
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To inform libpng about your function, use
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png_set_read_status_fn(png_ptr, read_row_callback);
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.SS Width and height limits
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The PNG specification allows the width and height of an image to be as
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large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns.
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Since very few applications really need to process such large images,
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we have imposed an arbitrary 1-million limit on rows and columns.
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Larger images will be rejected immediately with a png_error() call. If
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you wish to override this limit, you can use
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png_set_user_limits(png_ptr, width_max, height_max);
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to set your own limits, or use width_max = height_max = 0x7fffffffL
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to allow all valid dimensions (libpng may reject some very large images
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anyway because of potential buffer overflow conditions).
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You should put this statement after you create the PNG structure and
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before calling png_read_info(), png_read_png(), or png_process_data().
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If you need to retrieve the limits that are being applied, use
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width_max = png_get_user_width_max(png_ptr);
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height_max = png_get_user_height_max(png_ptr);
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.SS Unknown-chunk handling
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Now you get to set the way the library processes unknown chunks in the
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@@ -1160,6 +1145,38 @@ instances of png_set_keep_unknown_chunks(), the final instance will
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take precedence. The IHDR and IEND chunks should not be named in
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chunk_list; if they are, libpng will process them normally anyway.
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.SS User limits
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The PNG specification allows the width and height of an image to be as
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large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns.
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Since very few applications really need to process such large images,
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we have imposed an arbitrary 1-million limit on rows and columns.
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Larger images will be rejected immediately with a png_error() call. If
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you wish to override this limit, you can use
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png_set_user_limits(png_ptr, width_max, height_max);
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to set your own limits, or use width_max = height_max = 0x7fffffffL
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to allow all valid dimensions (libpng may reject some very large images
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anyway because of potential buffer overflow conditions).
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You should put this statement after you create the PNG structure and
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before calling png_read_info(), png_read_png(), or png_process_data().
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If you need to retrieve the limits that are being applied, use
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width_max = png_get_user_width_max(png_ptr);
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height_max = png_get_user_height_max(png_ptr);
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The PNG specification sets no limit on the number of ancillary chunks
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allowed in a PNG datastream. You can impose a limit on the total number
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of sPLT, tEXt, iTXt, zTXt, and unknown chunks that will be stored, with
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png_set_chunk_cache_max(png_ptr, user_chunk_cache_max);
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where 0x7fffffffL means unlimited. You can retrieve this limit with
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chunk_cache_max = png_get_chunk_cache_max(png_ptr);
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.SS The high-level read interface
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At this point there are two ways to proceed; through the high-level
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@@ -3729,13 +3746,13 @@ application:
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.SH IX. Y2K Compliance in libpng
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August 19, 2008
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August 20, 2008
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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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This is your unofficial assurance that libpng from version 0.71 and
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upward through 1.4.0beta32 are Y2K compliant. It is my belief that earlier
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upward through 1.4.0beta33 are Y2K compliant. It is my belief that earlier
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versions were also Y2K compliant.
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Libpng only has three year fields. One is a 2-byte unsigned integer that
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@@ -3902,7 +3919,7 @@ the first widely used release:
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1.2.12 13 10212 12.so.0.12[.0]
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1.4.0beta9-14 14 10400 14.so.0.0[.0]
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1.2.13 13 10213 12.so.0.13[.0]
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1.4.0beta15-32 14 10400 14.so.0.0[.0]
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1.4.0beta15-33 14 10400 14.so.0.0[.0]
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Henceforth the source version will match the shared-library minor
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and patch numbers; the shared-library major version number will be
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@@ -3958,7 +3975,7 @@ 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 1.4.0beta32 - August 19, 2008:
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Libpng version 1.4.0beta33 - August 20, 2008:
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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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@@ -3979,7 +3996,7 @@ included in the libpng distribution, the latter shall prevail.)
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If you modify libpng you may insert additional notices immediately following
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this sentence.
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libpng versions 1.2.6, August 15, 2004, through 1.4.0beta32, August 19, 2008, are
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libpng versions 1.2.6, August 15, 2004, through 1.4.0beta33, August 20, 2008, 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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@@ -4078,7 +4095,7 @@ 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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August 19, 2008
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August 20, 2008
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.\" end of man page
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