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[devel] Updated commentary about the png_rgb_to_gray() default coefficients

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Glenn Randers-Pehrson 2011-07-29 12:31:16 -05:00
parent b17c75b222
commit 6c98897a64
4 changed files with 35 additions and 13 deletions
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6
ANNOUNCE
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@ -1,5 +1,5 @@
Libpng 1.5.5beta04 - July 28, 2011 Libpng 1.5.5beta04 - July 29, 2011
This is not intended to be a public release. It will be replaced This is not intended to be a public release. It will be replaced
within a few weeks by a public version or by another test version. within a few weeks by a public version or by another test version.
@ -40,8 +40,10 @@ Version 1.5.5beta03 [July 27, 2011]
changes to pngrutil.c to cast results where C++ expects it but C does not. changes to pngrutil.c to cast results where C++ expects it but C does not.
Minor editing of libpng.3 and libpng-manual.txt. Minor editing of libpng.3 and libpng-manual.txt.
Version 1.5.5beta04 [July 28, 2011] Version 1.5.5beta04 [July 29, 2011]
Revised CMakeLists.txt (Clifford Yapp) Revised CMakeLists.txt (Clifford Yapp)
Updated commentary about the png_rgb_to_gray() default coefficients
in the manual and in pngrtran.c
Send comments/corrections/commendations to png-mng-implement at lists.sf.net: Send comments/corrections/commendations to png-mng-implement at lists.sf.net:
(subscription required; visit (subscription required; visit

4
CHANGES
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@ -3524,8 +3524,10 @@ Version 1.5.5beta03 [July 27, 2011]
changes to pngrutil.c to cast results where C++ expects it but C does not. changes to pngrutil.c to cast results where C++ expects it but C does not.
Minor editing of libpng.3 and libpng-manual.txt. Minor editing of libpng.3 and libpng-manual.txt.
Version 1.5.5beta04 [July 28, 2011] Version 1.5.5beta04 [July 29, 2011]
Revised CMakeLists.txt (Clifford Yapp) Revised CMakeLists.txt (Clifford Yapp)
Updated commentary about the png_rgb_to_gray() default coefficients
in the manual and in pngrtran.c
Send comments/corrections/commendations to png-mng-implement at lists.sf.net Send comments/corrections/commendations to png-mng-implement at lists.sf.net
(subscription required; visit (subscription required; visit

15
libpng-manual.txt
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@ -1,6 +1,6 @@
libpng-manual.txt - A description on how to use and modify libpng libpng-manual.txt - A description on how to use and modify libpng
libpng version 1.5.5beta04 - July 28, 2011 libpng version 1.5.5beta04 - July 29, 2011
Updated and distributed by Glenn Randers-Pehrson Updated and distributed by Glenn Randers-Pehrson
<glennrp at users.sourceforge.net> <glennrp at users.sourceforge.net>
Copyright (c) 1998-2011 Glenn Randers-Pehrson Copyright (c) 1998-2011 Glenn Randers-Pehrson
@ -11,7 +11,7 @@ libpng-manual.txt - A description on how to use and modify libpng
Based on: Based on:
libpng versions 0.97, January 1998, through 1.5.5beta04 - July 28, 2011 libpng versions 0.97, January 1998, through 1.5.5beta04 - July 29, 2011
Updated and distributed by Glenn Randers-Pehrson Updated and distributed by Glenn Randers-Pehrson
Copyright (c) 1998-2011 Glenn Randers-Pehrson Copyright (c) 1998-2011 Glenn Randers-Pehrson
@ -1677,8 +1677,17 @@ space, as recommended in the Charles Poynton's Colour FAQ,
<http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9> <http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9>
Y = 0.2126 * R + 0.7152 * G + 0.0722 * B
Previous versions of this document, 1998 through 2002, recommended a slightly
different formula:
Y = 0.212671 * R + 0.715160 * G + 0.072169 * B Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
Libpng uses an integer approximation:
Y = (6968 * R + 23434 * G + 2366 * B)/32768
The calculation is done in a linear colorspace, if the image gamma The calculation is done in a linear colorspace, if the image gamma
can be determined. can be determined.
@ -4500,7 +4509,7 @@ Other rules can be inferred by inspecting the libpng source.
XIV. Y2K Compliance in libpng XIV. Y2K Compliance in libpng
July 28, 2011 July 29, 2011
Since the PNG Development group is an ad-hoc body, we can't make Since the PNG Development group is an ad-hoc body, we can't make
an official declaration. an official declaration.

23
libpng.3
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@ -1,4 +1,4 @@
.TH LIBPNG 3 "July 28, 2011" .TH LIBPNG 3 "July 29, 2011"
.SH NAME .SH NAME
libpng \- Portable Network Graphics (PNG) Reference Library 1.5.5beta04 libpng \- Portable Network Graphics (PNG) Reference Library 1.5.5beta04
.SH SYNOPSIS .SH SYNOPSIS
@ -955,7 +955,7 @@ Following is a copy of the libpng-manual.txt file that accompanies libpng.
.SH LIBPNG.TXT .SH LIBPNG.TXT
libpng-manual.txt - A description on how to use and modify libpng libpng-manual.txt - A description on how to use and modify libpng
libpng version 1.5.5beta04 - July 28, 2011 libpng version 1.5.5beta04 - July 29, 2011
Updated and distributed by Glenn Randers-Pehrson Updated and distributed by Glenn Randers-Pehrson
<glennrp at users.sourceforge.net> <glennrp at users.sourceforge.net>
Copyright (c) 1998-2011 Glenn Randers-Pehrson 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: Based on:
libpng versions 0.97, January 1998, through 1.5.5beta04 - July 28, 2011 libpng versions 0.97, January 1998, through 1.5.5beta04 - July 29, 2011
Updated and distributed by Glenn Randers-Pehrson Updated and distributed by Glenn Randers-Pehrson
Copyright (c) 1998-2011 Glenn Randers-Pehrson Copyright (c) 1998-2011 Glenn Randers-Pehrson
@ -2632,8 +2632,17 @@ space, as recommended in the Charles Poynton's Colour FAQ,
<http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9> <http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9>
Y = 0.2126 * R + 0.7152 * G + 0.0722 * B
Previous versions of this document, 1998 through 2002, recommended a slightly
different formula:
Y = 0.212671 * R + 0.715160 * G + 0.072169 * B Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
Libpng uses an integer approximation:
Y = (6968 * R + 23434 * G + 2366 * B)/32768
The calculation is done in a linear colorspace, if the image gamma The calculation is done in a linear colorspace, if the image gamma
can be determined. can be determined.
@ -5456,7 +5465,7 @@ Other rules can be inferred by inspecting the libpng source.
.SH XIV. Y2K Compliance in libpng .SH XIV. Y2K Compliance in libpng
July 28, 2011 July 29, 2011
Since the PNG Development group is an ad-hoc body, we can't make Since the PNG Development group is an ad-hoc body, we can't make
an official declaration. an official declaration.
@ -5715,7 +5724,7 @@ possible without all of you.
Thanks to Frank J. T. Wojcik for helping with the documentation. Thanks to Frank J. T. Wojcik for helping with the documentation.
Libpng version 1.5.5beta04 - July 28, 2011: Libpng version 1.5.5beta04 - July 29, 2011:
Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc. Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net). Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
@ -5738,7 +5747,7 @@ this sentence.
This code is released under the libpng license. This code is released under the libpng license.
libpng versions 1.2.6, August 15, 2004, through 1.5.5beta04, July 28, 2011, are libpng versions 1.2.6, August 15, 2004, through 1.5.5beta04, July 29, 2011, are
Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
distributed according to the same disclaimer and license as libpng-1.2.5 distributed according to the same disclaimer and license as libpng-1.2.5
with the following individual added to the list of Contributing Authors with the following individual added to the list of Contributing Authors
@ -5837,7 +5846,7 @@ certification mark of the Open Source Initiative.
Glenn Randers-Pehrson Glenn Randers-Pehrson
glennrp at users.sourceforge.net glennrp at users.sourceforge.net
July 28, 2011 July 29, 2011
.\" end of man page .\" end of man page