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Re: fixing PNG images
From: |
Werner LEMBERG |
Subject: |
Re: fixing PNG images |
Date: |
Thu, 23 May 2013 18:42:36 +0200 (CEST) |
>> Note that libpng comes with a tool called `png-fix-too-far-back' to
>> fix such errors in PNG files. Is it OK to update all PNG files in
>> the lilypond repository? I've been able to successfully continue
>> compilation with the current SVN TeXlive binaries after running
>> this program on all PNG images.
>
> How did the problematic PNG files come about?
This is a good question. IIRC, the libpng people say that a
yet-to-be-identified program or library creates such faulty PNG
files. From the manual:
Libpng-1.6.0 and later use the CMF bytes at the beginning of the
IDAT stream to set the size of the sliding window for reading
instead of using the default 32-kbyte sliding window size. It was
discovered that there are hundreds of PNG files in the wild that
have incorrect CMF bytes that cause libpng to now issue a "too far
back" error and reject the file. Libpng-1.6.3 provides a way to
revert to the libpng-1.5.x behavior (ignoring the CMF bytes and
using a 32-kbyte sliding window), and provides a tool
(contrib/tools/png-fix-too-far-back) for optimizing the CMF bytes
correctly.
Werner
- fixing PNG images, Werner LEMBERG, 2013/05/23
- Re: fixing PNG images, David Kastrup, 2013/05/23
- Re: fixing PNG images,
Werner LEMBERG <=
- Re: fixing PNG images, Werner LEMBERG, 2013/05/26
- Re: fixing PNG images, Phil Holmes, 2013/05/26
- Re: fixing PNG images, Graham Percival, 2013/05/26
- Re: fixing PNG images, Werner LEMBERG, 2013/05/26
- Re: fixing PNG images, Phil Holmes, 2013/05/26
- Re: fixing PNG images, Phil Holmes, 2013/05/27
- Re: fixing PNG images, Werner LEMBERG, 2013/05/27