windowscodecs: read PNGs sequentially

Damjan Jovanovic damjan.jov at
Tue Oct 4 09:44:46 CDT 2011

* windowscodecs: read PNGs sequentially

In #24568, I found certain PNGs that won't open in Wine and some Linux
applications, but will open in Windows and other Linux applications.
Investigating the applications that opened it successfully showed that
they use push-model/progressive PNG parsing. I found that fixes Wine
too and, incorrectly believing that was the problem, submitted
d53e1a71f48e1456cd99965fdf0f40eeb805b8e3. But as my comments 6 and 7
to #24568 showed, that patch still didn't fix the problem on x86_64,
and I began to suspect an Ubuntu or libpng bug.

The PNG in question does open with all Linux applications in Ubuntu
11.04, thus proving it was an Ubuntu or libpng bug. But the push-model
parsing patch to Wine seems to have regressed parsing certain other
PNGs in #27635, leading to images that come out vertically squashed
(probably due to interlacing?).

This patch thus reinstates the original simple correct sequential
parsing which was never a problem, closes #27635, and subtracts 1 from ;-).

Damjan Jovanovic
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