Possible PNG bug IM 6.8.0.5 Q16 Mac OSX Snow Leopard

[fmw42]

IM 6.8.0.5 Q16 Mac OSX Snow Leopard

Gradients saved as PNGs are not appearing correct and have repeated patterns. They work fine with GIF and JPG.

convert -size 300x500 gradient: tmp.png
vs
convert -size 300x500 gradient: tmp.gif
convert -size 300x500 gradient: tmp.jpg

Similarly with radial-gradient

Note this was not an issue in IM 6.8.0.4 Q16. I just tested that and it looked fine.

[glennrp]

Something went wrong withreading and writing 16-bit images. I am seeing the
bug also, with Ubuntu-12.04 and IM-6.8.0-6 beta.

Code: Select all

convert -size 300x500 gradient: -depth 8 tmp.png

works OK (except that the PNG is darker than the GIF but that's another problem).

[edit] Reverting to coders/png.c from IM-6.8.0-4 does not fix the problem.
Rebuilding IM-6.8.0-4 with coders/png.c from IM-6.8.0-5 still works properly
It seems that 16-bit samples are in a different endian storage now. I am looking with
suspicion at the changes to magick/quantum.c, magick/quantum-import.c and
magick/quantum-export.c that occurred between -4 and -5.

[magick]

We can reproduce the problem and have a patch. Look for it in ImageMagick 6.8.0-6 Beta by sometime tomorrow.

[glennrp]

Fix is checked in to coders/png.c in SVN revision 10018 (IM6) and 10019 (IM7).

[fmw42]

verified that it is fixed in IM 6.8.0.6 Q16 Mac OSX Snow Leopard

[glennrp]

A fix for the too-dark PNG image mentioned above is fixed in
SVN revision 10061, IM-6.8.0-8.