#267 Transparency lost when converting from GIF to PNG

[Jacob Page]

When converting a transparent GIF to a PNG, the resulting PNG loses the transparency. This is only occurring when no resize is performed.

Command to reproduce:

gm convert Apple_transparent.gif -type Palette -colors 256 Test.PNG

The sample file is attached.

[Glenn Randers-Pehrson]

Shouldn't you have used "-type PaletteMatte" instead of "-type Palette"? The type Palette is opaque.

Hmm, I just tried that, and also simple
"gm convert Apple_transparent.gif Test.PNG" and
"gm convert Apple_transparent.gif -matte Test.PNG" and in all cases transparency was lost. So there's a bug here.

[Juraj Komacka]

seems like a regression to me "gm convert Apple_transparent.gif Test.PNG" (binary equal with outputs using -matte) produces different output for

• gm 1.3.12 2010-03-08 Q8 with libpng 1.2.46 (Ubuntu 12.04) - Test_1.3.12.PNG (fine)
• gm 1.3.16 2012-06-23 Q8 with libpng 1.2.49-1 (Debian Wheezy 7.1) - Test_1.3.16.PNG (wrong)

[Bob Friesenhahn]

I am able to reproduce this problem with 1.3.20.

[Glenn Randers-Pehrson]

I have pushed a fix to the mercurial repository ( http://sourceforge.net/p/graphicsmagick/code/ci/b702174de86ec43450f9201d48c98c407c2662ef/ )

[Bob Friesenhahn]

The problem seems to be gone now. All of the GM tests are passing, including running under valgrind.

[Bob Friesenhahn]

Closing as fixed.