gif output and transparency - ImageMagick 6.6.4-1 fedora 14

[jbh97]

Hello - this is my first post here so firstly - thanks for the incredibly useful software!

I'm having an issue with gif transparency...which I am hoping someone can confirm as a bug or user error (I am assuming the first as previous versions of imagemagick seemed to behave differently)....

Previously (eg with ImageMagick 6.4.0) when converting from pngs to gifs eg

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convert right.png right.gif

or manipulating gifs eg:

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convert right.gif -transparent white right.gif

would yield a gif with suitable transparency. But using the latest fedora 14 binary release (ImageMagick 6.6.4-1 2010-10-05 Q16) yields a gif with an opaque (white) background. I cannot seem to find a recipie to output a gif with any transparency.....

example
input png
output of convert right.png right.gif:

Bug or user error? If a bug - is there a workaround?

Thanks in advance

[anthony]

There certainally seems to be a bug.

The GIF loses transparency when I do...

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convert right.png right.gif

But converting to MIFF and displaying shows the MIFF still has transparency.

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convert right.png right.miff

Doing the same though MIFF however does NOT fix the problem

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convert right.png right.miff
convert right.miff right.gif

The MIFF shows a transparent background, but the GIF does not!

So whatever is the problem is still present in the MIFF intermediate file format.
As that format has a text based header for ALL image meta data it much be one of the following...

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sed -n '/^\f$/q; p' right.miff

id=ImageMagick version=1.0
class=DirectClass colors=0 matte=True
columns=16 rows=16 depth=8
colorspace=RGB
compression=Zip quality=0
units=PixelsPerCentimeter
resolution=35.43x35.43
page=16x16+0+0
date:create={2010-11-15T13:56:57+10:00}
date:modify={2010-11-15T13:56:57+10:00}
Software={www.inkscape.org}

As you can see transparency is enabled 'matte=True', But I can not see anything else that could be causing the save to GIF to fail. Everything about the header appears right!

Trying a different tack... using 'txt' image to remove all meta data!

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convert right.png right.txt
convert right.txt right.gif

I still get a GIF without transparency!
And yet the 'IM Enumerated Text Image' file clearly shows pixels with transparency.


Basically I can prettywell be assured that the GIF save for this image and just the image data, is causing it to 'loose transparency. No meta-data is causing the problem.


This is definitely a BUG! but it is only involving image data, not meta-data.

[magick]

We can reproduce the problem you posted and have a patch in ImageMagick 6.6.5-9 available by sometime tomorrow. Thanks.