This is a summary of Bug 352262 – 32bit bitmaps (*.bmp) appear blank (
http://bugzilla.gnome.org/show_bug.cgi?id=352262 ) which as Sven said
is important to be settled before releasing 2.4 version.
After bmp plug-in has been updated it, among other things, started
parsing bytes which were thought to be alpha channel. When bitmap
contained valid alpha data in these bytes (which can be created with
PS or some other app), this feature worked as expected. However, when
bitmap was saved in 32 bit format without alpha, all those bytes
became 0. As the result, image appeared completely blank on the
The main question: should those bytes be ignored (as it is done by
many applications) or should some workaround be used (in case we want
to support 32bit bitmaps with alpha channel)?
Unfortunately, we were unable to find any official documentation
dealing with the problem.
Programming Windows, 5th Edition (Charles Petzold - MS Press, 1998)
tells that those bytes should be 0. In other words, they should be
ignored while loading and set to 0 while saving.
P.S. Results of the discussion could be useful when solving Bug 65534.
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