Quoting j_mach_wust j_mach_wust <[EMAIL PROTECTED]>:

saulgoode wrote:

It works by replacing the non-transparent portion of
each layer with the result of merging the layer with
the layers below (actually the "projection" of the
layers below it).

That sounds as if it's still impossible to preserve
semi-transparency while converting to indexed in the

It is impossible to preserve semi-transparency for GIF files in general; the format does not permit it. The GIF file specification permits ONE color to be treated as a "skip this pixel entirely", there is no allowance for any partially transparent pixels. This has nothing to do with the GIMP, it is a limitation of the file format.

Matthias Julius wrote:

How much does this reduce the file size?

I don't remember exactly, but I thought I tried it and
it significantly reduced the file size, so therefore I
kept doing it.

I'm confused now.

The PNG file format specification permits a similar indexed encoding scheme as the GIF format; thus a PNG file should, at a minimum, be able to replicate the GIF file's compression ratio. Some image programs (Photoshop, for example) *used to* inefficiently convert indexed images to 24-bit RGB PNGs which resulted in dramatic increases in file size. This was done at a time when those programs did not fully support the PNG specification, I very much doubt that any software suffers from this lapse anymore (well, maybe some of Microsoft's offerings).
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