Scripsit Sven Neumann

> If someone would write a PNG save plug-in that actually uses the
> full alpha channel information for indexed images,

One cannot do this, in general, because an indexed PNG stores a single
alpha value for each palette entry. An image with an unrestricted
alpha channel would most likely lead to more color/alpha combinations
than the 256 palette slots available in PNG.

> But it's more likely that we will soon drop indexed mode completely and
> push handling of indexed color to the load and save plug-ins.

I can see good software-engineering reasons to want to eliminate
indexed representation internally, but from a usability standpoint it
will be a loss not to be able to restrict the possible color values to
a predetermined palette.

Imagine finding out only after several hours of editing that some of
the pixels you intended to be (255,192,53) accidentally became
(255,192,54), and others became (255,188,53) and a few of the
(64,64,0) became (64,64,3), and this is a source of immense confusion
to software later your build process, which recognizes exactly those
colors to have a special meaning, and now you have to go through a few
dozen layers to find all of the misfit pixels and correct their color
one layer and color at a time. Indexed editing prevents making the
mistake in the first place; if I have not explicitly added
(255,192,54) to the palette I know that I'll not risk finding it in
the output.

Henning Makholm                                      "Punctuation, is? fun!"
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