Subject: bug#77104: 31.0.50; Transparent png image background is ignored in frames with alpha-background

From: Ihor Radchenko <[email-masked]>
Date: Wed, 19 Mar 2025 16:57:01 +0000

Alan Third <[email-masked]> writes:

> I think the problem is that Emacs has never handled image
> transparency, so it sets the transparent pixels of the image to the
> frame's background colour. There's quite a bit of fiddling to manage
> this with changing backgrounds and so on.
>
> I'm not sure what would be required for drawing transparent images to
> the glass. On NS I think it would be near trivial as the toolkit will
> handle it for us, but I don't know about others. For example I have a
> memory of being told that some terms don't clear under images so
> drawing a transparent image might show the previous pixels.

Then, how does :mask 'heuristic works? It somehow manages to set certain
pixels to be truly transparent. If so, why is it a problem setting
pixels that have transparent color in the image truly transparent in
exactly the same way?

-- 
Ihor Radchenko // yantar92,
Org mode maintainer,
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