bug#59242: 29.0.50; Poor quality for WebP images

[Eli Zaretskii]

> Cc: 59242@debbugs.gnu.org, Evgeny Zajcev <lg.zevlg@gmail.com>
> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Mon, 14 Aug 2023 02:11:56 +0200
> 
> Po Lu <luangruo@yahoo.com> writes:
> 
> > > Evgeny Zajcev <lg.zevlg@gmail.com> writes:
> >
> > > Looks like partial transparency is incorrectly applied for webp images.
> 
> Thanks for the bug report.
> 
> > Stefan, I see the following code in image.c:
> [...]
> > So if the webp library does not blend itself, I think we will have to do
> > that for it.  Am I missing anything here?
> 
> Yes, the old code was not right.  The attached patch should add proper
> alpha blending for webp images.  I have tested it with the example
> images here: https://developers.google.com/speed/webp/gallery2
> 
> Evgeny, could you please test this patch and report back?  It should
> apply cleanly both against master and emacs-29.

Thanks, but please install this on master, not on the emacs-29 branch,
even if this patch does work.  It's too late for such changes on the
release branch.