bug#47040: 27.1; PNG binary transparency is ignored

[Lars Ingebrigtsen]

ynyaaa@gmail.com writes:

> Red pixels in the both images have 0 for alpha value, so they should be
> transparent and invisible, but transparent1.png is displayed as a red
> square with a green frame in a emacs buffer.
>
> transparent2.png is displayed as a white square with a green frame as
> expected.
>
> When they are displayed in a chrome browser, inner squares of the both
> images are displayed as transparent.

I'm unable to reproduce this in Emacs 27.1 in Debian/bullseye, so this
may be a Windows-specific problem.  It may also be fixed in Emacs 28,
since the transparency code has gotten a lot of work.  Would it be
possible for you to check in Emacs 28 whether this problem is still
present there?

If not, can somebody else with Windows and Emacs 28 check whether the
problem is still present?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no