bug#65188: 29.1; WEBP image not displayed

[Eli Zaretskii <eliz@gnu.org>]

> From: Corwin Brust <corwin@bru.st>
> Date: Thu, 10 Aug 2023 02:24:38 -0500
> Cc: awrhygty@outlook.com, 65188@debbugs.gnu.org
> 
> On Thu, Aug 10, 2023 at 1:34 AM Eli Zaretskii <eliz@gnu.org> wrote:
> >
> > > From: awrhygty@outlook.com
> > > Date: Thu, 10 Aug 2023 09:20:52 +0900
> > >
> > >
> > > I installed emacs 29 from:
> > >   https://ftp.gnu.org/gnu/emacs/windows/emacs-29/emacs-29.1_1-installer.exe
> > > When find-file with WEBP images, they are not displayed visually,
> > > and emacs reports:
> > >   Cannot display image: (Invalid image specification)
> > > There exists c:/Emacs/emacs-29.1/bin/libwebp-7.dll in the same directory
> > >  of emacs.exe.
> > >
> > > image-types
> > > => (bmp svg webp png gif tiff jpeg xpm xbm pbm)
> > > (image-type-available-p 'webp)
> > > => nil
> >
> > This might mean your libwebp-7.dll is incompatible with Emacs you have
> > (e.g., it's a 32-bit DLL, not 64-bit DLL), or Emacs cannot load it for
> > some other reason.
> >
> > Corwin, can you please verify that the binary on the GNU FTP site can
> > display WebP images when a suitable libwebp DLL is available?  The
> > Emacs 29.1 I built myself here is definitely capable of displaying
> > WebP images.
> >
> 
> Yes, AFAICT it is working as expected. I used ProcessExplorer
> (filtering on Emacs then Search | DLL for the webp) to check Emacs
> really used the DLL  from the full-zip.  I did this from
> emacs-29.1_1.zip from GNU FTP (after first doing the same steps using
> my local "cache" of the last release  build's PREFIX folder, keep
> around for this sort of question).
> 
> Predictably:
> (image-type-available 'webp) => t, over here

Thanks.  So this leaves us with the other possibility: that
libwebp-7.dll on the OP's machine is the cause of the problem.  Where
did you download that DLL?