bug#28692: Emacs fails to display images

[Diego Nicola Barbato <dnbarbato@posteo.de>]

Hello Ludo,

ludo@gnu.org (Ludovic Courtès) writes:

> Hello Diego,
>
> Diego Nicola Barbato <dnbarbato@posteo.de> skribis:
>
>> Several of emacs image related features have stopped working properly:
>> * Eww does not render images showing empty squares instead.
>> * When visiting an image in a buffer and pressing n to visit the next
>>   image the next image is either not displayed at all (showing an empty
>>   square instead) or a thumbnail sized version is displayed.
>> * Transformations such as "Fit to Window Width" or "Rotate Image" do not
>>   work at all. The following error message is displayed instead:
>>   ImageMagick error: no decode delegate for this image format `PBM' @
>>   error/constitute.c/ReadImage/504
>>   (This happens with all image formats not just .pbm)
>
> Indeed, I experience this with DocView as well (when resizing), which
> leads to:
>
>   ImageMagick error: no decode delegate for this image format `PNG' @ error/constitute.c/ReadImage/504
>
> Could it be a CLI change in ImageMagick?  The package was upgraded in
> 87a9c53b7ca08bd490c94fe5579c3f26c19be78c.
>
> Ludo’.

I believe the bug was introduced in
030030f4416b54285dcdd58bddb863c0e6bda4c4. It appears to be a known bug
in ImageMagick (https://github.com/ImageMagick/ImageMagick/issues/825),
which was already present in version 6.9.9-15.
It has been fixed in version 6.9.9-18
(https://github.com/ImageMagick/ImageMagick/blob/ImageMagick-6/ChangeLog).

Diego