bug#18333: 24.3.93; ImageMagick: ICO image in multiple sizes is not shown correctly

[Lars Ingebrigtsen]

YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp> writes:

> 4. Invoke Emacs and evaluate the following expression in *scratch*:
>
>     (let (sizes)
>       (dotimes (i 3)
>       (push (image-size
>              (create-image "~/wikipedia.ico" 'imagemagick nil :index i) t)
>             sizes))
>       sizes)
>
>    The expected result is ((16 . 16) (32 . 32) (48 . 48)) or its
>    permutation, but the actual one is ((16 . 16) (16 . 16) (16 . 16)).

This bug is still present in Emacs 27.

imagemagick_compute_animated_image (which gets the data out of
multi-image files) assumes that all the images have the same size,
because it was written to handle animated GIFs (where this is the
case).  But for ico files, the logic is wrong.

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