Update libvips to v8.12.2 and enable ImageMagick API bindings

[erichmachado]

This should fix processing Gif images.

Related issue:

libvips/libvips#2574

[matthewford]

Within the issue #16 , there is talk about not using the imagemagic bindings and using cgif instead

[erichmachado]

Within the issue #16 , there is talk about not using the imagemagic bindings and using cgif instead

Hi @matthewford, thank you for pointing that out.

I saw that issue also, but since apparently there is no cgif package available for the platform versions supported here, one way to support those images without static linking that library is by enabling the Magick API bindings so that Vips is at least able to fallback to it correctly. See this comment.

Since ImageMagick is already provided by Heroku, I imagine that this would be a low-effort solution to support these images in those platform versions. We could then handle migrating to cgif/libspng as a separate effort.

[brandoncc]

This is great @erichmachado, thank you for putting in the work here. I'd really rather use cgif instead of libmagick, since that is what John recommends and it has better performance and output quality. Is there any reason that we would want to support libmagick other than fixing gif saving?

[brandoncc]

I'm going to go ahead and merge this, as I agree with your idea of migrating to cgif/libspng as a separate effort. Thanks again for the work you have done.