feat: added support for SVG image sequence with lst files

[rodolforg]

with the fix provided by PR #2789 (commit 25f28b1),
it was finally viable to implement this (simple) feature :)

fix #965

[ice0]

Merged. Thank you!

[ice0]

@rodolforg
Forgot to ask: does this function only work when mod_imagemagick is enabled?

[rodolforg]

Yes

[rodolforg]

Same for tiff.
Ppm can be with imagemagick or mod_ppm
Jpeg can be with imagemagick or mod_jpeg

[rodolforg]

As alternative we could have ffmpeg (if compiled with librsvg support) or create a Magick++ importer

[rodolforg]

Should I create a Magick++ importer?

[ice0]

Should I create a Magick++ importer?

I was planning to discuss switching from ImageMagick to GraphicsMagick because we have issues with ImageMagick on Windows and macOS (or maybe add a mod_graphicsmagick as alternative).

The Autotools build currently does not work on macOS because ImageMagick adds -omp flags that cannot be handled correctly by libtool/clang toolchain. This can be solved by switching to GCC compiler for autotools build, but I prefer to use clang on macOS (since it's a native compiler). Anyway CMake build works fine so it's not a critical issue.

Another issue is broken MSYS2 and macOS builds (with latest ImageMagick). This can be resolved by adding tests to MSYS2/Homebrew so they can't update ImageMagick until issue is fixed.

Also I am not sure if switching to GraphicsMagick will fix this issues.

So yes, it would be a nice feature if you're interested, but we can skip it if it's too complicated.