Implement gdk-pixbuf loader

[ohwgiles]

Providing a gdk-pixbuf loader module means applications such as gpicview and pcmanfm automatically gain HEIF support.

There are probably some improvements to be made, it would be especially nice to use the embedded thumbnails, but application code doesn't seem to reliably indicate to gdk-pixbuf that a thumbnail could be returned

[farindk]

Thank you, this is great.

@fancycode : I guess we will have to put this into a separate package in order to remove the dependency on gdk-pixbuf for the main library. Can you have a look how to do this?

Note: we might also need a post-install script that runs

cache_file=`pkg-config gdk-pixbuf-2.0 --variable gdk_pixbuf_cache_file`
gdk-pixbuf-query-loaders >$cache_file

to immediately update the cache of existing loaders.

[farindk]

I have pulled this into the feature branch ohwgiles-feature/gdk-pixbuf where we can add the necessary changes.

To do:

• cmake: compilation should be optional
• autoconf: add compilation

[ohwgiles]

Thanks for the positive reception. I've added a commit to optionally compile the loader. I left it to default ON but maybe you want to change that.

I'm not sure I can help with the autoconf.

Regarding the post-install script to update the cache, I suggest this is better left to distributions, since as soon as you build deb/rpm/etc it has to be done differently, not to mention when cross-compiling.

[fancycode]

Thanks! I added support for autoconf/automake and integrated building with Travis CI in fcfed0a.

Travis: https://travis-ci.org/strukturag/libheif/builds/488412771
AppVeyor: https://ci.appveyor.com/project/strukturag/libheif/builds/22102433

Please cherry-pick this to your branch and also resolve the commented issues.

[fancycode]

Thanks! I added support for autoconf/automake and integrated building with Travis CI in fcfed0a.

Travis: https://travis-ci.org/strukturag/libheif/builds/488412771
AppVeyor: https://ci.appveyor.com/project/strukturag/libheif/builds/22102433

Please cherry-pick this to your branch and also resolve the commented issues.

[fancycode]

You mention GPL here (https://github.com/strukturag/libheif/pull/107/files#diff-6206122bfef85e4e34d08571ef26db03R169) but the file has a LGPL header, please either change the header to the GPL version or mention LGPL below. Also, please put a COPYING file in the gdk-pixbuf folder if it's GPL - similar to our examples which are MIT licensed or the GO code (which is GPL).

[ohwgiles]

My mistake - I intended LGPLv3. Fix pushed.

[fancycode]

This check is not needed. The subdirectory can determine if gdk-pixbuf is available and conditionally build it then.

[ohwgiles]

Well yes, but IMO it's nice to always be explicit about desired features and then use find_package(.. REQUIRED). Anyway this is also fine.

[fancycode]

I moved the GDK_PIXBUF_ENABLE_BACKEND define in the code to avoid duplication with the autoconf/automake scripts.

[ohwgiles]

👍

[fancycode]

Regarding the post-install script to update the cache, I suggest this is better left to distributions, since as soon as you build deb/rpm/etc it has to be done differently, not to mention when cross-compiling.

I agree, this is something that should be done by the packaging.

[fancycode]

@fancycode : I guess we will have to put this into a separate package in order to remove the dependency on gdk-pixbuf for the main library. Can you have a look how to do this?

Similar as we do with the thumbnailer: the package libgdk-pixbuf2.0-dev will be added as build-dependency and the resulting library will be put in a separate binary package that then has a dependency on the libheif package, libgdk-pixbuf2.0-0 and whatever else will be pulled in during linking. This (new) binary package will also run the post-install script to update the cache.

[farindk]

Yes, sounds good.

[fancycode]

Thanks for your contribution!