Head's up for those that build Sigil from source

[KevinH]

Hi All,

The Epub 3.4 spec has introduced two new base image formats: avif and jxl.
Unfortunately Qt QImage has no support for either of them. And QtWebEngine/Chrome still has no out of the box support for the jxl format.

So if you look at our Sigil-Ebook repo, you will see a new repository called qtimageformats2.

In this repository we collected all the different repositories into one build to create Qt image plugins for both the avif and jxl formats. These plugins have been added to our official Qt builds for Windows and MacOS and so our next release will include them.

That means when Sigil-2.8.5 is officially released ImageTab AdjustImage and other tools that use QImage will now support those new avif and jxl formats for Read and Write.

That still leaves the issue of no jxl image support in QtWebEngine / Chrome / Electron, and thus in our Preview, View Image, etc.

To work around this until QtWebEngine reaches a Chrome build that actually supports jxl and turns it on (Chrome build 155) we are using our URLSchemeHandler to "polyfill" the jxl image by converting it on the fly behind the scenes to a PNG image (to assure no image degradation losses) for QtWebEngine.

Please note the epub itself and that jxl image are unchanged!

The png is just shown by Preview, nothing more. When an jxl image is asked for by QtWebEngine we deliver a png image instead so inside Preview everything works and you see the exact same thing you would have seen if jxl was supported in the QtWebEngine/Chrome.

So what does this mean for you ...

- the next release of Sigil will allow support for avif and jxl images as required by the Epub 3.4 spec.

From a building your own Sigil standpoint, you will need to use one of our recent Qt builds that has the new image format plugins installed, or if you build your own Qt, you will need to git clone:

https://github.com/Sigil-Ebook/qtimageformats2.git

Then try your own build of the plugins and then hand install them in your Qt builds *before* building Sigil.

Both DiapDealer and I would be happy to help you get initial builds of qtimageformats2 going to build the qavif and qjpegxl6 Qt image plugins if you decide to go that route.

Just post in this thread any questions or issues you run into.

For those of you that use my latest Qt6.10.2 builds on MacOS (downloaded from my personal BuildSigilOnMac release page) for your builds of Sigil, the plugins are already installed in that build and all should just work.

For those of you using DiapDealer's Windows Qt builds for your builds, just download the latest version in a few days (some kinks are still being worked out) and you should be good to go.

As for Linux builders: On recent Linux KDE distributions both jxl and avif qt plugins already exist and everything should just work. On other Linux distributions you should be able to build our qtimageformats2 repo out of the box with few issues.

Just post in this thread any questions or issues you run into.

Thanks!

[DiapDealer]

I'm pretty sure I have the Windows kinks worked out. For those who use my custom-built Qt6.10.2 for building Sigil on Windows, you'll need to download it again to get the support for avif and jxl.

https://github.com/dougmassay/win-qt...s/tag/v5.212-1

I changed the name slightly (so I don't get confused about what is what). On that release page, the archive you want is named Qt6.10.2ci_x64_VS2026a.7z

Yes... I just added an 'a' to it.

Pull the latest changes from Sigil's github repo to make sure your Sigil builds will incorporate the new plugins.

I'm working on getting the Linux AppImage up to speed as we speak.

[BeckyEbook]

I built it without any problems on Windows, and I can confirm that the AVIF and JXL images work.

[DiapDealer]

Great! Thanks for reporting back. I've got the Linux AppImage build updated and working as well.

[DNSB]

My build under Windows 11 allows me to insert JXL/AVIF images and they seem to display correctly if a bit slowly. OTOH, the Delete Unused Media Files tool will happily mark those files for deletion.

My latest test build for Windows can be downloaded from the link in the Downloading Sigil test builds for Windows thread.

My test ePub is attached to this message.