Release Note · Swift Toolkit Version 3.7.0

We are pleased to release the Readium Swift Toolkit 3.7.0. This update brings significant improvements to how comics are handled, improves performance for large documents, and streamlines our localization sources.

Release Note · Swift Toolkit Version 3.7.0


Browse the full release on GitHub

Improved reading for comics and image-based publications


This release focuses heavily on improving the reading experience for image-based publications. Firstly, we have added support for JXL (JPEG XL) bitmap images, allowing for high-quality images at smaller file sizes. Please note that JXL is decoded natively on iOS 17+.

Furthermore, you can now display Divina publications and CBZ files directly within the fixed-layout EPUB navigator. The toolkit now also recognizes EPUB files that consist solely of bitmap images and treats them as Divina publications. Additionally, we now extract metadata from ⁠ComicInfo.xml files in CBZ archives, ensuring better cataloging for comics.

Finally, we've introduced cover fallbacks. If a publication doesn’t have a declared cover, the toolkit will now automatically use the first resource in the reading order as the cover (provided it is a bitmap image).

Performance improvements for the Navigator

In this version, we've introduced a few improvements for the Navigator. First off, to prevent UI freezes when loading large files and for a smoother experience, PDF documents are now opened off the main thread.

Secondly, we’ve added a new⁠ offsetFirstPage preference for fixed-layout EPUBs. This gives you control over whether the first page appears alone or alongside the second page when spreads are enabled.

Enhanced metadata for audio publications


For those building audiobook experiences, we’ve improved metadata extraction for standalone audio files (e.g., MP3s). The parser now extracts  narrators and merges artist metadata into ⁠authors, aligning with conventions used by popular audiobook tools.

Technical updates and breaking changes

The 3.7.0 version of the toolkit comes with some important information to note.

  • Deployment target minimum: Please note that the minimum deployment target is now iOS 15.0.
  • Localization sources: We have moved our accessibility and LCP localized strings to the thorium-locales repository to centralize translation efforts.
  • LCP Dialog Redesign: The authentication dialog has been redesigned. This includes a breaking change regarding localization keys. If your app overrides these strings, please check the migration guide to update your key mappings.

For a complete list of all fixes, deprecations, and technical details, please view the release on GitHub. Many thanks to Mickaël MenuLeonard Beus and all our contributors for making this release possible!