Images converter to JPEG XL

From the App Store Source

Image converter to JPEG XL - allows export images to JPEG XL from JPEG, JPEG2000, PNG, HEIC (HEIF), BMP, TIFF and GIF* files with customizable encoding options; - supports lossless transcoding of JPEG** files to JPEG XL, with size reduction and the ability to restore the original JPEG file back; - can use multi-threading (multitasking)***, significantly increasing the processing speed; - processes files locally on your device, so it respects your privacy and security; - advertising-free; - without collecting personal data; - lightweight, based on native technologies without third-party dependencies; - has a simple, minimalist interface. Warnings! JPEG XL is a relatively new format and converters for it are still under active development. The app has known and still unsolved limitations: *The app will not create an animated image from a GIF file. **Metadata of source images are preserved only in "Lossless JPEG transcoding" mode for source JPEG files, in other cases metadata will be ignored. ***RAM consumption by the encoder on which this app relies in some modes for some large images may be higher than the limit available on some devices. Therefore, multithreading and the ability to reduce the quality (fixed unchangeable value 100% - highest quality) of output images will not be available on some devices. Uninstalling this app will also delete the folder of this app displayed in the Files app, so before uninstalling the app, make sure that you have moved your necessary converted files to another safe location!

Every number in these answers comes from the data shown above on this page.