GIMP 2.10.2 just got support for the new image format HEIF, derived by H.265, via libheif. Would be pretty nice to be able to view HEIF pictures in Gwenview too.
Seems the hype (GIMP, Krita, …) is reaching Gwenview ;) Nevertheless, is there any reason this needs specific support inside Gwenview? Normally we simply make use of the image read/write support https://doc.qt.io/archives/qt-5.10/qtimageformats-index.html and https://phabricator.kde.org/source/kimageformats/ are providing. Adding format support upstream is also needed for proper thumbnail support in Dolphin and elsewhere too. That said, that's for the static image portion. Not sure yet about the "image sequences" part, perhaps this can be handled like GIFs and other animations are handled currently (i.e. also via QImage). See also digiKam's Bug 393408.
digiKam just implemented HEIF support. I'm guessing they implemeted it themselves without adding support to KImageFormats?
I've added code for HEIF support in this pull request: https://invent.kde.org/frameworks/kimageformats/-/merge_requests/1
*** Bug 423687 has been marked as a duplicate of this bug. ***
https://invent.kde.org/frameworks/kimageformats/-/merge_requests/1
https://invent.kde.org/frameworks/kimageformats/-/merge_requests/16