Please see the release notes for v1.21.0: https://github.com/strukturag/libheif/releases/tag/v1.21.0 This patch release only fixes a build error with some GCC versions because of a missing `#include`. If you didn't get any build error, you do not need this updated patch release.

Fixes a bug in decoder plugin loading. If you don't use plugins, you don't need this patch release.

Sequences: - API for reading and writing image sequences. Currently only intra-coded sequences are supported. Support for sequences with inter-prediction will be added soon. - API for reading and writing metadata sequences. The metadata tracks can contain any raw timed data. - Support for SAI (sample auxiliary information). Timed samples (from image sequences or metadata) can have auxiliary data attached. Currently we support TAI timestamps and GIMI content description IDs. - Support for track references. - The API for sequences is described here: https://github.com/strukturag/libheif/wiki/Reading-and-Writing-Sequences Other new features: - You can specify a security limit for the maximum total memory libheif may use for decoding. This is easier to handle than specifying limits on the maximum image size or single memory allocations. - Support for TAI timestamps (in images and sequences) has been promoted from experimental to stable. - FFMPEG plugin now supports HDR decoding - Header files are now split into individual headers by topic. However, it should still be backwards compatible with `heif.h` being a catch-all covering the old content. For new functionality (sequences, TAI), you will need to include the specific headers. - All struct names of the API are now also typedefs.

- Set `essential` flag for transformative properties as required by MIAF. This fixes the display of AVIF images with transformations encoded by libheif in Chrome, which checks whether this flag is set. This mainly affected images encoded by ImageMagick. - If the environment variable `LIBHEIF_SECURITY_LIMITS` is set to `OFF`, libheif will not check any security limits. This can be used if a user works with large images and the application software does not allow to adjust the libheif security limits. - Resolved processing 16-bit JPEG-2000

Fixes a build error with SVT-AV1 encoder plugin when using reduced symbol visibility (#1480).

Bugfix release. Additionally, there are the following changes: - C++ and Go wrapper licenses have been changed to MIT - supports SVT-AV1 v3.0.0 encoder - support emscripten builds for ES6 modules

fix `heif_image_handle_is_premultiplied_alpha()` #1394

- fixes a race condition that may lead to some image tiles not being included in the output image (#1379) - fix a potential crash when querying overlay image information Because of the first issue, I strongly recommend to upgrade to v1.19.3.