libavif

libavif decodes AVIF images to premultiplied RGBA8 pixels from Dart. The package builds libavif and its decoder from source through Dart native assets; applications do not download or bundle repository-hosted prebuilt binaries.

The decoder backend is dav1d, with libyuv accelerating supported YUV-to-RGBA conversions. The package does not link libaom or fall back to a platform decoder.

final bytes = await File('image.avif').readAsBytes();
final frame = await Avif.decode(bytes);

print('${frame.width} × ${frame.height}');
print(frame.pixels); // Premultiplied RGBA8.

Avif.decode runs on a bounded pool of persistent native workers, keeping codec CPU work off the calling isolate without creating an isolate for each image. Avif.startDecode exposes cancellation for scrollable or otherwise short-lived consumers. Avif.decodeSync is available for worker isolates and command-line pipelines that already control scheduling. All three accept AvifDecodeOptions with explicit thread, dimension, and pixel limits.

Call await Avif.warmUp() during application startup to prepare that worker pool off the calling isolate before the first image is requested. Repeated calls share one initialization.

Use targetWidth and targetHeight to scale during native decode, before the RGBA allocation. Decoded pixels transfer directly into a finalizer-owned Dart view without a second pixel-buffer copy:

final thumbnail = await Avif.decode(
  bytes,
  targetWidth: 256,
  targetHeight: 256,
);

Supplying one target dimension preserves aspect ratio. Supplying both requests that exact size. Source dimensions and target dimensions remain subject to the configured safety limits.

Animated and still images share the stateful sequence API:

final decoder = await AvifSequenceDecoder.open(bytes, targetWidth: 256);
try {
  print(decoder.info.frameCount);
  print(decoder.info.repetition);
  AvifSequenceFrame? frame;
  while ((frame = await decoder.nextFrame()) != null) {
    render(frame!.image.pixels, duration: frame.duration);
  }
  await decoder.reset(); // Rewind for another playback.
} finally {
  decoder.dispose();
}

Set prefetchFirstFrame: true when the first frame will be consumed immediately. Opening then decodes frame zero in the same native worker job, and the first nextFrame call returns it without another queue round trip.

The decoder preserves per-frame timing and finite, infinite, or unknown repetition metadata. It owns its encoded input until dispose, serializes frame operations through the bounded native worker pool, and supports cancellation while opening. Avif.decode remains deliberately static-only so callers cannot accidentally reduce an animation to its first frame.

Avif.nativeVersion, Avif.nativeCodecVersions, and Avif.nativeFeatures report the exact linked build. This source release reports libyuv:1924 as a required acceleration feature.

Render transforms that would change the displayed image fail with AvifErrorCode.unsupported. Web is not supported by this native-assets package.

The vendored libavif source is version 1.4.2. The vendored dav1d source is version 1.5.4, and libyuv is the exact revision pinned by libavif 1.4.2. All retain their BSD licenses in the vendored source tree.

Building requires Rust, CMake, Meson, and Ninja on the host. x86 and x64 targets additionally require NASM. Missing tools are reported as build errors; the package never downloads source or substitutes another decoder. iOS targets require iOS 13 or newer.