prepareCameraFrameFromImage function

CameraFrame? prepareCameraFrameFromImage(
  1. Object cameraImage, {
  2. CameraFrameRotation? rotation,
  3. bool? isBgra,
})

Convenience wrapper around prepareCameraFrame that accepts any object duck-typed to package:camera's CameraImage (i.e. exposing width, height, and a planes iterable of objects with bytes, bytesPerRow, and bytesPerPixel getters).

This keeps flutter_litert free of a hard dependency on package:camera while letting callers pass a CameraImage directly:

camera.startImageStream((CameraImage image) async {
  final frame = prepareCameraFrameFromImage(image);
  if (frame == null) return;
  final faces = await detector.detectFacesFromCameraFrame(frame);
});

Throws at runtime (NoSuchMethodError / TypeError) if cameraImage does not expose the expected shape; this is an acceptable tradeoff vs. either adding a camera dep here or asking every caller to write a plane mapper.

When isBgra is null, a desktop single-plane frame's byte order comes from the image's format.raw: 'BGRA' selects BGRA and 'RGBA' selects RGBA. camera_desktop 2.x reports 'BGRA' on every desktop platform, while 1.x reported 'RGBA' on Linux and Windows. Any other value, including a missing format or a non-string raw, falls back to BGRA on macOS and RGBA elsewhere. An explicit isBgra always wins.

See prepareCameraFrame for parameter semantics.

Implementation

CameraFrame? prepareCameraFrameFromImage(
  Object cameraImage, {
  CameraFrameRotation? rotation,
  bool? isBgra,
}) {
  // ignore: avoid_dynamic_calls
  final dynamic dyn = cameraImage;
  final int width = dyn.width as int;
  final int height = dyn.height as int;
  final Iterable<dynamic> rawPlanes = dyn.planes as Iterable<dynamic>;
  final planes = <CameraPlane>[
    for (final dynamic p in rawPlanes)
      (
        bytes: p.bytes as Uint8List,
        rowStride: p.bytesPerRow as int,
        pixelStride: (p.bytesPerPixel as int?) ?? 1,
      ),
  ];
  return prepareCameraFrame(
    width: width,
    height: height,
    planes: planes,
    rotation: rotation,
    isBgra: isBgra ?? _defaultIsBgra(dyn),
  );
}