camera_input_image.dart

InputImage? _inputImageFromCameraImage(CameraImage image) {
    if (_controller == null) return null;

    // get image rotation
    // it is used in android to convert the InputImage from Dart to Java: https://github.com/flutter-ml/google_ml_kit_flutter/blob/master/packages/google_mlkit_commons/android/src/main/java/com/google_mlkit_commons/InputImageConverter.java
    // `rotation` is not used in iOS to convert the InputImage from Dart to Obj-C: https://github.com/flutter-ml/google_ml_kit_flutter/blob/master/packages/google_mlkit_commons/ios/Classes/MLKVisionImage%2BFlutterPlugin.m
    // in both platforms `rotation` and `camera.lensDirection` can be used to compensate `x` and `y` coordinates on a canvas: https://github.com/flutter-ml/google_ml_kit_flutter/blob/master/packages/example/lib/vision_detector_views/painters/coordinates_translator.dart
    final camera = _cameras[_cameraIndex];
    final sensorOrientation = camera.sensorOrientation;
    // print(
    //     'lensDirection: ${camera.lensDirection}, sensorOrientation: $sensorOrientation, ${_controller?.value.deviceOrientation} ${_controller?.value.lockedCaptureOrientation} ${_controller?.value.isCaptureOrientationLocked}');
    InputImageRotation? rotation;
    if (Platform.isIOS) {
      rotation = InputImageRotationValue.fromRawValue(sensorOrientation);
    } else if (Platform.isAndroid) {
      var rotationCompensation =
          _orientations[_controller!.value.deviceOrientation];
      if (rotationCompensation == null) return null;
      if (camera.lensDirection == CameraLensDirection.front) {
        // front-facing
        rotationCompensation = (sensorOrientation + rotationCompensation) % 360;
      } else {
        // back-facing
        rotationCompensation =
            (sensorOrientation - rotationCompensation + 360) % 360;
      }
      rotation = InputImageRotationValue.fromRawValue(rotationCompensation);
      // print('rotationCompensation: $rotationCompensation');
    }
    if (rotation == null) return null;
    // print('final rotation: $rotation');

    // get image format
    final format = InputImageFormatValue.fromRawValue(image.format.raw);
    // validate format depending on platform
    // only supported formats:
    // * nv21 for Android
    // * bgra8888 for iOS
    if (format == null ||
        (Platform.isAndroid && format != InputImageFormat.nv21) ||
        (Platform.isIOS && format != InputImageFormat.bgra8888)) return null;

    // since format is constraint to nv21 or bgra8888, both only have one plane
    if (image.planes.length != 1) return null;
    final plane = image.planes.first;

    // compose InputImage using bytes
    return InputImage.fromBytes(
      bytes: plane.bytes,
      metadata: InputImageMetadata(
        size: Size(image.width.toDouble(), image.height.toDouble()),
        rotation: rotation, // used only in Android
        format: format, // used only in iOS
        bytesPerRow: plane.bytesPerRow, // used only in iOS
      ),
    );
  }
}