getRegion method

Future<Image> getRegion({ required int x, required int y, required int width, required int height, })

Implementation

Future<Image> getRegion({
  required int x,
  required int y,
  required int width,
  required int height,
}) async {
  await _paintingContext.doIntermediateRasterization();
  final sourceImage = (_paintingContext.intermediateImage ?? _paintingContext.publishedImage)!;

  final sourceData = await sourceImage.toByteData();
  final destinationData = Uint8List(width * height * 4);
  final rowLength = width * 4;

  for (int row = 0; row < height; row += 1) {
    final sourceRowOffset = _getBitmapPixelOffset(
      imageWidth: sourceImage.width,
      x: x,
      y: y + row,
    );
    final destinationRowOffset = _getBitmapPixelOffset(
      imageWidth: width,
      x: 0,
      y: row,
    );

    destinationData.setRange(
      destinationRowOffset,
      destinationRowOffset + rowLength - 1,
      Uint8List.view(sourceData!.buffer, sourceRowOffset, rowLength),
    );
  }

  final codec = await ImageDescriptor.raw(
    await ImmutableBuffer.fromUint8List(destinationData),
    width: width,
    height: height,
    pixelFormat: PixelFormat.rgba8888,
  ).instantiateCodec();

  return (await codec.getNextFrame()).image;
}