decodeYUV420SP function

Image decodeYUV420SP(CameraImage image)

Implementation

img.Image decodeYUV420SP(CameraImage image) {
  final int width = image.width;
  final int height = image.height;

  Uint8List yuv420sp = image.planes[0].bytes;
  final outImg =
      img.Image(width: width, height: height); // default numChannels is 3

  final int frameSize = width * height;

  for (int j = 0, yp = 0; j < height; j++) {
    int uvp = frameSize + (j >> 1) * width, u = 0, v = 0;
    for (int i = 0; i < width; i++, yp++) {
      int y = (0xff & yuv420sp[yp]) - 16;
      if (y < 0) y = 0;
      if ((i & 1) == 0) {
        v = (0xff & yuv420sp[uvp++]) - 128;
        u = (0xff & yuv420sp[uvp++]) - 128;
      }
      int y1192 = 1192 * y;
      int r = (y1192 + 1634 * v);
      int g = (y1192 - 833 * v - 400 * u);
      int b = (y1192 + 2066 * u);

      if (r < 0) {
        r = 0;
      } else if (r > 262143) {
        r = 262143;
      }
      if (g < 0) {
        g = 0;
      } else if (g > 262143) {
        g = 262143;
      }
      if (b < 0) {
        b = 0;
      } else if (b > 262143) {
        b = 262143;
      }

      // I don't know how these r, g, b values are defined, I'm just copying what you had bellow and
      // getting their 8-bit values.
      outImg.setPixelRgb(i, j, ((r << 6) & 0xff0000) >> 16,
          ((g >> 2) & 0xff00) >> 8, (b >> 10) & 0xff);

      /*rgb[yp] = 0xff000000 |
            ((r << 6) & 0xff0000) |
            ((g >> 2) & 0xff00) |
            ((b >> 10) & 0xff);*/
    }
  }
  return outImg;
}