drawImage function Null safety

Image drawImage(
  1. Image dst,
  2. Image src,
  3. {int? dstX,
  4. int? dstY,
  5. int? dstW,
  6. int? dstH,
  7. int? srcX,
  8. int? srcY,
  9. int? srcW,
  10. int? srcH,
  11. bool blend = true}
)

Draw the image src onto the image dst.

In other words, drawImage will take an rectangular area from src of width src_w and height src_h at position (src_x,src_y) and place it in a rectangular area of dst of width dst_w and height dst_h at position (dst_x,dst_y).

If the source and destination coordinates and width and heights differ, appropriate stretching or shrinking of the image fragment will be performed. The coordinates refer to the upper left corner. This function can be used to copy regions within the same image (if dst is the same as src) but if the regions overlap the results will be unpredictable.

Implementation

Image drawImage(Image dst, Image src,
    {int? dstX,
    int? dstY,
    int? dstW,
    int? dstH,
    int? srcX,
    int? srcY,
    int? srcW,
    int? srcH,
    bool blend = true}) {
  dstX ??= 0;
  dstY ??= 0;
  srcX ??= 0;
  srcY ??= 0;
  srcW ??= src.width;
  srcH ??= src.height;
  dstW ??= (dst.width < src.width) ? dstW = dst.width : src.width;
  dstH ??= (dst.height < src.height) ? dst.height : src.height;

  if (blend) {
    for (var y = 0; y < dstH; ++y) {
      for (var x = 0; x < dstW; ++x) {
        final stepX = (x * (srcW / dstW)).toInt();
        final stepY = (y * (srcH / dstH)).toInt();
        final srcPixel = src.getPixel(srcX + stepX, srcY + stepY);
        drawPixel(dst, dstX + x, dstY + y, srcPixel);
      }
    }
  } else {
    for (var y = 0; y < dstH; ++y) {
      for (var x = 0; x < dstW; ++x) {
        final stepX = (x * (srcW / dstW)).toInt();
        final stepY = (y * (srcH / dstH)).toInt();
        final srcPixel = src.getPixel(srcX + stepX, srcY + stepY);
        dst.setPixel(dstX + x, dstY + y, srcPixel);
      }
    }
  }

  return dst;
}