Function Image.blitRectMask

Blits src_rect area from src image to this image at the coordinates given by dst. src pixel is copied onto dst if the corresponding mask pixel's alpha value is not 0. src image and mask image must have the same size (width and height) but they can have different formats.

void blitRectMask (
  Image src,
  Image mask,
  const(Rect2) src_rect,
  const(Vector2) dst
) nothrow @nogc;