Function Image.blendRectMask

Alpha-blends src_rect from src image to this image using mask image at coordinates dst. Alpha channels are required for both src and mask. dst pixels and src pixels will blend 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 blendRectMask (
  Image src,
  Image mask,
  const(Rect2) src_rect,
  const(Vector2) dst
) nothrow @nogc;