public void copyAlphaFrom(CPColorBmp bmp, CPRect r) {
		r.clip(getSize());

		for (int j = r.top; j < r.bottom; j++) {
			for (int i = r.left; i < r.right; i++) {
				data[j * width + i] = (data[j * width + i] & 0xffffff) | (bmp.data[j * width + i] & 0xff000000);
			}
		}
	}