code: void initializeFromRect(Envelope2D src, Envelope2D dest) {
  		if (src.isEmpty() || dest.isEmpty() || 0 == src.getWidth()
  				|| 0 == src.getHeight())
  			setZero();
  		else {
  			xy = yx = 0;
  			xx = dest.getWidth() / src.getWidth();
  			yy = dest.getHeight() / src.getHeight();
  			xd = dest.xmin - src.xmin * xx;
  			yd = dest.ymin - src.ymin * yy;
  		}
  	}
docs: Initialize transformation from two rectangles.