To get the x and y of the dashed rectangle you show, the obvious way is simply:
x1r = min(x1, x2);
x2r = max(x1, x2);
y1r = min(y1, y2);
y2r = max(y1, y2);
Of course the radii have nothing to do with that rectangle. They only matter if you want the bounding box of both circles, in which case you'd do this:
x1r = min(x1-r1, x2-r2);
x2r = max(x1+r1, x2+r2);
y1r = min(y1-r1, y2-r2);
y2r = max(y1+r1, y2+r2);
But that's so obvious I'm sure you've already thought about that, so that must not be what you mean. Please describe EXACTLY what "transform" means to you? Like a series of images where the circles gradually morph into rectangles or whatever.
