I have, what I thought, was a simple problem. I wanted to overlay an existing bitmap with a translucent square to indicate the area of interest to the user. My difficulty is removing the square when the user moves to a different area of the bitmap. At the moment I am going to redraw the original bitmap and add the new square but this is very slow.
Is there a quicker method? My original intention was to use XOR but various sites state that it doesn't exist in GDI+.