I have a small rectangle ( graphic in PNG ) that is loaded then made as a mutable image in code.

What I need to do is cut out random chunks of it, this isn't the problem.

The problem is that drawing on it so the underneath becomes transparent ( the rectangle is drawed over the background during the game ).

If set my drawing colour to be transparent, you don't see the chunks taken out which I get because your drawing nothing on something.
Is it possible to draw in a certain colour, and then make that colour transparent afterwards ??

Many Thanks in advance