Android :: How To Paint Transparency - Swiss Cheese Style

To explain i have a bitmap which is constructed as follows

Paint a rectangle color yellow I want now to paint a smaller circle over the top of the rectangle, but i want to use transparency. so that the circle results as a hole in the rectangle. {like swiss cheese with holes }

So if i painted the bitmap over a background the background would still be visible in the Circle/hole.

setting the drawcolor drawColor(Color.TRANSPARENT) just paints a transparent object. i.e. it doesn't erase the circle area of the rectangle.

How to do...?

One option is to set the circle color to say black and then look for an option to replace black with transparent within the bitmap.... but i can't find a solution for this either.