I need to slide an image over another image. The bottom image is a picture. The top image is a ring with a thick solid border. I want to move the ring over the image like a magnifying glass. My problem is how do I make the ring have a transparent circular area so when it moves it shows the image below?
I was planning to use bitmap threshold() but it the sourceRect (e.g. the area for transparency) parameter is rectangular. Does anyone know if this will work with a rounded rectangle? Or is there some other trick I should look at.