iPhone SDK: How to Draw a Rounded Rectangle With a Semi-Transparent Gradient and a Drop Shadow

Answer 1

1. Fill the rounded rectangle with the shadow. Do this fill at 100% opacity—you'll effect the transparency in the next step.
2. Fill the same rounded rectangle without the shadow, using Destination Out blend mode, at (1.0 - the desired opacity). For example, if you want 40%, do the Destination-Out draw at 60%. Think of it as subtracting that much from the opacity of the image.