Core Graphics: Mask Image, add Overlay and Underlay

How can I mask an image, add an overlay and an underlay to the masked image with Core Graphics? (for instance: a document icon consists out of a mask png, a page curl png and a base with shadow) Can someone give me a best pr开发者_运维问答actice?

• Draw the underlay with CGContextDrawImage().
• Push a graphics context state with CGContextSaveGState().
• Load the mask and add it to the context using CGContextClipToMask().
• Draw your content.
• Pop the graphics context with CGContextRestoreGState().
• Draw your overlay image with CGContextDrawImage().