quartz-2d

Blending a semi transparent PNG with color-dodge

Hello, I'm trying to draw a 32-bit premultiplied PNG UIImage on top of a previously drawn background using color-dodge blend mode. The PNG image contains a small opaque white rectangle with anti-aliased edges that fade into transparency, so there are semi-transparent pixels. For some reason color-dodge seem to treat the semi-transparent...

Free hand drawing on the iphone/ipad

Hi I am pretty new to graphics but I want to create an iphone/ipad app that does free hand drawing. That is as the finger moves, a path is painted. Where do I start (books, resources, etc)? The stuff I see on apple's docs talk about lines and arcs. These are simple. They talk about bezier curves briefly. Is this what I should be looking...