I've been searching desperately online for a way to do this, but the only thing I've found is the PC only AlphaWorks. I would like to be able to save the transparency effects of blend modes like Screen and Multiply into my image. There MUST be a way of doing of this... Surely?! I'm working with images of clouds, so need the varying levels of transparency you get around their edges, so tools like the magic wand aren't really an option.
Any ideas, help, advice, etc would be greatly appreciated.