Using PNG is not advisable at this stage. There are currently different specs for PNG files. Some programs save them as 32 bit, some save them as 24 bit, and some programs swap the order of the alpha channel. I am not an expert on this, but I have tried using PNG across different editors and graphics programs, and the results always vary. CorelDraw, Photoshop and Paint Shop Pro all treat PNG's differently, and EditStudio and Adobe Premiere also treat PNG's differently. PS This is from own experience, and not the authoritive final word on PNG's.

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