I was working on a flash-based project recently which consisted of alot of bitmaps. I always export my bitmaps from Photoshop as png-24, since I always find they yield the best results and have the best support for transparency. The problem I was having in the project I was working on was that when I imported the image, it work look fine- just as how I outputted it from Photoshop. But when I exported the movie, the bitmap lost some of details and replaced jagged grungy edges with straight ones, this was not what I wanted since the site was a ruff & grungy style. I finally discovered that Flash was exporting the image as a jpg, changing it to exporting as a png fixed the problem giving the me the jagged grungy lines I was looking for.