You could make a hybrid solution where Pillow supported formation (which should be the vast majority of your input) go through its filters while other formats are run through ImageMagick to be converted into something Pillow understands so they can be stuffed into the front end.<p>If you support JPEG, PNG, and GIF you will have 99% of the user data supported.  Very few people upload RLE TARGA to webpages these days.