I have fought with trying to remember the syntax for Imagemagik’s convert command for years. I finaly caved in [from my normal position of “if you can’t do it from the commandline, then you are a wimp” and sought out a gui to help me quickly convert images to use on a website. Or to just roll a picture 90 or 180 degrees. The easy solution and a standard ubuntu repository file is “converseen”. It can do batch conversions or on selected files. Gets the job done without the challenge of looking up all the arguments for “convert”.