Rich Morgan writes "Convert is a command line tool used for manipulating graphics files. There are many handy uses for this tool and today I'm going to show you how to use it for some basic image manipulation tasks.
You may be asking yourself, "Why should I use convert instead of the Gimp or another GUI-based graphics program?" There are many reasons why you might prefer to use a non-GUI tool. For example, you can easily use convert in a shell script to resize graphics files for a website. Or you could write a shell script to batch convert every BMP in your home directory to PNG's or make thumbnails out of large images. Plus I like to use convert when I have a small or repetative job that I don't really need a full-blown GUI app like the Gimp."