ImageMagick and GD are 2 of the most popular graphic software libraries nowadays. They make the dynamic creation and editing of images and graphs on a site feasible, so they ought to be present on a web server if you host your websites on it and you would like to have something different from static images with fixed dimensions. If ImageMagick and GD are installed, you shall be able to edit any image in many different ways - generate thumbnails, change the colors, flip it, blur it, and so forth. Of course, these adjustments are possible if the script application that you use on your site permits you to do such things. The two libraries could be used with many programming languages - PHP, Python, Perl, and so on., and support over a hundred frequently used image formats that you'll be able to work with - PNG, PSD, JPEG, TIFF, GIF and many others.