ImageMagick and GD are 2 of the most widespread graphic software libraries out there. They make the dynamic creation and editing of images and graphs on a site doable, so they should be set up on a server if you host your sites on it and you prefer to have something different than static images with fixed dimensions. If ImageMagick and GD are installed, you shall be able to edit any image in a variety of ways - generate thumbnails, change the colors, flip it, blur it, etcetera. However, these changes are feasible if the script application which you use on your site permits you to do such things. The 2 libraries can be used with numerous web development languages - PHP, Python, Perl, etcetera., and support more than 100 commonly used image formats which you will be able to work with - PNG, PSD, JPEG, TIFF, GIF and many more.