ImageMagick and GD are two of the most widespread graphic software libraries available on the market. 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 websites on it and you would want to have something different than static images with fixed dimensions. If ImageMagick and GD are set up, you shall be able to edit any image in many ways - generate thumbnails, change the colors, flip it, blur it, and so on. However, these modifications are possible if the script app which you employ on your site enables you to do such things. The two libraries could be used with a lot of programming languages - PHP, Python, Perl, etc., and support over 100 frequently used image formats that you will be able to work with - PNG, PSD, JPEG, TIFF, GIF and many more.