ImageMagick and GD are 2 of the most popular graphic software libraries available. They make the dynamic creation and editing of images and graphs on a website doable, so they need to be available on a web server if you host your websites on it and you would like to have something different than static images with fixed dimensions. If ImageMagick and GD are present, you will be able to edit any image in a variety of ways - generate thumbnails, change the colors, flip it, blur it, and so forth. However, these adjustments are doable if the script app that you employ on your website allows you to perform such things. The two libraries could be used with numerous website development languages - PHP, Python, Perl, etcetera., and support over 100 frequently used image formats which you'll be able to work with - PNG, PSD, JPEG, TIFF, GIF and others.