ImageMagick is a neat little free and open-source image manipulation software suite to create, edit, compose, or convert bitmap images. It can read and write images in over 100 formats, GIF, JPEG, PDF, PNG, Postscript, SVG, and TIFF. Use ImageMagick to resize, flip, mirror, rotate, distort, shear and transform images, and more. It runs on Linux, Windows, Mac Os X, iOS, Android OS, and others. It is commonly run in command line to batch-process image, but GUI is available.