ImageMagick

ImageMagick is a program capable of reading, converting, and displaying images in an enormous number of formats thanks to the large number of libraries it includes.

With ImageMagick, you can crop and rotate your images, add effects, combine text and polygons, etc.

The program supports almost 100 different image formats, from the most popular like TIFF, JPG, PNG, GIF, BMP, and PDF, to more specific ones.

ImageMagick also works as an image converter.

Plus, the program is completely free and distributed with its source code in case you want to alter or improve the way it works.