Netpbm is a toolkit for conversion of images between a variety of different formats, as well as to allow a few basic image operations. There are over 180 separate tools in the package.
netpbm-9.8: description + notes
The idea behind Netpbm is to define 3 very basic (and inefficient) portable graphics formats: PBM for black and white, PGM for grayscale, and PPM for color. These are collectively referred to as PNM. To convert from one common graphics format to another, you use a PNM format as an intermediate format. So if you want to convert among N image formats, you only need 2*N conversion filters, instead of the N^2 you would need if you wrote each conversion tool separately.
In addition to the converters, the package includes some simple tools for manipulating the portable formats. For example, you can shrink an image or cut the top 10% off or make a mirror image.
The package README file has more information, as does the Netpbm project page
To auto-install this package, go back and click on the respective install icon.