ImageMagick 7
Free and open source voxel art tools - editor, thumbnailer and format
A fast image processing library with low memory needs
A portable, multi-platform, command-line driven graphing utility
Swiss army knife of image processing
A collection of packages providing extra functionality for GNU Octave
Advanced PNG optimization program
Improved JPEG encoder
Retro Computer Image Library
medical image conversion utility
Drawing, graphics conversion, software development, administration.
Various small and useful command-line utilities
Extend abcm2ps to support direct generation of PNG, SVG and PDF files
Image processing library in C/C++
Convert Netpbm programs to GIMP plug-ins
converts between IGES file and text file
Rayshade raytracer
Convert BMP images into Sixel images