Netpbm

Netpbm (originally named Pbmplus) is an open source image processing toolkit. It has its own native image file formats.

It includes a library, and a collection of utility programs. Relevant to file formats is its extensive suite of image format conversion utilities, which convert various formats to or from one of its native formats. Most of the utilities are self-contained, with only a few common third-party libraries (libtiff, libjpeg, libpng, zlib) required by some utilities.