Netpbm is based on the Pbmplus package (release: 10 Dec 91)
Description:
A series of tools for converting a variety of image formats to and from a set of portable formats, and hence between each other. The four formats are: PBM for bitmaps (1 bit per pixel) PGM for grayscale images PPM for full colour images PNM for context-independent manipulations, and other formats. These formats are upwards-compatible, and tools can read files in lower-resolution formats. In addition there are some simple tools for manipulating the various formats.
