PBMPlus files are created by Jef Poskanzer's PBMPlus Portable Bitmap Utilities. PBMPlus uses three different file types. These are the Portable Bitmap (PBM), Portable Graymap (PGM), and Portable Pixmap (PPM) formats. PBM can store monochrome (black & white) bitmaps only. PGM additionally stores grayscale bitmaps, and PPM can store color bitmaps. There is also a fourth format; Portable Anymap (PNM). PNM is not a different file format in itself, but a file of type PNM can hold any of the three PBMPlus file types listed above.
The default extension is PNM.
Supporting Platforms and Applications:
PBMPlus files are common under UNIX and on Intel-based PCs.
In conformance with Jef Poskanzer's specifications of 1990. The full specification is included below.
A PNM file can hold one of the three PBMPlus formats below.
· Portable Bitmap (PBM)
· Portable Graymap (PGM)
· Portable Pixmap (PPM)