The Netpbm formats are a family of simple raster image file formats, associated with the Netpbm library and suite of image processing utilities.
- PBM (portable bitmap) is a bi-level image format.
- PGM (portable graymap) is a grayscale image format.
- PPM (portable pixmap) is a color image format.
- PNM (portable anymap) is a collective name for PBM, PGM, and PPM. A .pnm file may use any of those formats.
- PAM: Refer to PAM (Portable Arbitrary Map). Although PAM is one of the Netpbm formats, it's different enough that it's best documented in a separate article.
Each file begins with two ASCII characters, which serve as a signature.
The PBM, PGM, and PPM formats come in two varieties: a text ("plain") format, and a binary ("raw") format.