Netpbm formats
From Just Solve the File Format Problem
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Overview
The Netpbm formats are a set of uncompressed 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 not really a format, but is a collective name for PBM, PGM, and PPM.
PAM (portable arbitrary map) is a more sophisticated format which supports everything the PBM, PGM, and PPM formats do, and then some.
The PBM, PGM, and PPM formats come in two varieties: a text ("plain") format, and a binary ("raw") format. PAM is binary-only.
Identification
Each file begins with two ASCII characters, which serve as a signature.
- PBM, text:
P1(PRONOM:x-fmt/164) - PGM, text:
P2(PRONOM:fmt/407) - PPM, text:
P3(PRONOM:x-fmt/178) - PBM, binary:
P4(PRONOM:fmt/409) - PGM, binary:
P5(PRONOM:fmt/406) - PPM, binary:
P6(PRONOM:fmt/408) - PAM:
P7(PRONOM:fmt/405, incorrectly named "Portable Any Map" as of 3/2013)
