.pgm File — Portable Graymap

PGM (Portable Graymap) is a grayscale image format that is part of the Netpbm family of image formats. PGM files store grayscale pixel values either as ASCII text (P2 format) or raw binary (P5 format), with a simple header specifying width, height, and maximum gray value. The format supports grayscale values from 1-bit (black and white) up to 16-bit depth (65,535 shades of gray). PGM's extreme simplicity makes it one of the easiest image formats to read, write, and process programmatically, requiring no compression library or complex parsing. This simplicity has made PGM and its Netpbm siblings (PBM for bitmaps, PPM for color) popular in computer science education, image processing research, scientific computing, and Unix pipeline workflows. The ASCII variant is human-readable — you can view and edit pixel values in a text editor. PGM files can be converted to and from other formats using Netpbm tools or ImageMagick. While impractical for everyday image use due to lack of compression, PGM remains valuable in algorithmic image processing contexts.