.PGM File Extension

Grayscale image file encoded with either one or two bytes (8 or 16 bits) per pixel; contains header information and a grid of numbers that represent different shades of gray from black (0) to white (up to 65,536); typically stored in ASCII text format, but also has a binary representation.

PGM files include a header that defines the PGM format type ("P2" for text or "P5" for binary), image width and height, and the maximum number of shades. While binary PGM files may contain multiple images, ASCII PGM files may only include one image.

PGM files may also be called "portable greymap" files.