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Portable Graymap (.pgm)

The PGM which is an acronym for Portable Gray-Map is a simple structured grayscale raster image format. It is actually part of Netpbm, an open-source package of graphics programs used in Unix operating systems.
Because of its simple and general design, it's easy to develop programs to convert, manipulate and create the image. The file contents could be either ASCII or binary defined in its simple always ASCII header information.

PGM Specifications

Name Portable Graymap
File Extension(s) .pgm
Category Raster Images
Use For Easily exchange binary images between platforms back in the '80s.
Developer Jeffrey A. Poskanzer
MIME Type(s) image/x-portable-graymap
License N/A
File Sample(s) N/A
Compression None
Max Dimensions N/A
Color Modes
Mode Bits Description
Grayscale 8 and 16 Each pixel is represented by either 1 or 2 bytes defined in the Maximum Gray Value.
True color N/A PGM has no distinct true color mode.
Indexed color N/A PGM has no distinct indexed color mode.
Greyscale with alpha N/A PGM does not support an alpha channel.
True color with alpha N/A PGM does not support an alpha channel.
Animation No
Transparency No
Interlacing No
Metadata No
Layers No
Multipage No