- Extension
- .g4
- .pgm
- Format
- Binary
- Binary
- Category
- Fax
- Raster Image
- Developer
- Computer Fax Systems (CFS)
- Jef Poskanzer
- Description
- Group 4 (G4) used for black and white lossless compression to maintain high-quality images, commonly used in TIFF format compression by fax machines. A picture is seen as black dots and lines on a blank page; the fewer the dots and lines are, the lesser the file size.
- A PGM file is a grayscale image file saved in the portable gray map (PGM) format and encoded with one or two bytes (8 or 16 bits) per pixel. It contains header information and a grid of numbers that represent different shades of gray from black (0) to white (up to 65,536). PGM files are typically stored in ASCII text format, but also have a binary representation.
- MIME Type
- image/g4fax
- image/x-portable-graymap
