8-bit grayscale image file; may contain different shades of gray and transparent pixels; formatted in a text format, in which numbers are used to represent how light or dark each pixel is.
PGM files are also called "portable greymap" files.
Program(s) that open pgm files
Mac: Netpbm; Adobe Photoshop with CartaPGM plug-in; Editable with a text editor Windows: Netpbm; Corel Paint Shop Pro; Adobe Photoshop with CartaPGM plug-in; Editable with a text editor
Unix: Netpbm; Editable with a text editor
Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/pgm
