The Portable Bitmap Utilities consists of Portable Greymap Utilities (PGM), Portable Pixmap Utilities (PPM), and Portable Anymap Utilities (PNG). Their source is the UNIX environment.

 

For PBM files, you can read and write the following bits per pixel: 1.

For PGM files, you can read and write the following bits per pixel: 8 (Grayscale).

For PPM files, you can read and write the following bits per pixel: 24.