Pbmplus

Netpbm is an open-source package of graphics programs and a programming library, used mainly in the Unix world. It is included in all major open-source Unix-like operating system distributions and also works on other Unix-like operating systems, Windows, Unix operating systems such as macOS, and other platforms.

Netpbm defines a set of graphics formats called the Netpbm formats:

Netpbm contains over 220 separate programs in the package, most of which have "pbm", "pgm", "ppm", "pam", or "pnm" in their names. For example, you might use pamscale to shrink an image by 10%, pamcomp to overlay one image on top of another, pbmtext to create an image of text or reduce the number of colors in an image with pnmquant.

The Netpbm package can, for example, use two successive conversion programs to turn a picture in the PBM format into a .bmp file:

This is more commonly done as a pipeline, to save execution time and to avoid leaving a temporary somepic.ppm file around:

The Netpbm programs are frequently used as intermediates to convert between obscure formats. For instance, there may be no tool to convert an X11 window dump (XWD format) directly to a Macintosh PICT file, but one can do this by running xwdtopnm, then ppmtopict. (Tools which say that they output PNM output either PBM, PGM or PPM. Tools importing PNM will read any of the three formats.) As a more complex example, Netpbm tools can convert 48×48 XBM to Ikon and eventually X-Face.

The PBM (black and white) format was invented by Jef Poskanzer in the mid-1980s. At the time, there was no standard, reliable way to send binary files in email, and attempting to send anything other than 7-bit ASCII in email often resulted in data corruption. PBM was designed to allow images to be sent via email without being corrupted. Poskanzer released the forerunner of Netpbm, called Pbmplus in 1988. By the end of 1988, Poskanzer had developed the PGM (greyscale) and PPM (color) formats and released them with Pbmplus.