ppmtospu - convert a PPM image to an Atari Spectrum 512 image
All options can be abbreviated to their shortest unique prefix. You may use two hyphens instead of one. You may separate an option name and its value with white space instead of an equals sign.
This program is part of Netpbm(1).
This program converts from the PPM format to the uncompressed Spectrum 512 image format used on Atari ST computers.
Input comes from the file you name with the ppmfile argument, or Standard Input by default. Output goes to Standard Output.
The input must be 320 pixels wide by 200 pixels high. If you have an image of a different size, you can use pamcut or pamscale to force it to these dimensions.
This is the default.
Copyright (C) 1990 by Steve Belczyk
This program was new in Netpbm 10.58 (March 2012).
But it was written in 1990. Steve Belczyk posted it along with sputoppm, spctoppm, pi1toppm, and pi1toppm - all programs for dealing with Atari image formats - to comp.sources.misc on July 15, 1990. For reasons that have been lost to history, all of these entered the Netpbm (then Pbmplus) distribution except ppmtospu.
Georges Kesseler wondered In March 2012 why there was no counterpart to sputoppm in Netpbm and searched the web, finding only one reference to ppmtopsu: the 1990 comp.sources.misc posting, including the source code. He emailed the Netpbm maintainer suggesting it be added.