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dither is a set of programs written to allow you to use big printers sensibly,
although it has many other applications.
I got fed up with attempts that my HP designjet printer was making at rendering
large images, so I thought i'd fix it.
netpbm doesn't have a convient format for storing 3bit images so I added
the PCM format: it's exactly like the PBM format only it starts P0 and after
the point where the normal bitmap data ends there are two more sections of
bitmap data. The three bitmaps being the Red Green and Blue components.
If you are interested in color space correction take a look at my colors project.
The tools are as follows:
3pbmtopcm - converts from three PBM files into a PCM file (cf rgb3toppm).
dither - which actually does the dither using either boustropendonic
Floyd-Steinberg, a Koch curve algorythm or just simple thresholding.
pcmlines - which extracts scan lines from a PCM file to another (smaller)
PCM file [useful if you need to chop you image for printing]
pcmto3pbm - converts from PCM to three PBM files one each for red,green
and blue (cf ppmtorgb3).
pcmtopcl - convert from PCM to a particularly small subset of colour
PCL5 that almost all HP printers can understand.
pcmtoppm - convert from PCM to PPM.
and finally - a patched version of xv-3.10a which can read PCM files
The command line tools have no limit [other than your disk size and the size of void *] on the size
of image they can process. I routinely use them to process images of the order of 2-3Gb.
