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       ppmtosixel - convert a portable pixmap into DEC sixel format


       ppmtosixel [-raw] [-margin] [ppmfile]


       Reads a portable pixmap as input.  Produces sixel commands (SIX) as output.  The output is
       formatted for color printing, e.g. for a DEC LJ250 color inkjet printer.

       If RGB values from the PPM file do not have maxval=100, the RGB values  are  rescaled.   A
       printer  control  header  and  a color assignment table begin the SIX file.  Image data is
       written in a compressed format by default.  A printer control footer ends the image file.


       -raw   If specified, each pixel will be explicitly described in the image file.   If  -raw
              is  not  specified,  output  will  default  to compressed format in which identical
              adjacent pixels are replaced by "repeat pixel" commands.  A raw file  is  often  an
              order of magnitude larger than a compressed file and prints much slower.

              If  -margin  is  not  specified, the image will be start at the left margin (of the
              window, paper, or whatever).  If -margin is specified, a 1.5 inch left margin  will
              offset the image.


       Generally,  sixel  files  must reach the printer unfiltered.  Use the lpr -x option or cat
       filename > /dev/tty0?.


       Upon rescaling, truncation of the least significant bits of RGB values may result in  poor
       color conversion.  If the original PPM maxval was greater than 100, rescaling also reduces
       the image depth.  While the actual RGB values from the ppm file are more or less retained,
       the  color palette of the LJ250 may not match the colors on your screen.  This seems to be
       a printer limitation.




       Copyright (C) 1991 by Rick Vinci.

                                          26 April 1991                             ppmtosixel(1)