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TO8(1)                 DragonFly General Commands Manual                TO8(1)


NAME

       to8 - Convert a 24 bit RLE file to eight bits using dithering.


SYNOPSIS

       to8 [ -g display_gamma ] [ -{iI} image_gamma ] [ -o outfile ] [ infile
       ]


DESCRIPTION

       To8 Converts an image with 24 bit pixel values (eight bits each of red,
       green and blue) to eight bits of color using a dithered color map (the
       special color map is automatically written into the output file).  If
       no input file is specified, to8 reads from stdin.  If no output file is
       specified with -o it writes the result to the standard output.

       Other options allow control over the gamma, or contrast, of the image.
       The dithering process assumes that the incoming image has a gamma of
       1.0 (i.e., a 200 in the input represents an intensity twice that of a
       100.)  If this is not the case, the input values must be adjusted
       before dithering via the -i or -I option.  The input file may also
       specify the gamma of the image via a picture comment (see below).  The
       output display is assumed to have a gamma of 2.5 (standard for color TV
       monitors).  This may be modified via the -g option if a display with a
       different gamma is used.

       To8 will put a picture comment into the output file indicating the
       display gamma assumed in constructing the dithering color map.


OPTIONS

       -i image_gamma
              Specify the gamma (contrast) of the image.  A low contrast
              image, suited for direct display without compensation on a high
              contrast monitor (as most monitors are) will have a gamma of
              less than one.  The default image gamma is 1.0.  Image gamma may
              also be specified by a picture comment in the RLE (5) file of
              the form image_gamma=gamma.  The command line argument will
              override the value in the file if specified.

       -I image_gamma
              An alternate method of specifying the image gamma, the number
              following -I is the gamma of the display for which the image was
              originally computed (and is therefore 1.0 divided by the actual
              gamma of the image).  Image display gamma may also be specified
              by a picture comment in the RLE (5) file of the form
              display_gamma=gamma.  The command line argument will override
              the value in the file if specified.

       -g display_gamma
              Specify the gamma of the X display monitor.  The default value
              is 2.5, suitable for most color TV monitors (this is the gamma
              value assumed by the NTSC video standard).

       -o outfile
              If specified, the output will be written to this file.  If
              outfile is "-", or if it is not specified, the output will be
              written to the standard output stream.


SEE ALSO

       tobw(1), getx11(1), mcut(1), rlequant(1), urt(1), dither(3), RLE(5).


AUTHOR

       Spencer Thomas

4th Berkeley Distribution       Month DD, YYYY                          TO8(1)

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