TO8(1)                                                   TO8(1)





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

SYNOPSIS
       to8 [ -g display_gamma ] [ -{iI} image_gamma ] [ -o out-
       file ] [ 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 pic-
       ture 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 com-
              mand 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 speci-
              fied, 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



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