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       gamma4scanimage  gamma  [shadow  [highlight  [maxin  [max­


       The tool gamma4scanimage creates a gamma table in the for­
       mat  expected  by  scanimage.  You  can  define a gamma, a
       shadow and a highlight value. You  also  can  specify  the
       size  (maxin)  and  maximum  output  value (maxout) of the
       gamma table.

       gamma is a floating point value, neutral value is 1.0,  if
       the value is larger than 1.0 then the image gets brighter.

       shadow defines the minmum input value that is necessary to
       create an output value larger than zero.  shadow has to be
       in the range [0..maxin]. Its default value is 0.

       highlight defines the maximum input value that produces an
       output  value smaller than maxout.  highlight has to be in
       the range [0..maxin], highlight  has  to  be  larger  than
       shadow.  Its  default value is the same as maxin (16383 if
       not set).

       maxin defines the  size  of  the  gamma  table.  The  size
       depends  on  the  scanner/backend.   If the scanner uses 8
       bits gamma input then maxin has to be set to 255,  for  10
       bits  1023,  for  12  bits  4095,  for  14 bits 16383. The
       default is 16383.  To find out what value maxin has to  be
       call   scanimage   with   a   very   large   gamma   table
       [0]0-[99999]255 then scanimage  prints  an  error  message
       with the needed size of the gamma table.

       maxout  defines  the  maximum output value. Take a look at
       the output of scanimage -h to find out what maxout has  to
       be. The default value is 255.


       scanimage  --custom-gamma=yes --gamma-table `gamma4scanim­
       age 1.8 0 11500 16383 255` >image.pnm




       Oliver Rauch


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