tiffdither

 

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 TIFFDITHER(1)                                       TIFFDITHER(1)
 
 
 
NAME
        tiffdither  -  convert  a greyscale image to bilevel using
        dithering
 
SYNOPSIS
        tiffdither [ options ] input.tif output.tif
 
DESCRIPTION
        tiffdither converts a single channel 8-bit greyscale image
        to a bilevel image using Floyd-Steinberg error propagation
        with threholding.
 
OPTIONS
        -c     Specify the compression to use for data written  to
               the  output file: none for no compression, packbits
               for PackBits  compression,  lzw  for  Lempel-Ziv  &
               Welch  compression, zip for Deflate compression, g3
               for CCITT Group 3 (T.4)  compression,  and  g4  for
               CCITT   Group  4  (T.6)  compression.   By  default
               tiffdither will  compress  data  according  to  the
               value  of  the  Compression tag found in the source
               file.
 
               The CCITT Group 3 and  Group  4  compression  algo­
               rithms can only be used with bilevel data.
 
               Group  3 compression can be specified together with
               several T.4-specific options: 1d for  1-dimensional
               encoding,  2d  for 2-dimensional encoding, and fill
               to force each encoded scanline to be zero-filled so
               that the terminating EOL code lies on a byte bound­
               ary.  Group 3-specific  options  are  specified  by
               appending  a  ``:''-separated  list  to  the ``g3''
               option; e.g.  -c g3:2d:fill to get 2D-encoded  data
               with byte-aligned EOL codes.
 
               LZW  compression  can  be specified together with a
               predictor value.  A predictor  value  of  2  causes
               each  scanline of the output image to undergo hori­
               zontal differencing before it is encoded;  a  value
               of  1  forces  each  scanline to be encoded without
               differencing.  LZW-specific options  are  specified
               by  appending a ``:''-separated list to the ``lzw''
               option; e.g.  -c lzw:2  for  LZW  compression  with
               horizontal differencing.
 
        -f     Specify the bit fill order to use in writing output
               data.  By default, tiffdither  will  create  a  new
               file  with  the  same  fill  order as the original.
               Specifying -f lsb2msb will force data to be written
               with  the  FillOrder  tag set to LSB2MSB , while -f
               msb2lsb will force data to be written with the Fil­
               lOrder tag set to MSB2LSB .
 
        -t     Set  the threshold value for dithering.  By default
               the threshold value is 128.
 
NOTES
        The dither algorithm is taken from the tiffmedian(1)  pro­
        gram (written by Paul Heckbert).
 
SEE ALSO
        pal2rgb(1),     fax2tiff(1),    tiffinfo(1),    tiffcp(1),
        tiff2bw(1), libtiff(3)
 
 
 
                          October 15, 1995           TIFFDITHER(1)

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