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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 thresholding.

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 algorithms 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  boundary.   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  horizontal 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 FillOrder tag set
          to MSB2LSB .

   -r     Make each strip have no more than the given number of rows.

   -t     Set the threshold value for dithering.  By default the threshold
          value is 128.

NOTES

   The  dither  algorithm is taken from the tiffmedian(1) program (written
   by Paul Heckbert).

SEE ALSO

   pal2rgb(1),   fax2tiff(1),    tiffinfo(1),    tiffcp(1),    tiff2bw(1),
   libtiff(3TIFF)

   Libtiff library home page: http://www.simplesystems.org/libtiff/



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