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/

libtiff                                        September 20, 2005                                  TIFFDITHER(1)