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/