NAME

       tiffdither - convert a greyscale TIFF 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 compress
              Specify the compression to use for data written to the output file:

                               ┌────────────┬──────────────────────────────────┐
                               │Compression │ Description                      │
                               ├────────────┼──────────────────────────────────┤
                               │none        │ no compression                   │
                               ├────────────┼──────────────────────────────────┤
                               │packbits    │ PackBits compression             │
                               ├────────────┼──────────────────────────────────┤
                               │lzw         │ Lempel-Ziv & Welch compression   │
                               ├────────────┼──────────────────────────────────┤
                               │zip         │ Deflate compression              │
                               ├────────────┼──────────────────────────────────┤
                               │g3          │ CCITT Group 3 (T.4) compression  │
                               ├────────────┼──────────────────────────────────┤
                               │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 program (written by Paul Heckbert).

SEE ALSO

       pal2rgb (1), fax2tiff (1), tiffinfo (1), tiffcp (1), tiff2bw (3tiff)

AUTHOR

       LibTIFF contributors

COPYRIGHT

       1988-2023, LibTIFF contributors