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TIFFDITHER(1)          DragonFly General Commands Manual         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/

libtiff                       September 20, 2005                 TIFFDITHER(1)

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