TIFFDITHER(1)							 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 compres-
	      sion, 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  out-
	      put  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 .

       -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.remotesensing.org/libtiff/



libtiff 		      September 20, 2005		 TIFFDITHER(1)

NAME - SYNOPSIS - DESCRIPTION - OPTIONS - NOTES - SEE ALSO -