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  threhold-
       ing.

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	with-
	      out   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  thresh-
	      old 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(3)



			       October 15, 1995			TIFFDITHER(1)

UNIX/Linux commands referenced on this page:

1. convert
2. zip
3. file