1TIFFDITHER(1)               General Commands Manual              TIFFDITHER(1)
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NAME

6       tiffdither - convert a greyscale image to bilevel using dithering
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SYNOPSIS

9       tiffdither [ options ] input.tif output.tif
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DESCRIPTION

12       tiffdither converts a single channel 8-bit greyscale image to a bilevel
13       image using Floyd-Steinberg error propagation with thresholding.
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OPTIONS

16       -c     Specify the compression to use for data written  to  the  output
17              file:  none  for  no compression, packbits for PackBits compres‐
18              sion, lzw for Lempel-Ziv & Welch compression,  zip  for  Deflate
19              compression,  g3 for CCITT Group 3 (T.4) compression, and g4 for
20              CCITT Group 4 (T.6) compression.   By  default  tiffdither  will
21              compress  data  according  to  the  value of the Compression tag
22              found in the source file.
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24              The CCITT Group 3 and Group 4 compression algorithms can only be
25              used with bilevel data.
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27              Group  3  compression  can  be  specified  together with several
28              T.4-specific options: 1d  for  1-dimensional  encoding,  2d  for
29              2-dimensional  encoding, and fill to force each encoded scanline
30              to be zero-filled so that the terminating EOL  code  lies  on  a
31              byte  boundary.   Group  3-specific  options  are  specified  by
32              appending a ``:''-separated list to the ``g3'' option; e.g.   -c
33              g3:2d:fill to get 2D-encoded data with byte-aligned EOL codes.
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35              LZW  compression  can  be  specified  together  with a predictor
36              value.  A predictor value of 2 causes each scanline of the  out‐
37              put  image  to  undergo  horizontal  differencing  before  it is
38              encoded; a value of 1 forces each scanline to be encoded without
39              differencing.  LZW-specific options are specified by appending a
40              ``:''-separated list to the ``lzw'' option; e.g.  -c  lzw:2  for
41              LZW compression with horizontal differencing.
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43       -f     Specify  the  bit  fill order to use in writing output data.  By
44              default, tiffdither will create a new file with  the  same  fill
45              order as the original.  Specifying -f lsb2msb will force data to
46              be written with the FillOrder tag set  to  LSB2MSB  ,  while  -f
47              msb2lsb will force data to be written with the FillOrder tag set
48              to MSB2LSB .
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50       -t     Set the threshold value for dithering.  By default the threshold
51              value is 128.
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NOTES

54       The  dither  algorithm is taken from the tiffmedian(1) program (written
55       by Paul Heckbert).
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SEE ALSO

58       pal2rgb(1),   fax2tiff(1),    tiffinfo(1),    tiffcp(1),    tiff2bw(1),
59       libtiff(3TIFF)
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61       Libtiff library home page: http://www.remotesensing.org/libtiff/
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65libtiff                       September 20, 2005                 TIFFDITHER(1)