src/tiff/man/tiffdither.1

   1 .\" $Id: tiffdither.1,v 1.3 2005/11/02 11:07:19 dron Exp $
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   3 .\" Copyright (c) 1990-1997 Sam Leffler
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  25 .if n .po 0
  26 .TH TIFFDITHER 1 "September 20, 2005" "libtiff"
  27 .SH NAME
  28 tiffdither \- convert a greyscale image to bilevel using dithering
  29 .SH SYNOPSIS
  30 .B tiffdither
  31 [
  32 .I options
  33 ]
  34 .I input.tif
  35 .I output.tif
  36 .SH DESCRIPTION
  37 .I tiffdither
  38 converts a single channel 8-bit greyscale image to a bilevel image
  39 using Floyd-Steinberg error propagation with thresholding.
  40 .SH OPTIONS
  41 .TP
  42 .B \-c
  43 Specify the compression to use for data written to the output file:
  44 .B none
  45 for no compression,
  46 .B packbits
  47 for PackBits compression,
  48 .B lzw
  49 for Lempel-Ziv & Welch compression,
  50 .B zip
  51 for Deflate compression,
  52 .B g3
  53 for CCITT Group 3 (T.4) compression,
  54 and
  55 .B g4
  56 for CCITT Group 4 (T.6) compression.
  57 By default
  58 .I tiffdither
  59 will compress data according to the value of the
  60 .I Compression
  61 tag found in the source file.
  62 .IP
  63 The
  64 .SM CCITT
  65 Group 3 and Group 4 compression algorithms can only
  66 be used with bilevel data.
  67 .IP
  68 Group 3 compression can be specified together with several
  69 T.4-specific options:
  70 .B 1d
  71 for 1-dimensional encoding,
  72 .B 2d
  73 for 2-dimensional encoding,
  74 and
  75 .B fill
  76 to force each encoded scanline to be zero-filled so that the
  77 terminating EOL code lies on a byte boundary.
  78 Group 3-specific options are specified by appending a ``:''-separated
  79 list to the ``g3'' option; e.g.
  80 .B "\-c g3:2d:fill"
  81 to get 2D-encoded data with byte-aligned EOL codes.
  82 .IP
  83 .SM LZW
  84 compression can be specified together with a
  85 .I predictor
  86 value.
  87 A predictor value of 2 causes
  88 each scanline of the output image to undergo horizontal
  89 differencing before it is encoded; a value
  90 of 1 forces each scanline to be encoded without differencing.
  91 LZW-specific options are specified by appending a ``:''-separated
  92 list to the ``lzw'' option; e.g.
  93 .B "\-c lzw:2"
  94 for
  95 .SM LZW
  96 compression with horizontal differencing.
  97 .TP
  98 .B \-f
  99 Specify the bit fill order to use in writing output data.
 100 By default,
 101 .I tiffdither
 102 will create a new file with the same fill order as the original.
 103 Specifying
 104 .B "\-f lsb2msb"
 105 will force data to be written with the FillOrder tag set to
 106 .SM LSB2MSB ,
 107 while
 108 .B "\-f msb2lsb"
 109 will force data to be written with the FillOrder tag set to
 110 .SM MSB2LSB .
 111 .TP
 112 .B \-t
 113 Set the threshold value for dithering.
 114 By default the threshold value is 128.
 115 .SH NOTES
 116 The dither algorithm is taken from the
 117 .BR tiffmedian (1)
 118 program (written by Paul Heckbert).
 119 .SH "SEE ALSO"
 120 .BR pal2rgb (1),
 121 .BR fax2tiff (1),
 122 .BR tiffinfo (1),
 123 .BR tiffcp (1),
 124 .BR tiff2bw (1),
 125 .BR libtiff (3TIFF)
 126 .PP
 127 Libtiff library home page:
 128 .BR http://www.remotesensing.org/libtiff/