src/tiff/man/tiffdither.1

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