src/tiff/man/tiffmedian.1

   1 .\" $Id: tiffmedian.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 TIFFMEDIAN 1 "November 2, 2005" "libtiff"
  27 .SH NAME
  28 tiffmedian \- apply the median cut algorithm to data in a
  29 .SM TIFF
  30 file
  31 .SH SYNOPSIS
  32 .B tiffmedian
  33 [
  34 .I options
  35 ]
  36 .I input.tif
  37 .I output.tif
  38 .SH DESCRIPTION
  39 .I tiffmedian
  40 applies the median cut algorithm to an
  41 .SM RGB
  42 image in
  43 .I input.tif
  44 to generate a palette image that is written to
  45 .IR output.tif .
  46 The generated colormap has, by default, 256 entries.
  47 The image data is quantized by mapping each
  48 pixel to the closest color values in the colormap.
  49 .SH OPTIONS
  50 .TP
  51 .B \-c
  52 Specify the compression to use for data written to the output file:
  53 .B none
  54 for no compression,
  55 .B packbits
  56 for PackBits compression,
  57 .B lzw
  58 for Lempel-Ziv & Welch compression,
  59 and
  60 .B zip
  61 for Deflate compression.
  62 By default
  63 .I tiffmedian
  64 will compress data according to the value of the
  65 .I Compression
  66 tag found in the source file.
  67 .IP
  68 .SM LZW
  69 compression can be specified together with a
  70 .I predictor
  71 value.
  72 A predictor value of 2 causes
  73 each scanline of the output image to undergo horizontal
  74 differencing before it is encoded; a value
  75 of 1 forces each scanline to be encoded without differencing.
  76 LZW-specific options are specified by appending a ``:''-separated
  77 list to the ``lzw'' option; e.g.
  78 .B "\-c lzw:2"
  79 for
  80 .SM LZW
  81 compression with horizontal differencing.
  82 .TP
  83 .B \-C
  84 Specify the number of entries to use in the generated colormap.
  85 By default all 256 entries/colors are used.
  86 .TP
  87 .B \-f
  88 Apply Floyd-Steinberg dithering before selecting a colormap entry.
  89 .TP
  90 .B \-r
  91 Specify the number of rows (scanlines) in each strip of data
  92 written to the output file.
  93 By default,
  94 .I tiffmedian
  95 attempts to set the rows/strip
  96 that no more than 8 kilobytes of data appear in a strip.
  97 .SH NOTES
  98 This program is derived from Paul Heckbert's
  99 .I median
 100 program.
 101 .SH "SEE ALSO"
 102 .BR pal2rgb (1),
 103 .BR tiffinfo (1),
 104 .BR tiffcp (1),
 105 .BR tiffcmp (1),
 106 .BR libtiff (3TIFF)
 107 .PP
 108 .BR "Color Image Quantization for Frame Buffer Display",
 109 Paul Heckbert, SIGGRAPH proceedings, 1982, pp. 297-307.
 110 .PP
 111 Libtiff library home page:
 112 .BR http://www.remotesensing.org/libtiff/