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7 <title>TIFFDITHER</title>

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11 <h1 align=center>TIFFDITHER</h1>

 <a href="#NAME">NAME</a><br>

 <a href="#SYNOPSIS">SYNOPSIS</a><br>

 <a href="#DESCRIPTION">DESCRIPTION</a><br>

 <a href="#OPTIONS">OPTIONS</a><br>

 <a href="#NOTES">NOTES</a><br>

 <a href="#SEE ALSO">SEE ALSO</a><br>

19 <hr>

20 <a name="NAME"></a>

21 <h2>NAME</h2>

22

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28 <p>tiffdither − convert a greyscale image to bilevel

29 using dithering</p>

30 </td>

31 </table>

32 <a name="SYNOPSIS"></a>

33 <h2>SYNOPSIS</h2>

34

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 <p><b>tiffdither</b> [ <i>options</i> ] <i>input.tif

41 output.tif</i></p>

42 </td>

43 </table>

44 <a name="DESCRIPTION"></a>

45 <h2>DESCRIPTION</h2>

46

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52 <p><i>tiffdither</i> converts a single channel 8-bit

53 greyscale image to a bilevel image using Floyd-Steinberg

54 error propagation with thresholding.</p>

55 </td>

56 </table>

57 <a name="OPTIONS"></a>

58 <h2>OPTIONS</h2>

59

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66 <p><b>−c</b></p>

67 </td>

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69 <td width="80%">

71 <p>Specify the compression to use for data written to the

72 output file: <b>none</b> for no compression, <b>packbits</b>

73 for PackBits compression, <b>lzw</b> for Lempel-Ziv &

74 Welch compression, <b>zip</b> for Deflate compression,

 <b>g3</b> for CCITT Group 3 (T.4) compression, and <b>g4</b>

76 for CCITT Group 4 (T.6) compression. By default

77 <i>tiffdither</i> will compress data according to the value

78 of the <i>Compression</i> tag found in the source file.</p>

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81 </td>

82 </table>

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 <p>The <small>CCITT</small> Group 3 and Group 4 compression

90 algorithms can only be used with bilevel data.</p>

91

92 <p>Group 3 compression can be specified together with

 several T.4-specific options: <b>1d</b> for 1-dimensional

94 encoding, <b>2d</b> for 2-dimensional encoding, and

95 <b>fill</b> to force each encoded scanline to be zero-filled

96 so that the terminating EOL code lies on a byte boundary.

97 Group 3-specific options are specified by appending a

98 ‘‘:’’-separated list to the

99 ‘‘g3’’ option; e.g. <b>−c

100 g3:2d:fill</b> to get 2D-encoded data with byte-aligned EOL

101 codes.</p>

102

103 <p><small>LZW</small> compression can be specified together

104 with a <i>predictor</i> value. A predictor value of 2 causes

105 each scanline of the output image to undergo horizontal

106 differencing before it is encoded; a value of 1 forces each

107 scanline to be encoded without differencing. LZW-specific

108 options are specified by appending a

109 ‘‘:’’-separated list to the

110 ‘‘lzw’’ option; e.g. <b>−c

111 lzw:2</b> for <small>LZW</small> compression with horizontal

112 differencing.</p>

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114 </table>

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121

122 <p><b>−f</b></p>

123 </td>

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125 <td width="80%">

126

127 <p>Specify the bit fill order to use in writing output

128 data. By default, <i>tiffdither</i> will create a new file

129 with the same fill order as the original. Specifying

130 <b>−f lsb2msb</b> will force data to be written with

131 the <i>FillOrder</i> tag set to <small>LSB2MSB ,</small>

132 while <b>−f msb2lsb</b> will force data to be written

133 with the <i>Fill- Order</i> tag set to <small>MSB2LSB

134 .</small></p>

135 </td>

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137 </td>

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141

142 <p><b>−t</b></p>

143 </td>

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145 <td width="80%">

146

147 <p>Set the threshold value for dithering. By default the

148 threshold value is 128.</p>

149 </td>

150 <td width="0%">

151 </td>

152 </table>

153 <a name="NOTES"></a>

154 <h2>NOTES</h2>

155

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161 <p>The dither algorithm is taken from the

162 <b>tiffmedian</b>(1) program (written by Paul Heckbert).</p>

163 </td>

164 </table>

165 <a name="SEE ALSO"></a>

166 <h2>SEE ALSO</h2>

167

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 <p><b>pal2rgb</b>(1), <b>fax2tiff</b>(1),

 <b>tiffinfo</b>(1), <b>tiffcp</b>(1), <b>tiff2bw</b>(1),

175 <b>libtiff</b>(3TIFF)</p>

176

177 <p>Libtiff library home page:

178 <b>http://www.remotesensing.org/libtiff/</b></p>

179 </td>

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