| 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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| 2 | <!DOCTYPE thresholds [
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| 3 | <!ELEMENT thresholds (threshold)+>
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| 4 | <!ELEMENT threshold (description , levels)>
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| 5 | <!ELEMENT description (CDATA)>
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| 6 | <!ELEMENT levels (CDATA)>
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| 7 | <!ATTLIST threshold map ID #REQUIRED>
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| 8 | <!ATTLIST levels width CDATA #REQUIRED>
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| 9 | <!ATTLIST levels height CDATA #REQUIRED>
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| 10 | <!ATTLIST levels divisor CDATA #REQUIRED>
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| 11 | ]>
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| 12 | <!--
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| 13 | Threshold Maps for Ordered Posterized Dither
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| 14 |
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| 15 | Each "<threshold>" element defines the map name, description, and an array
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| 16 | of "levels" used to provide the threshold map for ordered dithering and
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| 17 | digital halftoning.
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| 18 |
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| 19 | The "alias" attribute provides a backward compatible name for this threshold
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| 20 | map (pre-dating IM v6.2.9-6), and are deprecated.
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| 21 |
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| 22 | The description is a english description of what the threshold map achieves
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| 23 | and is only used for 'listing' the maps.
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| 24 |
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| 25 | The map itself is a rectangular array of integers or threshold "levels"
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| 26 | of the given "width" and "height" declared within the enclosing <levels>
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| 27 | element. That is "width*height" integers or "levels" *must* be provided
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| 28 | within each map.
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| 29 |
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| 30 | Each of the "levels" integer values (each value representing the threshold
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| 31 | intensity "level/divisor" at which that pixel is turned on. The "levels"
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| 32 | integers given can be any postive integers between "0" and the "divisor",
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| 33 | excluding those limits.
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| 34 |
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| 35 | The "divisor" not only defines the upper limit and threshold divisor for each
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| 36 | "level" but also the total number of pseudo-levels the threshold mapping
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| 37 | creates and fills with a dither pattern. That is a ordered bitmap dither
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| 38 | of a pure greyscale gradient will use a maximum of "divisor" ordered bitmap
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| 39 | patterns, including the patterns with all the pixels 'on' and all the pixel
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| 40 | 'off'. It may define less patterns than that, but the color channels will
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| 41 | be thresholded in units based on "divisor".
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| 42 |
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| 43 | Alternatively for a multi-level posterization, ImageMagick inserts
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| 44 | "divisor-2" dither patterns (as defined by the threshold map) between each of
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| 45 | channel color level produced.
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| 46 |
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| 47 | For example the map "o2x2" has a divisor of 5, which will define 3 bitmap
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| 48 | patterns plus the patterns with all pixels 'on' and 'off'. A greyscale
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| 49 | gradient will thus have 5 distinct areas.
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| 50 | -->
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| 51 | <thresholds>
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| 52 |
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| 53 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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| 54 | Minimal Dither and Non-Dither Threshold Maps
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| 55 | -->
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| 56 | <threshold map="threshold" alias="1x1">
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| 57 | <description>Threshold Non-Dither</description>
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| 58 | <levels width="1" height="1" divisor="2">
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| 59 | 1
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| 60 | </levels>
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| 61 | </threshold>
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| 62 |
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| 63 | <threshold map="checks" alias="2x1">
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| 64 | <description>Checkerboard Dither</description>
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| 65 | <levels width="2" height="2" divisor="3">
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| 66 | 1 2
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| 67 | 2 1
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| 68 | </levels>
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| 69 | </threshold>
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| 70 |
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| 71 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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| 72 | Diffused Pixel Ordered Dither Patterns
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| 73 | -->
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| 74 | <threshold map="o2x2" alias="2x2">
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| 75 | <description>Ordered 2x2 Diffused Pixel</description>
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| 76 | <levels width="2" height="2" divisor="5">
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| 77 | 1 3
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| 78 | 4 2
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| 79 | </levels>
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| 80 | </threshold>
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| 81 |
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| 82 | <threshold map="o3x3" alias="3x3">
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| 83 | <description>Ordered 4x4 Diffused Pixel</description>
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| 84 | <levels width="3" height="3" divisor="10">
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| 85 | 3 7 4
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| 86 | 6 1 9
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| 87 | 2 8 5
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| 88 | </levels>
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| 89 | </threshold>
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| 90 |
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| 91 | <threshold map="o4x4" alias="4x4">
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| 92 | <!--
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| 93 | From "Dithering Algorithms"
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| 94 | http://www.efg2.com/Lab/Library/ImageProcessing/DHALF.TXT
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| 95 | -->
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| 96 | <description>Ordered 4x4 Diffused Pixel</description>
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| 97 | <levels width="4" height="4" divisor="17">
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| 98 | 1 9 3 11
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| 99 | 13 5 15 7
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| 100 | 4 12 2 10
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| 101 | 16 8 14 6
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| 102 | </levels>
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| 103 | </threshold>
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| 104 |
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| 105 | <threshold map="o8x8" alias="8x8">
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| 106 | <!-- Extracted from original 'OrderedDither()' Function -->
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| 107 | <description>Ordered 8x8 Diffused Pixel</description>
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| 108 | <levels width="8" height="8" divisor="65">
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| 109 | 1 49 13 61 4 52 16 64
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| 110 | 33 17 45 29 36 20 48 32
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| 111 | 9 57 5 53 12 60 8 56
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| 112 | 41 25 37 21 44 28 40 24
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| 113 | 3 51 15 63 2 50 14 62
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| 114 | 35 19 47 31 34 18 46 30
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| 115 | 11 59 7 55 10 58 6 54
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| 116 | 43 27 39 23 42 26 38 22
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| 117 | </levels>
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| 118 | </threshold>
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| 119 |
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| 120 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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| 121 | Halftones - Angled 45 degrees
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| 122 |
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| 123 | Initially added to ImageMagick by Glenn Randers-Pehrson, IM v6.2.8-6,
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| 124 | modified to be more halftone-like by Anthony, IM v6.2.9-7 Larger halftone
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| 125 | patterns still needed to be added.
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| 126 | -->
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| 127 | <threshold map="h4x4a" alias="4x1">
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| 128 | <description>Halftone 4x4 (angled)</description>
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| 129 | <levels width="4" height="4" divisor="9">
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| 130 | 4 2 7 5
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| 131 | 3 1 8 6
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| 132 | 7 5 4 2
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| 133 | 8 6 3 1
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| 134 | </levels>
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| 135 | </threshold>
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| 136 |
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| 137 | <threshold map="h6x6a" alias="6x1">
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| 138 | <description>Halftone 6x6 (angled)</description>
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| 139 | <levels width="6" height="6" divisor="19">
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| 140 | 14 13 10 8 2 3
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| 141 | 16 18 12 7 1 4
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| 142 | 15 17 11 9 6 5
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| 143 | 8 2 3 14 13 10
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| 144 | 7 1 4 16 18 12
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| 145 | 9 6 5 15 17 11
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| 146 | </levels>
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| 147 | </threshold>
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| 148 |
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| 149 | <threshold map="h8x8a" alias="8x1">
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| 150 | <description>Halftone 8x8 (angled)</description>
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| 151 | <levels width="8" height="8" divisor="33">
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| 152 | 13 7 8 14 17 21 22 18
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| 153 | 6 1 3 9 28 31 29 23
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| 154 | 5 2 4 10 27 32 30 24
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| 155 | 16 12 11 15 20 26 25 19
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| 156 | 17 21 22 18 13 7 8 14
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| 157 | 28 31 29 23 6 1 3 9
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| 158 | 27 32 30 24 5 2 4 10
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| 159 | 20 26 25 19 16 12 11 15
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| 160 | </levels>
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| 161 | </threshold>
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| 162 |
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| 163 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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| 164 | Halftones - Orthogonally Aligned, or Un-angled
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| 165 |
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| 166 | Initially added by Anthony Thyssen, IM v6.2.9-5 using techniques from
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| 167 | "Dithering & Halftoning" by Gernot Haffmann
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| 168 | http://www.fho-emden.de/~hoffmann/hilb010101.pdf
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| 169 | -->
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| 170 | <threshold map="h4x4o">
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| 171 | <description>Halftone 4x4 (orthogonal)</description>
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| 172 | <levels width="4" height="4" divisor="17">
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| 173 | 7 13 11 4
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| 174 | 12 16 14 8
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| 175 | 10 15 6 2
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| 176 | 5 9 3 1
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| 177 | </levels>
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| 178 | </threshold>
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| 179 |
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| 180 | <threshold map="h6x6o">
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| 181 | <description>Halftone 6x6 (orthogonal)</description>
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| 182 | <levels width="6" height="6" divisor="37">
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| 183 | 7 17 27 14 9 4
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| 184 | 21 29 33 31 18 11
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| 185 | 24 32 36 34 25 22
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| 186 | 19 30 35 28 20 10
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| 187 | 8 15 26 16 6 2
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| 188 | 5 13 23 12 3 1
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| 189 | </levels>
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| 190 | </threshold>
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| 191 |
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| 192 | <threshold map="h8x8o">
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| 193 | <description>Halftone 8x8 (orthogonal)</description>
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| 194 | <levels width="8" height="8" divisor="65">
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| 195 | 7 21 33 43 36 19 9 4
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| 196 | 16 27 51 55 49 29 14 11
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| 197 | 31 47 57 61 59 45 35 23
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| 198 | 41 53 60 64 62 52 40 38
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| 199 | 37 44 58 63 56 46 30 22
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| 200 | 15 28 48 54 50 26 17 10
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| 201 | 8 18 34 42 32 20 6 2
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| 202 | 5 13 25 39 24 12 3 1
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| 203 | </levels>
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| 204 | </threshold>
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| 205 |
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| 206 | <threshold map="h16x16o">
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| 207 | <!--
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| 208 | Direct extract from "Dithering & Halftoning" by Gernot Haffmann.
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| 209 | This may need some fine tuning for symmetry of the halftone dots,
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| 210 | as it was a mathematically formulated pattern.
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| 211 | -->
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| 212 | <description>Halftone 16x16 (orthogonal)</description>
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| 213 | <levels width="16" height="16" divisor="257">
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| 214 | 4 12 24 44 72 100 136 152 150 134 98 70 42 23 11 3
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| 215 | 7 16 32 52 76 104 144 160 158 142 102 74 50 31 15 6
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| 216 | 19 27 40 60 92 132 168 180 178 166 130 90 58 39 26 18
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| 217 | 36 48 56 80 124 176 188 204 203 187 175 122 79 55 47 35
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| 218 | 64 68 84 116 164 200 212 224 223 211 199 162 114 83 67 63
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| 219 | 88 96 112 156 192 216 232 240 239 231 214 190 154 111 95 87
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| 220 | 108 120 148 184 208 228 244 252 251 243 226 206 182 147 119 107
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| 221 | 128 140 172 196 219 235 247 256 255 246 234 218 194 171 139 127
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| 222 | 126 138 170 195 220 236 248 253 254 245 233 217 193 169 137 125
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| 223 | 106 118 146 183 207 227 242 249 250 241 225 205 181 145 117 105
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| 224 | 86 94 110 155 191 215 229 238 237 230 213 189 153 109 93 85
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| 225 | 62 66 82 115 163 198 210 221 222 209 197 161 113 81 65 61
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| 226 | 34 46 54 78 123 174 186 202 201 185 173 121 77 53 45 33
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| 227 | 20 28 37 59 91 131 167 179 177 165 129 89 57 38 25 17
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| 228 | 8 13 29 51 75 103 143 159 157 141 101 73 49 30 14 5
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| 229 | 1 9 21 43 71 99 135 151 149 133 97 69 41 22 10 2
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| 230 | </levels>
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| 231 | </threshold>
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| 232 |
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| 233 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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| 234 | Special Purpose Dithers
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| 235 | -->
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| 236 |
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| 237 | </thresholds>
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