1 <?xml version="1.0" encoding="ISO-8859-1"?> 2 <!DOCTYPE thresholds [ 3 <!ELEMENT thresholds (threshold)+> 4 <!ELEMENT threshold (description , levels)> 5 <!ELEMENT description (CDATA)> 6 <!ELEMENT levels (CDATA)> 7 <!ATTLIST threshold map ID #REQUIRED> 8 <!ATTLIST levels width CDATA #REQUIRED> 9 <!ATTLIST levels height CDATA #REQUIRED> 10 <!ATTLIST levels divisor CDATA #REQUIRED> 11 ]> 12 <!-- 13 Threshold Maps for Ordered Posterized Dither 14 15 Each "<threshold>" element defines the map name, description, and an array 16 of "levels" used to provide the threshold map for ordered dithering and 17 digital halftoning. 18 19 The "alias" attribute provides a backward compatible name for this threshold 20 map (pre-dating IM v6.2.9-6), and are deprecated. 21 22 The description is a english description of what the threshold map achieves 23 and is only used for 'listing' the maps. 24 25 The map itself is a rectangular array of integers or threshold "levels" 26 of the given "width" and "height" declared within the enclosing <levels> 27 element. That is "width*height" integers or "levels" *must* be provided 28 within each map. 29 30 Each of the "levels" integer values (each value representing the threshold 31 intensity "level/divisor" at which that pixel is turned on. The "levels" 32 integers given can be any postive integers between "0" and the "divisor", 33 excluding those limits. 34 35 The "divisor" not only defines the upper limit and threshold divisor for each 36 "level" but also the total number of pseudo-levels the threshold mapping 37 creates and fills with a dither pattern. That is a ordered bitmap dither 38 of a pure greyscale gradient will use a maximum of "divisor" ordered bitmap 39 patterns, including the patterns with all the pixels 'on' and all the pixel 40 'off'. It may define less patterns than that, but the color channels will 41 be thresholded in units based on "divisor". 42 43 Alternatively for a multi-level posterization, ImageMagick inserts 44 "divisor-2" dither patterns (as defined by the threshold map) between each of 45 channel color level produced. 46 47 For example the map "o2x2" has a divisor of 5, which will define 3 bitmap 48 patterns plus the patterns with all pixels 'on' and 'off'. A greyscale 49 gradient will thus have 5 distinct areas. 50 --> 51 <thresholds> 52 53 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - 54 Minimal Dither and Non-Dither Threshold Maps 55 --> 56 <threshold map="threshold" alias="1x1"> 57 <description>Threshold 1x1 (non-dither)</description> 58 <levels width="1" height="1" divisor="2"> 59 1 60 </levels> 61 </threshold> 62 63 <threshold map="checks" alias="2x1"> 64 <description>Checkerboard 2x1 (dither)</description> 65 <levels width="2" height="2" divisor="3"> 66 1 2 67 2 1 68 </levels> 69 </threshold> 70 71 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - 72 (dispersed) Ordered Dither Patterns 73 --> 74 <threshold map="o2x2" alias="2x2"> 75 <description>Ordered 2x2 (dispersed)</description> 76 <levels width="2" height="2" divisor="5"> 77 1 3 78 4 2 79 </levels> 80 </threshold> 81 82 <threshold map="o3x3" alias="3x3"> 83 <description>Ordered 3x3 (dispersed)</description> 84 <levels width="3" height="3" divisor="10"> 85 3 7 4 86 6 1 9 87 2 8 5 88 </levels> 89 </threshold> 90 91 <threshold map="o4x4" alias="4x4"> 92 <!-- 93 From "Dithering Algorithms" 94 http://www.efg2.com/Lab/Library/ImageProcessing/DHALF.TXT 95 --> 96 <description>Ordered 4x4 (dispersed)</description> 97 <levels width="4" height="4" divisor="17"> 98 1 9 3 11 99 13 5 15 7 100 4 12 2 10 101 16 8 14 6 102 </levels> 103 </threshold> 104 105 <threshold map="o8x8" alias="8x8"> 106 <!-- Extracted from original 'OrderedDither()' Function --> 107 <description>Ordered 8x8 (dispersed)</description> 108 <levels width="8" height="8" divisor="65"> 109 1 49 13 61 4 52 16 64 110 33 17 45 29 36 20 48 32 111 9 57 5 53 12 60 8 56 112 41 25 37 21 44 28 40 24 113 3 51 15 63 2 50 14 62 114 35 19 47 31 34 18 46 30 115 11 59 7 55 10 58 6 54 116 43 27 39 23 42 26 38 22 117 </levels> 118 </threshold> 119 120 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - 121 Halftones - Angled 45 degrees 122 123 Initially added to ImageMagick by Glenn Randers-Pehrson, IM v6.2.8-6, 124 modified to be more symmetrical with intensity by Anthony, IM v6.2.9-7 125 126 These patterns initially start as circles, but then form diamonds 127 pattern at the 50% threshold level, before forming negated circles, 128 as it approached the other threshold extereme. 129 --> 130 <threshold map="h4x4a" alias="4x1"> 131 <description>Halftone 4x4 (angled)</description> 132 <levels width="4" height="4" divisor="9"> 133 4 2 7 5 134 3 1 8 6 135 7 5 4 2 136 8 6 3 1 137 </levels> 138 </threshold> 139 140 <threshold map="h6x6a" alias="6x1"> 141 <description>Halftone 6x6 (angled)</description> 142 <levels width="6" height="6" divisor="19"> 143 14 13 10 8 2 3 144 16 18 12 7 1 4 145 15 17 11 9 6 5 146 8 2 3 14 13 10 147 7 1 4 16 18 12 148 9 6 5 15 17 11 149 </levels> 150 </threshold> 151 152 <threshold map="h8x8a" alias="8x1"> 153 <description>Halftone 8x8 (angled)</description> 154 <levels width="8" height="8" divisor="33"> 155 13 7 8 14 17 21 22 18 156 6 1 3 9 28 31 29 23 157 5 2 4 10 27 32 30 24 158 16 12 11 15 20 26 25 19 159 17 21 22 18 13 7 8 14 160 28 31 29 23 6 1 3 9 161 27 32 30 24 5 2 4 10 162 20 26 25 19 16 12 11 15 163 </levels> 164 </threshold> 165 166 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - 167 Halftones - Orthogonally Aligned, or Un-angled 168 169 Initially added by Anthony Thyssen, IM v6.2.9-5 using techniques from 170 "Dithering & Halftoning" by Gernot Haffmann 171 http://www.fho-emden.de/~hoffmann/hilb010101.pdf 172 173 These patterns initially start as circles, but then form square 174 pattern at the 50% threshold level, before forming negated circles, 175 as it approached the other threshold extereme. 176 --> 177 <threshold map="h4x4o"> 178 <description>Halftone 4x4 (orthogonal)</description> 179 <levels width="4" height="4" divisor="17"> 180 7 13 11 4 181 12 16 14 8 182 10 15 6 2 183 5 9 3 1 184 </levels> 185 </threshold> 186 187 <threshold map="h6x6o"> 188 <description>Halftone 6x6 (orthogonal)</description> 189 <levels width="6" height="6" divisor="37"> 190 7 17 27 14 9 4 191 21 29 33 31 18 11 192 24 32 36 34 25 22 193 19 30 35 28 20 10 194 8 15 26 16 6 2 195 5 13 23 12 3 1 196 </levels> 197 </threshold> 198 199 <threshold map="h8x8o"> 200 <description>Halftone 8x8 (orthogonal)</description> 201 <levels width="8" height="8" divisor="65"> 202 7 21 33 43 36 19 9 4 203 16 27 51 55 49 29 14 11 204 31 47 57 61 59 45 35 23 205 41 53 60 64 62 52 40 38 206 37 44 58 63 56 46 30 22 207 15 28 48 54 50 26 17 10 208 8 18 34 42 32 20 6 2 209 5 13 25 39 24 12 3 1 210 </levels> 211 </threshold> 212 213 <threshold map="h16x16o"> 214 <!-- 215 Direct extract from "Dithering & Halftoning" by Gernot Haffmann. 216 This may need some fine tuning for symmetry of the halftone dots, 217 as it was a mathematically formulated pattern. 218 --> 219 <description>Halftone 16x16 (orthogonal)</description> 220 <levels width="16" height="16" divisor="257"> 221 4 12 24 44 72 100 136 152 150 134 98 70 42 23 11 3 222 7 16 32 52 76 104 144 160 158 142 102 74 50 31 15 6 223 19 27 40 60 92 132 168 180 178 166 130 90 58 39 26 18 224 36 48 56 80 124 176 188 204 203 187 175 122 79 55 47 35 225 64 68 84 116 164 200 212 224 223 211 199 162 114 83 67 63 226 88 96 112 156 192 216 232 240 239 231 214 190 154 111 95 87 227 108 120 148 184 208 228 244 252 251 243 226 206 182 147 119 107 228 128 140 172 196 219 235 247 256 255 246 234 218 194 171 139 127 229 126 138 170 195 220 236 248 253 254 245 233 217 193 169 137 125 230 106 118 146 183 207 227 242 249 250 241 225 205 181 145 117 105 231 86 94 110 155 191 215 229 238 237 230 213 189 153 109 93 85 232 62 66 82 115 163 198 210 221 222 209 197 161 113 81 65 61 233 34 46 54 78 123 174 186 202 201 185 173 121 77 53 45 33 234 20 28 37 59 91 131 167 179 177 165 129 89 57 38 25 17 235 8 13 29 51 75 103 143 159 157 141 101 73 49 30 14 5 236 1 9 21 43 71 99 135 151 149 133 97 69 41 22 10 2 237 </levels> 238 </threshold> 239 240 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - 241 Halftones - Orthogonally Expanding Circle Patterns 242 243 Added by Glenn Randers-Pehrson, 4 Nov 2010, ImageMagick 6.6.5-6 244 245 Rather than producing a diamond 50% threshold pattern, these 246 continue to generate larger (overlapping) circles. They are 247 more like a true halftone pattern formed by covering a surface 248 with either pure white or pure black circular dots. 249 250 WARNING: true halftone patterns only use true circles even in 251 areas of highly varying intensity. Threshold dither patterns 252 can generate distorted circles in such areas. 253 --> 254 255 <threshold map="c5x5b" alias="c5x5"> 256 <description>Circles 5x5 (black)</description> 257 <levels width="5" height="5" divisor="26"> 258 1 21 16 15 4 259 5 17 20 19 14 260 6 21 25 24 12 261 7 18 22 23 11 262 2 8 9 10 3 263 </levels> 264 </threshold> 265 266 267 <threshold map="c5x5w"> 268 <description>Circles 5x5 (white)</description> 269 <levels width="5" height="5" divisor="26"> 270 25 21 10 11 22 271 20 9 6 7 12 272 19 5 1 2 13 273 18 8 4 3 14 274 24 17 16 15 23 275 </levels> 276 </threshold> 277 278 <threshold map="c6x6b" alias="c6x6"> 279 <description>Circles 6x6 (black)</description> 280 <levels width="6" height="6" divisor="37"> 281 1 5 14 13 12 4 282 6 22 28 27 21 11 283 15 29 35 34 26 20 284 16 30 36 33 25 19 285 7 23 31 32 24 10 286 2 8 17 18 9 3 287 </levels> 288 </threshold> 289 290 <threshold map="c6x6w"> 291 <description>Circles 6x6 (white)</description> 292 <levels width="6" height="6" divisor="37"> 293 36 32 23 24 25 33 294 31 15 9 10 16 26 295 22 8 2 3 11 17 296 21 7 1 4 12 18 297 30 14 6 5 13 27 298 35 29 20 19 28 34 299 </levels> 300 </threshold> 301 302 <threshold map="c7x7b" alias="c7x7"> 303 <description>Circles 7x7 (black)</description> 304 <levels width="7" height="7" divisor="50"> 305 3 9 18 28 17 8 2 306 10 24 33 39 32 23 7 307 19 34 44 48 43 31 16 308 25 40 45 49 47 38 27 309 20 35 41 46 42 29 15 310 11 21 36 37 28 22 6 311 4 12 13 26 14 5 1 312 </levels> 313 </threshold> 314 315 316 <threshold map="c7x7w"> 317 <description>Circles 7x7 (white)</description> 318 <levels width="7" height="7" divisor="50"> 319 47 41 32 22 33 42 48 320 40 26 17 11 18 27 43 321 31 16 6 2 7 19 34 322 25 10 5 1 3 12 23 323 30 15 9 4 8 20 35 324 39 29 14 13 21 28 44 325 46 38 37 24 36 45 49 326 </levels> 327 </threshold> 328 329 330 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - 331 Special Purpose Dithers 332 --> 333 334 </thresholds> 335
