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