Gitiles
Code Review Sign In
gerrit-public.fairphone.software / platform / external / ImageMagick / af8d6655e12345c48d687558c0665070d206a942 / . / www / api / quantize.html
blob: 7384a1ba4102a4a465f293b9b424a803a7537017 [file] [log] [blame]
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
2 "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
3<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" dir="ltr">
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]4<head>
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
6 <meta name="verify-v1" content="g222frIIxcQTrvDR3NBRUSKP3AnMNoqxOkIniCEkV7U="/>
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]7 <title>ImageMagick: MagickCore, C API for ImageMagick: Reduce the Number of Unique Colors in an Image</title>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]8 <meta http-equiv="Content-Language" content="en-US"/>
9 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
10 <meta http-equiv="Reply-to" content="magick-users@imagemagick.org"/>
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]11 <meta name="Application-name" content="ImageMagick"/>
cristyaf8d6652011-02-04 21:57:45 +0000[diff] [blame^]12 <meta name="Description" content="Use ImageMagick to convert, edit, or compose bitmap images in a variety of formats. In addition resize, rotate, shear, distort and transform images."/>
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]13 <meta name="Application-url" content="http://www.imagemagick.org"/>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]14 <meta name="Generator" content="PHP"/>
15 <meta name="Keywords" content="magickcore, c, api, for, imagemagick:, reduce, the, number, of, unique, colors, in, an, image, ImageMagick, ImageMagic, MagickCore, MagickWand, PerlMagick, Magick++, RMagick, PythonMagick, JMagick, TclMagick, Image, Magick, Magic, Wand, ImageMagickObject, Swiss, Army, Knife, Image, Processing"/>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]16 <meta name="Rating" content="GENERAL"/>
17 <meta name="Robots" content="INDEX, FOLLOW"/>
18 <meta name="Generator" content="ImageMagick Studio LLC"/>
19 <meta name="Author" content="ImageMagick Studio LLC"/>
20 <meta name="Revisit-after" content="2 DAYS"/>
21 <meta name="Resource-type" content="document"/>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]22 <meta name="Copyright" content="Copyright (c) 1999-2011 ImageMagick Studio LLC"/>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]23 <meta name="Distribution" content="Global"/>
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]24 <link rel="icon" href="../../images/wand.png"/>
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]25 <link rel="shortcut icon" href="../../images/wand.ico" type="images/x-icon"/>
26 <link rel="meta" type="application/rdf+xml" title="ICI" href="http://imagemagick.org/ici.rdf"/>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]27 <link rel="stylesheet" href="http://www.google.com/cse/style/look/default.css" type="text/css" />
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]28 <style type="text/css" media="all">
29 @import url("../../www/magick.css");
30 </style>
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]31 <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js"></script>
cristy361f4662010-12-31 23:02:52 +0000[diff] [blame]32 <script type="text/javascript" src="../fancybox/jquery.fancybox-1.3.4.pack.js"></script>
33 <link rel="stylesheet" type="text/css" href="../fancybox/jquery.fancybox-1.3.4.css" media="screen" />
34 <script type="text/javascript">
35 $(document).ready(function() {
36 $("a[href$=.jpg],a[href$=.png],a[href$=.gif]").fancybox({
37 'transitionIn' : 'elastic',
38 'transitionOut' : 'elastic',
39 'overlayShow' : false,
40 'opacity' : true
41 });
42 });
43 </script>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]44</head>
45
46<body id="www-imagemagick-org">
47<div class="titlebar">
48<a href="../../index.html">
49 <img src="../../images/script.png" alt="[ImageMagick]"
50 style="width: 350px; height: 60px; margin: 28px auto; float: left;" /></a>
51<a href="http://www.networkredux.com">
52 <img src="../../images/networkredux.png" alt="[sponsor]"
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]53 style="margin-top: 42px; border: 0px; float: left;" /></a>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]54<a href="http://www.imagemagick.org/discourse-server/">
cristyaf8d6652011-02-04 21:57:45 +0000[diff] [blame^]55 <img src="../../images/logo.jpg"
56 alt="ImageMagick Logo"
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]57 style="width: 123px; height: 118px; border: 0px; float: right;" /></a>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]58<a href="../../index.html">
cristyaf8d6652011-02-04 21:57:45 +0000[diff] [blame^]59 <img src="../../images/sprite.jpg"
60 alt="ImageMagick Sprite"
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]61 style="width: 114px; height: 118px; border: 0px; float: right;" /></a>
62</div>
63
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]64<div class="westbar">
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]65
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]66<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]67 <a title="About ImageMagick" href="../../index.html">About ImageMagick</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]68</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]69<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]70<div class="menu">
cristybb503372010-05-27 20:51:26 +0000[diff] [blame]71 <a title="Binary Releases" href="../../www/binary-releases.html">Binary Releases</a>
72</div>
73<div class="sub">
74 <a title="Binary Release: Unix" href="../../www/binary-releases.html#unix">Unix</a>
75</div>
76<div class="sub">
77 <a title="Binary Release: MacOS X" href="../../www/binary-releases.html#macosx">Mac OS X</a>
78</div>
79<div class="sub">
80 <a title="Binary Release: Windows" href="../../www/binary-releases.html#windows">Windows</a>
81</div>
82<div class="sep"></div>
83<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]84 <a title="Command-line Tools" href="../../www/command-line-tools.html">Command-line Tools</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]85</div>
86<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]87 <a title="Command-line Tools: Processing" href="../../www/command-line-processing.html">Processing</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]88</div>
89<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]90 <a title="Command-line Tools: Options" href="../../www/command-line-options.html">Options</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]91</div>
92<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]93 <a title="Command-line Tools: Usage" href="http://www.imagemagick.org/Usage/">Usage</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]94</div>
95<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]96 <a title="Program Interfaces" href="../../www/api.html">Program Interfaces</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]97</div>
98<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]99 <a title="Program Interface: MagickWand" href="../../www/magick-wand.html">MagickWand</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]100</div>
101<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]102 <a title="Program Interface: MagickCore" href="../../www/magick-core.html">MagickCore</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]103</div>
104<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]105 <a title="Program Interface: PerlMagick" href="../../www/perl-magick.html">PerlMagick</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]106</div>
107<div class="sub">
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]108 <a title="Program Interface: Magick++" href="../../www/magick++.html">Magick++</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]109</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]110<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]111<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]112 <a title="Install from Source" href="../../www/install-source.html">Install from Source</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]113</div>
114<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]115 <a title="Install from Source: Unix" href="../../www/install-source.html#unix">Unix</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]116</div>
117<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]118 <a title="Install from Source: Windows" href="../../www/install-source.html#windows">Windows</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]119 </div>
120<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]121 <a title="Resources" href="../../www/resources.html">Resources</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]122</div>
cristybb503372010-05-27 20:51:26 +0000[diff] [blame]123<div class="menu">
124 <a title="Architecture" href="../../www/architecture.html">Architecture</a>
125</div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]126<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]127 <a title="Download" href="../../www/download.html">Download</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]128</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]129<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]130<div class="menu">
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]131 <a title="Search" href="../../www/search.html">Search</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]132</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]133<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]134<div class="menu">
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]135 <a title="Site Map" href="../../www/sitemap.html">Site Map</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]136</div>
137<div class="sub">
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]138 <a title="Site Map: Links" href="../../www/links.html">Links</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]139</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]140<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]141<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]142 <a title="Sponsors" href="../../www/sponsors.html">Sponsors:</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]143
144<div class="sponsbox">
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]145<div class="sponsor">
cristyaf8d6652011-02-04 21:57:45 +0000[diff] [blame^]146 <a title="Sponsor: Best Web Hosting" href="http://webhostinggeeks.com">Best Web Hosting</a><!-- 201110010720 -->
147</div>
148<div class="sponsor">
149 <a title="Sponsor: Web Hosting Ratings" href="http://webhostingrating.com">Web Hosting Ratings</a><!-- 201110010720 -->
150</div>
151<div class="sponsor">
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]152 <a title="Sponsor: Druckerei" href="http://www.allesdruck.de">Druckerei</a><!-- 201106010240 -->
153</div>
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]154<div class="sponsor">
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]155 <a title="Sponsor: Web Hosting" href="http://www.bodhost.com/hosting.shtml">Web Hosting</a><!-- 201104010090 -->
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]156</div>
157<div class="sponsor">
cristyc5baf4f2010-08-31 15:05:33 +0000[diff] [blame]158 <a title="Sponsor: Image Converter" href="http://www.batchphoto.com">Image Converter</a><!-- 201103010900 Bits Coffee-->
159</div>
160<div class="sponsor">
cristy851dbce2010-08-06 21:40:00 +0000[diff] [blame]161 <a title="Sponsor: Flyer drucken" href="http://www.online-druck.biz">Flyer drucken</a><!-- 201109010900 Floeter-->
162</div>
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]163<div class="sponsor">
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]164 <a title="Sponsor: Druckerei" href="http://print24.com/de/">Druckerei</a><!-- 201110010720 -->
165</div>
166<div class="sponsor">
cristyaf8d6652011-02-04 21:57:45 +0000[diff] [blame^]167 <a title="Sponsor: Free Catalogs" href="http://www.who-sells-it.com/">Free Catalogs</a><!-- 20120801000600 -->
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]168</div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]169</div>
170</div>
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]171</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]172
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]173<div class="eastbar">
174 <script type="text/javascript">
175 <!--
176 google_ad_client = "pub-3129977114552745";
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]177 google_ad_slot = "0574824969";
178 google_ad_width = 160;
179 google_ad_height = 600;
180 //-->
181 </script>
182 <script type="text/javascript"
183 src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
184 </script>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]185</div>
186
187<div class="main">
188
cristy307ba182010-12-25 01:00:34 +0000[diff] [blame]189<h1>Module quantize
190 Methods</h1>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]191<p class="navigation-index">[<a href="#QuantizeImage">QuantizeImage</a> &bull; <a href="#AcquireQuantizeInfo">AcquireQuantizeInfo</a> &bull; <a href="#CloneQuantizeInfo">CloneQuantizeInfo</a> &bull; <a href="#CompressImageColormap">CompressImageColormap</a> &bull; <a href="#DestroyQuantizeInfo">DestroyQuantizeInfo</a> &bull; <a href="#GetImageQuantizeError">GetImageQuantizeError</a> &bull; <a href="#GetQuantizeInfo">GetQuantizeInfo</a> &bull; <a href="#PosterizeImage">PosterizeImage</a> &bull; <a href="#QuantizeImage">QuantizeImage</a> &bull; <a href="#QuantizeImages">QuantizeImages</a> &bull; <a href="#RemapImage">RemapImage</a> &bull; <a href="#RemapImages">RemapImages</a> &bull; <a href="#SetGrayscaleImage">SetGrayscaleImage</a>]</p>
192
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]193<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
194_8c.html" id="QuantizeImage">QuantizeImage</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]195<div class="doc-section">
196
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]197<p>QuantizeImage() takes a standard RGB or monochrome images and quantizes them down to some fixed number of colors.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]198
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]199<p>For purposes of color allocation, an image is a set of n pixels, where each pixel is a point in RGB space. RGB space is a 3-dimensional vector space, and each pixel, Pi, is defined by an ordered triple of red, green, and blue coordinates, (Ri, Gi, Bi).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]200
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]201<p>Each primary color component (red, green, or blue) represents an intensity which varies linearly from 0 to a maximum value, Cmax, which corresponds to full saturation of that color. Color allocation is defined over a domain consisting of the cube in RGB space with opposite vertices at (0,0,0) and (Cmax, Cmax, Cmax). QUANTIZE requires Cmax = 255.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]202
203<p>The algorithm maps this domain onto a tree in which each node represents a cube within that domain. In the following discussion these cubes are defined by the coordinate of two opposite vertices:</p>
204
205<pre class="text">
206 the origin.
207</pre>
208
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]209<p>The tree's root node represents the entire domain, (0,0,0) through (Cmax,Cmax,Cmax). Each lower level in the tree is generated by subdividing one node's cube into eight smaller cubes of equal size. This corresponds to bisecting the parent cube with planes passing through the midpoints of each edge.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]210
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]211<p>The basic algorithm operates in three phases: Classification, Reduction, and Assignment. Classification builds a color description tree for the image. Reduction collapses the tree until the number it represents, at most, the number of colors desired in the output image. Assignment defines the output image's color map and sets each pixel's color by restorage_class in the reduced tree. Our goal is to minimize the numerical discrepancies between the original colors and quantized colors (quantization error).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]212
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]213<p>Classification begins by initializing a color description tree of sufficient depth to represent each possible input color in a leaf. However, it is impractical to generate a fully-formed color description tree in the storage_class phase for realistic values of Cmax. If colors components in the input image are quantized to k-bit precision, so that Cmax= 2k-1, the tree would need k levels below the root node to allow representing each possible input color in a leaf. This becomes prohibitive because the tree's total number of nodes is 1 + sum(i=1, k, 8k).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]214
215<p>A complete tree would require 19,173,961 nodes for k = 8, Cmax = 255.</p>
216<h5>avoid building a fully populated tree, QUANTIZE</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]217<p>(1) Initializes data structures for nodes only as they are needed; (2) Chooses a maximum depth for the tree as a function of the desired number of colors in the output image (currently log2(colormap size)).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]218
219<p>For each pixel in the input image, storage_class scans downward from the root of the color description tree. At each level of the tree it identifies the single node which represents a cube in RGB space containing the pixel's color. It updates the following data for each such node:</p>
220
221<pre class="text">
222 n1: Number of pixels whose color is contained in the RGB cube which
223 this node represents;
224</pre>
225
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]226<p>n2: Number of pixels whose color is not represented in a node at lower depth in the tree; initially, n2 = 0 for all nodes except leaves of the tree.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]227
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]228<p>Sr, Sg, Sb: Sums of the red, green, and blue component values for all pixels not classified at a lower depth. The combination of these sums and n2 will ultimately characterize the mean color of a set of pixels represented by this node.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]229
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]230<p>E: the distance squared in RGB space between each pixel contained within a node and the nodes' center. This represents the quantization error for a node.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]231
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]232<p>Reduction repeatedly prunes the tree until the number of nodes with n2 > 0 is less than or equal to the maximum number of colors allowed in the output image. On any given iteration over the tree, it selects those nodes whose E count is minimal for pruning and merges their color statistics upward. It uses a pruning threshold, Ep, to govern node selection as follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]233
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]234<p>Ep = 0 while number of nodes with (n2 > 0) > required maximum number of colors prune all nodes such that E <= Ep Set Ep to minimum E in remaining nodes</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]235
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]236<p>This has the effect of minimizing any quantization error when merging two nodes together.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]237
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]238<p>When a node to be pruned has offspring, the pruning procedure invokes itself recursively in order to prune the tree from the leaves upward. n2, Sr, Sg, and Sb in a node being pruned are always added to the corresponding data in that node's parent. This retains the pruned node's color characteristics for later averaging.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]239
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]240<p>For each node, n2 pixels exist for which that node represents the smallest volume in RGB space containing those pixel's colors. When n2 > 0 the node will uniquely define a color in the output image. At the beginning of reduction, n2 = 0 for all nodes except a the leaves of the tree which represent colors present in the input image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]241
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]242<p>The other pixel count, n1, indicates the total number of colors within the cubic volume which the node represents. This includes n1 - n2 pixels whose colors should be defined by nodes at a lower level in the tree.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]243
244<p>Assignment generates the output image from the pruned tree. The output</p>
245<h5>parts</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]246<p>(1) A color map, which is an array of color descriptions (RGB triples) for each color present in the output image; (2) A pixel array, which represents each pixel as an index into the color map array.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]247
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]248<p>First, the assignment phase makes one pass over the pruned color description tree to establish the image's color map. For each node with n2 > 0, it divides Sr, Sg, and Sb by n2 . This produces the mean color of all pixels that classify no lower than this node. Each of these colors becomes an entry in the color map.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]249
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]250<p>Finally, the assignment phase reclassifies each pixel in the pruned tree to identify the deepest node containing the pixel's color. The pixel's value in the pixel array becomes the index of this node's mean color in the color map.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]251
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]252<p>This method is based on a similar algorithm written by Paul Raveling.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]253
254 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]255<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
256_8c.html" id="AcquireQuantizeInfo">AcquireQuantizeInfo</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]257<div class="doc-section">
258
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]259<p>AcquireQuantizeInfo() allocates the QuantizeInfo structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]260
261<p>The format of the AcquireQuantizeInfo method is:</p>
262
263<pre class="code">
264 QuantizeInfo *AcquireQuantizeInfo(const ImageInfo *image_info)
265</pre>
266
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]267<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]268
269<h5>image_info</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]270<p>the image info.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]271
272 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]273<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
274_8c.html" id="CloneQuantizeInfo">CloneQuantizeInfo</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]275<div class="doc-section">
276
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]277<p>CloneQuantizeInfo() makes a duplicate of the given quantize info structure, or if quantize info is NULL, a new one.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]278
279<p>The format of the CloneQuantizeInfo method is:</p>
280
281<pre class="code">
282 QuantizeInfo *CloneQuantizeInfo(const QuantizeInfo *quantize_info)
283</pre>
284
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]285<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]286
287<h5>clone_info</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]288<p>Method CloneQuantizeInfo returns a duplicate of the given quantize info, or if image info is NULL a new one.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]289
290<h5>quantize_info</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]291<p>a structure of type info.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]292
293 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]294<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
295_8c.html" id="CompressImageColormap">CompressImageColormap</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]296<div class="doc-section">
297
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]298<p>CompressImageColormap() compresses an image colormap by removing any duplicate or unused color entries.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]299
300<p>The format of the CompressImageColormap method is:</p>
301
302<pre class="code">
303 MagickBooleanType CompressImageColormap(Image *image)
304</pre>
305
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]306<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]307
308<h5>image</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]309<p>the image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]310
311 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]312<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
313_8c.html" id="DestroyQuantizeInfo">DestroyQuantizeInfo</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]314<div class="doc-section">
315
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]316<p>DestroyQuantizeInfo() deallocates memory associated with an QuantizeInfo structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]317
318<p>The format of the DestroyQuantizeInfo method is:</p>
319
320<pre class="code">
321 QuantizeInfo *DestroyQuantizeInfo(QuantizeInfo *quantize_info)
322</pre>
323
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]324<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]325
326<h5>quantize_info</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]327<p>Specifies a pointer to an QuantizeInfo structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]328
329 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]330<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
331_8c.html" id="GetImageQuantizeError">GetImageQuantizeError</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]332<div class="doc-section">
333
334<p>GetImageQuantizeError() measures the difference between the original and quantized images. This difference is the total quantization error. The error is computed by summing over all pixels in an image the distance squared in RGB space between each reference pixel value and its quantized value. These values are computed:</p>
335
336<pre class="text">
337 o mean_error_per_pixel: This value is the mean error for any single
338 pixel in the image.
339</pre>
340
341<h5>normalized_mean_square_error</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]342<p>This value is the normalized mean quantization error for any single pixel in the image. This distance measure is normalized to a range between 0 and 1. It is independent of the range of red, green, and blue values in the image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]343
344<h5>normalized_maximum_square_error</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]345<p>Thsi value is the normalized maximum quantization error for any single pixel in the image. This distance measure is normalized to a range between 0 and 1. It is independent of the range of red, green, and blue values in your image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]346
347<p>The format of the GetImageQuantizeError method is:</p>
348
349<pre class="code">
350 MagickBooleanType GetImageQuantizeError(Image *image)
351</pre>
352
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]353<p>A description of each parameter follows.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]354
355<h5>image</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]356<p>the image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]357
358 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]359<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
360_8c.html" id="GetQuantizeInfo">GetQuantizeInfo</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]361<div class="doc-section">
362
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]363<p>GetQuantizeInfo() initializes the QuantizeInfo structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]364
365<p>The format of the GetQuantizeInfo method is:</p>
366
367<pre class="code">
368 GetQuantizeInfo(QuantizeInfo *quantize_info)
369</pre>
370
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]371<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]372
373<h5>quantize_info</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]374<p>Specifies a pointer to a QuantizeInfo structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]375
376 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]377<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
378_8c.html" id="PosterizeImage">PosterizeImage</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]379<div class="doc-section">
380
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]381<p>PosterizeImage() reduces the image to a limited number of colors for a "poster" effect.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]382
383<p>The format of the PosterizeImage method is:</p>
384
385<pre class="code">
cristybb503372010-05-27 20:51:26 +0000[diff] [blame]386 MagickBooleanType PosterizeImage(Image *image,const size_t levels,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]387 const MagickBooleanType dither)
388</pre>
389
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]390<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]391
392<h5>image</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]393<p>Specifies a pointer to an Image structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]394
395<h5>levels</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]396<p>Number of color levels allowed in each channel. Very low values (2, 3, or 4) have the most visible effect.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]397
398<h5>dither</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]399<p>Set this integer value to something other than zero to dither the mapped image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]400
401 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]402<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
403_8c.html" id="QuantizeImage">QuantizeImage</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]404<div class="doc-section">
405
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]406<p>QuantizeImage() analyzes the colors within a reference image and chooses a fixed number of colors to represent the image. The goal of the algorithm is to minimize the color difference between the input and output image while minimizing the processing time.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]407
408<p>The format of the QuantizeImage method is:</p>
409
410<pre class="code">
411 MagickBooleanType QuantizeImage(const QuantizeInfo *quantize_info,
412 Image *image)
413</pre>
414
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]415<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]416
417<h5>quantize_info</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]418<p>Specifies a pointer to an QuantizeInfo structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]419
420<h5>image</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]421<p>the image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]422
423 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]424<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
425_8c.html" id="QuantizeImages">QuantizeImages</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]426<div class="doc-section">
427
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]428<p>QuantizeImages() analyzes the colors within a set of reference images and chooses a fixed number of colors to represent the set. The goal of the algorithm is to minimize the color difference between the input and output images while minimizing the processing time.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]429
430<p>The format of the QuantizeImages method is:</p>
431
432<pre class="code">
433 MagickBooleanType QuantizeImages(const QuantizeInfo *quantize_info,
434 Image *images)
435</pre>
436
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]437<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]438
439<h5>quantize_info</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]440<p>Specifies a pointer to an QuantizeInfo structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]441
442<h5>images</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]443<p>Specifies a pointer to a list of Image structures.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]444
445 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]446<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
447_8c.html" id="RemapImage">RemapImage</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]448<div class="doc-section">
449
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]450<p>RemapImage() replaces the colors of an image with the closest color from a reference image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]451
452<p>The format of the RemapImage method is:</p>
453
454<pre class="code">
455 MagickBooleanType RemapImage(const QuantizeInfo *quantize_info,
456 Image *image,const Image *remap_image)
457</pre>
458
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]459<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]460
461<h5>quantize_info</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]462<p>Specifies a pointer to an QuantizeInfo structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]463
464<h5>image</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]465<p>the image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]466
467<h5>remap_image</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]468<p>the reference image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]469
470 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]471<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
472_8c.html" id="RemapImages">RemapImages</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]473<div class="doc-section">
474
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]475<p>RemapImages() replaces the colors of a sequence of images with the closest color from a reference image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]476
477<p>The format of the RemapImage method is:</p>
478
479<pre class="code">
480 MagickBooleanType RemapImages(const QuantizeInfo *quantize_info,
481 Image *images,Image *remap_image)
482</pre>
483
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]484<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]485
486<h5>quantize_info</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]487<p>Specifies a pointer to an QuantizeInfo structure.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]488
489<h5>images</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]490<p>the image sequence.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]491
492<h5>remap_image</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]493<p>the reference image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]494
495 </div>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]496<h2><a href="http://www.wizards-toolkit.org/api/MagickCore/quantize
497_8c.html" id="SetGrayscaleImage">SetGrayscaleImage</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]498<div class="doc-section">
499
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]500<p>SetGrayscaleImage() converts an image to a PseudoClass grayscale image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]501
502<p>The format of the SetGrayscaleImage method is:</p>
503
504<pre class="code">
505 MagickBooleanType SetGrayscaleImage(Image *image)
506</pre>
507
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]508<p>A description of each parameter follows:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]509
510<h5>image</h5>
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]511<p>The image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]512
513 </div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]514
515</div>
516
517<div id="linkbar">
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]518 <span id="linkbar-west">&nbsp;</span>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]519 <span id="linkbar-center">
520 <a href="http://www.imagemagick.org/discourse-server/">Discourse Server</a> &bull;
cristya8902942010-07-30 00:49:52 +0000[diff] [blame]521 <a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">Studio</a>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]522 </span>
523 <span id="linkbar-east">&nbsp;</span>
524 </div>
525 <div class="footer">
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]526 <span id="footer-west">&copy; 1999-2011 ImageMagick Studio LLC</span>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]527 <span id="footer-east"> <a href="../http://www.imagemagick.org/script/contact.php">Contact the Wizards</a></span>
528 </div>
529 <div style="clear: both; margin: 0; width: 100%; "></div>
cristya8902942010-07-30 00:49:52 +0000[diff] [blame]530 <script type="text/javascript">
531 var _gaq = _gaq || [];
532 _gaq.push(['_setAccount', 'UA-17690367-1']);
533 _gaq.push(['_trackPageview']);
534
535 (function() {
536 var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
537 ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
538 var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
539 })();
540 </script>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]541</body>
542</html>