Gitiles
Code Review Sign In
gerrit-public.fairphone.software / platform / external / ImageMagick / e4017e34baec05ee0a45800ed8efb2ff6d5c9f5a / . / www / architecture.html
blob: 99cd35859da791fe2148b238f0b430077bf0b6f1 [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: Architecture</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"/>
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]12 <meta name="Description" content="ImageMagick is a software suite to create, edit, compose, or convert bitmap images in a variety of formats. Use ImageMagick to scale, 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="architecture, 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"/>
cristy7e41fe82010-12-04 23:12:08 +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"/>
27 <style type="text/css" media="all">
28 @import url("../www/magick.css");
29 </style>
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]30 <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]31 <script type="text/javascript" src="../fancybox/jquery.fancybox-1.3.4.pack.js"></script>
32 <link rel="stylesheet" type="text/css" href="../fancybox/jquery.fancybox-1.3.4.css" media="screen" />
33 <script type="text/javascript">
34 $(document).ready(function() {
35 $("a[href$=.jpg],a[href$=.png],a[href$=.gif]").fancybox({
36 'transitionIn' : 'elastic',
37 'transitionOut' : 'elastic',
38 'overlayShow' : false,
39 'opacity' : true
40 });
41 });
42 </script>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]43</head>
44
45<body id="www-imagemagick-org">
46<div class="titlebar">
47<a href="../index.html">
48 <img src="../images/script.png" alt="[ImageMagick]"
49 style="width: 350px; height: 60px; margin: 28px auto; float: left;" /></a>
50<a href="http://www.networkredux.com">
51 <img src="../images/networkredux.png" alt="[sponsor]"
52 style="margin: 45px auto; border: 0px; float: left;" /></a>
53<a href="http://www.imagemagick.org/discourse-server/">
54 <img src="../images/logo.jpg" alt=""
55 style="width: 114px; height: 118px; border: 0px; float: right;" /></a>
56<a href="../index.html">
57 <img src="../images/sprite.jpg" alt=""
58 style="width: 114px; height: 118px; border: 0px; float: right;" /></a>
59</div>
60
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]61<div class="westbar">
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]62
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]63<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]64 <a title="About ImageMagick" href="../index.html">About ImageMagick</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]65</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]66<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]67<div class="menu">
cristybb503372010-05-27 20:51:26 +0000[diff] [blame]68 <a title="Binary Releases" href="../www/binary-releases.html">Binary Releases</a>
69</div>
70<div class="sub">
71 <a title="Binary Release: Unix" href="../www/binary-releases.html#unix">Unix</a>
72</div>
73<div class="sub">
74 <a title="Binary Release: MacOS X" href="../www/binary-releases.html#macosx">Mac OS X</a>
75</div>
76<div class="sub">
77 <a title="Binary Release: Windows" href="../www/binary-releases.html#windows">Windows</a>
78</div>
79<div class="sep"></div>
80<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]81 <a title="Command-line Tools" href="../www/command-line-tools.html">Command-line Tools</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]82</div>
83<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]84 <a title="Command-line Tools: Processing" href="../www/command-line-processing.html">Processing</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: Options" href="../www/command-line-options.html">Options</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: Usage" href="http://www.imagemagick.org/Usage/">Usage</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]91</div>
92<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]93 <a title="Program Interfaces" href="../www/api.html">Program Interfaces</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]94</div>
95<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]96 <a title="Program Interface: MagickWand" href="../www/magick-wand.html">MagickWand</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: MagickCore" href="../www/magick-core.html">MagickCore</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: PerlMagick" href="../www/perl-magick.html">PerlMagick</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]103</div>
104<div class="sub">
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]105 <a title="Program Interface: Magick++" href="../www/magick++.html">Magick++</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]106</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]107<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]108<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]109 <a title="Install from Source" href="../www/install-source.html">Install from Source</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]110</div>
111<div class="sub">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]112 <a title="Install from Source: Unix" href="../www/install-source.html#unix">Unix</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: Windows" href="../www/install-source.html#windows">Windows</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]116 </div>
117<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]118 <a title="Resources" href="../www/resources.html">Resources</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]119</div>
cristybb503372010-05-27 20:51:26 +0000[diff] [blame]120<div class="menu">
121 <a title="Architecture" href="../www/architecture.html">Architecture</a>
122</div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]123<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]124 <a title="Download" href="../www/download.html">Download</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]125</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]126<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]127<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]128 <a title="Search" href="http://www.imagemagick.org/script/search.php">Search</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]129</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]130<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]131<div class="menu">
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]132 <a title="Site Map" href="../www/sitemap.html">Site Map</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]133</div>
134<div class="sub">
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]135 <a title="Site Map: Links" href="../www/links.html">Links</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]136</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]137<div class="sep"></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]138<div class="menu">
cristy83a272e2010-05-07 20:40:35 +0000[diff] [blame]139 <a title="Sponsors" href="../www/sponsors.html">Sponsors:</a>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]140
141<div class="sponsbox">
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]142<div class="sponsor">
143 <a title="Sponsor: Web Hosting" href="http://www.bodhost.com/hosting.html">Web Hosting</a><!-- 201104010090 -->
cristy7d52cd62010-10-01 17:26:59 +0000[diff] [blame]144</div>
145<div class="sponsor">
146 <a title="Sponsor: Druckerei" href="http://print24.com/de/">Druckerei</a><!-- 201110010720 -->
cristy73fd1cd2010-09-12 19:14:25 +0000[diff] [blame]147</div>
148<div class="sponsor">
cristyc5baf4f2010-08-31 15:05:33 +0000[diff] [blame]149 <a title="Sponsor: Image Converter" href="http://www.batchphoto.com">Image Converter</a><!-- 201103010900 Bits Coffee-->
150</div>
151<div class="sponsor">
cristy851dbce2010-08-06 21:40:00 +0000[diff] [blame]152 <a title="Sponsor: Flyer drucken" href="http://www.online-druck.biz">Flyer drucken</a><!-- 201109010900 Floeter-->
153</div>
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]154<div class="sponsor">
155 <a title="Sponsor: Free Catalogs" href="http://www.who-sells-it.com/">Free Catalogs</a><!-- 20120801000600 -->
156</div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]157</div>
158</div>
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]159</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]160
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]161<div class="eastbar">
162 <script type="text/javascript">
163 <!--
164 google_ad_client = "pub-3129977114552745";
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]165 google_ad_slot = "0574824969";
166 google_ad_width = 160;
167 google_ad_height = 600;
168 //-->
169 </script>
170 <script type="text/javascript"
171 src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
172 </script>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]173</div>
174
175<div class="main">
176
177
178
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]179<h1>The <em>Magick</em> Behind ImageMagick</h1>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]180<p class="navigation-index">[<a href="#overview">Architecture Overview</a> &bull; <a href="#cache">The Pixel Cache</a> &bull; <a href="#stream">Streaming Pixels</a> &bull; <a href="#properties">Image Properties and Profiles</a> &bull; <a href="#tera-pixel">Large Image Support</a> &bull; <a href="#threads">Threads of Execution</a> &bull; <a href="#distributed">Heterogeneous Distributed Processing</a> &bull; <a href="#coders">Custom Image Coders</a> &bull; <a href="#filters">Custom Image Filters</a>]</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]181
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]182
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]183<div class="doc-section">
184<p>The citizens of Oz were quite content with their benefactor, the all-powerful Wizard. They accepted his wisdom and benevolence without ever questioning the who, why, and where of his power. Like the citizens of Oz, if you feel comfortable that ImageMagick can help you convert, edit, or compose your images without knowing what goes on behind the curtain, feel free to skip this section. However, if you want to know more about the software and algorithms behind ImageMagick, read on. To fully benefit from this discussion, you should be comfortable with image nomenclature and be familiar with computer programming.</p>
185</div>
186
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]187<h2><a id="overview"></a>Architecture Overview</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]188<div class="doc-section">
189
190<p>An image typically consists of a rectangular region of pixels and metadata. To convert, edit, or compose an image in an efficient manner we need convenient access to any pixel anywhere within the region (and sometimes outside the region). And in the case of an image sequence, we need access to any pixel of any region of any image in the sequence. However, there are hundreds of image formats such JPEG, TIFF, PNG, GIF, etc., that makes it difficult to access pixels on demand. Within these formats we find differences in:</p>
191
192<ul>
193 <li>colorspace (e.g RGB, CMYK, YUV, Lab, etc.)</li>
194 <li>bit depth (.e.g 1, 4, 8, 12, 16, etc.)</li>
195 <li>storage format (e.g. unsigned, signed, float, double, etc.)</li>
196 <li>compression (e.g. uncompressed, RLE, Zip, BZip, etc.)</li>
197 <li>orientation (i.e. top-to-bottom, right-to-left, etc.),</li>
198 <li>layout (.e.g. raw, interspersed with opcodes, etc.)</li>
199</ul>
200
201<p>In addition, some image pixels may require attenuation, some formats permit more than one frame, and some formats contain vector graphics that must first be rasterized (converted from vector to pixels).</p>
202
203<p>An efficient implementation of an image processing algorithm may require we get or set:</p>
204
205<ul>
206 <li>one pixel a time (e.g. pixel at location 10,3)</li>
207 <li>a single scanline (e.g. all pixels from row 4)</li>
208 <li>a few scanlines at once (e.g. pixel rows 4-7)</li>
209 <li>a single column or columns of pixels (e.g. all pixels from column 11)</li>
210 <li>an arbitrary region of pixels from the image (e.g. pixels defined at 10,7 to 10,19)</li>
211 <li>a pixel in random order (e.g. pixel at 14,15 and 640,480)</li>
212 <li>pixels from two different images (e.g. pixel at 5,1 from image 1 and pixel at 5,1 from image 2)</li>
213 <li>pixels outside the boundaries of the image (e.g. pixel at -1,-3)</li>
214 <li>a pixel component that is unsigned or in a floating-point representation (e.g. 0.17836)</li>
215 <li>a high-dynamic range pixel that can include negative values as well as values that exceed the quantum depth (e.g. -0.00716)</li>
216 <li>one or more pixels simultaneously in different threads of execution</li>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]217 <li>all the pixels in memory to take advantage of speed-ups offered by executing in concert across heterogeneous platforms consisting of CPUs, GPUs, and other processors</li>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]218</ul>
219
220<p>In addition, some images include a clip mask that define which pixels are eligible to be updated. Pixels outside the area defined by the clip mask remain untouched.</p>
221
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]222<p>Given the varied image formats and image processing requirements, we implemented the ImageMagick <a href="#cache">pixel cache</a> to provide convenient sequential or parallel access to any pixel on demand anywhere inside the image region (we call these <a href="#authentic-pixels">authentic pixels</a>) and from any image in a sequence. In addition, the pixel cache permits access to pixels outside the boundaries defined by the image (we call these <a href="#virtual-pixels">virtual pixels</a>).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]223
cristy320dd6e2010-04-16 20:11:40 +0000[diff] [blame]224<p>In addition to pixels, images have a plethora of <a href="#properties">image properties and profiles</a>. Properties include the well known attributes such as width, height, depth, and colorspace. An image may have optional properties which might include the image author, a comment, a create date, and others. Some images also include profiles for color management, or EXIF, IPTC, 8BIM, or XMP informational profiles. ImageMagick provides command line options and programming methods to get, set, or view image properties or profiles or apply profiles.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]225
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]226<p>ImageMagick consists of more than 400,000 lines of C code and optionally depends on several million lines of code in dependent libraries (e.g. JPEG, PNG, TIFF libraries). Given that, one might expect a huge architecture document. However, a great majority of image processing is simply accessing pixels and its metadata and our simple and elegant implementation makes this easy for the ImageMagick developer. We discuss the implementation of the pixel cache and getting and setting image properties and profiles in the next few sections. Next, we discuss using ImageMagick within a <a href="#threads">thread</a> of execution. In the final sections, we discuss <a href="#coders">image coders</a> to read or write a particular image format followed by a few words on creating a <a href="#filters">filter</a> to access or update pixels based on your custom requirements.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]227
228</div>
229
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]230<h2><a id="cache"></a>The Pixel Cache</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]231<div class="doc-section">
232
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]233<p>The ImageMagick pixel cache is a repository for image pixels with up to 5 channels. The first 4 channels are stored contiguously and an optional second area follows with 1 channel. The channels are at the depth specified when ImageMagick was built. The channel depths are 8 bits-per-pixel component for the Q8 version of ImageMagick, 16 bits-per-pixel component for the Q16 version, and 32 bits-per-pixel component for the Q32 version. By default pixel components are unsigned quantities, however, if you use the <a href="../www/high-dynamic-range.html">high dynamic-range</a> version of ImageMagick, the components are 32-bit floating point. The primary 4 channels can hold any value but typically contain red, green, blue, and alpha intensities or cyan, magenta, yellow, and alpha intensities. The optional fifth channel contains the colormap indexes for colormapped images or the black channel for CMYK images. The pixel cache storage may be heap memory, anonymous memory mapped memory, disk-backed memory mapped, or on disk. The pixel cache is reference-counted. Only the cache properties are copied when the cache is cloned. The cache pixels are subsequently copied only when you signal your intention to update any of the pixels.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]234
235<h3>Create the Pixel Cache</h3>
236<div class="doc-section">
237
238<p>The pixel cache is associated with an image when it is created and it is initialized when you try to get or put pixels. Here are three common methods to associate a pixel cache with an image:</p>
239
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]240<dl>
241<dt>Create an image canvas initialized to the background color:</dt>
242<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]243 image=AllocateImage(image_info);
244 if (SetImageExtent(image,640,480) == MagickFalse)
245 { /* an exception was thrown */ }
246 (void) QueryMagickColor("red",&amp;image-&gt;background_color,&amp;image-&gt;exception);
247 SetImageBackgroundColor(image);
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]248</p></dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]249
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]250<dt>Create an image from a JPEG image on disk:</dt>
251<dd><p class="code">
252 (void) strcpy(image_info-&gt;filename,"image.jpg"):
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]253 image=ReadImage(image_info,exception);
254 if (image == (Image *) NULL)
255 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]256</p></dd>
257<dt>Create an image from a memory based image:</dt>
258<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]259 image=BlobToImage(blob_info,blob,extent,exception);
260 if (image == (Image *) NULL)
261 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]262</p></dd>
263</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]264
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]265<p>In our discussion of the pixel cache, we use the <a href="../www/magick-core.html">MagickCore API</a> to illustrate our points, however, the principles are the same for other program interfaces to ImageMagick.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]266
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]267<p>When the pixel cache is initialized, pixels are scaled from whatever bit depth they originated from to that required by the pixel cache. For example, a 1-channel 1-bit monochrome PBM image is scaled to a 4 channel 8-bit RGBA image, if you are using the Q8 version of ImageMagick, and 16-bit RGBA for the Q16 version. You can determine which version you have with the <a href="../www/command-line-options.html#version">&#x2011;version</a> option: </p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]268
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]269<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Version: ImageMagick 6.6.7-0 2010-01-01 Q16 http://www.imagemagick.org</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]270<p>As you can see, the convenience of the pixel cache sometimes comes with a trade-off in storage (e.g. storing a 1-bit monochrome image as 16-bit RGBA is wasteful) and speed (i.e. storing the entire image in memory is generally slower than accessing one scanline of pixels at a time). In most cases, the benefits of the pixel cache typically outweigh any disadvantages.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]271</div>
272
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]273<h3><a id="authentic-pixels"></a>Access the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]274<div class="doc-section">
275
276<p>Once the pixel cache is associated with an image, you typically want to get, update, or put pixels into it. We refer to pixels inside the image region as <em>authentic pixels</em> and outside the region as <em>virtual pixels</em>. Use these methods to access the pixels in the cache:</p>
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]277<dl>
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]278 <li><a href="../www/api/cache.html#GetVirtualPixels">GetVirtualPixels()</a> gets pixels that you do not intend to modify or pixels that lie outside the image region (e.g. pixel @ -1,-3)</li>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]279 <li><a href="../www/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> gets pixels that you intend to modify</li>
280 <li><a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> queue pixels that you intend to modify</li>
281 <li><a href="../www/api/cache.html#SyncAuthenticPixels">SyncAuthenticPixels()</a> update the pixel cache with any modified pixels</li>
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]282</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]283
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]284<p>Here is a typical <a href="../www/magick-core.html">MagickCore</a> code snippet for manipulating pixels in the pixel cache. In our example, we copy pixels from the input image to the output image and decrease the intensity by 10%:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]285
286<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]287 const PixelPacket
288 *p;
289
290 PixelPacket
291 *q;
292
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]293 ssize_t
294 x,
295 y;
296
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]297 destination=CloneImage(source,source->columns,source->rows,MagickTrue,
298 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]299 if (destination == (Image *) NULL)
300 { /* an exception was thrown */ }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]301 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]302 {
303 p=GetVirtualPixels(source,0,y,source-&gt;columns,1,exception);
304 q=GetAuthenticPixels(destination,0,y,destination-&gt;columns,1,exception);
305 if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL)
306 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]307 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]308 {
309 q-&gt;red=90*p-&gt;red/100;
310 q-&gt;green=90*p-&gt;green/100;
311 q-&gt;blue=90*p-&gt;blue/100;
312 q-&gt;opacity=90*p-&gt;opacity/100;
313 p++;
314 q++;
315 }
316 if (SyncAuthenticPixels(destination,exception) == MagickFalse)
317 break;
318 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]319 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]320 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]321</div>
322
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]323<p>When we first create the destination image by cloning the source image, the pixel cache pixels are not copied. They are only copied when you signal your intentions to modify the pixel cache by calling <a href="../www/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> or <a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a>. Use <a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> if you want to set new pixel values rather than update existing ones. You could use GetAuthenticPixels() to set pixel values but it is slightly more efficient to use QueueAuthenticPixels() instead. Finally, use <a href="../www/api/cache.html#SyncAuthenticPixels">SyncAuthenticPixels()</a> to ensure any updated pixels are pushed to the pixel cache.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]324
325<p>Recall how we mentioned that the indexes of a colormapped image or the black channel of a CMYK image are stored separately. Use <a href="../www/api/cache.html#GetVirtualIndexes">GetVirtualIndexes()</a> (to read the indexes) or <a href="../www/api/cache.html#GetAuthenticIndexes">GetAuthenticIndexes()</a> (to update the indexes) to gain access to this channel. For example, to print the colormap indexes, use:</p>
326
327<pre class="code">
328 const IndexPacket
329 *indexes;
330
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]331 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]332 {
333 p=GetVirtualPixels(source,0,y,source-&gt;columns,1);
334 if (p == (const PixelPacket *) NULL)
335 break;
336 indexes=GetVirtualIndexes(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]337 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]338 (void) printf("%d\n",indexes[x];
339 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]340 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]341 /* an exception was thrown */
342</pre>
343
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]344<p>The pixel cache manager decides whether to give you direct or indirect access to the image pixels. In some cases the pixels are staged to an intermediate buffer-- and that is why you must call SyncAuthenticPixels() to ensure this buffer is <em>pushed</em> out to the pixel cache to guarantee the corresponding pixels in the cache are updated. For this reason we recommend that you only read or update a scanline or a few scanlines of pixels at a time. However, you can get any rectangular region of pixels you want. GetAuthenticPixels() requires that the region you request is within the bounds of the image area. For a 640 by 480 image, you can get a scanline of 640 pixels at row 479 but if you ask for a scanline at row 480, an exception is returned (rows are numbered starting at 0). GetVirtualPixels() does not have this constraint. For example,</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]345
346<pre class="code">
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]347 p=GetVirtualPixels(source,-3,-3,source-&gt;columns+3,6,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]348</pre>
349
350<p>gives you the pixels you asked for without complaint, even though some are not within the confines of the image region.</p>
351</div>
352
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]353<h3><a id="virtual-pixels"></a>Virtual Pixels</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]354<div class="doc-section">
355
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]356<p>There are a plethora of image processing algorithms that require a neighborhood of pixels about a pixel of interest. The algorithm typically includes a caveat concerning how to handle pixels around the image boundaries, known as edge pixels. With virtual pixels, you do not need to concern yourself about special edge processing other than choosing which virtual pixel method is most appropriate for your algorithm.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]357 <p>Access to the virtual pixels are controlled by the <a href="../www/api/cache.html#SetImageVirtualPixelMethod">SetImageVirtualPixelMethod()</a> method from the MagickCore API or the <a href="../www/command-line-options.html#virtual-pixel">&#x2011;virtual&#x2011;pixel</a> option from the command line. The methods include:</p>
358
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]359<pre class="text" style="font-size: 90%;">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]360 background: the area surrounding the image is the background color
361 black: the area surrounding the image is black
362 checker-tile: alternate squares with image and background color
363 dither: non-random 32x32 dithered pattern
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]364 edge: extend the edge pixel toward infinity (default)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]365 gray: the area surrounding the image is gray
366 horizontal-tile: horizontally tile the image, background color above/below
367 horizontal-tile-edge: horizontally tile the image and replicate the side edge pixels
368 mirror: mirror tile the image
369 random: choose a random pixel from the image
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]370 tile: tile the image
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]371 transparent: the area surrounding the image is transparent blackness
372 vertical-tile: vertically tile the image, sides are background color
373 vertical-tile-edge: vertically tile the image and replicate the side edge pixels
374 white: the area surrounding the image is white
375</pre>
376
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]377</div>
378
379<h3>Cache Storage and Resource Requirements</h3>
380<div class="doc-section">
381
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]382<p>Recall that this simple and elegant design of the ImageMagick pixel cache comes at a cost in terms of storage and processing speed. The pixel cache storage requirements scales with the area of the image and the bit depth of the pixel components. For example, if we have a 640 by 480 image and we are using the Q16 version of ImageMagick, the pixel cache consumes image <em>width * height * bit-depth / 8 * channels</em> bytes or approximately 2.3 mebibytes (i.e. 640 * 480 * 2 * 4). Not too bad, but what if your image is 25000 by 25000 pixels? The pixel cache requires approximately 4.7 gibibytes of storage. Ouch. ImageMagick accounts for possible huge storage requirements by caching large images to disk rather than memory. Typically the pixel cache is stored in memory using heap memory. If heap memory is exhausted, pixels are stored in in an anonymous map; if the anonymous memory map is exhausted, we create the pixel cache on disk and attempt to memory-map it; and if memory-map memory is exhausted, we simply use standard disk I/O. Disk storage is cheap but it is also very slow, upwards of 1000 times slower than memory. We can get some speed improvements, up to 5 times, if we use memory mapping to the disk-based cache. These decisions about storage are made <em>automagically</em> by the pixel cache manager negotiating with the operating system. However, you can influence how the pixel cache manager allocates the pixel cache with <em>cache resource limits</em>. The limits include:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]383
384<dl class="doc">
385 <dt class="doc">files</dt>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]386 <dd>maximum number of open pixel cache files. When this limit is exceeded, any subsequent pixels cached to disk are closed and reopened on demand. This behavior permits a large number of images to be accessed simultaneously on disk, but without a speed penalty due to repeated open/close calls.</dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]387 <dt class="doc">area</dt>
388 <dd>maximum area in bytes of any one image that can reside in the pixel cache memory. If this limit is exceeded, the image is automagically cached to disk.</dd>
389 <dt class="doc">memory</dt>
390 <dd>maximum amount of memory in bytes to allocate for the pixel cache from the anonymous mapped memory or the heap.</dd>
391 <dt class="doc">map</dt>
392 <dd>maximum amount of memory map in bytes to allocate for the pixel cache.</dd>
393 <dt class="doc">disk</dt>
394 <dd>maximum amount of disk space in bytes permitted for use by the pixel cache. If this limit is exceeded, the pixel cache is not created and a fatal exception is thrown.</dd>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]395 <dt class="doc">thread</dt>
396 <dd>maximum number of threads that are permitted to run in parallel.</dd>
397 <dt class="doc">time</dt>
398 <dd>maximum number of seconds that the process is permitted to execute. When this limit is exceeded, an exception is thrown and processing stops.</dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]399</dl>
400
401<p>To determine the current setting of these limits, use this command:</p>
402
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]403<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -list resource</span></p><pre class="text">
404File Area Memory Map Disk Thread Time
cristy2c839602010-04-03 02:32:08 +0000[diff] [blame]405-------------------------------------------------------------------------------
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]406 768 1.0386GB 3.8692GiB 7.7384GiB unlimited 4 unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]407</pre>
408
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]409<p>You can set these limits either as a <a href="../www/resources.html#configure">policy</a> (see <a href="../www/source/policy.xml">policy.xml</a>), with an <a href="../www/resources.html#environment">environment variable</a>, with the <a href="../www/command-line-options.html#limit">-limit</a> command line option, or with the <a href="../www/api/resource.html#SetMagickResourceLimit">SetMagickResourceLimit()</a> MagickCore API method. As an example, our online web interface to ImageMagick, <a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">ImageMagick Studio</a>, has an area limit of 64 megabytes, a memory limit of 128 mebibytes and a map limit of 256 mebibytes and a disk limit of 1 gigabytes. Since we process multiple simultaneous sessions, we don't want any one session consuming all the available memory. Instead large images are cached to disk. If the image is too large and exceeds the pixel cache disk limit, the program exits. In addition, we place a 60 second time limit to prevent any run-away processing tasks.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]410
411<p>Note, the cache limits are global, meaning if you create several images, the combined resource requirements are compared to the limit to determine the pixel cache storage disposition.</p>
412</div>
413
414<h3>Cache Views</h3>
415<div class="doc-section">
416
417<p>GetVirtualPixels(), GetAuthenticPixels(), QueueAuthenticPixels(), and SyncAuthenticPixels() from the MagickCore API can only deal with one pixel cache area per image at a time. Suppose you want to access the first and last scanline from the same image at the same time? The solution is to use a <em>cache view</em>. A cache view permits you to access as many areas simultaneously in the pixel cache as you require. The cache view <a href="../www/api/cache-view.html">methods</a> behave like the previous methods except you must first open a view and close it when you are finished with it. Here is a snippet of MagickCore code that permits us to access two areas of an image simultaneously:</p>
418
419<pre class="code">
420 CacheView
421 *view_1,
422 *view_2;
423
424 view_1=OpenCacheView(source);
425 view_2=OpenCacheView(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]426 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]427 {
428 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]429 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,
430 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]431 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
432 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]433 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]434 {
435 /* do something with u &amp; v here */
436 }
437 }
438 view_1=CloseCacheView(view_1);
439 view_2=CloseCacheView(view_2);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]440 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]441 { /* an exception was thrown */ }
442</pre>
443</div>
444
445<h3>Magick Persistent Cache Format</h3>
446<div class="doc-section">
447
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]448<p>Recall that each image format is decoded by ImageMagick and the pixels are deposited in the pixel cache. If you write an image, the pixels are read from the pixel cache and encoded as required by the format you are writing (e.g. GIF, PNG, etc.). The Magick Persistent Cache (MPC) format is designed to eliminate the overhead of decoding and encoding pixels to and from an image format. MPC writes two files. One, with the extension <kbd>.mpc</kbd>, retains all the properties associated with the image or image sequence (e.g. width, height, colorspace, etc.) and the second, with the extension <kbd>.cache</kbd>, is the pixel cache in the native raw format. When reading an MPC image file, ImageMagick reads the image properties and memory maps the pixel cache on disk eliminating the need for decoding the image pixels. The tradeoff is in disk space. MPC is generally larger in file size than most other image formats.</p>
cristy5063d812010-10-19 16:28:10 +0000[diff] [blame]449<p>The most efficient use of MPC image files is a write-once, read-many-times pattern. For example, your workflow requires extracting random blocks of pixels from the source image. Rather than re-reading and possibly decompressing the source image each time, we use MPC and map the image directly to memory.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]450</div>
451
452<h3>Best Practices</h3>
453<div class="doc-section">
454
455<p>Although you can request any pixel from the pixel cache, any block of pixels, any scanline, multiple scanlines, any row, or multiple rows with the GetVirtualPixels(), GetAuthenticPixels(), QueueAuthenticPixels, GetCacheViewVirtualPixels(), GetCacheViewAuthenticPixels(), and QueueCacheViewAuthenticPixels() methods, ImageMagick is optimized to return a few pixels or a few pixels rows at time. There are additional optimizations if you request a single scanline or a few scanlines at a time. These methods also permit random access to the pixel cache, however, ImageMagick is optimized for sequential access.</p>
456
457<p>If you update pixels returned from GetAuthenticPixels() or GetCacheViewAuthenticPixels(), don't forget to call SyncAuthenticPixels() or SyncCacheViewAuthenticPixels() respectively to ensure your changes are synchronized with the pixel cache.</p>
458
459<p>Use QueueAuthenticPixels() or QueueCacheViewAuthenticPixels() if you are setting an initial pixel value. The GetAuthenticPixels() or GetCacheViewAuthenticPixels() method reads pixels from the cache and if you are setting an initial pixel value, this read is unnecessary. Don't forget to call SyncAuthenticPixels() or SyncCacheViewAuthenticPixels() respectively to push your updates to the pixel cache.</p>
460
461<p>GetVirtualPixels(), GetAuthenticPixels(), QueueAuthenticPixels(), and SyncAuthenticPixels() are slightly more efficient than their cache view counter-parts. However, cache views are required if you need access to more than one region of the image simultaneously or if more than one <a href="#threads">thread of execution</a> is accessing the image.</p>
462
463<p>You can request pixels outside the bounds of the image with GetVirtualPixels() or GetCacheViewVirtualPixels(), however, it is more efficient to request pixels within the confines of the image region.</p>
464
465<p>Although you can force the pixel cache to disk using appropriate resource limits, disk access can be upwards of 1000 times slower than memory access. For fast, efficient, access to the pixel cache, try to keep the pixel cache in heap memory or anonymous mapped memory.</p>
466
467<p>The ImageMagick Q16 version of ImageMagick permits you to read and write 16 bit images without scaling but the pixel cache consumes twice as much resources as the Q8 version. If your system has constrained memory or disk resources, consider the Q8 version of ImageMagick. In addition, the Q8 version typically executes faster than the Q16 version.</p>
468
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]469<p>A great majority of image formats and algorithms restrict themselves to a fixed range of pixel values from 0 to some maximum value, for example, the Q16 version of ImageMagick permit intensities from 0 to 65535. High dynamic-range imaging (HDRI), however, permits a far greater dynamic range of exposures (i.e. a large difference between light and dark areas) than standard digital imaging techniques. HDRI accurately represents the wide range of intensity levels found in real scenes ranging from the brightest direct sunlight to the deepest darkest shadows. Enable <a href="../www/high-dynamic-range.html">HDRI</a> at ImageMagick build time to deal with high dynamic-range images, but be mindful that each pixel component is a 32-bit floating point value. In addition, pixel values are not clamped by default so some algorithms may perform differently than the non-HDRI version.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]470
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]471<p>If you are dealing with large images, make sure the pixel cache is written to a disk area with plenty of free space. Under Unix, this is typically <kbd>/tmp</kbd> and for Windows, <kbd>c:/temp</kbd>. You can tell ImageMagick to write the pixel cache to an alternate location with the MAGICK_TEMPORARY_PATH environment variable. For example,</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]472
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]473<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>export MAGICK_TEMPORARY_PATH=/data/magick</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]474
475<p>If you plan on processing the same image many times, consider the MPC format. Reading a MPC image has near-zero overhead because its in the native pixel cache format eliminating the need for decoding the image pixels. Here is an example:</p>
476
477<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.tif image.mpc</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.mpc -crop 100x100+0+0 +repage 1.png</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.mpc -crop 100x100+100+0 +repage 2.png</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.mpc -crop 100x100+200+0 +repage 3.png</span></p>
478<p>MPC is ideal for web sites. It reduces the overhead of reading and writing an image. We use it exclusively at our <a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">online image studio</a>.</p>
479</div>
480
481</div>
482
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]483<h2><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]484<div class="doc-section">
485
486<p>ImageMagick provides for streaming pixels as they are read from or written to an image. This has several advantages over the pixel cache. The time and resources consumed by the pixel cache scale with the area of an image, whereas the pixel stream resources scale with the width of an image. The disadvantage is the pixels must be consumed as they are streamed so there is no persistence.</p>
487
488<p>Use <a href="../www/api/stream.html#ReadStream">ReadStream()</a> or <a href="../www/api/stream.html#WriteStream">WriteStream()</a> with an appropriate callback method in your MagickCore program to consume the pixels as they are streaming. Here's an abbreviated example of using ReadStream:</p>
489
490<pre class="code">
491static size_t StreamHandler(const Image *image,const void *pixels,
492 const size_t columns)
493{
494 /* process pixels here */
495 return(columns);
496}
497
498...
499/* invoke the pixel stream here */
500image=ReadStream(image_info,&amp;StreamHandler,exception);
501</pre>
502
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]503<p>We also provide a lightweight tool, <a href="../www/stream.html">stream</a>, to stream one or more pixel components of the image or portion of the image to your choice of storage formats. It writes the pixel components as they are read from the input image a row at a time making <a href="../www/stream.html">stream</a> desirable when working with large images or when you require raw pixel components.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]504
505</div>
506
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]507<h2><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]508<div class="doc-section">
509
510<p>Images have metadata associated with them in the form of properties (e.g. width, height, description, etc.) and profiles (e.g. EXIF, IPTC, color management). ImageMagick provides convenient methods to get, set, or update image properties and get, set, update, or apply profiles. Some of the more popular image properties are associated with the Image structure in the MagickCore API. For example:</p>
511
512<pre class="code">
513 (void) printf("image width: %lu, height: %lu\n",image-&gt;columns,image-&gt;rows);
514</pre>
515
516<p>For a great majority of image properties, such as an image comment or description, we use the <a href="../www/api/property.html#GetImageProperty">GetImageProperty()</a> and <a href="../www/api/property.html#SetImageProperty">SetImageProperty()</a> methods. Here we set a property and fetch it right back:</p>
517
518<pre class="code">
519 const char
520 *comment;
521
522 (void) SetImageProperty(image,"comment","This space for rent");
523 comment=GetImageProperty(image,"comment");
524 if (comment == (const char *) NULL)
525 (void) printf("Image comment: %s\n",comment);
526</pre>
527
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]528<p>ImageMagick supports artifacts with the GetImageArtifact() and SetImageArtifact() methods. Artifacts are stealth properties that are not exported to image formats (e.g. PNG).</p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]529
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]530<p>Image profiles are handled with <a href="../www/api/profile.html#GetImageProfile">GetImageProfile()</a>, <a href="../www/api/profile.html#SetImageProfile">SetImageProfile()</a>, and <a href="../www/api/profile.html#ProfileImage">ProfileImage()</a> methods. Here we set a profile and fetch it right back:</p>
531
532<pre class="code">
533 StringInfo
534 *profile;
535
536 profile=AcquireStringInfo(length);
537 SetStringInfoDatum(profile,my_exif_profile);
538 (void) SetImageProfile(image,"EXIF",profile);
539 DestroyStringInfo(profile);
540 profile=GetImageProfile(image,"EXIF");
541 if (profile != (StringInfo *) NULL)
542 (void) PrintStringInfo(stdout,"EXIF",profile);
543</pre>
544
545</div>
546
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]547<h2><a id="tera-pixel"></a>Large Image Support</h2>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]548<div class="doc-section">
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]549<p>ImageMagick can read, process, or write mega-, giga-, or tera-pixel image sizes. An image width or height can range from 1 to 2 giga-pixels on a 32 bit OS and up to 9 exa-pixels on a 64-bit OS. Note, that some image formats have restrictions on image size. For example, Photoshop images are limited to 300,000 pixels for width or height. Here we resize an image to a quarter million pixels square:</p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]550
551<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert logo: -resize 250000x250000 logo.miff</span></p>
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]552<p>For large images, ImageMagick will likely create a pixel cache on disk. Make sure you have plenty of temporary disk space. If your default temporary disk partition is too small, tell ImageMagick to use another partition with plenty of free space. For example:</p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]553
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]554<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -define registry:temporary-path=/data/tmp logo: \ <br/> -resize 250000x250000 logo.miff</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]555<p>To ensure large images do not consume all the memory on your system, force the image pixels to memory-mapped disk with resource limits:</p>
556
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]557<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -define registry:temporary-path=/data/tmp -limit memory 16mb \ <br/> logo: -resize 250000x250000 logo.miff</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]558<p>Here we force all image pixels to disk:</p>
559
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]560<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -define registry:temporary-path=/data/tmp -limit area 0 \ <br/> logo: -resize 250000x250000 logo.miff</span></p>
cristybac7a162010-06-15 19:57:29 +0000[diff] [blame]561<p>Caching pixels to disk is about 1000 times slower than memory. Expect long run times when processing large images on disk with ImageMagick. You can monitor progress with this command:</p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]562
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]563<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -monitor -define registry:temporary-path=/data/tmp -limit area 0 \ <br/> logo: -resize 250000x250000 logo.miff</span></p></div>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]564
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]565<h2><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]566<div class="doc-section">
567
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]568<p>Many of ImageMagick's internal algorithms are threaded to take advantage of speed-ups offered by the multicore processor chips. However, you are welcome to use ImageMagick algorithms in your threads of execution with the exception of the MagickCore's GetVirtualPixels(), GetAuthenticPixels(), QueueAuthenticPixels(), or SyncAuthenticPixels() pixel cache methods. These methods are intended for one thread of execution only with the exception of an OpenMP parallel section. To access the pixel cache with more than one thread of execution, use a cache view. We do this for the <a href="../www/api/composite.html#CompositeImage">CompositeImage()</a> method, for example. Suppose we want to composite a single image over a different image in each thread of execution. If we use GetVirtualPixels(), the results are unpredictable because multiple threads would likely be asking for different areas of the pixel cache simultaneously. Instead we use GetCacheViewVirtualPixels() which creates a unique view for each thread of execution ensuring our program behaves properly regardless of how many threads are invoked. The other program interfaces, such as the <a href="../www/magick-wand.html">MagickWand API</a>, are completely thread safe so there are no special precautions for threads of execution.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]569
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]570<p>Here is an example of how ImageMagick can take advantage of threads of execution with the <a href="http://en.wikipedia.org/wiki/OpenMP">OpenMP</a> programming paradigm:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]571
572<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]573{
574 CacheView
575 *image_view;
576
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]577 MagickBooleanType
578 status;
579
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]580 ssize_t
581 y;
582
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]583 status=MagickTrue;
584 image_view=AcquireCacheView(image);
585 #pragma omp parallel for schedule(dynamic,4) shared(status)
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]586 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]587 {
588 register IndexPacket
589 *indexes;
590
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]591 register PixelPacket
592 *q;
593
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]594 register ssize_t
595 x;
596
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]597 if (status == MagickFalse)
598 continue;
599 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
600 if (q == (PixelPacket *) NULL)
601 {
602 status=MagickFalse;
603 continue;
604 }
605 indexes=GetCacheViewAuthenticIndexQueue(image_view);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]606 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]607 {
608 q-&gt;red= ...
609 q-&gt;green= ...
610 q-&gt;blue= ...
611 q-&gt;opacity= ...
612 if (indexes != (IndexPacket *) NULL)
613 indexes[x]= ...
614 q++;
615 }
616 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
617 status=MagickFalse;
618 }
619 image_view=DestroyCacheView(image_view);
620 if (status == MagickFalse)
621 perror("something went wrong");
622}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]623</div>
624
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]625
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]626<p>If you call the ImageMagick API from your OpenMP-enabled application and you intend to dynamically increase the number of threads available in subsequent parallel regions, be sure to perform the increase <em>before</em> you call the API otherwise ImageMagick may fault.</p>
627
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]628<p><a href="../www/api/wand-view.html">MagickWand</a> supports wand views. A view iterates over the entire, or portion, of the image in parallel and for each row of pixels, it invokes a callback method you provide. This limits most of your parallel programming activity to just that one module. There are similar methods in <a href="../www/api/image-view.html">MagickCore</a>. For an example, see the same sigmoidal contrast algorithm implemented in both <a href="../www/magick-wand.html#wand-view">MagickWand</a> and <a href="../www/magick-core.html#image-view">MagickCore</a>.</p>
cristyfe7ce342010-06-22 15:41:50 +0000[diff] [blame]629
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]630<p>In most circumstances, the default number of threads is set to the number of processor cores on your system for optimal performance. However, if your system is hyperthreaded or if you are running on a virtual host and only a subset of the processors are available to your server instance, you might get an increase in performance by setting the thread <a href="../www/resources.html#configure">policy</a> or the <a href="../www/resources.html#environment">MAGICK_THREAD_LIMIT</a> environment variable. For example, your virtual host has 8 processors but only 2 are assigned to your server instance. The default of 8 threads can cause severe performance problems. One solution is to limit the number of threads to the available processors in your <a href="../www/source/policy.xml">policy.xml</a> configuration file:</p>
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]631
632<pre class="text">
633 &lt;policy domain="resource" name="thread" value="2"/>
634</pre>
635
636<p>Or suppose your 12 core hyperthreaded computer defaults to 24 threads. Set the MAGICK_THREAD_LIMIT environment variable and you will likely get improved performance:</p>
637
638<pre class="text">
639 export MAGICK_THREAD_LIMIT=12
640</pre>
641
642<p>The OpenMP committee has not defined the behavior of mixing OpenMP with other threading models such as Posix threads. However, using modern releases of Linux, OpenMP and Posix threads appear to interoperate without complaint. If you want to use Posix threads from a program module that calls one of the ImageMagick application programming interfaces (e.g. MagickCore, MagickWand, Magick++, etc.) from Mac OS X or an older Linux release, you may need to disable OpenMP support within ImageMagick. Add the <kbd>--disable-openmp</kbd> option to the configure script command line and rebuild and reinstall ImageMagick.</p>
643
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]644</div>
645
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]646<h2><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]647<div class="doc-section">
648<p>ImageMagick includes support for heterogeneous distributed processing with the <a href="http://en.wikipedia.org/wiki/OpenCL">OpenCL</a> framework. OpenCL kernels within ImageMagick permit image processing algorithms to execute across heterogeneous platforms consisting of CPUs, GPUs, and other processors. Depending on your platform, speed-ups can be an order of magnitude faster than the traditional single CPU.</p>
649
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]650<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]651
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]652<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Features: OpenMP OpenCL</span></p>
653<p>If so, run this command to realize a significant speed-up for image convolution:</p>
654
cristy4949d522010-03-12 18:41:34 +0000[diff] [blame]655<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.png convolve '-1, -1, -1, -1, 9, -1, -1, -1, -1' \ <br/> convolve.png</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]656<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
657
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]658<p>Here is an example OpenCL kernel that convolves an image:</p>
659
660<div class="viewport">
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]661static inline long ClampToCanvas(const long offset,const ulong range)
662{
663 if (offset &lt; 0L)
664 return(0L);
665 if (offset >= range)
666 return((long) (range-1L));
667 return(offset);
668}
669
670static inline CLQuantum ClampToQuantum(const double value)
671{
672 if (value &lt; 0.0)
673 return((CLQuantum) 0);
674 if (value >= (double) QuantumRange)
675 return((CLQuantum) QuantumRange);
676 return((CLQuantum) (value+0.5));
677}
678
679__kernel void Convolve(const __global CLPixelType *source,__constant double *filter,
680 const ulong width,const ulong height,__global CLPixelType *destination)
681{
682 const ulong columns = get_global_size(0);
683 const ulong rows = get_global_size(1);
684
685 const long x = get_global_id(0);
686 const long y = get_global_id(1);
687
688 const double scale = (1.0/QuantumRange);
689 const long mid_width = (width-1)/2;
690 const long mid_height = (height-1)/2;
691 double4 sum = { 0.0, 0.0, 0.0, 0.0 };
692 double gamma = 0.0;
693 register ulong i = 0;
694
695 for (long v=(-mid_height); v &lt;= mid_height; v++)
696 {
697 for (long u=(-mid_width); u &lt;= mid_width; u++)
698 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]699 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
700 columns);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]701 const double alpha=scale*(QuantumRange-source[index].w);
702 sum.x+=alpha*filter[i]*source[index].x;
703 sum.y+=alpha*filter[i]*source[index].y;
704 sum.z+=alpha*filter[i]*source[index].z;
705 sum.w+=filter[i]*source[index].w;
706 gamma+=alpha*filter[i];
707 i++;
708 }
709 }
710
711 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
712 const ulong index=y*columns+x;
713 destination[index].x=ClampToQuantum(gamma*sum.x);
714 destination[index].y=ClampToQuantum(gamma*sum.y);
715 destination[index].z=ClampToQuantum(gamma*sum.z);
716 destination[index].w=ClampToQuantum(sum.w);
717};
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]718</div>
719
cristy37f02952010-03-24 19:47:41 +0000[diff] [blame]720<p>See <a href="http://trac.imagemagick.org/browser/ImageMagick/trunk/magick/accelerate.c">magick/accelerate.c</a> for a complete implementation of image convolution with an OpenCL kernel.</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]721
722</div>
723
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]724<h2><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]725<div class="doc-section">
726
727<p>An image coder (i.e. encoder / decoder) is responsible for registering, optionally classifying, optionally reading, optionally writing, and unregistering one image format (e.g. PNG, GIF, JPEG, etc.). Registering an image coder alerts ImageMagick a particular format is available to read or write. While unregistering tells ImageMagick the format is no longer available. The classifying method looks at the first few bytes of an image and determines if the image is in the expected format. The reader sets the image size, colorspace, and other properties and loads the pixel cache with the pixels. The reader returns a single image or an image sequence (if the format supports multiple images per file), or if an error occurs, an exception and a null image. The writer does the reverse. It takes the image properties and unloads the pixel cache and writes them as required by the image format.</p>
728
729<p>Here is a listing of a sample <a href="../www/source/mgk.c">custom coder</a>. It reads and writes images in the MGK image format which is simply an ID followed by the image width and height followed by the RGB pixel values.</p>
730
731<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]732/*
733 Include declarations.
734*/
735#include "magick/studio.h"
736#include "magick/blob.h"
737#include "magick/blob-private.h"
738#include "magick/colorspace.h"
739#include "magick/exception.h"
740#include "magick/exception-private.h"
741#include "magick/image.h"
742#include "magick/image-private.h"
743#include "magick/list.h"
744#include "magick/magick.h"
745#include "magick/memory_.h"
746#include "magick/monitor.h"
747#include "magick/monitor-private.h"
748#include "magick/quantum-private.h"
749#include "magick/static.h"
750#include "magick/string_.h"
751#include "magick/module.h"
752
753/*
754 Forward declarations.
755*/
756static MagickBooleanType
757 WriteMGKImage(const ImageInfo *,Image *);
758
759/*
760%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
761% %
762% %
763% %
764% I s M G K %
765% %
766% %
767% %
768%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
769%
770% IsMGK() returns MagickTrue if the image format type, identified by the
771% magick string, is MGK.
772%
773% The format of the IsMGK method is:
774%
775% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
776%
777% A description of each parameter follows:
778%
779% o magick: This string is generally the first few bytes of an image file
780% or blob.
781%
782% o length: Specifies the length of the magick string.
783%
784*/
785static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
786{
787 if (length &lt; 7)
788 return(MagickFalse);
789 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
790 return(MagickTrue);
791 return(MagickFalse);
792}
793
794/*
795%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
796% %
797% %
798% %
799% R e a d M G K I m a g e %
800% %
801% %
802% %
803%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
804%
805% ReadMGKImage() reads a MGK image file and returns it. It allocates
806% the memory necessary for the new Image structure and returns a pointer to
807% the new image.
808%
809% The format of the ReadMGKImage method is:
810%
811% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
812%
813% A description of each parameter follows:
814%
815% o image_info: the image info.
816%
817% o exception: return any errors or warnings in this structure.
818%
819*/
820static Image *ReadMGKImage(const ImageInfo *image_info,
821 ExceptionInfo *exception)
822{
823 char
824 buffer[MaxTextExtent];
825
826 Image
827 *image;
828
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]829 MagickBooleanType
830 status;
831
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]832 register PixelPacket
833 *q;
834
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]835 register size_t
836 x;
837
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]838 register unsigned char
839 *p;
840
841 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]842 count,
843 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]844
845 unsigned char
846 *pixels;
847
848 unsigned long
849 columns,
850 rows;
851
852 /*
853 Open image file.
854 */
855 assert(image_info != (const ImageInfo *) NULL);
856 assert(image_info-&gt;signature == MagickSignature);
857 if (image_info-&gt;debug != MagickFalse)
858 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
859 assert(exception != (ExceptionInfo *) NULL);
860 assert(exception-&gt;signature == MagickSignature);
861 image=AcquireImage(image_info);
862 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
863 if (status == MagickFalse)
864 {
865 image=DestroyImageList(image);
866 return((Image *) NULL);
867 }
868 /*
869 Read MGK image.
870 */
871 (void) ReadBlobString(image,buffer); /* read magic number */
872 if (IsMGK(buffer,7) == MagickFalse)
873 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
874 (void) ReadBlobString(image,buffer);
875 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
876 if (count &lt;= 0)
877 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
878 do
879 {
880 /*
881 Initialize image structure.
882 */
883 image-&gt;columns=columns;
884 image-&gt;rows=rows;
885 image-&gt;depth=8;
886 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
887 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
888 break;
889 /*
890 Convert MGK raster image to pixel packets.
891 */
892 if (SetImageExtent(image,0,0) == MagickFalse)
893 {
894 InheritException(exception,&amp;image-&gt;exception);
895 return(DestroyImageList(image));
896 }
897 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
898 if (pixels == (unsigned char *) NULL)
899 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]900 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]901 {
902 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
903 if (count != (ssize_t) (3*image-&gt;columns))
904 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
905 p=pixels;
906 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
907 if (q == (PixelPacket *) NULL)
908 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]909 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]910 {
911 q-&gt;red=ScaleCharToQuantum(*p++);
912 q-&gt;green=ScaleCharToQuantum(*p++);
913 q-&gt;blue=ScaleCharToQuantum(*p++);
914 q++;
915 }
916 if (SyncAuthenticPixels(image,exception) == MagickFalse)
917 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]918 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]919 (SetImageProgress(image,LoadImageTag,y,image&gt;>rows) == MagickFalse))
920 break;
921 }
922 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
923 if (EOFBlob(image) != MagickFalse)
924 {
925 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
926 break;
927 }
928 /*
929 Proceed to next image.
930 */
931 if (image_info-&gt;number_scenes != 0)
932 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
933 break;
934 *buffer='\0';
935 (void) ReadBlobString(image,buffer);
936 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
937 if (count != 0)
938 {
939 /*
940 Allocate next image structure.
941 */
942 AcquireNextImage(image_info,image);
943 if (GetNextImageInList(image) == (Image *) NULL)
944 {
945 image=DestroyImageList(image);
946 return((Image *) NULL);
947 }
948 image=SyncNextImageInList(image);
949 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
950 if (status == MagickFalse)
951 break;
952 }
953 } while (count != 0);
954 (void) CloseBlob(image);
955 return(GetFirstImageInList(image));
956}
957
958/*
959%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
960% %
961% %
962% %
963% R e g i s t e r M G K I m a g e %
964% %
965% %
966% %
967%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
968%
969% RegisterMGKImage() adds attributes for the MGK image format to
970% the list of supported formats. The attributes include the image format
971% tag, a method to read and/or write the format, whether the format
972% supports the saving of more than one frame to the same file or blob,
973% whether the format supports native in-memory I/O, and a brief
974% description of the format.
975%
976% The format of the RegisterMGKImage method is:
977%
978% unsigned long RegisterMGKImage(void)
979%
980*/
981ModuleExport unsigned long RegisterMGKImage(void)
982{
983 MagickInfo
984 *entry;
985
986 entry=SetMagickInfo("MGK");
987 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
988 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
989 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
990 entry-&gt;description=ConstantString("MGK");
991 entry-&gt;module=ConstantString("MGK");
992 (void) RegisterMagickInfo(entry);
993 return(MagickImageCoderSignature);
994}
995
996/*
997%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
998% %
999% %
1000% %
1001% U n r e g i s t e r M G K I m a g e %
1002% %
1003% %
1004% %
1005%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1006%
1007% UnregisterMGKImage() removes format registrations made by the
1008% MGK module from the list of supported formats.
1009%
1010% The format of the UnregisterMGKImage method is:
1011%
1012% UnregisterMGKImage(void)
1013%
1014*/
1015ModuleExport void UnregisterMGKImage(void)
1016{
1017 (void) UnregisterMagickInfo("MGK");
1018}
1019
1020/*
1021%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1022% %
1023% %
1024% %
1025% W r i t e M G K I m a g e %
1026% %
1027% %
1028% %
1029%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1030%
1031% WriteMGKImage() writes an image to a file in red, green, and blue
1032% MGK rasterfile format.
1033%
1034% The format of the WriteMGKImage method is:
1035%
1036% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1037%
1038% A description of each parameter follows.
1039%
1040% o image_info: the image info.
1041%
1042% o image: The image.
1043%
1044*/
1045static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1046{
1047 char
1048 buffer[MaxTextExtent];
1049
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1050 MagickBooleanType
1051 status;
1052
1053 MagickOffsetType
1054 scene;
1055
1056 register const PixelPacket
1057 *p;
1058
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1059 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1060 x;
1061
1062 register unsigned char
1063 *q;
1064
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1065 ssize_t
1066 y;
1067
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1068 unsigned char
1069 *pixels;
1070
1071 /*
1072 Open output image file.
1073 */
1074 assert(image_info != (const ImageInfo *) NULL);
1075 assert(image_info-&gt;signature == MagickSignature);
1076 assert(image != (Image *) NULL);
1077 assert(image-&gt;signature == MagickSignature);
1078 if (image-&gt;debug != MagickFalse)
1079 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1080 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1081 if (status == MagickFalse)
1082 return(status);
1083 scene=0;
1084 do
1085 {
1086 /*
1087 Allocate memory for pixels.
1088 */
1089 if (image-&gt;colorspace != RGBColorspace)
1090 (void) SetImageColorspace(image,RGBColorspace);
1091 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1092 3UL*sizeof(*pixels));
1093 if (pixels == (unsigned char *) NULL)
1094 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1095 /*
1096 Initialize raster file header.
1097 */
1098 (void) WriteBlobString(image,"id=mgk\n");
1099 (void) FormatMagickString(buffer,MaxTextExtent,"%lu %lu\n",
1100 image-&gt;columns,image-&gt;rows);
1101 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1102 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1103 {
1104 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1105 if (p == (const PixelPacket *) NULL)
1106 break;
1107 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1108 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1109 {
1110 *q++=ScaleQuantumToChar(p-&gt;red);
1111 *q++=ScaleQuantumToChar(p-&gt;green);
1112 *q++=ScaleQuantumToChar(p-&gt;blue);
1113 p++;
1114 }
1115 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1116 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1117 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1118 break;
1119 }
1120 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1121 if (GetNextImageInList(image) == (Image *) NULL)
1122 break;
1123 image=SyncNextImageInList(image);
1124 status=SetImageProgress(image,SaveImagesTag,scene,
1125 GetImageListLength(image));
1126 if (status == MagickFalse)
1127 break;
1128 scene++;
1129 } while (image_info-&gt;adjoin != MagickFalse);
1130 (void) CloseBlob(image);
1131 return(MagickTrue);
1132}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1133</div>
1134
1135<p>To invoke the custom coder from the command line, use these commands:</p>
1136
1137<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert logo: logo.mgk</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>display logo.mgk</span></p>
1138<p>We provide the <a href="ftp://ftp.imagemagick.org/pub/ImageMagick/kits/MagickCoderKit-1.0.0.tar.gz">Magick Coder Kit</a> to help you get started writing your own custom coder.</p>
1139
1140</div>
1141
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1142<h2><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1143<div class="doc-section">
1144
1145<p>ImageMagick provides a convenient mechanism for adding your own custom image processing algorithms. We call these image filters and they are invoked from the command line with the <a href="../www/command-line-options.html#process">-process</a> option or from the MagickCore API method <a href="../www/api/module.html#ExecuteModuleProcess">ExecuteModuleProcess()</a>.</p>
1146
1147<p>Here is a listing of a sample <a href="../www/source/analyze.c">custom image filter</a>. It computes a few statistics such as the pixel brightness and saturation mean and standard-deviation.</p>
1148
1149<div class="viewport">
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1150#include &lt;stdio.h&gt;
1151#include &lt;stdlib.h&gt;
1152#include &lt;string.h&gt;
1153#include &lt;time.h&gt;
1154#include &lt;assert.h&gt;
1155#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1156#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1157
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1158/*
1159%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1160% %
1161% %
1162% %
1163% a n a l y z e I m a g e %
1164% %
1165% %
1166% %
1167%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1168%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1169% analyzeImage() computes the brightness and saturation mean, standard
1170% deviation, kurtosis and skewness and stores these values as attributes
1171% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1172%
1173% The format of the analyzeImage method is:
1174%
1175% unsigned long analyzeImage(Image *images,const int argc,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1176% char **argv,ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1177%
1178% A description of each parameter follows:
1179%
1180% o image: the address of a structure of type Image.
1181%
1182% o argc: Specifies a pointer to an integer describing the number of
1183% elements in the argument vector.
1184%
1185% o argv: Specifies a pointer to a text array containing the command line
1186% arguments.
1187%
1188% o exception: return any errors or warnings in this structure.
1189%
1190*/
1191ModuleExport unsigned long analyzeImage(Image **images,const int argc,
1192 const char **argv,ExceptionInfo *exception)
1193{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1194 char
1195 text[MaxTextExtent];
1196
1197 double
1198 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1199 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1200 brightness_mean,
1201 brightness_standard_deviation,
1202 brightness_kurtosis,
1203 brightness_skewness,
1204 brightness_sum_x,
1205 brightness_sum_x2,
1206 brightness_sum_x3,
1207 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1208 hue,
1209 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1210 saturation_mean,
1211 saturation_standard_deviation,
1212 saturation_kurtosis,
1213 saturation_skewness,
1214 saturation_sum_x,
1215 saturation_sum_x2,
1216 saturation_sum_x3,
1217 saturation_sum_x4;
1218
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1219 Image
1220 *image;
1221
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1222 assert(images != (Image **) NULL);
1223 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1224 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1225 (void) argc;
1226 (void) argv;
1227 image=(*images);
1228 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1229 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1230 CacheView
1231 *image_view;
1232
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1233 MagickBooleanType
1234 status;
1235
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1236 ssize_t
1237 y;
1238
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1239 brightness_sum_x=0.0;
1240 brightness_sum_x2=0.0;
1241 brightness_sum_x3=0.0;
1242 brightness_sum_x4=0.0;
1243 brightness_mean=0.0;
1244 brightness_standard_deviation=0.0;
1245 brightness_kurtosis=0.0;
1246 brightness_skewness=0.0;
1247 saturation_sum_x=0.0;
1248 saturation_sum_x2=0.0;
1249 saturation_sum_x3=0.0;
1250 saturation_sum_x4=0.0;
1251 saturation_mean=0.0;
1252 saturation_standard_deviation=0.0;
1253 saturation_kurtosis=0.0;
1254 saturation_skewness=0.0;
1255 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1256 status=MagickTrue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1257 image_view=AcquireCacheView(image);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1258#if defined(MAGICKCORE_OPENMP_SUPPORT)
1259 #pragma omp parallel for schedule(dynamic,4) shared(status)
1260#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1261 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1262 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1263 register const PixelPacket
1264 *p;
1265
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1266 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1267 x;
1268
1269 if (status == MagickFalse)
1270 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1271 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1272 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1273 {
1274 status=MagickFalse;
1275 continue;
1276 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1277 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1278 {
1279 ConvertRGBToHSB(p-&gt;red,p-&gt;green,p-&gt;blue,&amp;hue,&amp;saturation,&amp;brightness);
1280 brightness*=QuantumRange;
1281 brightness_sum_x+=brightness;
1282 brightness_sum_x2+=brightness*brightness;
1283 brightness_sum_x3+=brightness*brightness*brightness;
1284 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1285 saturation*=QuantumRange;
1286 saturation_sum_x+=saturation;
1287 saturation_sum_x2+=saturation*saturation;
1288 saturation_sum_x3+=saturation*saturation*saturation;
1289 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1290 area++;
1291 p++;
1292 }
1293 }
1294 image_view=DestroyCacheView(image_view);
1295 if (area &lt;= 0.0)
1296 break;
1297 brightness_mean=brightness_sum_x/area;
1298 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_mean);
1299 (void) SetImageProperty(image,"filter:brightness:mean",text);
1300 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1301 area*brightness_sum_x/area));
1302 (void) FormatMagickString(text,MaxTextExtent,"%g",
1303 brightness_standard_deviation);
1304 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1305 if (brightness_standard_deviation != 0)
1306 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1307 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1308 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1309 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1310 brightness_standard_deviation*brightness_standard_deviation*
1311 brightness_standard_deviation)-3.0;
1312 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_kurtosis);
1313 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1314 if (brightness_standard_deviation != 0)
1315 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1316 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1317 brightness_mean)/(brightness_standard_deviation*
1318 brightness_standard_deviation*brightness_standard_deviation);
1319 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_skewness);
1320 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1321 saturation_mean=saturation_sum_x/area;
1322 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_mean);
1323 (void) SetImageProperty(image,"filter:saturation:mean",text);
1324 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1325 area*saturation_sum_x/area));
1326 (void) FormatMagickString(text,MaxTextExtent,"%g",
1327 saturation_standard_deviation);
1328 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1329 if (saturation_standard_deviation != 0)
1330 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1331 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1332 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1333 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1334 saturation_standard_deviation*saturation_standard_deviation*
1335 saturation_standard_deviation)-3.0;
1336 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_kurtosis);
1337 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1338 if (saturation_standard_deviation != 0)
1339 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1340 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1341 saturation_mean)/(saturation_standard_deviation*
1342 saturation_standard_deviation*saturation_standard_deviation);
1343 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_skewness);
1344 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1345 }
1346 return(MagickImageFilterSignature);
1347}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1348</div>
1349
1350<p>To invoke the custom filter from the command line, use this command:</p>
1351
1352<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert logo: -process analyze -verbose info:</span><span class='crtout'>Image: logo: <br/>
1353 Format: LOGO (ImageMagick Logo) <br/>
1354 Class: PseudoClass <br/>
1355 Geometry: 640x480 <br/>
1356 ... <br/>
1357 filter:brightness:kurtosis: 8.98864 <br/>
1358 filter:brightness:mean: 238.096 <br/>
1359 filter:brightness:skewness: -3.04519 <br/>
1360 filter:brightness:standard-deviation: 46.3286 <br/>
1361 filter:saturation:kurtosis: 5.9137 <br/>
1362 filter:saturation:mean: 23.4635 <br/>
1363 filter:saturation:skewness: 2.71874 <br/>
1364 filter:saturation:standard-deviation: 64.7734</span></p>
1365
1366<p>We provide the <a href="ftp://ftp.imagemagick.org/pub/ImageMagick/kits/MagickFilterKit-1.0.0.tar.gz">Magick Filter Kit</a> to help you get started writing your own custom image filter.</p>
1367
1368</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1369
1370</div>
1371
1372<div id="linkbar">
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]1373 <span id="linkbar-west">&nbsp;</span>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1374 <span id="linkbar-center">
1375 <a href="http://www.imagemagick.org/discourse-server/">Discourse Server</a> &bull;
cristya8902942010-07-30 00:49:52 +0000[diff] [blame]1376 <a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">Studio</a>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1377 </span>
1378 <span id="linkbar-east">&nbsp;</span>
1379 </div>
1380 <div class="footer">
cristy7e41fe82010-12-04 23:12:08 +0000[diff] [blame]1381 <span id="footer-west">&copy; 1999-2011 ImageMagick Studio LLC</span>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1382 <span id="footer-east"> <a href="http://www.imagemagick.org/script/contact.php">Contact the Wizards</a></span>
1383 </div>
1384 <div style="clear: both; margin: 0; width: 100%; "></div>
cristya8902942010-07-30 00:49:52 +0000[diff] [blame]1385 <script type="text/javascript">
1386 var _gaq = _gaq || [];
1387 _gaq.push(['_setAccount', 'UA-17690367-1']);
1388 _gaq.push(['_trackPageview']);
1389
1390 (function() {
1391 var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
1392 ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
1393 var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
1394 })();
1395 </script>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1396</body>
1397</html>