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gerrit-public.fairphone.software / platform / external / ImageMagick / eed6cb663d33342848fce694ad45fe2db637547f / . / www / architecture.html
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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">
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]3<html version="-//W3C//DTD XHTML 1.1//EN"
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cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]8<head>
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]9 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
cristy1efc1ab2011-08-01 14:47:02 +0000[diff] [blame]10 <meta name="google-site-verification" content="MxsMq6bdLOx0KSuz1MY6yG9ZTIJ7_7DVRfl5NCAT5Yg"/>
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]11 <title>ImageMagick: Architecture</title>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]12 <meta http-equiv="Content-Language" content="en-US"/>
13 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
14 <meta http-equiv="Reply-to" content="magick-users@imagemagick.org"/>
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]15 <meta name="Application-name" content="ImageMagick"/>
cristye6e84152011-06-06 14:16:49 +0000[diff] [blame]16 <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 automagically."/>
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]17 <meta name="Application-url" content="http://www.imagemagick.org"/>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]18 <meta name="Generator" content="PHP"/>
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]19 <meta name="Keywords" content="architecture, ImageMagick, PerlMagick, image processing, OpenMP, software development library, image, photo, software, Magick++, MagickWand"/>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]20 <meta name="Rating" content="GENERAL"/>
21 <meta name="Robots" content="INDEX, FOLLOW"/>
22 <meta name="Generator" content="ImageMagick Studio LLC"/>
23 <meta name="Author" content="ImageMagick Studio LLC"/>
24 <meta name="Revisit-after" content="2 DAYS"/>
25 <meta name="Resource-type" content="document"/>
cristy1454be72011-12-19 01:52:48 +0000[diff] [blame]26 <meta name="Copyright" content="Copyright (c) 1999-2012 ImageMagick Studio LLC"/>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]27 <meta name="Distribution" content="Global"/>
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]28 <link rel="icon" href="../images/wand.png"/>
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]29 <link rel="shortcut icon" href="../images/wand.ico" type="images/x-icon"/>
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]30 <link rel="canonical" href="http://www.imagemagick.org" />
cristy3c98a4f2010-08-13 20:09:41 +0000[diff] [blame]31 <link rel="meta" type="application/rdf+xml" title="ICI" href="http://imagemagick.org/ici.rdf"/>
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]32 <!-- Add jQuery library -->
33 <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7/jquery.min.js"></script>
34
35 <!-- Optionaly include easing and/or mousewheel plugins -->
36 <script type="text/javascript" src="http://www.imagemagick.org/fancybox/jquery.easing-1.3.pack.js"></script>
37 <script type="text/javascript" src="http://www.imagemagick.org/fancybox/jquery.mousewheel-3.0.6.pack.js"></script>
38
39 <!-- Add fancyBox -->
40 <link rel="stylesheet" href="http://www.imagemagick.org/fancybox/jquery.fancybox.css?v=2.0.3" type="text/css" media="screen" />
41 <script type="text/javascript" src="http://www.imagemagick.org/fancybox/jquery.fancybox.pack.js?v=2.0.3"></script>
42
43 <!-- Optionaly include button and/or thumbnail helpers -->
44 <link rel="stylesheet" href="http://www.imagemagick.org/fancybox/helpers/jquery.fancybox-buttons.css?v=2.0.3" type="text/css" media="screen" />
45 <script type="text/javascript" src="http://www.imagemagick.org/fancybox/helpers/jquery.fancybox-buttons.js?v=2.0.3"></script>
46
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48 <script type="text/javascript" src="http://www.imagemagick.org/fancybox/helpers/jquery.fancybox-thumbs.js?v=2.0.3"></script>
49 <script type="text/javascript">
50 $(document).ready(function() {
51 $(".fancybox").fancybox();
52 });
53 </script>
54 <!-- ImageMagick style -->
cristy7a40ba82011-01-08 20:31:18 +0000[diff] [blame]55 <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]56 <style type="text/css" media="all">
57 @import url("../www/magick.css");
58 </style>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]59</head>
60
61<body id="www-imagemagick-org">
62<div class="titlebar">
cristyb52981c2011-03-19 17:09:31 +0000[diff] [blame]63<div style="margin: 17px auto; float: left;">
64 <script type="text/javascript">
65 <!--
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75</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]76<a href="http://www.imagemagick.org/discourse-server/">
cristyaf8d6652011-02-04 21:57:45 +0000[diff] [blame]77 <img src="../images/logo.jpg"
78 alt="ImageMagick Logo"
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]79 style="width: 123px; height: 118px; border: 0px; float: right;" /></a>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]80<a href="../index.html">
cristyaf8d6652011-02-04 21:57:45 +0000[diff] [blame]81 <img src="../images/sprite.jpg"
82 alt="ImageMagick Sprite"
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]83 style="width: 114px; height: 118px; border: 0px; float: right;" /></a>
84</div>
85
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93</div>
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122<div class="sub">
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148 <a title="Architecture" href="../www/architecture.html">Architecture</a>
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241<div class="main">
242
243
244
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]245<h1>The <em>Magick</em> Behind ImageMagick</h1>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]246<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]247
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]248
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]249<div class="doc-section">
250<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>
251</div>
252
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]253<h2><a id="overview"></a>Architecture Overview</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]254<div class="doc-section">
255
256<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>
257
258<ul>
259 <li>colorspace (e.g RGB, CMYK, YUV, Lab, etc.)</li>
260 <li>bit depth (.e.g 1, 4, 8, 12, 16, etc.)</li>
261 <li>storage format (e.g. unsigned, signed, float, double, etc.)</li>
262 <li>compression (e.g. uncompressed, RLE, Zip, BZip, etc.)</li>
263 <li>orientation (i.e. top-to-bottom, right-to-left, etc.),</li>
264 <li>layout (.e.g. raw, interspersed with opcodes, etc.)</li>
265</ul>
266
267<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>
268
269<p>An efficient implementation of an image processing algorithm may require we get or set:</p>
270
271<ul>
272 <li>one pixel a time (e.g. pixel at location 10,3)</li>
273 <li>a single scanline (e.g. all pixels from row 4)</li>
274 <li>a few scanlines at once (e.g. pixel rows 4-7)</li>
275 <li>a single column or columns of pixels (e.g. all pixels from column 11)</li>
276 <li>an arbitrary region of pixels from the image (e.g. pixels defined at 10,7 to 10,19)</li>
277 <li>a pixel in random order (e.g. pixel at 14,15 and 640,480)</li>
278 <li>pixels from two different images (e.g. pixel at 5,1 from image 1 and pixel at 5,1 from image 2)</li>
279 <li>pixels outside the boundaries of the image (e.g. pixel at -1,-3)</li>
280 <li>a pixel component that is unsigned or in a floating-point representation (e.g. 0.17836)</li>
281 <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>
282 <li>one or more pixels simultaneously in different threads of execution</li>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]283 <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]284</ul>
285
286<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>
287
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]288<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]289
cristy320dd6e2010-04-16 20:11:40 +0000[diff] [blame]290<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]291
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]292<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]293
294</div>
295
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]296<h2><a id="cache"></a>The Pixel Cache</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]297<div class="doc-section">
298
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]299<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]300
301<h3>Create the Pixel Cache</h3>
302<div class="doc-section">
303
304<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>
305
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]306<dl>
307<dt>Create an image canvas initialized to the background color:</dt>
308<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]309 image=AllocateImage(image_info);
310 if (SetImageExtent(image,640,480) == MagickFalse)
311 { /* an exception was thrown */ }
312 (void) QueryMagickColor("red",&amp;image-&gt;background_color,&amp;image-&gt;exception);
313 SetImageBackgroundColor(image);
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]314</p></dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]315
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]316<dt>Create an image from a JPEG image on disk:</dt>
317<dd><p class="code">
318 (void) strcpy(image_info-&gt;filename,"image.jpg"):
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]319 image=ReadImage(image_info,exception);
320 if (image == (Image *) NULL)
321 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]322</p></dd>
323<dt>Create an image from a memory based image:</dt>
324<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]325 image=BlobToImage(blob_info,blob,extent,exception);
326 if (image == (Image *) NULL)
327 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]328</p></dd>
329</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]330
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]331<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]332
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]333<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]334
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]335<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>identify -version</span><span class='crtout'>Version: ImageMagick 6.7.5-0 2012-01-25 Q16 http://www.imagemagick.org</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]336<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]337</div>
338
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]339<h3><a id="authentic-pixels"></a>Access the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]340<div class="doc-section">
341
342<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>
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]343<ul>
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]344 <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]345 <li><a href="../www/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> gets pixels that you intend to modify</li>
346 <li><a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> queue pixels that you intend to modify</li>
347 <li><a href="../www/api/cache.html#SyncAuthenticPixels">SyncAuthenticPixels()</a> update the pixel cache with any modified pixels</li>
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]348</ul>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]349
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]350<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]351
352<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]353 const PixelPacket
354 *p;
355
356 PixelPacket
357 *q;
358
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]359 ssize_t
360 x,
361 y;
362
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]363 destination=CloneImage(source,source->columns,source->rows,MagickTrue,
364 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]365 if (destination == (Image *) NULL)
366 { /* an exception was thrown */ }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]367 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]368 {
369 p=GetVirtualPixels(source,0,y,source-&gt;columns,1,exception);
370 q=GetAuthenticPixels(destination,0,y,destination-&gt;columns,1,exception);
371 if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL)
372 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]373 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]374 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]375 SetPixelRed(q,90*p-&gt;red/100);
376 SetPixelGreen(q,90*p-&gt;green/100);
377 SetPixelBlue(q,90*p-&gt;blue/100);
378 SetPixelOpacity(q,90*p-&gt;opacity/100);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]379 p++;
380 q++;
381 }
382 if (SyncAuthenticPixels(destination,exception) == MagickFalse)
383 break;
384 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]385 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]386 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]387</div>
388
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]389<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]390
cristy84134182011-06-15 22:59:00 +0000[diff] [blame]391<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#GetVirtualIndexQueue">GetVirtualIndexQueue()</a> (to read the indexes) or <a href="../www/api/cache.html#GetAuthenticIndexQueue">GetAuthenticIndexQueue()</a> (to update the indexes) to gain access to this channel. For example, to print the colormap indexes, use:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]392
393<pre class="code">
394 const IndexPacket
395 *indexes;
396
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]397 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]398 {
399 p=GetVirtualPixels(source,0,y,source-&gt;columns,1);
400 if (p == (const PixelPacket *) NULL)
401 break;
cristy84134182011-06-15 22:59:00 +0000[diff] [blame]402 indexes=GetVirtualIndexQueue(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]403 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]404 (void) printf("%d\n",GetPixelIndex(indexes+x));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]405 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]406 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]407 /* an exception was thrown */
408</pre>
409
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]410<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]411
412<pre class="code">
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]413 p=GetVirtualPixels(source,-3,-3,source-&gt;columns+3,6,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]414</pre>
415
416<p>gives you the pixels you asked for without complaint, even though some are not within the confines of the image region.</p>
417</div>
418
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]419<h3><a id="virtual-pixels"></a>Virtual Pixels</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]420<div class="doc-section">
421
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]422<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]423 <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>
424
cristy4c54bbb2011-03-17 13:53:13 +0000[diff] [blame]425<pre class="text" style="font-size: 83.3333%;">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]426 background: the area surrounding the image is the background color
427 black: the area surrounding the image is black
428 checker-tile: alternate squares with image and background color
429 dither: non-random 32x32 dithered pattern
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]430 edge: extend the edge pixel toward infinity (default)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]431 gray: the area surrounding the image is gray
432 horizontal-tile: horizontally tile the image, background color above/below
433 horizontal-tile-edge: horizontally tile the image and replicate the side edge pixels
434 mirror: mirror tile the image
435 random: choose a random pixel from the image
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]436 tile: tile the image
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]437 transparent: the area surrounding the image is transparent blackness
438 vertical-tile: vertically tile the image, sides are background color
439 vertical-tile-edge: vertically tile the image and replicate the side edge pixels
440 white: the area surrounding the image is white
441</pre>
442
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]443</div>
444
445<h3>Cache Storage and Resource Requirements</h3>
446<div class="doc-section">
447
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]448<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]449
450<dl class="doc">
451 <dt class="doc">files</dt>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]452 <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]453 <dt class="doc">area</dt>
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]454 <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 and optionally memory-mapped.</dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]455 <dt class="doc">memory</dt>
456 <dd>maximum amount of memory in bytes to allocate for the pixel cache from the anonymous mapped memory or the heap.</dd>
457 <dt class="doc">map</dt>
458 <dd>maximum amount of memory map in bytes to allocate for the pixel cache.</dd>
459 <dt class="doc">disk</dt>
460 <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]461 <dt class="doc">thread</dt>
462 <dd>maximum number of threads that are permitted to run in parallel.</dd>
463 <dt class="doc">time</dt>
464 <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]465</dl>
466
467<p>To determine the current setting of these limits, use this command:</p>
468
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]469<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>identify -list resource</span></p><pre class="text">
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]470File Area Memory Map Disk Thread Time
cristy2c839602010-04-03 02:32:08 +0000[diff] [blame]471-------------------------------------------------------------------------------
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]472 768 1.0386GB 3.8692GiB 7.7384GiB unlimited 4 unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]473</pre>
474
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]475<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]476
477<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>
478</div>
479
480<h3>Cache Views</h3>
481<div class="doc-section">
482
483<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>
484
485<pre class="code">
486 CacheView
487 *view_1,
488 *view_2;
489
cristye9a32c32011-04-07 01:11:05 +0000[diff] [blame]490 view_1=AcquireCacheView(source);
491 view_2=AcquireCacheView(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]492 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]493 {
494 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]495 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,
496 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]497 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
498 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]499 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]500 {
501 /* do something with u &amp; v here */
502 }
503 }
cristye9a32c32011-04-07 01:11:05 +0000[diff] [blame]504 view_2=DestroyCacheView(view_2);
505 view_1=DestroyCacheView(view_1);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]506 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]507 { /* an exception was thrown */ }
508</pre>
509</div>
510
511<h3>Magick Persistent Cache Format</h3>
512<div class="doc-section">
513
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]514<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]515<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]516</div>
517
518<h3>Best Practices</h3>
519<div class="doc-section">
520
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]521<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. Although you can access scanlines of pixels sequentially from the last row of the image to the first, you may get a performance boost if you access scanlines from the first row of the image to the last, in sequentual order.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]522
523<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>
524
525<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>
526
527<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>
528
529<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>
530
531<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>
532
533<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>
534
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]535<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]536
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]537<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]538
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]539<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>export MAGICK_TEMPORARY_PATH=/data/magick</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]540
541<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>
542
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]543<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert image.tif image.mpc</span><span class='crtout'></span><span class="crtprompt"> $ </span><span class='crtin'>convert image.mpc -crop 100x100+0+0 +repage 1.png</span><span class='crtout'></span><span class="crtprompt"> $ </span><span class='crtin'>convert image.mpc -crop 100x100+100+0 +repage 2.png</span><span class='crtout'></span><span class="crtprompt"> $ </span><span class='crtin'>convert image.mpc -crop 100x100+200+0 +repage 3.png</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]544<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>
545</div>
546
547</div>
548
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]549<h2><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]550<div class="doc-section">
551
552<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>
553
554<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>
555
556<pre class="code">
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]557static size_t StreamPixels(const Image *image,const void *pixels,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]558 const size_t columns)
559{
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]560 register const PixelPacket
561 *p;
562
563 MyData
564 *my_data;
565
566 my_data=(MyData *) image->client_data;
567 p=(PixelPacket *) pixels;
568 if (p != (const PixelPacket *) NULL)
569 {
570 /* process pixels here */
571 }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]572 return(columns);
573}
574
575...
576/* invoke the pixel stream here */
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]577image_info->client_data=(void *) MyData;
578image=ReadStream(image_info,&amp;StreamPixels,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]579</pre>
580
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]581<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. A majority of the image formats stream pixels (red, green, and blue) from left to right and top to bottom. However, a few formats do not support this common ordering (e.g. the PSD format).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]582
583</div>
584
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]585<h2><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]586<div class="doc-section">
587
588<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>
589
590<pre class="code">
591 (void) printf("image width: %lu, height: %lu\n",image-&gt;columns,image-&gt;rows);
592</pre>
593
594<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>
595
596<pre class="code">
597 const char
598 *comment;
599
600 (void) SetImageProperty(image,"comment","This space for rent");
601 comment=GetImageProperty(image,"comment");
602 if (comment == (const char *) NULL)
603 (void) printf("Image comment: %s\n",comment);
604</pre>
605
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]606<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]607
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]608<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>
609
610<pre class="code">
611 StringInfo
612 *profile;
613
614 profile=AcquireStringInfo(length);
615 SetStringInfoDatum(profile,my_exif_profile);
616 (void) SetImageProfile(image,"EXIF",profile);
617 DestroyStringInfo(profile);
618 profile=GetImageProfile(image,"EXIF");
619 if (profile != (StringInfo *) NULL)
620 (void) PrintStringInfo(stdout,"EXIF",profile);
621</pre>
622
623</div>
624
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]625<h2><a id="tera-pixel"></a>Large Image Support</h2>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]626<div class="doc-section">
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]627<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]628
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]629<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize 250000x250000 logo.miff</span></p>
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]630<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]631
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]632<p class='crt'><span class="crtprompt"> $ </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]633<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>
634
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]635<p class='crt'><span class="crtprompt"> $ </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]636<p>Here we force all image pixels to disk:</p>
637
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]638<p class='crt'><span class="crtprompt"> $ </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]639<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]640
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]641<p class='crt'><span class="crtprompt"> $ </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]642
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]643<h2><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]644<div class="doc-section">
645
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]646<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]647
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]648<p>Here is an MagickCore code snippet that takes advantage of threads of execution with the <a href="../www/parallel.html">OpenMP</a> programming paradigm:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]649
650<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]651{
652 CacheView
653 *image_view;
654
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]655 MagickBooleanType
656 status;
657
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]658 ssize_t
659 y;
660
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]661 status=MagickTrue;
662 image_view=AcquireCacheView(image);
663 #pragma omp parallel for schedule(dynamic,4) shared(status)
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]664 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]665 {
666 register IndexPacket
667 *indexes;
668
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]669 register PixelPacket
670 *q;
671
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]672 register ssize_t
673 x;
674
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]675 if (status == MagickFalse)
676 continue;
677 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
678 if (q == (PixelPacket *) NULL)
679 {
680 status=MagickFalse;
681 continue;
682 }
683 indexes=GetCacheViewAuthenticIndexQueue(image_view);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]684 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]685 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]686 SetPixelRed(q,...);
687 SetPixelGreen(q,...);
688 SetPixelBlue(q,...);
689 SetPixelOpacity(q,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]690 if (indexes != (IndexPacket *) NULL)
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]691 SetPixelIndex(indexes+x,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]692 q++;
693 }
694 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
695 status=MagickFalse;
696 }
697 image_view=DestroyCacheView(image_view);
698 if (status == MagickFalse)
699 perror("something went wrong");
700}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]701</div>
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]702<p>This code snippet converts an uncompressed Windows bitmap to a Magick++ image:</p>
703<div class="viewport">
704#include "Magick++.h"
705#include &lt;assert.h&gt;
706#include "omp.h"
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]707
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]708void ConvertBMPToImage(const BITMAPINFOHEADER *bmp_info,
709 const unsigned char *restrict pixels,Magick::Image *image)
710{
711 /*
712 Prepare the image so that we can modify the pixels directly.
713 */
714 assert(bmp_info->biCompression == BI_RGB);
715 assert(bmp_info->biWidth == image->columns());
716 assert(abs(bmp_info->biHeight) == image->rows());
717 image->modifyImage();
718 if (bmp_info->biBitCount == 24)
719 image->type(MagickCore::TrueColorType);
720 else
721 image->type(MagickCore::TrueColorMatteType);
722 register unsigned int bytes_per_row=bmp_info->biWidth*bmp_info->biBitCount/8;
723 if (bytes_per_row % 4 != 0) {
724 bytes_per_row=bytes_per_row+(4-bytes_per_row % 4); // divisible by 4.
725 }
726 /*
727 Copy all pixel data, row by row.
728 */
729 #pragma omp parallel for
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]730 for (int y=0; y &lt; int(image->rows()); y++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]731 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]732 int
733 row;
734
735 register const unsigned char
736 *restrict p;
737
738 register MagickCore::PixelPacket
739 *restrict q;
740
741 row=(bmp_info->biHeight > 0) ? (image->rows()-y-1) : y;
742 p=pixels+row*bytes_per_row;
743 q=image->setPixels(0,y,image->columns(),1);
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]744 for (int x=0; x &lt; int(image->columns()); x++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]745 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]746 SetPixelBlue(q,p[0]);
747 SetPixelGreen(q,p[1]);
748 SetPixelRed(q,p[2]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]749 if (bmp_info->biBitCount == 32) {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]750 SetPixelOpacity(q,p[3]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]751 }
752 q++;
753 p+=bmp_info->biBitCount/8;
754 }
755 image->syncPixels(); // sync pixels to pixel cache.
756 }
757 return;
758}
759</div>
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]760
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]761<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>
762
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]763<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]764
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]765<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]766
767<pre class="text">
768 &lt;policy domain="resource" name="thread" value="2"/>
769</pre>
770
771<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>
772
773<pre class="text">
774 export MAGICK_THREAD_LIMIT=12
775</pre>
776
777<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>
778
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]779<h4>Threading Performance</h4>
780<p>It can be difficult to predict behavior in a parallel environment. Performance might depend on a number of factors including the compiler, the version of the OpenMP library, the processor type, the number of cores, the amount of memory, whether hyperthreading is enabled, the mix of applications that are executing concurrently with ImageMagick, or the particular image-processing algorithm you utilize. The only way to be certain of optimal performance, in terms of the number of threads, is to benchmark. ImageMagick includes progressive threading when benchmarking a command and returns the elapsed time and efficiency for one or more threads. This can help you identify how many threads is the most efficient in your environment. Here is an example benchmark for threads 1-8:</p>
781<pre class="text">
782convert -bench 40 model.png -sharpen 0x1 null:
783Performance[1]: 10i 0.712ips 1.000e 14.000u 0:14.040
784Performance[2]: 10i 1.362ips 0.657e 14.550u 0:07.340
785Performance[3]: 10i 2.033ips 0.741e 14.530u 0:04.920
786Performance[4]: 10i 2.667ips 0.789e 14.590u 0:03.750
787Performance[5]: 10i 3.236ips 0.820e 14.970u 0:03.090
788Performance[6]: 10i 3.802ips 0.842e 15.280u 0:02.630
789Performance[7]: 10i 4.274ips 0.857e 15.540u 0:02.340
790Performance[8]: 10i 4.831ips 0.872e 15.680u 0:02.070
791</pre>
792<p>In certain cases, it might be optimal to set the number of threads to 1 or to disable OpenMP completely.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]793</div>
794
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]795<h2><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]796<div class="doc-section">
797<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>
798
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]799<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]800
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]801<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>identify -version</span><span class='crtout'>Features: OpenMP OpenCL</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]802<p>If so, run this command to realize a significant speed-up for image convolution:</p>
803
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]804<p class='crt'><span class="crtprompt"> $ </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]805<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
806
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]807<p>Here is an example OpenCL kernel that convolves an image:</p>
808
809<div class="viewport">
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]810static inline long ClampToCanvas(const long offset,const ulong range)
811{
812 if (offset &lt; 0L)
813 return(0L);
814 if (offset >= range)
815 return((long) (range-1L));
816 return(offset);
817}
818
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]819static inline CLQuantum ClampToQuantum(const float value)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]820{
821 if (value &lt; 0.0)
822 return((CLQuantum) 0);
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]823 if (value >= (float) QuantumRange)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]824 return((CLQuantum) QuantumRange);
825 return((CLQuantum) (value+0.5));
826}
827
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]828__kernel void Convolve(const __global CLPixelType *source,__constant float *filter,
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]829 const ulong width,const ulong height,__global CLPixelType *destination)
830{
831 const ulong columns = get_global_size(0);
832 const ulong rows = get_global_size(1);
833
834 const long x = get_global_id(0);
835 const long y = get_global_id(1);
836
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]837 const float scale = (1.0/QuantumRange);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]838 const long mid_width = (width-1)/2;
839 const long mid_height = (height-1)/2;
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]840 float4 sum = { 0.0, 0.0, 0.0, 0.0 };
841 float gamma = 0.0;
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]842 register ulong i = 0;
843
844 for (long v=(-mid_height); v &lt;= mid_height; v++)
845 {
846 for (long u=(-mid_width); u &lt;= mid_width; u++)
847 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]848 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
849 columns);
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]850 const float alpha=scale*(QuantumRange-source[index].w);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]851 sum.x+=alpha*filter[i]*source[index].x;
852 sum.y+=alpha*filter[i]*source[index].y;
853 sum.z+=alpha*filter[i]*source[index].z;
854 sum.w+=filter[i]*source[index].w;
855 gamma+=alpha*filter[i];
856 i++;
857 }
858 }
859
860 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
861 const ulong index=y*columns+x;
862 destination[index].x=ClampToQuantum(gamma*sum.x);
863 destination[index].y=ClampToQuantum(gamma*sum.y);
864 destination[index].z=ClampToQuantum(gamma*sum.z);
865 destination[index].w=ClampToQuantum(sum.w);
866};
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]867</div>
868
cristy37f02952010-03-24 19:47:41 +0000[diff] [blame]869<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]870
871</div>
872
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]873<h2><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]874<div class="doc-section">
875
876<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>
877
878<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>
879
880<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]881/*
882 Include declarations.
883*/
884#include "magick/studio.h"
885#include "magick/blob.h"
886#include "magick/blob-private.h"
887#include "magick/colorspace.h"
888#include "magick/exception.h"
889#include "magick/exception-private.h"
890#include "magick/image.h"
891#include "magick/image-private.h"
892#include "magick/list.h"
893#include "magick/magick.h"
894#include "magick/memory_.h"
895#include "magick/monitor.h"
896#include "magick/monitor-private.h"
897#include "magick/quantum-private.h"
898#include "magick/static.h"
899#include "magick/string_.h"
900#include "magick/module.h"
901
902/*
903 Forward declarations.
904*/
905static MagickBooleanType
906 WriteMGKImage(const ImageInfo *,Image *);
907
908/*
909%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
910% %
911% %
912% %
913% I s M G K %
914% %
915% %
916% %
917%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
918%
919% IsMGK() returns MagickTrue if the image format type, identified by the
920% magick string, is MGK.
921%
922% The format of the IsMGK method is:
923%
924% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
925%
926% A description of each parameter follows:
927%
928% o magick: This string is generally the first few bytes of an image file
929% or blob.
930%
931% o length: Specifies the length of the magick string.
932%
933*/
934static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
935{
936 if (length &lt; 7)
937 return(MagickFalse);
938 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
939 return(MagickTrue);
940 return(MagickFalse);
941}
942
943/*
944%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
945% %
946% %
947% %
948% R e a d M G K I m a g e %
949% %
950% %
951% %
952%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
953%
954% ReadMGKImage() reads a MGK image file and returns it. It allocates
955% the memory necessary for the new Image structure and returns a pointer to
956% the new image.
957%
958% The format of the ReadMGKImage method is:
959%
960% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
961%
962% A description of each parameter follows:
963%
964% o image_info: the image info.
965%
966% o exception: return any errors or warnings in this structure.
967%
968*/
969static Image *ReadMGKImage(const ImageInfo *image_info,
970 ExceptionInfo *exception)
971{
972 char
973 buffer[MaxTextExtent];
974
975 Image
976 *image;
977
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]978 MagickBooleanType
979 status;
980
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]981 register PixelPacket
982 *q;
983
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]984 register size_t
985 x;
986
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]987 register unsigned char
988 *p;
989
990 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]991 count,
992 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]993
994 unsigned char
995 *pixels;
996
997 unsigned long
998 columns,
999 rows;
1000
1001 /*
1002 Open image file.
1003 */
1004 assert(image_info != (const ImageInfo *) NULL);
1005 assert(image_info-&gt;signature == MagickSignature);
1006 if (image_info-&gt;debug != MagickFalse)
1007 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
1008 assert(exception != (ExceptionInfo *) NULL);
1009 assert(exception-&gt;signature == MagickSignature);
1010 image=AcquireImage(image_info);
1011 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
1012 if (status == MagickFalse)
1013 {
1014 image=DestroyImageList(image);
1015 return((Image *) NULL);
1016 }
1017 /*
1018 Read MGK image.
1019 */
1020 (void) ReadBlobString(image,buffer); /* read magic number */
1021 if (IsMGK(buffer,7) == MagickFalse)
1022 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1023 (void) ReadBlobString(image,buffer);
1024 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1025 if (count &lt;= 0)
1026 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1027 do
1028 {
1029 /*
1030 Initialize image structure.
1031 */
1032 image-&gt;columns=columns;
1033 image-&gt;rows=rows;
1034 image-&gt;depth=8;
1035 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
1036 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
1037 break;
1038 /*
1039 Convert MGK raster image to pixel packets.
1040 */
1041 if (SetImageExtent(image,0,0) == MagickFalse)
1042 {
1043 InheritException(exception,&amp;image-&gt;exception);
1044 return(DestroyImageList(image));
1045 }
1046 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
1047 if (pixels == (unsigned char *) NULL)
1048 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1049 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1050 {
1051 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
1052 if (count != (ssize_t) (3*image-&gt;columns))
1053 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
1054 p=pixels;
1055 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
1056 if (q == (PixelPacket *) NULL)
1057 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1058 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1059 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1060 SetPixelRed(q,ScaleCharToQuantum(*p++));
1061 SetPixelGreen(q,ScaleCharToQuantum(*p++));
1062 SetPixelBlue(q,ScaleCharToQuantum(*p++));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1063 q++;
1064 }
1065 if (SyncAuthenticPixels(image,exception) == MagickFalse)
1066 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1067 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1068 (SetImageProgress(image,LoadImageTag,y,image&gt;>rows) == MagickFalse))
1069 break;
1070 }
1071 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1072 if (EOFBlob(image) != MagickFalse)
1073 {
1074 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
1075 break;
1076 }
1077 /*
1078 Proceed to next image.
1079 */
1080 if (image_info-&gt;number_scenes != 0)
1081 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
1082 break;
1083 *buffer='\0';
1084 (void) ReadBlobString(image,buffer);
1085 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1086 if (count != 0)
1087 {
1088 /*
1089 Allocate next image structure.
1090 */
1091 AcquireNextImage(image_info,image);
1092 if (GetNextImageInList(image) == (Image *) NULL)
1093 {
1094 image=DestroyImageList(image);
1095 return((Image *) NULL);
1096 }
1097 image=SyncNextImageInList(image);
1098 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
1099 if (status == MagickFalse)
1100 break;
1101 }
1102 } while (count != 0);
1103 (void) CloseBlob(image);
1104 return(GetFirstImageInList(image));
1105}
1106
1107/*
1108%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1109% %
1110% %
1111% %
1112% R e g i s t e r M G K I m a g e %
1113% %
1114% %
1115% %
1116%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1117%
1118% RegisterMGKImage() adds attributes for the MGK image format to
1119% the list of supported formats. The attributes include the image format
1120% tag, a method to read and/or write the format, whether the format
1121% supports the saving of more than one frame to the same file or blob,
1122% whether the format supports native in-memory I/O, and a brief
1123% description of the format.
1124%
1125% The format of the RegisterMGKImage method is:
1126%
1127% unsigned long RegisterMGKImage(void)
1128%
1129*/
1130ModuleExport unsigned long RegisterMGKImage(void)
1131{
1132 MagickInfo
1133 *entry;
1134
1135 entry=SetMagickInfo("MGK");
1136 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
1137 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
1138 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
1139 entry-&gt;description=ConstantString("MGK");
1140 entry-&gt;module=ConstantString("MGK");
1141 (void) RegisterMagickInfo(entry);
1142 return(MagickImageCoderSignature);
1143}
1144
1145/*
1146%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1147% %
1148% %
1149% %
1150% U n r e g i s t e r M G K I m a g e %
1151% %
1152% %
1153% %
1154%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1155%
1156% UnregisterMGKImage() removes format registrations made by the
1157% MGK module from the list of supported formats.
1158%
1159% The format of the UnregisterMGKImage method is:
1160%
1161% UnregisterMGKImage(void)
1162%
1163*/
1164ModuleExport void UnregisterMGKImage(void)
1165{
1166 (void) UnregisterMagickInfo("MGK");
1167}
1168
1169/*
1170%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1171% %
1172% %
1173% %
1174% W r i t e M G K I m a g e %
1175% %
1176% %
1177% %
1178%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1179%
1180% WriteMGKImage() writes an image to a file in red, green, and blue
1181% MGK rasterfile format.
1182%
1183% The format of the WriteMGKImage method is:
1184%
1185% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1186%
1187% A description of each parameter follows.
1188%
1189% o image_info: the image info.
1190%
1191% o image: The image.
1192%
1193*/
1194static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1195{
1196 char
1197 buffer[MaxTextExtent];
1198
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1199 MagickBooleanType
1200 status;
1201
1202 MagickOffsetType
1203 scene;
1204
1205 register const PixelPacket
1206 *p;
1207
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1208 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1209 x;
1210
1211 register unsigned char
1212 *q;
1213
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1214 ssize_t
1215 y;
1216
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1217 unsigned char
1218 *pixels;
1219
1220 /*
1221 Open output image file.
1222 */
1223 assert(image_info != (const ImageInfo *) NULL);
1224 assert(image_info-&gt;signature == MagickSignature);
1225 assert(image != (Image *) NULL);
1226 assert(image-&gt;signature == MagickSignature);
1227 if (image-&gt;debug != MagickFalse)
1228 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1229 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1230 if (status == MagickFalse)
1231 return(status);
1232 scene=0;
1233 do
1234 {
1235 /*
1236 Allocate memory for pixels.
1237 */
1238 if (image-&gt;colorspace != RGBColorspace)
1239 (void) SetImageColorspace(image,RGBColorspace);
1240 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1241 3UL*sizeof(*pixels));
1242 if (pixels == (unsigned char *) NULL)
1243 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1244 /*
1245 Initialize raster file header.
1246 */
1247 (void) WriteBlobString(image,"id=mgk\n");
1248 (void) FormatMagickString(buffer,MaxTextExtent,"%lu %lu\n",
1249 image-&gt;columns,image-&gt;rows);
1250 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1251 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1252 {
1253 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1254 if (p == (const PixelPacket *) NULL)
1255 break;
1256 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1257 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1258 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1259 *q++=ScaleQuantumToChar(GetPixelRed(p));
1260 *q++=ScaleQuantumToChar(GetPixelGreen(p));
1261 *q++=ScaleQuantumToChar(GetPixelBlue(p));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1262 p++;
1263 }
1264 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1265 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1266 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1267 break;
1268 }
1269 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1270 if (GetNextImageInList(image) == (Image *) NULL)
1271 break;
1272 image=SyncNextImageInList(image);
1273 status=SetImageProgress(image,SaveImagesTag,scene,
1274 GetImageListLength(image));
1275 if (status == MagickFalse)
1276 break;
1277 scene++;
1278 } while (image_info-&gt;adjoin != MagickFalse);
1279 (void) CloseBlob(image);
1280 return(MagickTrue);
1281}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1282</div>
1283
1284<p>To invoke the custom coder from the command line, use these commands:</p>
1285
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]1286<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: logo.mgk</span><span class='crtout'></span><span class="crtprompt"> $ </span><span class='crtin'>display logo.mgk</span></p>
1287<p>We provide the <a href="http://www.imagemagick.org/download/kits/MagickCoderKit-1.0.0.tar.gz">Magick Coder Kit</a> to help you get started writing your own custom coder.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1288
1289</div>
1290
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1291<h2><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1292<div class="doc-section">
1293
1294<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>
1295
1296<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>
1297
1298<div class="viewport">
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1299#include &lt;stdio.h&gt;
1300#include &lt;stdlib.h&gt;
1301#include &lt;string.h&gt;
1302#include &lt;time.h&gt;
1303#include &lt;assert.h&gt;
1304#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1305#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1306
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1307/*
1308%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1309% %
1310% %
1311% %
1312% a n a l y z e I m a g e %
1313% %
1314% %
1315% %
1316%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1317%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1318% analyzeImage() computes the brightness and saturation mean, standard
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]1319% deviation, kurtosis and skewness and stores these values as attributes
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1320% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1321%
1322% The format of the analyzeImage method is:
1323%
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1324% size_t analyzeImage(Image *images,const int argc,char **argv,
1325% ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1326%
1327% A description of each parameter follows:
1328%
1329% o image: the address of a structure of type Image.
1330%
1331% o argc: Specifies a pointer to an integer describing the number of
1332% elements in the argument vector.
1333%
1334% o argv: Specifies a pointer to a text array containing the command line
1335% arguments.
1336%
1337% o exception: return any errors or warnings in this structure.
1338%
1339*/
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1340ModuleExport size_t analyzeImage(Image **images,const int argc,const char **argv,
1341 ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1342{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1343 char
1344 text[MaxTextExtent];
1345
1346 double
1347 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1348 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1349 brightness_mean,
1350 brightness_standard_deviation,
1351 brightness_kurtosis,
1352 brightness_skewness,
1353 brightness_sum_x,
1354 brightness_sum_x2,
1355 brightness_sum_x3,
1356 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1357 hue,
1358 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1359 saturation_mean,
1360 saturation_standard_deviation,
1361 saturation_kurtosis,
1362 saturation_skewness,
1363 saturation_sum_x,
1364 saturation_sum_x2,
1365 saturation_sum_x3,
1366 saturation_sum_x4;
1367
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1368 Image
1369 *image;
1370
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1371 assert(images != (Image **) NULL);
1372 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1373 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1374 (void) argc;
1375 (void) argv;
1376 image=(*images);
1377 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1378 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1379 CacheView
1380 *image_view;
1381
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1382 MagickBooleanType
1383 status;
1384
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1385 ssize_t
1386 y;
1387
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1388 brightness_sum_x=0.0;
1389 brightness_sum_x2=0.0;
1390 brightness_sum_x3=0.0;
1391 brightness_sum_x4=0.0;
1392 brightness_mean=0.0;
1393 brightness_standard_deviation=0.0;
1394 brightness_kurtosis=0.0;
1395 brightness_skewness=0.0;
1396 saturation_sum_x=0.0;
1397 saturation_sum_x2=0.0;
1398 saturation_sum_x3=0.0;
1399 saturation_sum_x4=0.0;
1400 saturation_mean=0.0;
1401 saturation_standard_deviation=0.0;
1402 saturation_kurtosis=0.0;
1403 saturation_skewness=0.0;
1404 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1405 status=MagickTrue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1406 image_view=AcquireCacheView(image);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1407#if defined(MAGICKCORE_OPENMP_SUPPORT)
1408 #pragma omp parallel for schedule(dynamic,4) shared(status)
1409#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1410 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1411 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1412 register const PixelPacket
1413 *p;
1414
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1415 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1416 x;
1417
1418 if (status == MagickFalse)
1419 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1420 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1421 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1422 {
1423 status=MagickFalse;
1424 continue;
1425 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1426 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1427 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1428 ConvertRGBToHSB(GetPixelRed(p),GetPixelGreen(p),GetPixelBue(p),&amp;hue,&amp;saturation,&amp;brightness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1429 brightness*=QuantumRange;
1430 brightness_sum_x+=brightness;
1431 brightness_sum_x2+=brightness*brightness;
1432 brightness_sum_x3+=brightness*brightness*brightness;
1433 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1434 saturation*=QuantumRange;
1435 saturation_sum_x+=saturation;
1436 saturation_sum_x2+=saturation*saturation;
1437 saturation_sum_x3+=saturation*saturation*saturation;
1438 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1439 area++;
1440 p++;
1441 }
1442 }
1443 image_view=DestroyCacheView(image_view);
1444 if (area &lt;= 0.0)
1445 break;
1446 brightness_mean=brightness_sum_x/area;
1447 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_mean);
1448 (void) SetImageProperty(image,"filter:brightness:mean",text);
1449 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1450 area*brightness_sum_x/area));
1451 (void) FormatMagickString(text,MaxTextExtent,"%g",
1452 brightness_standard_deviation);
1453 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1454 if (brightness_standard_deviation != 0)
1455 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1456 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1457 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1458 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1459 brightness_standard_deviation*brightness_standard_deviation*
1460 brightness_standard_deviation)-3.0;
1461 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_kurtosis);
1462 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1463 if (brightness_standard_deviation != 0)
1464 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1465 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1466 brightness_mean)/(brightness_standard_deviation*
1467 brightness_standard_deviation*brightness_standard_deviation);
1468 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_skewness);
1469 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1470 saturation_mean=saturation_sum_x/area;
1471 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_mean);
1472 (void) SetImageProperty(image,"filter:saturation:mean",text);
1473 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1474 area*saturation_sum_x/area));
1475 (void) FormatMagickString(text,MaxTextExtent,"%g",
1476 saturation_standard_deviation);
1477 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1478 if (saturation_standard_deviation != 0)
1479 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1480 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1481 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1482 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1483 saturation_standard_deviation*saturation_standard_deviation*
1484 saturation_standard_deviation)-3.0;
1485 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_kurtosis);
1486 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1487 if (saturation_standard_deviation != 0)
1488 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1489 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1490 saturation_mean)/(saturation_standard_deviation*
1491 saturation_standard_deviation*saturation_standard_deviation);
1492 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_skewness);
1493 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1494 }
1495 return(MagickImageFilterSignature);
1496}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1497</div>
1498
1499<p>To invoke the custom filter from the command line, use this command:</p>
1500
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]1501<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -process "analyze" -verbose info:</span><span class='crtout'>Image: logo: <br/>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1502 Format: LOGO (ImageMagick Logo) <br/>
1503 Class: PseudoClass <br/>
1504 Geometry: 640x480 <br/>
1505 ... <br/>
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1506 filter:brightness:kurtosis: 8.17947 <br/>
1507 filter:brightness:mean: 60632.1 <br/>
1508 filter:brightness:skewness: -2.97118 <br/>
1509 filter:brightness:standard-deviation: 13742.1 <br/>
1510 filter:saturation:kurtosis: 4.33554 <br/>
1511 filter:saturation:mean: 5951.55 <br/>
1512 filter:saturation:skewness: 2.42848 <br/>
1513 filter:saturation:standard-deviation: 15575.9</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1514
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]1515<p>We provide the <a href="http://www.imagemagick.org/download/kits/MagickFilterKit-1.0.0.tar.gz">Magick Filter Kit</a> to help you get started writing your own custom image filter.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1516
1517</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1518
1519</div>
1520
1521<div id="linkbar">
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]1522 <span id="linkbar-west">&nbsp;</span>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1523 <span id="linkbar-center">
1524 <a href="http://www.imagemagick.org/discourse-server/">Discourse Server</a> &bull;
cristya8902942010-07-30 00:49:52 +0000[diff] [blame]1525 <a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">Studio</a>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1526 </span>
1527 <span id="linkbar-east">&nbsp;</span>
1528 </div>
1529 <div class="footer">
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame^]1530 <span id="footer-west">&copy; 1999-2011 ImageMagick Studio LLC</span>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1531 <span id="footer-east"> <a href="http://www.imagemagick.org/script/contact.php">Contact the Wizards</a></span>
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