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gerrit-public.fairphone.software / platform / external / ImageMagick / ac1b432d9174ca8c7abd5ad20e560509ea8b4546 / . / www / architecture.html
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cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]1<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
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cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]11 <title>ImageMagick: Architecture</title>
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cristy8ee7f242013-06-20 16:08:44 +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 or transform images automagically."/>
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]17 <meta name="application-url" content="http://www.imagemagick.org"/>
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cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]28 <link rel="icon" href="../images/wand.png"/>
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cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]30 <link rel="canonical" href="http://www.imagemagick.org" />
31 <link rel="meta" type="application/rdf+xml" title="ICI" href="http://imagemagick.org/ici.rdf"/>
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cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]33 <!-- Add jQuery library -->
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cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]38
39 <!-- Add fancyBox -->
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]40 <link rel="stylesheet" href="http://www.imagemagick.org/fancybox/source/jquery.fancybox.css?v=2.0.6" type="text/css" media="screen" />
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cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]48 <link rel="stylesheet" href="http://www.imagemagick.org/fancybox/source/helpers/jquery.fancybox-thumbs.css?v=2.0.6" type="text/css" media="screen" />
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cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]56
cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]57 <!-- ImageMagick style -->
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59 @import url("../www/magick.css");
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cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]221</div>
222
223<div class="main">
224
225
226
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]227<h1>The <em>Magick</em> Behind ImageMagick</h1>
cristydba8f1d2013-07-28 13:49:24 +0000[diff] [blame]228<p class="navigation-index">[<a href="architecture.html#overview">Architecture Overview</a> &#8226; <a href="architecture.html#cache">The Pixel Cache</a> &#8226; <a href="architecture.html#stream">Streaming Pixels</a> &#8226; <a href="architecture.html#properties">Image Properties and Profiles</a> &#8226; <a href="architecture.html#tera-pixel">Large Image Support</a> &#8226; <a href="architecture.html#threads">Threads of Execution</a> &#8226; <a href="architecture.html#distributed">Heterogeneous Distributed Processing</a> &#8226; <a href="architecture.html#coders">Custom Image Coders</a> &#8226; <a href="architecture.html#filters">Custom Image Filters</a>]</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]229
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]230
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]231<div class="doc-section">
232<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>
233</div>
234
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]235<h2><a id="overview"></a>Architecture Overview</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]236<div class="doc-section">
237
238<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>
239
240<ul>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]241 <li>colorspace (e.g sRGB, linear RGB, linear GRAY, CMYK, YUV, Lab, etc.)</li>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]242 <li>bit depth (.e.g 1, 4, 8, 12, 16, etc.)</li>
243 <li>storage format (e.g. unsigned, signed, float, double, etc.)</li>
244 <li>compression (e.g. uncompressed, RLE, Zip, BZip, etc.)</li>
245 <li>orientation (i.e. top-to-bottom, right-to-left, etc.),</li>
246 <li>layout (.e.g. raw, interspersed with opcodes, etc.)</li>
247</ul>
248
249<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>
250
251<p>An efficient implementation of an image processing algorithm may require we get or set:</p>
252
253<ul>
254 <li>one pixel a time (e.g. pixel at location 10,3)</li>
255 <li>a single scanline (e.g. all pixels from row 4)</li>
256 <li>a few scanlines at once (e.g. pixel rows 4-7)</li>
257 <li>a single column or columns of pixels (e.g. all pixels from column 11)</li>
258 <li>an arbitrary region of pixels from the image (e.g. pixels defined at 10,7 to 10,19)</li>
259 <li>a pixel in random order (e.g. pixel at 14,15 and 640,480)</li>
260 <li>pixels from two different images (e.g. pixel at 5,1 from image 1 and pixel at 5,1 from image 2)</li>
261 <li>pixels outside the boundaries of the image (e.g. pixel at -1,-3)</li>
262 <li>a pixel component that is unsigned or in a floating-point representation (e.g. 0.17836)</li>
263 <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>
264 <li>one or more pixels simultaneously in different threads of execution</li>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]265 <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]266</ul>
267
268<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>
269
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]270<p>Given the varied image formats and image processing requirements, we implemented the ImageMagick <a href="architecture.html#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="architecture.html#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="architecture.html#virtual-pixels">virtual pixels</a>).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]271
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]272<p>In addition to pixels, images have a plethora of <a href="architecture.html#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]273
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]274<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="architecture.html#threads">thread</a> of execution. In the final sections, we discuss <a href="architecture.html#coders">image coders</a> to read or write a particular image format followed by a few words on creating a <a href="architecture.html#filters">filter</a> to access or update pixels based on your custom requirements.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]275
276</div>
277
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]278<h2><a id="cache"></a>The Pixel Cache</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]279<div class="doc-section">
280
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]281<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="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]282
283<h3>Create the Pixel Cache</h3>
284<div class="doc-section">
285
286<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>
287
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]288<dl>
289<dt>Create an image canvas initialized to the background color:</dt>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]290<dd><p class="code">image=AllocateImage(image_info);
291if (SetImageExtent(image,640,480) == MagickFalse)
292 { /* an exception was thrown */ }
293(void) QueryMagickColor("red",&amp;image-&gt;background_color,&amp;image-&gt;exception);
294SetImageBackgroundColor(image);
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]295</p></dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]296
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]297<dt>Create an image from a JPEG image on disk:</dt>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]298<dd><p class="code">(void) strcpy(image_info-&gt;filename,"image.jpg"):
299image=ReadImage(image_info,exception);
300if (image == (Image *) NULL)
301 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]302</p></dd>
303<dt>Create an image from a memory based image:</dt>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]304<dd><p class="code">image=BlobToImage(blob_info,blob,extent,exception);
305if (image == (Image *) NULL)
306 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]307</p></dd>
308</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]309
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]310<p>In our discussion of the pixel cache, we use the <a href="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]311
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]312<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="command-line-options.html#version">&#x2011;version</a> option: </p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]313
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]314<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>identify -version</span><span class='crtout'>Version: ImageMagick 7.0.0-0 2013-06-16 Q16 http://www.imagemagick.org</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]315<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]316</div>
317
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]318<h3><a id="authentic-pixels"></a>Access the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]319<div class="doc-section">
320
321<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]322<ul>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]323 <li><a href="../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>
324 <li><a href="../api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> gets pixels that you intend to modify</li>
325 <li><a href="../api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> queue pixels that you intend to modify</li>
326 <li><a href="../api/cache.html#SyncAuthenticPixels">SyncAuthenticPixels()</a> update the pixel cache with any modified pixels</li>
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]327</ul>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]328
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]329<p>Here is a typical <a href="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]330
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]331<div class="viewport">const PixelPacket
332 *p;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]333
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]334PixelPacket
335 *q;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]336
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]337ssize_t
338 x,
339 y;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]340
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]341destination=CloneImage(source,source->columns,source->rows,MagickTrue,
342 exception);
343if (destination == (Image *) NULL)
344 { /* an exception was thrown */ }
345for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
346{
347 p=GetVirtualPixels(source,0,y,source-&gt;columns,1,exception);
348 q=GetAuthenticPixels(destination,0,y,destination-&gt;columns,1,exception);
349 if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL)
350 break;
351 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]352 {
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]353 SetPixelRed(q,90*p-&gt;red/100);
354 SetPixelGreen(q,90*p-&gt;green/100);
355 SetPixelBlue(q,90*p-&gt;blue/100);
356 SetPixelOpacity(q,90*p-&gt;opacity/100);
357 p++;
358 q++;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]359 }
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]360 if (SyncAuthenticPixels(destination,exception) == MagickFalse)
361 break;
362}
363if (y &lt; (ssize_t) source-&gt;rows)
364 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]365</div>
366
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]367<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="../api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> or <a href="../api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a>. Use <a href="../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="../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]368
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]369<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="../api/cache.html#GetVirtualIndexQueue">GetVirtualIndexQueue()</a> (to read the indexes) or <a href="../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]370
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]371<pre class="code">const IndexPacket
372 *indexes;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]373
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]374for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
375{
376 p=GetVirtualPixels(source,0,y,source-&gt;columns,1);
377 if (p == (const PixelPacket *) NULL)
378 break;
379 indexes=GetVirtualIndexQueue(source);
380 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
381 (void) printf("%d\n",GetPixelIndex(indexes+x));
382}
383if (y &lt; (ssize_t) source-&gt;rows)
384 /* an exception was thrown */
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]385</pre>
386
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]387<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]388
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]389<pre class="code">p=GetVirtualPixels(source,-3,-3,source-&gt;columns+3,6,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]390</pre>
391
392<p>gives you the pixels you asked for without complaint, even though some are not within the confines of the image region.</p>
393</div>
394
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]395<h3><a id="virtual-pixels"></a>Virtual Pixels</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]396<div class="doc-section">
397
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]398<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>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]399 <p>Access to the virtual pixels are controlled by the <a href="../api/cache.html#SetImageVirtualPixelMethod">SetImageVirtualPixelMethod()</a> method from the MagickCore API or the <a href="command-line-options.html#virtual-pixel">&#x2011;virtual&#x2011;pixel</a> option from the command line. The methods include:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]400
cristy4c54bbb2011-03-17 13:53:13 +0000[diff] [blame]401<pre class="text" style="font-size: 83.3333%;">
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]402background: the area surrounding the image is the background color
403black: the area surrounding the image is black
404checker-tile: alternate squares with image and background color
405dither: non-random 32x32 dithered pattern
406edge: extend the edge pixel toward infinity (default)
407gray: the area surrounding the image is gray
408horizontal-tile: horizontally tile the image, background color above/below
409horizontal-tile-edge: horizontally tile the image and replicate the side edge pixels
410mirror: mirror tile the image
411random: choose a random pixel from the image
412tile: tile the image
413transparent: the area surrounding the image is transparent blackness
414vertical-tile: vertically tile the image, sides are background color
415vertical-tile-edge: vertically tile the image and replicate the side edge pixels
416white: the area surrounding the image is white
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]417</pre>
418
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]419</div>
420
421<h3>Cache Storage and Resource Requirements</h3>
422<div class="doc-section">
423
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]424<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]425
426<dl class="doc">
427 <dt class="doc">files</dt>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]428 <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]429 <dt class="doc">area</dt>
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]430 <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]431 <dt class="doc">memory</dt>
432 <dd>maximum amount of memory in bytes to allocate for the pixel cache from the anonymous mapped memory or the heap.</dd>
433 <dt class="doc">map</dt>
434 <dd>maximum amount of memory map in bytes to allocate for the pixel cache.</dd>
435 <dt class="doc">disk</dt>
436 <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]437 <dt class="doc">thread</dt>
438 <dd>maximum number of threads that are permitted to run in parallel.</dd>
439 <dt class="doc">time</dt>
440 <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]441</dl>
442
443<p>To determine the current setting of these limits, use this command:</p>
444
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]445<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]446File Area Memory Map Disk Thread Time
cristy2c839602010-04-03 02:32:08 +0000[diff] [blame]447-------------------------------------------------------------------------------
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]448 768 1.0386GB 3.8692GiB 7.7384GiB unlimited 4 unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]449</pre>
450
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]451<p>You can set these limits either as a <a href="resources.html#configure">policy</a> (see <a href="../source/policy.xml">policy.xml</a>), with an <a href="resources.html#environment">environment variable</a>, with the <a href="command-line-options.html#limit">-limit</a> command line option, or with the <a href="../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>, includes these policy limits to prevent a denial-of-service:</p>
452<pre class="code">
453&lt;policymap>
454 &lt;policy domain="resource" name="temporary-path" value="/tmp"/>
455 &lt;policy domain="resource" name="memory" value="256MiB"/>
456 &lt;policy domain="resource" name="map" value="512MiB"/>
457 &lt;policy domain="resource" name="area" value="128MB"/>
458 &lt;policy domain="resource" name="disk" value="1GiB"/>
459 &lt;policy domain="resource" name="file" value="768"/>
460 &lt;policy domain="resource" name="thread" value="2"/>
461 &lt;policy domain="resource" name="throttle" value="0"/>
462 &lt;policy domain="resource" name="time" value="120"/>
463 &lt;policy domain="system" name="precision" value="6"/>
464 &lt;policy domain="cache" name="shared-secret" value="********"/>
465&lt;/policymap>
466</pre>
467<p>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 time limit to prevent any run-away processing tasks.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]468
469<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>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]470
471<p>To determine which type and how much resources are consumed by the pixel cache, add the <a href="command-line-options.html#debug">-debug cache</a> option:</p>
472<pre class="code">-> convert -debug cache logo: -sharpen 3x2 null:
4732013-05-17T13:33:42-05:00 0:00.000 0.000u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
474 destroy
4752013-05-17T13:33:42-05:00 0:00.000 0.000u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
476 open LOGO[0] (Heap Memory, 640x480x4 4.688MiB)
4772013-05-17T13:33:42-05:00 0:00.010 0.000u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
478 open LOGO[0] (Heap Memory, 640x480x3 3.516MiB)
4792013-05-17T13:33:42-05:00 0:00.010 0.000u 7.0.0 Cache convert: cache.c/ClonePixelCachePixels/1044/Cache
480 Memory => Memory
4812013-05-17T13:33:42-05:00 0:00.020 0.010u 7.0.0 Cache convert: cache.c/ClonePixelCachePixels/1044/Cache
482 Memory => Memory
4832013-05-17T13:33:42-05:00 0:00.020 0.010u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
484 open LOGO[0] (Heap Memory, 640x480x3 3.516MiB)
4852013-05-17T13:33:42-05:00 0:00.050 0.100u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
486 destroy LOGO[0]
4872013-05-17T13:33:42-05:00 0:00.050 0.100u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
488 destroy LOGO[0]
489</pre>
490<p>This command utilizes a pixel cache in memory. The logo consumed 4.688MiB and after it was sharpened, 3.516MiB.</p>
491</div>
492
493
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame^]494<h3>Distributed Pixel Cache</h3>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]495<div class="doc-section">
496<p>A distributed pixel cache is an extension of the traditional pixel cache available on a single host. The distributed pixel cache may span multiple servers so that it can grow in size and transactional capacity to support very large images. Start up the pixel cache server on one or more machines. When you read or operate on an image and the local pixel cache resources are exhausted, ImageMagick contacts one or more of these remote pixel servers to store or retrieve pixels.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]497</div>
498
499<h3>Cache Views</h3>
500<div class="doc-section">
501
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]502<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="../api/cache-view.html">methods</a> are analogous to 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 the first and last pixel row of the image simultaneously:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]503
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]504<pre class="code">CacheView
505 *view_1,
506 *view_2;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]507
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]508view_1=AcquireVirtualCacheView(source,exception);
509view_2=AcquireVirtualCacheView(source,exception);
510for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
511{
512 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
513 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,
514 exception);
515 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
516 break;
517 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]518 {
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]519 /* do something with u &amp; v here */
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]520 }
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]521}
522view_2=DestroyCacheView(view_2);
523view_1=DestroyCacheView(view_1);
524if (y &lt; (ssize_t) source-&gt;rows)
525 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]526</pre>
527</div>
528
529<h3>Magick Persistent Cache Format</h3>
530<div class="doc-section">
531
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]532<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 <code>.mpc</code>, retains all the properties associated with the image or image sequence (e.g. width, height, colorspace, etc.) and the second, with the extension <code>.cache</code>, 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]533<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]534</div>
535
536<h3>Best Practices</h3>
537<div class="doc-section">
538
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]539<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]540
541<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>
542
543<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>
544
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]545<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="architecture.html#threads">thread of execution</a> is accessing the image.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]546
547<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>
548
549<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>
550
551<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>
552
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]553<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="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 may have unexpected results due to out-of-band pixel values than the non-HDRI version.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]554
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]555<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 <code>/tmp</code> and for Windows, <code>c:/temp</code>. You can tell ImageMagick to write the pixel cache to an alternate location and conserver memory with these options:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]556
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]557<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert -limit memory 2GB -limit map 4GB -define registry:temporary-path=/data/tmp ...</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]558<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>
559
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]560<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]561<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>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]562<p>Many algorithms require a single sample intensity value from the red, green, and blue components of each pixel. By default we use Rec601Luma which requires a linear colorspace conversion using a power function-- given most source images are in the sRGB colorspace. A power function can slow down performance. To speed the process up, either first convert the image to a linear colorspace such as RGB or use the mathematical RGB average for intensity which does not require the power fuunction:</p>
563
564<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert image.jpg -set colorspace RGB -threshold 50% -set colorspace sRGB image.png</span><span class='crtout'></span><span class="crtprompt"> $ </span><span class='crtin'>convert image.jpg -intensity average -threshold 50% image.png</span></p></div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]565
566</div>
567
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]568<h2><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]569<div class="doc-section">
570
571<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>
572
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]573<p>Use <a href="../api/stream.html#ReadStream">ReadStream()</a> or <a href="../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>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]574
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]575<pre class="code">static size_t StreamPixels(const Image *image,const void *pixels,const size_t columns)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]576{
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]577 register const PixelPacket
578 *p;
579
580 MyData
581 *my_data;
582
583 my_data=(MyData *) image->client_data;
584 p=(PixelPacket *) pixels;
585 if (p != (const PixelPacket *) NULL)
586 {
587 /* process pixels here */
588 }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]589 return(columns);
590}
591
592...
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]593
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]594/* invoke the pixel stream here */
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]595image_info->client_data=(void *) MyData;
596image=ReadStream(image_info,&amp;StreamPixels,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]597</pre>
598
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]599<p>We also provide a lightweight tool, <a href="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="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]600
601</div>
602
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]603<h2><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]604<div class="doc-section">
605
606<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>
607
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]608<pre class="code">(void) printf("image width: %lu, height: %lu\n",image-&gt;columns,image-&gt;rows);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]609</pre>
610
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]611<p>For a great majority of image properties, such as an image comment or description, we use the <a href="../api/property.html#GetImageProperty">GetImageProperty()</a> and <a href="../api/property.html#SetImageProperty">SetImageProperty()</a> methods. Here we set a property and fetch it right back:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]612
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]613<pre class="code">const char
614 *comment;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]615
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]616(void) SetImageProperty(image,"comment","This space for rent");
617comment=GetImageProperty(image,"comment");
618if (comment == (const char *) NULL)
619 (void) printf("Image comment: %s\n",comment);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]620</pre>
621
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]622<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]623
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]624<p>Image profiles are handled with <a href="../api/profile.html#GetImageProfile">GetImageProfile()</a>, <a href="../api/profile.html#SetImageProfile">SetImageProfile()</a>, and <a href="../api/profile.html#ProfileImage">ProfileImage()</a> methods. Here we set a profile and fetch it right back:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]625
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]626<pre class="code">StringInfo
627 *profile;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]628
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]629profile=AcquireStringInfo(length);
630SetStringInfoDatum(profile,my_exif_profile);
631(void) SetImageProfile(image,"EXIF",profile);
632DestroyStringInfo(profile);
633profile=GetImageProfile(image,"EXIF");
634if (profile != (StringInfo *) NULL)
635 (void) PrintStringInfo(stdout,"EXIF",profile);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]636</pre>
637
638</div>
639
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]640<h2><a id="tera-pixel"></a>Large Image Support</h2>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]641<div class="doc-section">
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]642<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]643
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]644<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]645<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]646
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]647<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]648<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>
649
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]650<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]651<p>Here we force all image pixels to disk:</p>
652
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]653<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]654<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]655
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]656<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert -monitor -limit memory 2GiB -limit map 4GiB -define registry:temporary-path=/data/tmp \ <br/> logo: -resize 250000x250000 logo.miff</span></p><p>For really large images, or if there is limited resources on your host, you can utilize a distributed pixel cache on one or more remote hosts:</p>
657<pre class="text">
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame^]658convert -distribute-cache 6668 &amp; // start on 192.168.100.50
659convert -distribute-cache 6668 &amp; // start on 192.168.100.51
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]660convert -limit memory 2mb -limit map 2mb -limit disk 2gb \
661 -define registry:cache:hosts=192.168.100.50:6668,192.168.100.51:6668 \
662 myhugeimage.jpg -sharpen 5x2 myhugeimage.png
663</pre>
664</div>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]665
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]666<h2><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]667<div class="doc-section">
668
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]669<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="../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="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]670
cristy6ad765e2013-02-24 22:14:01 +0000[diff] [blame]671<p>Here is an MagickCore code snippet that takes advantage of threads of execution with the <a href="openmp.html">OpenMP</a> programming paradigm:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]672
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]673<div class="viewport">{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]674 CacheView
675 *image_view;
676
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]677 MagickBooleanType
678 status;
679
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]680 ssize_t
681 y;
682
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]683 status=MagickTrue;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]684 image_view=AcquireVirtualCacheView(image,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]685 #pragma omp parallel for schedule(dynamic,4) shared(status)
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]686 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]687 {
688 register IndexPacket
689 *indexes;
690
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]691 register PixelPacket
692 *q;
693
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]694 register ssize_t
695 x;
696
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]697 if (status == MagickFalse)
698 continue;
699 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
700 if (q == (PixelPacket *) NULL)
701 {
702 status=MagickFalse;
703 continue;
704 }
705 indexes=GetCacheViewAuthenticIndexQueue(image_view);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]706 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]707 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]708 SetPixelRed(q,...);
709 SetPixelGreen(q,...);
710 SetPixelBlue(q,...);
711 SetPixelOpacity(q,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]712 if (indexes != (IndexPacket *) NULL)
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]713 SetPixelIndex(indexes+x,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]714 q++;
715 }
716 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
717 status=MagickFalse;
718 }
719 image_view=DestroyCacheView(image_view);
720 if (status == MagickFalse)
721 perror("something went wrong");
722}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]723</div>
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]724<p>This code snippet converts an uncompressed Windows bitmap to a Magick++ image:</p>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]725<div class="viewport">#include "Magick++.h"
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]726#include &lt;assert.h&gt;
727#include "omp.h"
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]728
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]729void ConvertBMPToImage(const BITMAPINFOHEADER *bmp_info,
730 const unsigned char *restrict pixels,Magick::Image *image)
731{
732 /*
733 Prepare the image so that we can modify the pixels directly.
734 */
735 assert(bmp_info->biCompression == BI_RGB);
736 assert(bmp_info->biWidth == image->columns());
737 assert(abs(bmp_info->biHeight) == image->rows());
738 image->modifyImage();
739 if (bmp_info->biBitCount == 24)
740 image->type(MagickCore::TrueColorType);
741 else
742 image->type(MagickCore::TrueColorMatteType);
743 register unsigned int bytes_per_row=bmp_info->biWidth*bmp_info->biBitCount/8;
744 if (bytes_per_row % 4 != 0) {
745 bytes_per_row=bytes_per_row+(4-bytes_per_row % 4); // divisible by 4.
746 }
747 /*
748 Copy all pixel data, row by row.
749 */
750 #pragma omp parallel for
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]751 for (int y=0; y &lt; int(image->rows()); y++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]752 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]753 int
754 row;
755
756 register const unsigned char
757 *restrict p;
758
759 register MagickCore::PixelPacket
760 *restrict q;
761
762 row=(bmp_info->biHeight > 0) ? (image->rows()-y-1) : y;
763 p=pixels+row*bytes_per_row;
764 q=image->setPixels(0,y,image->columns(),1);
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]765 for (int x=0; x &lt; int(image->columns()); x++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]766 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]767 SetPixelBlue(q,p[0]);
768 SetPixelGreen(q,p[1]);
769 SetPixelRed(q,p[2]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]770 if (bmp_info->biBitCount == 32) {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]771 SetPixelOpacity(q,p[3]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]772 }
773 q++;
774 p+=bmp_info->biBitCount/8;
775 }
776 image->syncPixels(); // sync pixels to pixel cache.
777 }
778 return;
779}
780</div>
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]781
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]782<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>
783
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]784<p><a href="../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="../api/image-view.html">MagickCore</a>. For an example, see the same sigmoidal contrast algorithm implemented in both <a href="magick-wand.html#wand-view">MagickWand</a> and <a href="magick-core.html#image-view">MagickCore</a>.</p>
cristyfe7ce342010-06-22 15:41:50 +0000[diff] [blame]785
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]786<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="resources.html#configure">policy</a> or the <a href="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="../source/policy.xml">policy.xml</a> configuration file:</p>
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]787
788<pre class="text">
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]789&lt;policy domain="resource" name="thread" value="2"/>
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]790</pre>
791
792<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>
793
794<pre class="text">
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]795export MAGICK_THREAD_LIMIT=12
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]796</pre>
797
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]798<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 <code>--disable-openmp</code> option to the configure script command line and rebuild and reinstall ImageMagick.</p>
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]799
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]800<h4>Threading Performance</h4>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]801<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. For this benchmark we sharpen a 1920x1080 image of a model 10 times with 1 to 12 threads:</p>
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]802<pre class="text">
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]803convert -bench 10 model.png -sharpen 5x2 null:
804Performance[1]: 10i 1.135ips 1.000e 8.760u 0:08.810
805Performance[2]: 10i 2.020ips 0.640e 9.190u 0:04.950
806Performance[3]: 10i 2.786ips 0.710e 9.400u 0:03.590
807Performance[4]: 10i 3.378ips 0.749e 9.580u 0:02.960
808Performance[5]: 10i 4.032ips 0.780e 9.580u 0:02.480
809Performance[6]: 10i 4.566ips 0.801e 9.640u 0:02.190
810Performance[7]: 10i 3.788ips 0.769e 10.980u 0:02.640
811Performance[8]: 10i 4.115ips 0.784e 12.030u 0:02.430
812Performance[9]: 10i 4.484ips 0.798e 12.860u 0:02.230
813Performance[10]: 10i 4.274ips 0.790e 14.830u 0:02.340
814Performance[11]: 10i 4.348ips 0.793e 16.500u 0:02.300
815Performance[12]: 10i 4.525ips 0.799e 18.320u 0:02.210
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]816</pre>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]817<p>The suite spot is 6 threads. This makes sense since there are 6 physical cores. The other 6 are hyperthreads. It appears that sharpening does not benefit from hyperthreading.</p>
818<p>In certain cases, it might be optimal to set the number of threads to 1 or to disable OpenMP completely with the <a href="resources.html#environment">MAGICK_THREAD_LIMIT</a> environment variable, <a href="command-line-options.html#limit">-limit</a> command line option, or the <a href="resources.html#configure">policy.xml</a> configuration file.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]819</div>
820
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]821<h2><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]822<div class="doc-section">
823<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>
824
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]825<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]826
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]827<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]828<p>If so, run this command to realize a significant speed-up for image convolution:</p>
829
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]830<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]831<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
832
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]833<p>Here is an example OpenCL kernel that convolves an image:</p>
834
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]835<div class="viewport">static inline long ClampToCanvas(const long offset,const ulong range)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]836{
837 if (offset &lt; 0L)
838 return(0L);
839 if (offset >= range)
840 return((long) (range-1L));
841 return(offset);
842}
843
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]844static inline CLQuantum ClampToQuantum(const float value)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]845{
846 if (value &lt; 0.0)
847 return((CLQuantum) 0);
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]848 if (value >= (float) QuantumRange)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]849 return((CLQuantum) QuantumRange);
850 return((CLQuantum) (value+0.5));
851}
852
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]853__kernel void Convolve(const __global CLPixelType *source,__constant float *filter,
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]854 const ulong width,const ulong height,__global CLPixelType *destination)
855{
856 const ulong columns = get_global_size(0);
857 const ulong rows = get_global_size(1);
858
859 const long x = get_global_id(0);
860 const long y = get_global_id(1);
861
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]862 const float scale = (1.0/QuantumRange);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]863 const long mid_width = (width-1)/2;
864 const long mid_height = (height-1)/2;
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]865 float4 sum = { 0.0, 0.0, 0.0, 0.0 };
866 float gamma = 0.0;
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]867 register ulong i = 0;
868
869 for (long v=(-mid_height); v &lt;= mid_height; v++)
870 {
871 for (long u=(-mid_width); u &lt;= mid_width; u++)
872 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]873 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
874 columns);
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]875 const float alpha=scale*(QuantumRange-source[index].w);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]876 sum.x+=alpha*filter[i]*source[index].x;
877 sum.y+=alpha*filter[i]*source[index].y;
878 sum.z+=alpha*filter[i]*source[index].z;
879 sum.w+=filter[i]*source[index].w;
880 gamma+=alpha*filter[i];
881 i++;
882 }
883 }
884
885 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
886 const ulong index=y*columns+x;
887 destination[index].x=ClampToQuantum(gamma*sum.x);
888 destination[index].y=ClampToQuantum(gamma*sum.y);
889 destination[index].z=ClampToQuantum(gamma*sum.z);
890 destination[index].w=ClampToQuantum(sum.w);
891};
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]892</div>
893
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]894<p>See <a href="http://trac.imagemagick.org/browser/ImageMagick/branches/ImageMagick-6/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]895
896</div>
897
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]898<h2><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]899<div class="doc-section">
900
901<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>
902
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]903<p>Here is a listing of a sample <a href="../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>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]904
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]905<div class="viewport">/*
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]906 Include declarations.
907*/
908#include "magick/studio.h"
909#include "magick/blob.h"
910#include "magick/blob-private.h"
911#include "magick/colorspace.h"
912#include "magick/exception.h"
913#include "magick/exception-private.h"
914#include "magick/image.h"
915#include "magick/image-private.h"
916#include "magick/list.h"
917#include "magick/magick.h"
918#include "magick/memory_.h"
919#include "magick/monitor.h"
920#include "magick/monitor-private.h"
921#include "magick/quantum-private.h"
922#include "magick/static.h"
923#include "magick/string_.h"
924#include "magick/module.h"
925
926/*
927 Forward declarations.
928*/
929static MagickBooleanType
930 WriteMGKImage(const ImageInfo *,Image *);
931
932/*
933%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
934% %
935% %
936% %
937% I s M G K %
938% %
939% %
940% %
941%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
942%
943% IsMGK() returns MagickTrue if the image format type, identified by the
944% magick string, is MGK.
945%
946% The format of the IsMGK method is:
947%
948% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
949%
950% A description of each parameter follows:
951%
952% o magick: This string is generally the first few bytes of an image file
953% or blob.
954%
955% o length: Specifies the length of the magick string.
956%
957*/
958static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
959{
960 if (length &lt; 7)
961 return(MagickFalse);
962 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
963 return(MagickTrue);
964 return(MagickFalse);
965}
966
967/*
968%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
969% %
970% %
971% %
972% R e a d M G K I m a g e %
973% %
974% %
975% %
976%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
977%
978% ReadMGKImage() reads a MGK image file and returns it. It allocates
979% the memory necessary for the new Image structure and returns a pointer to
980% the new image.
981%
982% The format of the ReadMGKImage method is:
983%
984% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
985%
986% A description of each parameter follows:
987%
988% o image_info: the image info.
989%
990% o exception: return any errors or warnings in this structure.
991%
992*/
993static Image *ReadMGKImage(const ImageInfo *image_info,
994 ExceptionInfo *exception)
995{
996 char
997 buffer[MaxTextExtent];
998
999 Image
1000 *image;
1001
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1002 MagickBooleanType
1003 status;
1004
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1005 register PixelPacket
1006 *q;
1007
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1008 register size_t
1009 x;
1010
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1011 register unsigned char
1012 *p;
1013
1014 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1015 count,
1016 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1017
1018 unsigned char
1019 *pixels;
1020
1021 unsigned long
1022 columns,
1023 rows;
1024
1025 /*
1026 Open image file.
1027 */
1028 assert(image_info != (const ImageInfo *) NULL);
1029 assert(image_info-&gt;signature == MagickSignature);
1030 if (image_info-&gt;debug != MagickFalse)
1031 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
1032 assert(exception != (ExceptionInfo *) NULL);
1033 assert(exception-&gt;signature == MagickSignature);
1034 image=AcquireImage(image_info);
1035 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
1036 if (status == MagickFalse)
1037 {
1038 image=DestroyImageList(image);
1039 return((Image *) NULL);
1040 }
1041 /*
1042 Read MGK image.
1043 */
1044 (void) ReadBlobString(image,buffer); /* read magic number */
1045 if (IsMGK(buffer,7) == MagickFalse)
1046 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1047 (void) ReadBlobString(image,buffer);
1048 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1049 if (count &lt;= 0)
1050 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1051 do
1052 {
1053 /*
1054 Initialize image structure.
1055 */
1056 image-&gt;columns=columns;
1057 image-&gt;rows=rows;
1058 image-&gt;depth=8;
1059 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
1060 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
1061 break;
1062 /*
1063 Convert MGK raster image to pixel packets.
1064 */
1065 if (SetImageExtent(image,0,0) == MagickFalse)
1066 {
1067 InheritException(exception,&amp;image-&gt;exception);
1068 return(DestroyImageList(image));
1069 }
1070 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
1071 if (pixels == (unsigned char *) NULL)
1072 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1073 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1074 {
1075 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
1076 if (count != (ssize_t) (3*image-&gt;columns))
1077 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
1078 p=pixels;
1079 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
1080 if (q == (PixelPacket *) NULL)
1081 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1082 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1083 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1084 SetPixelRed(q,ScaleCharToQuantum(*p++));
1085 SetPixelGreen(q,ScaleCharToQuantum(*p++));
1086 SetPixelBlue(q,ScaleCharToQuantum(*p++));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1087 q++;
1088 }
1089 if (SyncAuthenticPixels(image,exception) == MagickFalse)
1090 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1091 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1092 (SetImageProgress(image,LoadImageTag,y,image&gt;>rows) == MagickFalse))
1093 break;
1094 }
1095 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1096 if (EOFBlob(image) != MagickFalse)
1097 {
1098 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
1099 break;
1100 }
1101 /*
1102 Proceed to next image.
1103 */
1104 if (image_info-&gt;number_scenes != 0)
1105 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
1106 break;
1107 *buffer='\0';
1108 (void) ReadBlobString(image,buffer);
1109 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1110 if (count != 0)
1111 {
1112 /*
1113 Allocate next image structure.
1114 */
1115 AcquireNextImage(image_info,image);
1116 if (GetNextImageInList(image) == (Image *) NULL)
1117 {
1118 image=DestroyImageList(image);
1119 return((Image *) NULL);
1120 }
1121 image=SyncNextImageInList(image);
1122 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
1123 if (status == MagickFalse)
1124 break;
1125 }
1126 } while (count != 0);
1127 (void) CloseBlob(image);
1128 return(GetFirstImageInList(image));
1129}
1130
1131/*
1132%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1133% %
1134% %
1135% %
1136% R e g i s t e r M G K I m a g e %
1137% %
1138% %
1139% %
1140%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1141%
1142% RegisterMGKImage() adds attributes for the MGK image format to
1143% the list of supported formats. The attributes include the image format
1144% tag, a method to read and/or write the format, whether the format
1145% supports the saving of more than one frame to the same file or blob,
1146% whether the format supports native in-memory I/O, and a brief
1147% description of the format.
1148%
1149% The format of the RegisterMGKImage method is:
1150%
1151% unsigned long RegisterMGKImage(void)
1152%
1153*/
1154ModuleExport unsigned long RegisterMGKImage(void)
1155{
1156 MagickInfo
1157 *entry;
1158
1159 entry=SetMagickInfo("MGK");
1160 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
1161 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
1162 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
1163 entry-&gt;description=ConstantString("MGK");
1164 entry-&gt;module=ConstantString("MGK");
1165 (void) RegisterMagickInfo(entry);
1166 return(MagickImageCoderSignature);
1167}
1168
1169/*
1170%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1171% %
1172% %
1173% %
1174% U n r e g i s t e r M G K I m a g e %
1175% %
1176% %
1177% %
1178%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1179%
1180% UnregisterMGKImage() removes format registrations made by the
1181% MGK module from the list of supported formats.
1182%
1183% The format of the UnregisterMGKImage method is:
1184%
1185% UnregisterMGKImage(void)
1186%
1187*/
1188ModuleExport void UnregisterMGKImage(void)
1189{
1190 (void) UnregisterMagickInfo("MGK");
1191}
1192
1193/*
1194%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1195% %
1196% %
1197% %
1198% W r i t e M G K I m a g e %
1199% %
1200% %
1201% %
1202%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1203%
1204% WriteMGKImage() writes an image to a file in red, green, and blue
1205% MGK rasterfile format.
1206%
1207% The format of the WriteMGKImage method is:
1208%
1209% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1210%
1211% A description of each parameter follows.
1212%
1213% o image_info: the image info.
1214%
1215% o image: The image.
1216%
1217*/
1218static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1219{
1220 char
1221 buffer[MaxTextExtent];
1222
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1223 MagickBooleanType
1224 status;
1225
1226 MagickOffsetType
1227 scene;
1228
1229 register const PixelPacket
1230 *p;
1231
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1232 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1233 x;
1234
1235 register unsigned char
1236 *q;
1237
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1238 ssize_t
1239 y;
1240
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1241 unsigned char
1242 *pixels;
1243
1244 /*
1245 Open output image file.
1246 */
1247 assert(image_info != (const ImageInfo *) NULL);
1248 assert(image_info-&gt;signature == MagickSignature);
1249 assert(image != (Image *) NULL);
1250 assert(image-&gt;signature == MagickSignature);
1251 if (image-&gt;debug != MagickFalse)
1252 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1253 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1254 if (status == MagickFalse)
1255 return(status);
1256 scene=0;
1257 do
1258 {
1259 /*
1260 Allocate memory for pixels.
1261 */
1262 if (image-&gt;colorspace != RGBColorspace)
1263 (void) SetImageColorspace(image,RGBColorspace);
1264 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1265 3UL*sizeof(*pixels));
1266 if (pixels == (unsigned char *) NULL)
1267 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1268 /*
1269 Initialize raster file header.
1270 */
1271 (void) WriteBlobString(image,"id=mgk\n");
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1272 (void) FormatLocaleString(buffer,MaxTextExtent,"%lu %lu\n",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1273 image-&gt;columns,image-&gt;rows);
1274 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1275 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1276 {
1277 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1278 if (p == (const PixelPacket *) NULL)
1279 break;
1280 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1281 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1282 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1283 *q++=ScaleQuantumToChar(GetPixelRed(p));
1284 *q++=ScaleQuantumToChar(GetPixelGreen(p));
1285 *q++=ScaleQuantumToChar(GetPixelBlue(p));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1286 p++;
1287 }
1288 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1289 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1290 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1291 break;
1292 }
1293 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1294 if (GetNextImageInList(image) == (Image *) NULL)
1295 break;
1296 image=SyncNextImageInList(image);
1297 status=SetImageProgress(image,SaveImagesTag,scene,
1298 GetImageListLength(image));
1299 if (status == MagickFalse)
1300 break;
1301 scene++;
1302 } while (image_info-&gt;adjoin != MagickFalse);
1303 (void) CloseBlob(image);
1304 return(MagickTrue);
1305}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1306</div>
1307
1308<p>To invoke the custom coder from the command line, use these commands:</p>
1309
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]1310<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>
1311<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]1312
1313</div>
1314
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1315<h2><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1316<div class="doc-section">
1317
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1318<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="command-line-options.html#process">-process</a> option or from the MagickCore API method <a href="../api/module.html#ExecuteModuleProcess">ExecuteModuleProcess()</a>.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1319
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1320<p>Here is a listing of a sample <a href="../source/analyze.c">custom image filter</a>. It computes a few statistics such as the pixel brightness and saturation mean and standard-deviation.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1321
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1322<div class="viewport">#include &lt;stdio.h&gt;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1323#include &lt;stdlib.h&gt;
1324#include &lt;string.h&gt;
1325#include &lt;time.h&gt;
1326#include &lt;assert.h&gt;
1327#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1328#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1329
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1330/*
1331%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1332% %
1333% %
1334% %
1335% a n a l y z e I m a g e %
1336% %
1337% %
1338% %
1339%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1340%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1341% analyzeImage() computes the brightness and saturation mean, standard
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]1342% deviation, kurtosis and skewness and stores these values as attributes
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1343% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1344%
1345% The format of the analyzeImage method is:
1346%
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1347% size_t analyzeImage(Image *images,const int argc,char **argv,
1348% ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1349%
1350% A description of each parameter follows:
1351%
1352% o image: the address of a structure of type Image.
1353%
1354% o argc: Specifies a pointer to an integer describing the number of
1355% elements in the argument vector.
1356%
1357% o argv: Specifies a pointer to a text array containing the command line
1358% arguments.
1359%
1360% o exception: return any errors or warnings in this structure.
1361%
1362*/
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1363ModuleExport size_t analyzeImage(Image **images,const int argc,const char **argv,
1364 ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1365{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1366 char
1367 text[MaxTextExtent];
1368
1369 double
1370 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1371 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1372 brightness_mean,
1373 brightness_standard_deviation,
1374 brightness_kurtosis,
1375 brightness_skewness,
1376 brightness_sum_x,
1377 brightness_sum_x2,
1378 brightness_sum_x3,
1379 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1380 hue,
1381 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1382 saturation_mean,
1383 saturation_standard_deviation,
1384 saturation_kurtosis,
1385 saturation_skewness,
1386 saturation_sum_x,
1387 saturation_sum_x2,
1388 saturation_sum_x3,
1389 saturation_sum_x4;
1390
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1391 Image
1392 *image;
1393
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1394 assert(images != (Image **) NULL);
1395 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1396 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1397 (void) argc;
1398 (void) argv;
1399 image=(*images);
1400 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1401 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1402 CacheView
1403 *image_view;
1404
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1405 MagickBooleanType
1406 status;
1407
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1408 ssize_t
1409 y;
1410
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1411 brightness_sum_x=0.0;
1412 brightness_sum_x2=0.0;
1413 brightness_sum_x3=0.0;
1414 brightness_sum_x4=0.0;
1415 brightness_mean=0.0;
1416 brightness_standard_deviation=0.0;
1417 brightness_kurtosis=0.0;
1418 brightness_skewness=0.0;
1419 saturation_sum_x=0.0;
1420 saturation_sum_x2=0.0;
1421 saturation_sum_x3=0.0;
1422 saturation_sum_x4=0.0;
1423 saturation_mean=0.0;
1424 saturation_standard_deviation=0.0;
1425 saturation_kurtosis=0.0;
1426 saturation_skewness=0.0;
1427 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1428 status=MagickTrue;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1429 image_view=AcquireVirtualCacheView(image,exception);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1430#if defined(MAGICKCORE_OPENMP_SUPPORT)
1431 #pragma omp parallel for schedule(dynamic,4) shared(status)
1432#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1433 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1434 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1435 register const PixelPacket
1436 *p;
1437
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1438 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1439 x;
1440
1441 if (status == MagickFalse)
1442 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1443 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1444 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1445 {
1446 status=MagickFalse;
1447 continue;
1448 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1449 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1450 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1451 ConvertRGBToHSB(GetPixelRed(p),GetPixelGreen(p),GetPixelBue(p),&amp;hue,&amp;saturation,&amp;brightness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1452 brightness*=QuantumRange;
1453 brightness_sum_x+=brightness;
1454 brightness_sum_x2+=brightness*brightness;
1455 brightness_sum_x3+=brightness*brightness*brightness;
1456 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1457 saturation*=QuantumRange;
1458 saturation_sum_x+=saturation;
1459 saturation_sum_x2+=saturation*saturation;
1460 saturation_sum_x3+=saturation*saturation*saturation;
1461 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1462 area++;
1463 p++;
1464 }
1465 }
1466 image_view=DestroyCacheView(image_view);
1467 if (area &lt;= 0.0)
1468 break;
1469 brightness_mean=brightness_sum_x/area;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1470 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_mean);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1471 (void) SetImageProperty(image,"filter:brightness:mean",text);
1472 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1473 area*brightness_sum_x/area));
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1474 (void) FormatLocaleString(text,MaxTextExtent,"%g",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1475 brightness_standard_deviation);
1476 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1477 if (brightness_standard_deviation != 0)
1478 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1479 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1480 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1481 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1482 brightness_standard_deviation*brightness_standard_deviation*
1483 brightness_standard_deviation)-3.0;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1484 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_kurtosis);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1485 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1486 if (brightness_standard_deviation != 0)
1487 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1488 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1489 brightness_mean)/(brightness_standard_deviation*
1490 brightness_standard_deviation*brightness_standard_deviation);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1491 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_skewness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1492 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1493 saturation_mean=saturation_sum_x/area;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1494 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_mean);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1495 (void) SetImageProperty(image,"filter:saturation:mean",text);
1496 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1497 area*saturation_sum_x/area));
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1498 (void) FormatLocaleString(text,MaxTextExtent,"%g",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1499 saturation_standard_deviation);
1500 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1501 if (saturation_standard_deviation != 0)
1502 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1503 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1504 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1505 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1506 saturation_standard_deviation*saturation_standard_deviation*
1507 saturation_standard_deviation)-3.0;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1508 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_kurtosis);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1509 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1510 if (saturation_standard_deviation != 0)
1511 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1512 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1513 saturation_mean)/(saturation_standard_deviation*
1514 saturation_standard_deviation*saturation_standard_deviation);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1515 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_skewness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1516 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1517 }
1518 return(MagickImageFilterSignature);
1519}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1520</div>
1521
1522<p>To invoke the custom filter from the command line, use this command:</p>
1523
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]1524<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]1525 Format: LOGO (ImageMagick Logo) <br/>
1526 Class: PseudoClass <br/>
1527 Geometry: 640x480 <br/>
1528 ... <br/>
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1529 filter:brightness:kurtosis: 8.17947 <br/>
1530 filter:brightness:mean: 60632.1 <br/>
1531 filter:brightness:skewness: -2.97118 <br/>
1532 filter:brightness:standard-deviation: 13742.1 <br/>
1533 filter:saturation:kurtosis: 4.33554 <br/>
1534 filter:saturation:mean: 5951.55 <br/>
1535 filter:saturation:skewness: 2.42848 <br/>
1536 filter:saturation:standard-deviation: 15575.9</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1537
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]1538<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]1539
1540</div>
cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]1541
1542</div>
1543
1544<div id="linkbar">
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame^]1545 <span id="linkbar-west"> </span>
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cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]1547 <span id="linkbar-center">
cristydba8f1d2013-07-28 13:49:24 +0000[diff] [blame]1548 <a href="http://www.imagemagick.org/discourse-server/">Discourse Server</a> &#8226;
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cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1550 <a href="http://jqmagick.imagemagick.org/">JqMagick</a>
cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]1551 </span>
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame^]1552 <span id="linkbar-east"> </span>
cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]1553 </div>
1554 <div class="footer">
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