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gerrit-public.fairphone.software / platform / external / ImageMagick / a2d6a8c0b149588619a78910f1eaa17679dddc82 / . / www / architecture.html
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cristy91469932014-07-25 11:00:25 +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]12 <title>ImageMagick: Architecture</title>
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cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]33
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40 <!-- Add fancyBox -->
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cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]51
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cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]57
cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]58 <!-- ImageMagick style -->
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cristy91469932014-07-25 11:00:25 +0000[diff] [blame]91 <img src="../images/logo.jpg"
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cristy91469932014-07-25 11:00:25 +0000[diff] [blame]95 <img src="../images/sprite.jpg"
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cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]214 <noscript>
215 <a href="http://flattr.com/thing/947300/Convert-Edit-And-Compose-Images" target="_blank">
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220
221<div class="main">
222
223
224
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]225<h1>The <em>Magick</em> Behind ImageMagick</h1>
cristy417eeb12013-07-28 18:48:22 +0000[diff] [blame]226<p class="navigation-index">[<a href="architecture.html#overview">Architecture Overview</a> • <a href="architecture.html#cache">The Pixel Cache</a> • <a href="architecture.html#stream">Streaming Pixels</a> • <a href="architecture.html#properties">Image Properties and Profiles</a> • <a href="architecture.html#tera-pixel">Large Image Support</a> • <a href="architecture.html#threads">Threads of Execution</a> • <a href="architecture.html#distributed">Heterogeneous Distributed Processing</a> • <a href="architecture.html#coders">Custom Image Coders</a> • <a href="architecture.html#filters">Custom Image Filters</a>]</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]227
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]228
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]229<div class="doc-section">
230<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>
231</div>
232
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]233<h2><a id="overview"></a>Architecture Overview</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]234<div class="doc-section">
235
236<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>
237
238<ul>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]239 <li>colorspace (e.g sRGB, linear RGB, linear GRAY, CMYK, YUV, Lab, etc.)</li>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]240 <li>bit depth (.e.g 1, 4, 8, 12, 16, etc.)</li>
241 <li>storage format (e.g. unsigned, signed, float, double, etc.)</li>
242 <li>compression (e.g. uncompressed, RLE, Zip, BZip, etc.)</li>
243 <li>orientation (i.e. top-to-bottom, right-to-left, etc.),</li>
244 <li>layout (.e.g. raw, interspersed with opcodes, etc.)</li>
245</ul>
246
247<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>
248
249<p>An efficient implementation of an image processing algorithm may require we get or set:</p>
250
251<ul>
252 <li>one pixel a time (e.g. pixel at location 10,3)</li>
253 <li>a single scanline (e.g. all pixels from row 4)</li>
254 <li>a few scanlines at once (e.g. pixel rows 4-7)</li>
255 <li>a single column or columns of pixels (e.g. all pixels from column 11)</li>
256 <li>an arbitrary region of pixels from the image (e.g. pixels defined at 10,7 to 10,19)</li>
257 <li>a pixel in random order (e.g. pixel at 14,15 and 640,480)</li>
258 <li>pixels from two different images (e.g. pixel at 5,1 from image 1 and pixel at 5,1 from image 2)</li>
259 <li>pixels outside the boundaries of the image (e.g. pixel at -1,-3)</li>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]260 <li>a pixel component that is unsigned (65311) or in a floating-point representation (e.g. 0.17836)</li>
261 <li>a high-dynamic range pixel that can include negative values (e.g. -0.00716) as well as values that exceed the quantum depth (e.g. 65931)</li>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]262 <li>one or more pixels simultaneously in different threads of execution</li>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]263 <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]264</ul>
265
266<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>
267
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]268<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 (i.e. <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 (i.e. <a href="architecture.html#virtual-pixels">virtual pixels</a>).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]269
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]270<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]271
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]272<p>ImageMagick consists of nearly a half million 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, elegant, and efficient 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]273
274</div>
275
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]276<h2><a id="cache"></a>The Pixel Cache</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]277<div class="doc-section">
278
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]279<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]280
281<h3>Create the Pixel Cache</h3>
282<div class="doc-section">
283
284<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>
285
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]286<dl>
287<dt>Create an image canvas initialized to the background color:</dt>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]288<dd><p class="code">image=AllocateImage(image_info);
289if (SetImageExtent(image,640,480) == MagickFalse)
290 { /* an exception was thrown */ }
291(void) QueryMagickColor("red",&amp;image-&gt;background_color,&amp;image-&gt;exception);
292SetImageBackgroundColor(image);
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]293</p></dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]294
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]295<dt>Create an image from a JPEG image on disk:</dt>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]296<dd><p class="code">(void) strcpy(image_info-&gt;filename,"image.jpg"):
297image=ReadImage(image_info,exception);
298if (image == (Image *) NULL)
299 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]300</p></dd>
301<dt>Create an image from a memory based image:</dt>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]302<dd><p class="code">image=BlobToImage(blob_info,blob,extent,exception);
303if (image == (Image *) NULL)
304 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]305</p></dd>
306</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]307
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]308<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]309
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]310<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]311
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]312<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Version: ImageMagick 6.8.9-5 2014-04-11 Q16 http://www.imagemagick.org</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]313<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]314</div>
315
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]316<h3><a id="authentic-pixels"></a>Access the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]317<div class="doc-section">
318
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]319<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 <a href="architecture.html#authentic-pixels">authentic pixels</a> and outside the region as <a href="architecture.html#virtual-pixels">virtual pixels</a>. Use these methods to access the pixels in the cache:</p>
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]320<ul>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]321 <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>
322 <li><a href="../api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> gets pixels that you intend to modify</li>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]323 <li><a href="../api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> queue pixels that you intend to set</li>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]324 <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]325</ul>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]326
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]327<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]328
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]329<div class="viewport">const PixelPacket
330 *p;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]331
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]332PixelPacket
333 *q;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]334
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]335ssize_t
336 x,
337 y;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]338
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]339destination=CloneImage(source,source->columns,source->rows,MagickTrue,
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]340 exception);
341if (destination == (Image *) NULL)
342 { /* an exception was thrown */ }
343for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
344{
345 p=GetVirtualPixels(source,0,y,source-&gt;columns,1,exception);
346 q=GetAuthenticPixels(destination,0,y,destination-&gt;columns,1,exception);
347 if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL)
348 break;
349 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]350 {
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]351 SetPixelRed(q,90*p-&gt;red/100);
352 SetPixelGreen(q,90*p-&gt;green/100);
353 SetPixelBlue(q,90*p-&gt;blue/100);
354 SetPixelOpacity(q,90*p-&gt;opacity/100);
355 p++;
356 q++;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]357 }
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]358 if (SyncAuthenticPixels(destination,exception) == MagickFalse)
359 break;
360}
361if (y &lt; (ssize_t) source-&gt;rows)
362 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]363</div>
364
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]365<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 or set 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]366
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]367<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]368
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]369<pre class="code">const IndexPacket
370 *indexes;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]371
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]372for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
373{
374 p=GetVirtualPixels(source,0,y,source-&gt;columns,1);
375 if (p == (const PixelPacket *) NULL)
376 break;
377 indexes=GetVirtualIndexQueue(source);
378 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
379 (void) printf("%d\n",GetPixelIndex(indexes+x));
380}
381if (y &lt; (ssize_t) source-&gt;rows)
382 /* an exception was thrown */
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]383</pre>
384
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]385<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]386
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]387<pre class="code">p=GetVirtualPixels(source,-3,-3,source-&gt;columns+3,6,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]388</pre>
389
390<p>gives you the pixels you asked for without complaint, even though some are not within the confines of the image region.</p>
391</div>
392
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]393<h3><a id="virtual-pixels"></a>Virtual Pixels</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]394<div class="doc-section">
395
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]396<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>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]397 <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]398
cristy4c54bbb2011-03-17 13:53:13 +0000[diff] [blame]399<pre class="text" style="font-size: 83.3333%;">
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]400background: the area surrounding the image is the background color
401black: the area surrounding the image is black
402checker-tile: alternate squares with image and background color
403dither: non-random 32x32 dithered pattern
404edge: extend the edge pixel toward infinity (default)
405gray: the area surrounding the image is gray
406horizontal-tile: horizontally tile the image, background color above/below
407horizontal-tile-edge: horizontally tile the image and replicate the side edge pixels
408mirror: mirror tile the image
409random: choose a random pixel from the image
410tile: tile the image
411transparent: the area surrounding the image is transparent blackness
412vertical-tile: vertically tile the image, sides are background color
413vertical-tile-edge: vertically tile the image and replicate the side edge pixels
414white: the area surrounding the image is white
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]415</pre>
416
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]417</div>
418
419<h3>Cache Storage and Resource Requirements</h3>
420<div class="doc-section">
421
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]422<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]423
424<dl class="doc">
425 <dt class="doc">files</dt>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]426 <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]427 <dt class="doc">area</dt>
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]428 <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]429 <dt class="doc">memory</dt>
430 <dd>maximum amount of memory in bytes to allocate for the pixel cache from the anonymous mapped memory or the heap.</dd>
431 <dt class="doc">map</dt>
432 <dd>maximum amount of memory map in bytes to allocate for the pixel cache.</dd>
433 <dt class="doc">disk</dt>
434 <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]435 <dt class="doc">thread</dt>
436 <dd>maximum number of threads that are permitted to run in parallel.</dd>
437 <dt class="doc">time</dt>
438 <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]439</dl>
440
441<p>To determine the current setting of these limits, use this command:</p>
442
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]443<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -list resource</span></p><pre class="text">
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]444File Area Memory Map Disk Thread Time
cristy2c839602010-04-03 02:32:08 +0000[diff] [blame]445-------------------------------------------------------------------------------
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]446 768 1.0386GB 3.8692GiB 7.7384GiB unlimited 4 unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]447</pre>
448
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]449<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 help prevent a denial-of-service:</p>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]450<pre class="code">
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]451&lt;policymap>
452 &lt;policy domain="resource" name="temporary-path" value="/tmp"/>
453 &lt;policy domain="resource" name="memory" value="256MiB"/>
454 &lt;policy domain="resource" name="map" value="512MiB"/>
455 &lt;policy domain="resource" name="area" value="128MB"/>
456 &lt;policy domain="resource" name="disk" value="1GiB"/>
457 &lt;policy domain="resource" name="file" value="768"/>
458 &lt;policy domain="resource" name="thread" value="2"/>
459 &lt;policy domain="resource" name="throttle" value="0"/>
460 &lt;policy domain="resource" name="time" value="120"/>
461 &lt;policy domain="system" name="precision" value="6"/>
462 &lt;policy domain="cache" name="shared-secret" value="********"/>
463&lt;/policymap>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]464</pre>
465<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]466
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]467<p>Note, the cache limits are global to each invocation of ImageMagick, 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]468
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]469<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 to the command-line:</p>
470<pre class="code">-> convert -debug cache logo: -sharpen 3x2 null:
4712013-12-17T13:33:42-05:00 0:00.000 0.000u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]472 destroy
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4732013-12-17T13:33:42-05:00 0:00.000 0.000u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]474 open LOGO[0] (Heap Memory, 640x480x4 4.688MiB)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4752013-12-17T13:33:42-05:00 0:00.010 0.000u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]476 open LOGO[0] (Heap Memory, 640x480x3 3.516MiB)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4772013-12-17T13:33:42-05:00 0:00.010 0.000u 7.0.0 Cache convert: cache.c/ClonePixelCachePixels/1044/Cache
478 Memory => Memory
4792013-12-17T13:33:42-05:00 0:00.020 0.010u 7.0.0 Cache convert: cache.c/ClonePixelCachePixels/1044/Cache
480 Memory => Memory
4812013-12-17T13:33:42-05:00 0:00.020 0.010u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]482 open LOGO[0] (Heap Memory, 640x480x3 3.516MiB)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4832013-12-17T13:33:42-05:00 0:00.050 0.100u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]484 destroy LOGO[0]
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4852013-12-17T13:33:42-05:00 0:00.050 0.100u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]486 destroy LOGO[0]
487</pre>
488<p>This command utilizes a pixel cache in memory. The logo consumed 4.688MiB and after it was sharpened, 3.516MiB.</p>
489</div>
490
491
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame]492<h3>Distributed Pixel Cache</h3>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]493<div class="doc-section">
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]494<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. The distributed pixel cache relies on network bandwidth to marshal pixels to and from the remote server. As such, it will likely be significantly slower than a pixel cache utilizing local storage (e.g. memory, disk, etc.).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]495</div>
496
497<h3>Cache Views</h3>
498<div class="doc-section">
499
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]500<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]501
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]502<pre class="code">CacheView
503 *view_1,
504 *view_2;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]505
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]506view_1=AcquireVirtualCacheView(source,exception);
507view_2=AcquireVirtualCacheView(source,exception);
508for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
509{
510 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]511 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,exception);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]512 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
513 break;
514 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]515 {
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]516 /* do something with u &amp; v here */
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]517 }
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]518}
519view_2=DestroyCacheView(view_2);
520view_1=DestroyCacheView(view_1);
521if (y &lt; (ssize_t) source-&gt;rows)
522 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]523</pre>
524</div>
525
526<h3>Magick Persistent Cache Format</h3>
527<div class="doc-section">
528
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]529<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]530<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]531</div>
532
533<h3>Best Practices</h3>
534<div class="doc-section">
535
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]536<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]537
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]538<p>You can get, modify, or set pixels in row or column order. However, it is more efficient to access the pixels by row rather than by column.</p>
539
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]540<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>
541
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]542<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 any pixel changes to the pixel cache.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]543
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]544<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]545
546<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>
547
548<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>
549
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]550<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 many 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>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]551
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]552<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]553
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]554<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]555
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]556<p class='crt'><span class="crtprompt"> $magick&gt; </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]557<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>
558
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]559<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.tif image.mpc</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.mpc -crop 100x100+0+0 +repage 1.png</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.mpc -crop 100x100+100+0 +repage 2.png</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.mpc -crop 100x100+200+0 +repage 3.png</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]560<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>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]561</div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]562
563</div>
564
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]565<h2><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]566<div class="doc-section">
567
568<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>
569
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]570<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]571
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]572<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]573{
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]574 register const PixelPacket
575 *p;
576
577 MyData
578 *my_data;
579
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]580 my_data=(MyData *) image->client_data;
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]581 p=(PixelPacket *) pixels;
582 if (p != (const PixelPacket *) NULL)
583 {
584 /* process pixels here */
585 }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]586 return(columns);
587}
588
589...
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]590
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]591/* invoke the pixel stream here */
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]592image_info->client_data=(void *) MyData;
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]593image=ReadStream(image_info,&amp;StreamPixels,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]594</pre>
595
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]596<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]597
598</div>
599
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]600<h2><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]601<div class="doc-section">
602
603<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>
604
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]605<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]606</pre>
607
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]608<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]609
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]610<pre class="code">const char
611 *comment;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]612
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]613(void) SetImageProperty(image,"comment","This space for rent");
614comment=GetImageProperty(image,"comment");
615if (comment == (const char *) NULL)
616 (void) printf("Image comment: %s\n",comment);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]617</pre>
618
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]619<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]620
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]621<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]622
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]623<pre class="code">StringInfo
624 *profile;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]625
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]626profile=AcquireStringInfo(length);
627SetStringInfoDatum(profile,my_exif_profile);
628(void) SetImageProfile(image,"EXIF",profile);
629DestroyStringInfo(profile);
630profile=GetImageProfile(image,"EXIF");
631if (profile != (StringInfo *) NULL)
632 (void) PrintStringInfo(stdout,"EXIF",profile);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]633</pre>
634
635</div>
636
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]637<h2><a id="tera-pixel"></a>Large Image Support</h2>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]638<div class="doc-section">
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]639<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]640
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]641<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert logo: -resize 250000x250000 logo.miff</span></p>
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]642<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]643
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]644<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -define registry:temporary-path=/data/tmp logo: \ <br/> -resize 250000x250000 logo.miff</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]645<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>
646
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]647<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -define registry:temporary-path=/data/tmp -limit memory 16mb \ <br/> logo: -resize 250000x250000 logo.miff</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]648<p>Here we force all image pixels to disk:</p>
649
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]650<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -define registry:temporary-path=/data/tmp -limit area 0 \ <br/> logo: -resize 250000x250000 logo.miff</span></p>
cristybac7a162010-06-15 19:57:29 +0000[diff] [blame]651<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]652
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]653<p class='crt'><span class="crtprompt"> $magick&gt; </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>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]654<pre class="text">
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame]655convert -distribute-cache 6668 &amp; // start on 192.168.100.50
656convert -distribute-cache 6668 &amp; // start on 192.168.100.51
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]657convert -limit memory 2mb -limit map 2mb -limit disk 2gb \
658 -define registry:cache:hosts=192.168.100.50:6668,192.168.100.51:6668 \
659 myhugeimage.jpg -sharpen 5x2 myhugeimage.png
660</pre>
661</div>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]662
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]663<h2><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]664<div class="doc-section">
665
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]666<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]667
cristyf1b8a092014-02-20 15:46:11 +0000[diff] [blame]668<p>Here is an MagickCore code snippet that takes advantage of threads of execution with the <a href="http://www.imagemagick.org/ImageMagick-7.0.0/www/openmp.html">OpenMP</a> programming paradigm:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]669
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]670<div class="viewport">CacheView
671 *image_view;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]672
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]673MagickBooleanType
674 status;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]675
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]676ssize_t
677 y;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]678
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]679status=MagickTrue;
680image_view=AcquireVirtualCacheView(image,exception);
681#pragma omp parallel for schedule(dynamic,4) shared(status)
682for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
683{
684 register IndexPacket
685 *indexes;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]686
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]687 register PixelPacket
688 *q;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]689
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]690 register ssize_t
691 x;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]692
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]693 if (status == MagickFalse)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]694 continue;
695 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
696 if (q == (PixelPacket *) NULL)
697 {
698 status=MagickFalse;
699 continue;
700 }
701 indexes=GetCacheViewAuthenticIndexQueue(image_view);
702 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
703 {
704 SetPixelRed(q,...);
705 SetPixelGreen(q,...);
706 SetPixelBlue(q,...);
707 SetPixelOpacity(q,...);
708 if (indexes != (IndexPacket *) NULL)
709 SetPixelIndex(indexes+x,...);
710 q++;
711 }
712 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
713 status=MagickFalse;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]714}
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]715image_view=DestroyCacheView(image_view);
716if (status == MagickFalse)
717 perror("something went wrong");
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]718</div>
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]719<p>This code snippet converts an uncompressed Windows bitmap to a Magick++ image:</p>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]720<div class="viewport">#include "Magick++.h"
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]721#include &lt;assert.h&gt;
722#include "omp.h"
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]723
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]724void ConvertBMPToImage(const BITMAPINFOHEADER *bmp_info,
725 const unsigned char *restrict pixels,Magick::Image *image)
726{
727 /*
728 Prepare the image so that we can modify the pixels directly.
729 */
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]730 assert(bmp_info->biCompression == BI_RGB);
731 assert(bmp_info->biWidth == image->columns());
732 assert(abs(bmp_info->biHeight) == image->rows());
733 image->modifyImage();
734 if (bmp_info->biBitCount == 24)
735 image->type(MagickCore::TrueColorType);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]736 else
cristydef23e52015-01-22 11:52:01 +0000[diff] [blame]737 image->type(MagickCore::TrueColorAlphaType);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]738 register unsigned int bytes_per_row=bmp_info->biWidth*bmp_info->biBitCount/8;
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]739 if (bytes_per_row % 4 != 0) {
740 bytes_per_row=bytes_per_row+(4-bytes_per_row % 4); // divisible by 4.
741 }
742 /*
743 Copy all pixel data, row by row.
744 */
745 #pragma omp parallel for
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]746 for (int y=0; y &lt; int(image->rows()); y++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]747 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]748 int
749 row;
750
751 register const unsigned char
752 *restrict p;
753
754 register MagickCore::PixelPacket
755 *restrict q;
756
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]757 row=(bmp_info->biHeight > 0) ? (image->rows()-y-1) : y;
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]758 p=pixels+row*bytes_per_row;
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]759 q=image->setPixels(0,y,image->columns(),1);
760 for (int x=0; x &lt; int(image->columns()); x++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]761 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]762 SetPixelBlue(q,p[0]);
763 SetPixelGreen(q,p[1]);
764 SetPixelRed(q,p[2]);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]765 if (bmp_info->biBitCount == 32) {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]766 SetPixelOpacity(q,p[3]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]767 }
768 q++;
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]769 p+=bmp_info->biBitCount/8;
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]770 }
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]771 image->syncPixels(); // sync pixels to pixel cache.
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]772 }
773 return;
774}
775</div>
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]776
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]777<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>
778
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]779<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]780
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]781<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]782
783<pre class="text">
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]784&lt;policy domain="resource" name="thread" value="2"/>
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]785</pre>
786
787<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>
788
789<pre class="text">
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]790export MAGICK_THREAD_LIMIT=12
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]791</pre>
792
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]793<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]794
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]795<h4>Threading Performance</h4>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]796<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]797<pre class="text">
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]798convert -bench 10 model.png -sharpen 5x2 null:
799Performance[1]: 10i 1.135ips 1.000e 8.760u 0:08.810
800Performance[2]: 10i 2.020ips 0.640e 9.190u 0:04.950
801Performance[3]: 10i 2.786ips 0.710e 9.400u 0:03.590
802Performance[4]: 10i 3.378ips 0.749e 9.580u 0:02.960
803Performance[5]: 10i 4.032ips 0.780e 9.580u 0:02.480
804Performance[6]: 10i 4.566ips 0.801e 9.640u 0:02.190
805Performance[7]: 10i 3.788ips 0.769e 10.980u 0:02.640
806Performance[8]: 10i 4.115ips 0.784e 12.030u 0:02.430
807Performance[9]: 10i 4.484ips 0.798e 12.860u 0:02.230
808Performance[10]: 10i 4.274ips 0.790e 14.830u 0:02.340
809Performance[11]: 10i 4.348ips 0.793e 16.500u 0:02.300
810Performance[12]: 10i 4.525ips 0.799e 18.320u 0:02.210
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]811</pre>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]812<p>The sweet spot for this example 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>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]813<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]814</div>
815
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]816<h2><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]817<div class="doc-section">
818<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>
819
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]820<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]821
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]822<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Features: OpenMP OpenCL</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]823<p>If so, run this command to realize a significant speed-up for image convolution:</p>
824
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]825<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.png -convolve '-1, -1, -1, -1, 9, -1, -1, -1, -1' \ <br/> convolve.png</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]826<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
827
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]828<p>Here is an example OpenCL kernel that convolves an image:</p>
829
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]830<div class="viewport">static inline long ClampToCanvas(const long offset,const ulong range)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]831{
832 if (offset &lt; 0L)
833 return(0L);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]834 if (offset >= range)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]835 return((long) (range-1L));
836 return(offset);
837}
838
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]839static inline CLQuantum ClampToQuantum(const float value)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]840{
841 if (value &lt; 0.0)
842 return((CLQuantum) 0);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]843 if (value >= (float) QuantumRange)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]844 return((CLQuantum) QuantumRange);
845 return((CLQuantum) (value+0.5));
846}
847
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]848__kernel void Convolve(const __global CLPixelType *source,__constant float *filter,
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]849 const ulong width,const ulong height,__global CLPixelType *destination)
850{
851 const ulong columns = get_global_size(0);
852 const ulong rows = get_global_size(1);
853
854 const long x = get_global_id(0);
855 const long y = get_global_id(1);
856
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]857 const float scale = (1.0/QuantumRange);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]858 const long mid_width = (width-1)/2;
859 const long mid_height = (height-1)/2;
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]860 float4 sum = { 0.0, 0.0, 0.0, 0.0 };
861 float gamma = 0.0;
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]862 register ulong i = 0;
863
864 for (long v=(-mid_height); v &lt;= mid_height; v++)
865 {
866 for (long u=(-mid_width); u &lt;= mid_width; u++)
867 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]868 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
869 columns);
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]870 const float alpha=scale*(QuantumRange-source[index].w);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]871 sum.x+=alpha*filter[i]*source[index].x;
872 sum.y+=alpha*filter[i]*source[index].y;
873 sum.z+=alpha*filter[i]*source[index].z;
874 sum.w+=filter[i]*source[index].w;
875 gamma+=alpha*filter[i];
876 i++;
877 }
878 }
879
880 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
881 const ulong index=y*columns+x;
882 destination[index].x=ClampToQuantum(gamma*sum.x);
883 destination[index].y=ClampToQuantum(gamma*sum.y);
884 destination[index].z=ClampToQuantum(gamma*sum.z);
885 destination[index].w=ClampToQuantum(sum.w);
886};
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]887</div>
888
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]889<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]890
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]891<p>Note, that under Windows, you might have an issue with TDR (Timeout Detection and Recovery of GPUs). Its purpose is to detect runaway tasks hanging the GPU by using an execution time threshold. For some older low-end GPUs running the OpenCL filters in ImageMagick, longer execution times might trigger the TDR mechanism and pre-empt the GPU image filter. When this happens, ImageMagick automatically falls back to the CPU code path and returns the expected results. To avoid pre-emption, increase the <a href="http://msdn.microsoft.com/en-us/library/windows/hardware/gg487368.aspx">TdrDelay</a> registry key.</p>
892
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]893</div>
894
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]895<h2><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]896<div class="doc-section">
897
898<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>
899
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]900<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]901
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]902<div class="viewport">/*
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]903 Include declarations.
904*/
905#include "magick/studio.h"
906#include "magick/blob.h"
907#include "magick/blob-private.h"
908#include "magick/colorspace.h"
909#include "magick/exception.h"
910#include "magick/exception-private.h"
911#include "magick/image.h"
912#include "magick/image-private.h"
913#include "magick/list.h"
914#include "magick/magick.h"
915#include "magick/memory_.h"
916#include "magick/monitor.h"
917#include "magick/monitor-private.h"
918#include "magick/quantum-private.h"
919#include "magick/static.h"
920#include "magick/string_.h"
921#include "magick/module.h"
922
923/*
924 Forward declarations.
925*/
926static MagickBooleanType
927 WriteMGKImage(const ImageInfo *,Image *);
928
929/*
930%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
931% %
932% %
933% %
934% I s M G K %
935% %
936% %
937% %
938%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
939%
940% IsMGK() returns MagickTrue if the image format type, identified by the
941% magick string, is MGK.
942%
943% The format of the IsMGK method is:
944%
945% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
946%
947% A description of each parameter follows:
948%
949% o magick: This string is generally the first few bytes of an image file
950% or blob.
951%
952% o length: Specifies the length of the magick string.
953%
954*/
955static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
956{
957 if (length &lt; 7)
958 return(MagickFalse);
959 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
960 return(MagickTrue);
961 return(MagickFalse);
962}
963
964/*
965%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
966% %
967% %
968% %
969% R e a d M G K I m a g e %
970% %
971% %
972% %
973%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
974%
975% ReadMGKImage() reads a MGK image file and returns it. It allocates
976% the memory necessary for the new Image structure and returns a pointer to
977% the new image.
978%
979% The format of the ReadMGKImage method is:
980%
981% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
982%
983% A description of each parameter follows:
984%
985% o image_info: the image info.
986%
987% o exception: return any errors or warnings in this structure.
988%
989*/
990static Image *ReadMGKImage(const ImageInfo *image_info,
991 ExceptionInfo *exception)
992{
993 char
994 buffer[MaxTextExtent];
995
996 Image
997 *image;
998
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]999 MagickBooleanType
1000 status;
1001
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1002 register PixelPacket
1003 *q;
1004
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1005 register size_t
1006 x;
1007
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1008 register unsigned char
1009 *p;
1010
1011 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1012 count,
1013 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1014
1015 unsigned char
1016 *pixels;
1017
1018 unsigned long
1019 columns,
1020 rows;
1021
1022 /*
1023 Open image file.
1024 */
1025 assert(image_info != (const ImageInfo *) NULL);
1026 assert(image_info-&gt;signature == MagickSignature);
1027 if (image_info-&gt;debug != MagickFalse)
1028 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
1029 assert(exception != (ExceptionInfo *) NULL);
1030 assert(exception-&gt;signature == MagickSignature);
1031 image=AcquireImage(image_info);
1032 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
1033 if (status == MagickFalse)
1034 {
1035 image=DestroyImageList(image);
1036 return((Image *) NULL);
1037 }
1038 /*
1039 Read MGK image.
1040 */
1041 (void) ReadBlobString(image,buffer); /* read magic number */
1042 if (IsMGK(buffer,7) == MagickFalse)
1043 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1044 (void) ReadBlobString(image,buffer);
1045 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1046 if (count &lt;= 0)
1047 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1048 do
1049 {
1050 /*
1051 Initialize image structure.
1052 */
1053 image-&gt;columns=columns;
1054 image-&gt;rows=rows;
1055 image-&gt;depth=8;
1056 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1057 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1058 break;
1059 /*
1060 Convert MGK raster image to pixel packets.
1061 */
1062 if (SetImageExtent(image,0,0) == MagickFalse)
1063 {
1064 InheritException(exception,&amp;image-&gt;exception);
1065 return(DestroyImageList(image));
1066 }
1067 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
1068 if (pixels == (unsigned char *) NULL)
1069 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1070 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1071 {
1072 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
1073 if (count != (ssize_t) (3*image-&gt;columns))
1074 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
1075 p=pixels;
1076 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
1077 if (q == (PixelPacket *) NULL)
1078 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1079 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1080 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1081 SetPixelRed(q,ScaleCharToQuantum(*p++));
1082 SetPixelGreen(q,ScaleCharToQuantum(*p++));
1083 SetPixelBlue(q,ScaleCharToQuantum(*p++));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1084 q++;
1085 }
1086 if (SyncAuthenticPixels(image,exception) == MagickFalse)
1087 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1088 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1089 (SetImageProgress(image,LoadImageTag,y,image&gt;>rows) == MagickFalse))
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1090 break;
1091 }
1092 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1093 if (EOFBlob(image) != MagickFalse)
1094 {
1095 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
1096 break;
1097 }
1098 /*
1099 Proceed to next image.
1100 */
1101 if (image_info-&gt;number_scenes != 0)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1102 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1103 break;
1104 *buffer='\0';
1105 (void) ReadBlobString(image,buffer);
1106 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1107 if (count != 0)
1108 {
1109 /*
1110 Allocate next image structure.
1111 */
1112 AcquireNextImage(image_info,image);
1113 if (GetNextImageInList(image) == (Image *) NULL)
1114 {
1115 image=DestroyImageList(image);
1116 return((Image *) NULL);
1117 }
1118 image=SyncNextImageInList(image);
1119 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
1120 if (status == MagickFalse)
1121 break;
1122 }
1123 } while (count != 0);
1124 (void) CloseBlob(image);
1125 return(GetFirstImageInList(image));
1126}
1127
1128/*
1129%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1130% %
1131% %
1132% %
1133% R e g i s t e r M G K I m a g e %
1134% %
1135% %
1136% %
1137%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1138%
1139% RegisterMGKImage() adds attributes for the MGK image format to
1140% the list of supported formats. The attributes include the image format
1141% tag, a method to read and/or write the format, whether the format
1142% supports the saving of more than one frame to the same file or blob,
1143% whether the format supports native in-memory I/O, and a brief
1144% description of the format.
1145%
1146% The format of the RegisterMGKImage method is:
1147%
1148% unsigned long RegisterMGKImage(void)
1149%
1150*/
1151ModuleExport unsigned long RegisterMGKImage(void)
1152{
1153 MagickInfo
1154 *entry;
1155
1156 entry=SetMagickInfo("MGK");
1157 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
1158 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
1159 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
1160 entry-&gt;description=ConstantString("MGK");
1161 entry-&gt;module=ConstantString("MGK");
1162 (void) RegisterMagickInfo(entry);
1163 return(MagickImageCoderSignature);
1164}
1165
1166/*
1167%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1168% %
1169% %
1170% %
1171% U n r e g i s t e r M G K I m a g e %
1172% %
1173% %
1174% %
1175%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1176%
1177% UnregisterMGKImage() removes format registrations made by the
1178% MGK module from the list of supported formats.
1179%
1180% The format of the UnregisterMGKImage method is:
1181%
1182% UnregisterMGKImage(void)
1183%
1184*/
1185ModuleExport void UnregisterMGKImage(void)
1186{
1187 (void) UnregisterMagickInfo("MGK");
1188}
1189
1190/*
1191%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1192% %
1193% %
1194% %
1195% W r i t e M G K I m a g e %
1196% %
1197% %
1198% %
1199%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1200%
1201% WriteMGKImage() writes an image to a file in red, green, and blue
1202% MGK rasterfile format.
1203%
1204% The format of the WriteMGKImage method is:
1205%
1206% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1207%
1208% A description of each parameter follows.
1209%
1210% o image_info: the image info.
1211%
1212% o image: The image.
1213%
1214*/
1215static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1216{
1217 char
1218 buffer[MaxTextExtent];
1219
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1220 MagickBooleanType
1221 status;
1222
1223 MagickOffsetType
1224 scene;
1225
1226 register const PixelPacket
1227 *p;
1228
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1229 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1230 x;
1231
1232 register unsigned char
1233 *q;
1234
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1235 ssize_t
1236 y;
1237
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1238 unsigned char
1239 *pixels;
1240
1241 /*
1242 Open output image file.
1243 */
1244 assert(image_info != (const ImageInfo *) NULL);
1245 assert(image_info-&gt;signature == MagickSignature);
1246 assert(image != (Image *) NULL);
1247 assert(image-&gt;signature == MagickSignature);
1248 if (image-&gt;debug != MagickFalse)
1249 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1250 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1251 if (status == MagickFalse)
1252 return(status);
1253 scene=0;
1254 do
1255 {
1256 /*
1257 Allocate memory for pixels.
1258 */
1259 if (image-&gt;colorspace != RGBColorspace)
1260 (void) SetImageColorspace(image,RGBColorspace);
1261 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1262 3UL*sizeof(*pixels));
1263 if (pixels == (unsigned char *) NULL)
1264 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1265 /*
1266 Initialize raster file header.
1267 */
1268 (void) WriteBlobString(image,"id=mgk\n");
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1269 (void) FormatLocaleString(buffer,MaxTextExtent,"%lu %lu\n",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1270 image-&gt;columns,image-&gt;rows);
1271 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1272 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1273 {
1274 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1275 if (p == (const PixelPacket *) NULL)
1276 break;
1277 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1278 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1279 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1280 *q++=ScaleQuantumToChar(GetPixelRed(p));
1281 *q++=ScaleQuantumToChar(GetPixelGreen(p));
1282 *q++=ScaleQuantumToChar(GetPixelBlue(p));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1283 p++;
1284 }
1285 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1286 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1287 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1288 break;
1289 }
1290 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1291 if (GetNextImageInList(image) == (Image *) NULL)
1292 break;
1293 image=SyncNextImageInList(image);
1294 status=SetImageProgress(image,SaveImagesTag,scene,
1295 GetImageListLength(image));
1296 if (status == MagickFalse)
1297 break;
1298 scene++;
1299 } while (image_info-&gt;adjoin != MagickFalse);
1300 (void) CloseBlob(image);
1301 return(MagickTrue);
1302}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1303</div>
1304
1305<p>To invoke the custom coder from the command line, use these commands:</p>
1306
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1307<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert logo: logo.mgk</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>display logo.mgk</span></p>
1308<p>We provide the <a href="http://www.imagemagick.org/download/kits/">Magick Coder Kit</a> to help you get started writing your own custom coder.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1309
1310</div>
1311
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1312<h2><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1313<div class="doc-section">
1314
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1315<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]1316
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1317<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]1318
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1319<div class="viewport">#include &lt;stdio.h&gt;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1320#include &lt;stdlib.h&gt;
1321#include &lt;string.h&gt;
1322#include &lt;time.h&gt;
1323#include &lt;assert.h&gt;
1324#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1325#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1326
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1327/*
1328%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1329% %
1330% %
1331% %
1332% a n a l y z e I m a g e %
1333% %
1334% %
1335% %
1336%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1337%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1338% analyzeImage() computes the brightness and saturation mean, standard
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]1339% deviation, kurtosis and skewness and stores these values as attributes
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1340% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1341%
1342% The format of the analyzeImage method is:
1343%
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1344% size_t analyzeImage(Image *images,const int argc,char **argv,
1345% ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1346%
1347% A description of each parameter follows:
1348%
1349% o image: the address of a structure of type Image.
1350%
1351% o argc: Specifies a pointer to an integer describing the number of
1352% elements in the argument vector.
1353%
1354% o argv: Specifies a pointer to a text array containing the command line
1355% arguments.
1356%
1357% o exception: return any errors or warnings in this structure.
1358%
1359*/
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1360ModuleExport size_t analyzeImage(Image **images,const int argc,const char **argv,
1361 ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1362{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1363 char
1364 text[MaxTextExtent];
1365
1366 double
1367 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1368 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1369 brightness_mean,
1370 brightness_standard_deviation,
1371 brightness_kurtosis,
1372 brightness_skewness,
1373 brightness_sum_x,
1374 brightness_sum_x2,
1375 brightness_sum_x3,
1376 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1377 hue,
1378 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1379 saturation_mean,
1380 saturation_standard_deviation,
1381 saturation_kurtosis,
1382 saturation_skewness,
1383 saturation_sum_x,
1384 saturation_sum_x2,
1385 saturation_sum_x3,
1386 saturation_sum_x4;
1387
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1388 Image
1389 *image;
1390
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1391 assert(images != (Image **) NULL);
1392 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1393 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1394 (void) argc;
1395 (void) argv;
1396 image=(*images);
1397 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1398 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1399 CacheView
1400 *image_view;
1401
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1402 MagickBooleanType
1403 status;
1404
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1405 ssize_t
1406 y;
1407
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1408 brightness_sum_x=0.0;
1409 brightness_sum_x2=0.0;
1410 brightness_sum_x3=0.0;
1411 brightness_sum_x4=0.0;
1412 brightness_mean=0.0;
1413 brightness_standard_deviation=0.0;
1414 brightness_kurtosis=0.0;
1415 brightness_skewness=0.0;
1416 saturation_sum_x=0.0;
1417 saturation_sum_x2=0.0;
1418 saturation_sum_x3=0.0;
1419 saturation_sum_x4=0.0;
1420 saturation_mean=0.0;
1421 saturation_standard_deviation=0.0;
1422 saturation_kurtosis=0.0;
1423 saturation_skewness=0.0;
1424 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1425 status=MagickTrue;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1426 image_view=AcquireVirtualCacheView(image,exception);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1427#if defined(MAGICKCORE_OPENMP_SUPPORT)
1428 #pragma omp parallel for schedule(dynamic,4) shared(status)
1429#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1430 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1431 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1432 register const PixelPacket
1433 *p;
1434
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1435 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1436 x;
1437
1438 if (status == MagickFalse)
1439 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1440 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1441 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1442 {
1443 status=MagickFalse;
1444 continue;
1445 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1446 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1447 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1448 ConvertRGBToHSB(GetPixelRed(p),GetPixelGreen(p),GetPixelBue(p),&amp;hue,&amp;saturation,&amp;brightness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1449 brightness*=QuantumRange;
1450 brightness_sum_x+=brightness;
1451 brightness_sum_x2+=brightness*brightness;
1452 brightness_sum_x3+=brightness*brightness*brightness;
1453 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1454 saturation*=QuantumRange;
1455 saturation_sum_x+=saturation;
1456 saturation_sum_x2+=saturation*saturation;
1457 saturation_sum_x3+=saturation*saturation*saturation;
1458 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1459 area++;
1460 p++;
1461 }
1462 }
1463 image_view=DestroyCacheView(image_view);
1464 if (area &lt;= 0.0)
1465 break;
1466 brightness_mean=brightness_sum_x/area;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1467 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_mean);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1468 (void) SetImageProperty(image,"filter:brightness:mean",text);
1469 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1470 area*brightness_sum_x/area));
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1471 (void) FormatLocaleString(text,MaxTextExtent,"%g",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1472 brightness_standard_deviation);
1473 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1474 if (brightness_standard_deviation != 0)
1475 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1476 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1477 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1478 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1479 brightness_standard_deviation*brightness_standard_deviation*
1480 brightness_standard_deviation)-3.0;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1481 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_kurtosis);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1482 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1483 if (brightness_standard_deviation != 0)
1484 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1485 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1486 brightness_mean)/(brightness_standard_deviation*
1487 brightness_standard_deviation*brightness_standard_deviation);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1488 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_skewness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1489 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1490 saturation_mean=saturation_sum_x/area;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1491 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_mean);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1492 (void) SetImageProperty(image,"filter:saturation:mean",text);
1493 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1494 area*saturation_sum_x/area));
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1495 (void) FormatLocaleString(text,MaxTextExtent,"%g",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1496 saturation_standard_deviation);
1497 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1498 if (saturation_standard_deviation != 0)
1499 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1500 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1501 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1502 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1503 saturation_standard_deviation*saturation_standard_deviation*
1504 saturation_standard_deviation)-3.0;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1505 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_kurtosis);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1506 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1507 if (saturation_standard_deviation != 0)
1508 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1509 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1510 saturation_mean)/(saturation_standard_deviation*
1511 saturation_standard_deviation*saturation_standard_deviation);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1512 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_skewness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1513 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1514 }
1515 return(MagickImageFilterSignature);
1516}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1517</div>
1518
1519<p>To invoke the custom filter from the command line, use this command:</p>
1520
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1521<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert logo: -process "analyze" -verbose info:</span><span class='crtout'>Image: logo: <br/>
1522 Format: LOGO (ImageMagick Logo) <br/>
1523 Class: PseudoClass <br/>
1524 Geometry: 640x480 <br/>
1525 ... <br/>
1526 filter:brightness:kurtosis: 8.17947 <br/>
1527 filter:brightness:mean: 60632.1 <br/>
1528 filter:brightness:skewness: -2.97118 <br/>
1529 filter:brightness:standard-deviation: 13742.1 <br/>
1530 filter:saturation:kurtosis: 4.33554 <br/>
1531 filter:saturation:mean: 5951.55 <br/>
1532 filter:saturation:skewness: 2.42848 <br/>
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1533 filter:saturation:standard-deviation: 15575.9</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1534
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1535<p>We provide the <a href="http://www.imagemagick.org/download/kits/">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]1536
1537</div>
cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]1538
1539</div>
1540
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cristyb56bb242014-11-25 17:12:48 +0000[diff] [blame]1553 <span id="footer-west">© 1999-2015 ImageMagick Studio LLC</span>
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cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]1557</body>
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