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gerrit-public.fairphone.software / platform / external / ImageMagick / 37b3d44f750973e7286c6e520c69823f6b04cde5 / . / 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"
92 alt="ImageMagick Logo" width="123" height="118"
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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">
cristy37b3d442015-02-28 14:00:30 +0000[diff] [blame^]444Resource limits:
445 Width: 100MP
446 Height: 100MP
447 Area: 25.181GB
448 Memory: 11.726GiB
449 Map: 23.452GiB
450 Disk: unlimited
451 File: 768
452 Thread: 12
453 Throttle: 0
454 Time: unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]455</pre>
456
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]457<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]458<pre class="code">
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]459&lt;policymap>
460 &lt;policy domain="resource" name="temporary-path" value="/tmp"/>
461 &lt;policy domain="resource" name="memory" value="256MiB"/>
462 &lt;policy domain="resource" name="map" value="512MiB"/>
cristy37b3d442015-02-28 14:00:30 +0000[diff] [blame^]463 &lt;policy domain="resource" name="width" value="100MP"/>
464 &lt;policy domain="resource" name="height" value="100MP"/>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]465 &lt;policy domain="resource" name="area" value="128MB"/>
466 &lt;policy domain="resource" name="disk" value="1GiB"/>
467 &lt;policy domain="resource" name="file" value="768"/>
468 &lt;policy domain="resource" name="thread" value="2"/>
469 &lt;policy domain="resource" name="throttle" value="0"/>
470 &lt;policy domain="resource" name="time" value="120"/>
471 &lt;policy domain="system" name="precision" value="6"/>
472 &lt;policy domain="cache" name="shared-secret" value="********"/>
473&lt;/policymap>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]474</pre>
475<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]476
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]477<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]478
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]479<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>
480<pre class="code">-> convert -debug cache logo: -sharpen 3x2 null:
4812013-12-17T13:33:42-05:00 0:00.000 0.000u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]482 destroy
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4832013-12-17T13:33:42-05:00 0:00.000 0.000u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]484 open LOGO[0] (Heap Memory, 640x480x4 4.688MiB)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4852013-12-17T13:33:42-05:00 0:00.010 0.000u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]486 open LOGO[0] (Heap Memory, 640x480x3 3.516MiB)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4872013-12-17T13:33:42-05:00 0:00.010 0.000u 7.0.0 Cache convert: cache.c/ClonePixelCachePixels/1044/Cache
488 Memory => Memory
4892013-12-17T13:33:42-05:00 0:00.020 0.010u 7.0.0 Cache convert: cache.c/ClonePixelCachePixels/1044/Cache
490 Memory => Memory
4912013-12-17T13:33:42-05:00 0:00.020 0.010u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]492 open LOGO[0] (Heap Memory, 640x480x3 3.516MiB)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4932013-12-17T13:33:42-05:00 0:00.050 0.100u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]494 destroy LOGO[0]
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]4952013-12-17T13:33:42-05:00 0:00.050 0.100u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]496 destroy LOGO[0]
497</pre>
498<p>This command utilizes a pixel cache in memory. The logo consumed 4.688MiB and after it was sharpened, 3.516MiB.</p>
499</div>
500
501
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame]502<h3>Distributed Pixel Cache</h3>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]503<div class="doc-section">
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]504<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]505</div>
506
507<h3>Cache Views</h3>
508<div class="doc-section">
509
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]510<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]511
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]512<pre class="code">CacheView
513 *view_1,
514 *view_2;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]515
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]516view_1=AcquireVirtualCacheView(source,exception);
517view_2=AcquireVirtualCacheView(source,exception);
518for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
519{
520 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]521 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,exception);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]522 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
523 break;
524 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]525 {
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]526 /* do something with u &amp; v here */
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]527 }
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]528}
529view_2=DestroyCacheView(view_2);
530view_1=DestroyCacheView(view_1);
531if (y &lt; (ssize_t) source-&gt;rows)
532 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]533</pre>
534</div>
535
536<h3>Magick Persistent Cache Format</h3>
537<div class="doc-section">
538
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]539<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]540<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]541</div>
542
543<h3>Best Practices</h3>
544<div class="doc-section">
545
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]546<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]547
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]548<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>
549
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]550<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>
551
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]552<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]553
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]554<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]555
556<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>
557
558<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>
559
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]560<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]561
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]562<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]563
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]564<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]565
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]566<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]567<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>
568
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]569<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]570<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]571</div>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]572
573</div>
574
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]575<h2><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]576<div class="doc-section">
577
578<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>
579
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]580<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]581
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]582<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]583{
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]584 register const PixelPacket
585 *p;
586
587 MyData
588 *my_data;
589
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]590 my_data=(MyData *) image->client_data;
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]591 p=(PixelPacket *) pixels;
592 if (p != (const PixelPacket *) NULL)
593 {
594 /* process pixels here */
595 }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]596 return(columns);
597}
598
599...
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]600
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]601/* invoke the pixel stream here */
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]602image_info->client_data=(void *) MyData;
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]603image=ReadStream(image_info,&amp;StreamPixels,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]604</pre>
605
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]606<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]607
608</div>
609
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]610<h2><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]611<div class="doc-section">
612
613<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>
614
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]615<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]616</pre>
617
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]618<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]619
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]620<pre class="code">const char
621 *comment;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]622
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]623(void) SetImageProperty(image,"comment","This space for rent");
624comment=GetImageProperty(image,"comment");
625if (comment == (const char *) NULL)
626 (void) printf("Image comment: %s\n",comment);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]627</pre>
628
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]629<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]630
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]631<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]632
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]633<pre class="code">StringInfo
634 *profile;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]635
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]636profile=AcquireStringInfo(length);
637SetStringInfoDatum(profile,my_exif_profile);
638(void) SetImageProfile(image,"EXIF",profile);
639DestroyStringInfo(profile);
640profile=GetImageProfile(image,"EXIF");
641if (profile != (StringInfo *) NULL)
642 (void) PrintStringInfo(stdout,"EXIF",profile);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]643</pre>
644
645</div>
646
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]647<h2><a id="tera-pixel"></a>Large Image Support</h2>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]648<div class="doc-section">
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]649<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]650
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]651<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]652<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]653
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]654<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]655<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>
656
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]657<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]658<p>Here we force all image pixels to disk:</p>
659
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]660<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]661<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]662
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]663<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]664<pre class="text">
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame]665convert -distribute-cache 6668 &amp; // start on 192.168.100.50
666convert -distribute-cache 6668 &amp; // start on 192.168.100.51
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]667convert -limit memory 2mb -limit map 2mb -limit disk 2gb \
668 -define registry:cache:hosts=192.168.100.50:6668,192.168.100.51:6668 \
669 myhugeimage.jpg -sharpen 5x2 myhugeimage.png
670</pre>
671</div>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]672
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]673<h2><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]674<div class="doc-section">
675
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]676<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]677
cristyf1b8a092014-02-20 15:46:11 +0000[diff] [blame]678<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]679
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]680<div class="viewport">CacheView
681 *image_view;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]682
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]683MagickBooleanType
684 status;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]685
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]686ssize_t
687 y;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]688
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]689status=MagickTrue;
690image_view=AcquireVirtualCacheView(image,exception);
691#pragma omp parallel for schedule(dynamic,4) shared(status)
692for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
693{
694 register IndexPacket
695 *indexes;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]696
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]697 register PixelPacket
698 *q;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]699
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]700 register ssize_t
701 x;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]702
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]703 if (status == MagickFalse)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]704 continue;
705 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
706 if (q == (PixelPacket *) NULL)
707 {
708 status=MagickFalse;
709 continue;
710 }
711 indexes=GetCacheViewAuthenticIndexQueue(image_view);
712 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
713 {
714 SetPixelRed(q,...);
715 SetPixelGreen(q,...);
716 SetPixelBlue(q,...);
717 SetPixelOpacity(q,...);
718 if (indexes != (IndexPacket *) NULL)
719 SetPixelIndex(indexes+x,...);
720 q++;
721 }
722 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
723 status=MagickFalse;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]724}
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]725image_view=DestroyCacheView(image_view);
726if (status == MagickFalse)
727 perror("something went wrong");
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]728</div>
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]729<p>This code snippet converts an uncompressed Windows bitmap to a Magick++ image:</p>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]730<div class="viewport">#include "Magick++.h"
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]731#include &lt;assert.h&gt;
732#include "omp.h"
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]733
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]734void ConvertBMPToImage(const BITMAPINFOHEADER *bmp_info,
735 const unsigned char *restrict pixels,Magick::Image *image)
736{
737 /*
738 Prepare the image so that we can modify the pixels directly.
739 */
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]740 assert(bmp_info->biCompression == BI_RGB);
741 assert(bmp_info->biWidth == image->columns());
742 assert(abs(bmp_info->biHeight) == image->rows());
743 image->modifyImage();
744 if (bmp_info->biBitCount == 24)
745 image->type(MagickCore::TrueColorType);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]746 else
cristy37b3d442015-02-28 14:00:30 +0000[diff] [blame^]747 image->type(MagickCore::TrueColorMatteType);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]748 register unsigned int bytes_per_row=bmp_info->biWidth*bmp_info->biBitCount/8;
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]749 if (bytes_per_row % 4 != 0) {
750 bytes_per_row=bytes_per_row+(4-bytes_per_row % 4); // divisible by 4.
751 }
752 /*
753 Copy all pixel data, row by row.
754 */
755 #pragma omp parallel for
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]756 for (int y=0; y &lt; int(image->rows()); y++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]757 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]758 int
759 row;
760
761 register const unsigned char
762 *restrict p;
763
764 register MagickCore::PixelPacket
765 *restrict q;
766
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]767 row=(bmp_info->biHeight > 0) ? (image->rows()-y-1) : y;
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]768 p=pixels+row*bytes_per_row;
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]769 q=image->setPixels(0,y,image->columns(),1);
770 for (int x=0; x &lt; int(image->columns()); x++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]771 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]772 SetPixelBlue(q,p[0]);
773 SetPixelGreen(q,p[1]);
774 SetPixelRed(q,p[2]);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]775 if (bmp_info->biBitCount == 32) {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]776 SetPixelOpacity(q,p[3]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]777 }
778 q++;
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]779 p+=bmp_info->biBitCount/8;
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]780 }
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]781 image->syncPixels(); // sync pixels to pixel cache.
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]782 }
783 return;
784}
785</div>
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]786
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]787<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>
788
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]789<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]790
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]791<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]792
793<pre class="text">
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]794&lt;policy domain="resource" name="thread" value="2"/>
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]795</pre>
796
797<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>
798
799<pre class="text">
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]800export MAGICK_THREAD_LIMIT=12
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]801</pre>
802
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]803<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]804
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]805<h4>Threading Performance</h4>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]806<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]807<pre class="text">
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]808convert -bench 10 model.png -sharpen 5x2 null:
809Performance[1]: 10i 1.135ips 1.000e 8.760u 0:08.810
810Performance[2]: 10i 2.020ips 0.640e 9.190u 0:04.950
811Performance[3]: 10i 2.786ips 0.710e 9.400u 0:03.590
812Performance[4]: 10i 3.378ips 0.749e 9.580u 0:02.960
813Performance[5]: 10i 4.032ips 0.780e 9.580u 0:02.480
814Performance[6]: 10i 4.566ips 0.801e 9.640u 0:02.190
815Performance[7]: 10i 3.788ips 0.769e 10.980u 0:02.640
816Performance[8]: 10i 4.115ips 0.784e 12.030u 0:02.430
817Performance[9]: 10i 4.484ips 0.798e 12.860u 0:02.230
818Performance[10]: 10i 4.274ips 0.790e 14.830u 0:02.340
819Performance[11]: 10i 4.348ips 0.793e 16.500u 0:02.300
820Performance[12]: 10i 4.525ips 0.799e 18.320u 0:02.210
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]821</pre>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]822<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]823<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]824</div>
825
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]826<h2><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]827<div class="doc-section">
828<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>
829
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]830<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]831
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]832<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]833<p>If so, run this command to realize a significant speed-up for image convolution:</p>
834
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]835<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]836<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
837
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]838<p>Here is an example OpenCL kernel that convolves an image:</p>
839
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]840<div class="viewport">static inline long ClampToCanvas(const long offset,const ulong range)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]841{
842 if (offset &lt; 0L)
843 return(0L);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]844 if (offset >= range)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]845 return((long) (range-1L));
846 return(offset);
847}
848
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]849static inline CLQuantum ClampToQuantum(const float value)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]850{
851 if (value &lt; 0.0)
852 return((CLQuantum) 0);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]853 if (value >= (float) QuantumRange)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]854 return((CLQuantum) QuantumRange);
855 return((CLQuantum) (value+0.5));
856}
857
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]858__kernel void Convolve(const __global CLPixelType *source,__constant float *filter,
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]859 const ulong width,const ulong height,__global CLPixelType *destination)
860{
861 const ulong columns = get_global_size(0);
862 const ulong rows = get_global_size(1);
863
864 const long x = get_global_id(0);
865 const long y = get_global_id(1);
866
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]867 const float scale = (1.0/QuantumRange);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]868 const long mid_width = (width-1)/2;
869 const long mid_height = (height-1)/2;
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]870 float4 sum = { 0.0, 0.0, 0.0, 0.0 };
871 float gamma = 0.0;
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]872 register ulong i = 0;
873
874 for (long v=(-mid_height); v &lt;= mid_height; v++)
875 {
876 for (long u=(-mid_width); u &lt;= mid_width; u++)
877 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]878 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
879 columns);
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]880 const float alpha=scale*(QuantumRange-source[index].w);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]881 sum.x+=alpha*filter[i]*source[index].x;
882 sum.y+=alpha*filter[i]*source[index].y;
883 sum.z+=alpha*filter[i]*source[index].z;
884 sum.w+=filter[i]*source[index].w;
885 gamma+=alpha*filter[i];
886 i++;
887 }
888 }
889
890 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
891 const ulong index=y*columns+x;
892 destination[index].x=ClampToQuantum(gamma*sum.x);
893 destination[index].y=ClampToQuantum(gamma*sum.y);
894 destination[index].z=ClampToQuantum(gamma*sum.z);
895 destination[index].w=ClampToQuantum(sum.w);
896};
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]897</div>
898
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]899<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]900
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]901<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>
902
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]903</div>
904
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]905<h2><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]906<div class="doc-section">
907
908<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>
909
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]910<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]911
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]912<div class="viewport">/*
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]913 Include declarations.
914*/
915#include "magick/studio.h"
916#include "magick/blob.h"
917#include "magick/blob-private.h"
918#include "magick/colorspace.h"
919#include "magick/exception.h"
920#include "magick/exception-private.h"
921#include "magick/image.h"
922#include "magick/image-private.h"
923#include "magick/list.h"
924#include "magick/magick.h"
925#include "magick/memory_.h"
926#include "magick/monitor.h"
927#include "magick/monitor-private.h"
928#include "magick/quantum-private.h"
929#include "magick/static.h"
930#include "magick/string_.h"
931#include "magick/module.h"
932
933/*
934 Forward declarations.
935*/
936static MagickBooleanType
937 WriteMGKImage(const ImageInfo *,Image *);
938
939/*
940%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
941% %
942% %
943% %
944% I s M G K %
945% %
946% %
947% %
948%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
949%
950% IsMGK() returns MagickTrue if the image format type, identified by the
951% magick string, is MGK.
952%
953% The format of the IsMGK method is:
954%
955% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
956%
957% A description of each parameter follows:
958%
959% o magick: This string is generally the first few bytes of an image file
960% or blob.
961%
962% o length: Specifies the length of the magick string.
963%
964*/
965static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
966{
967 if (length &lt; 7)
968 return(MagickFalse);
969 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
970 return(MagickTrue);
971 return(MagickFalse);
972}
973
974/*
975%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
976% %
977% %
978% %
979% R e a d M G K I m a g e %
980% %
981% %
982% %
983%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
984%
985% ReadMGKImage() reads a MGK image file and returns it. It allocates
986% the memory necessary for the new Image structure and returns a pointer to
987% the new image.
988%
989% The format of the ReadMGKImage method is:
990%
991% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
992%
993% A description of each parameter follows:
994%
995% o image_info: the image info.
996%
997% o exception: return any errors or warnings in this structure.
998%
999*/
1000static Image *ReadMGKImage(const ImageInfo *image_info,
1001 ExceptionInfo *exception)
1002{
1003 char
1004 buffer[MaxTextExtent];
1005
1006 Image
1007 *image;
1008
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1009 MagickBooleanType
1010 status;
1011
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1012 register PixelPacket
1013 *q;
1014
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1015 register size_t
1016 x;
1017
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1018 register unsigned char
1019 *p;
1020
1021 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1022 count,
1023 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1024
1025 unsigned char
1026 *pixels;
1027
1028 unsigned long
1029 columns,
1030 rows;
1031
1032 /*
1033 Open image file.
1034 */
1035 assert(image_info != (const ImageInfo *) NULL);
1036 assert(image_info-&gt;signature == MagickSignature);
1037 if (image_info-&gt;debug != MagickFalse)
1038 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
1039 assert(exception != (ExceptionInfo *) NULL);
1040 assert(exception-&gt;signature == MagickSignature);
1041 image=AcquireImage(image_info);
1042 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
1043 if (status == MagickFalse)
1044 {
1045 image=DestroyImageList(image);
1046 return((Image *) NULL);
1047 }
1048 /*
1049 Read MGK image.
1050 */
1051 (void) ReadBlobString(image,buffer); /* read magic number */
1052 if (IsMGK(buffer,7) == MagickFalse)
1053 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1054 (void) ReadBlobString(image,buffer);
1055 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1056 if (count &lt;= 0)
1057 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1058 do
1059 {
1060 /*
1061 Initialize image structure.
1062 */
1063 image-&gt;columns=columns;
1064 image-&gt;rows=rows;
1065 image-&gt;depth=8;
1066 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1067 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1068 break;
1069 /*
1070 Convert MGK raster image to pixel packets.
1071 */
1072 if (SetImageExtent(image,0,0) == MagickFalse)
1073 {
1074 InheritException(exception,&amp;image-&gt;exception);
1075 return(DestroyImageList(image));
1076 }
1077 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
1078 if (pixels == (unsigned char *) NULL)
1079 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1080 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1081 {
1082 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
1083 if (count != (ssize_t) (3*image-&gt;columns))
1084 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
1085 p=pixels;
1086 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
1087 if (q == (PixelPacket *) NULL)
1088 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1089 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1090 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1091 SetPixelRed(q,ScaleCharToQuantum(*p++));
1092 SetPixelGreen(q,ScaleCharToQuantum(*p++));
1093 SetPixelBlue(q,ScaleCharToQuantum(*p++));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1094 q++;
1095 }
1096 if (SyncAuthenticPixels(image,exception) == MagickFalse)
1097 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1098 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1099 (SetImageProgress(image,LoadImageTag,y,image&gt;>rows) == MagickFalse))
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1100 break;
1101 }
1102 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1103 if (EOFBlob(image) != MagickFalse)
1104 {
1105 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
1106 break;
1107 }
1108 /*
1109 Proceed to next image.
1110 */
1111 if (image_info-&gt;number_scenes != 0)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1112 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1113 break;
1114 *buffer='\0';
1115 (void) ReadBlobString(image,buffer);
1116 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1117 if (count != 0)
1118 {
1119 /*
1120 Allocate next image structure.
1121 */
1122 AcquireNextImage(image_info,image);
1123 if (GetNextImageInList(image) == (Image *) NULL)
1124 {
1125 image=DestroyImageList(image);
1126 return((Image *) NULL);
1127 }
1128 image=SyncNextImageInList(image);
1129 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
1130 if (status == MagickFalse)
1131 break;
1132 }
1133 } while (count != 0);
1134 (void) CloseBlob(image);
1135 return(GetFirstImageInList(image));
1136}
1137
1138/*
1139%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1140% %
1141% %
1142% %
1143% R e g i s t e r M G K I m a g e %
1144% %
1145% %
1146% %
1147%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1148%
1149% RegisterMGKImage() adds attributes for the MGK image format to
1150% the list of supported formats. The attributes include the image format
1151% tag, a method to read and/or write the format, whether the format
1152% supports the saving of more than one frame to the same file or blob,
1153% whether the format supports native in-memory I/O, and a brief
1154% description of the format.
1155%
1156% The format of the RegisterMGKImage method is:
1157%
1158% unsigned long RegisterMGKImage(void)
1159%
1160*/
1161ModuleExport unsigned long RegisterMGKImage(void)
1162{
1163 MagickInfo
1164 *entry;
1165
1166 entry=SetMagickInfo("MGK");
1167 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
1168 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
1169 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
1170 entry-&gt;description=ConstantString("MGK");
1171 entry-&gt;module=ConstantString("MGK");
1172 (void) RegisterMagickInfo(entry);
1173 return(MagickImageCoderSignature);
1174}
1175
1176/*
1177%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1178% %
1179% %
1180% %
1181% U n r e g i s t e r M G K I m a g e %
1182% %
1183% %
1184% %
1185%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1186%
1187% UnregisterMGKImage() removes format registrations made by the
1188% MGK module from the list of supported formats.
1189%
1190% The format of the UnregisterMGKImage method is:
1191%
1192% UnregisterMGKImage(void)
1193%
1194*/
1195ModuleExport void UnregisterMGKImage(void)
1196{
1197 (void) UnregisterMagickInfo("MGK");
1198}
1199
1200/*
1201%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1202% %
1203% %
1204% %
1205% W r i t e M G K I m a g e %
1206% %
1207% %
1208% %
1209%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1210%
1211% WriteMGKImage() writes an image to a file in red, green, and blue
1212% MGK rasterfile format.
1213%
1214% The format of the WriteMGKImage method is:
1215%
1216% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1217%
1218% A description of each parameter follows.
1219%
1220% o image_info: the image info.
1221%
1222% o image: The image.
1223%
1224*/
1225static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1226{
1227 char
1228 buffer[MaxTextExtent];
1229
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1230 MagickBooleanType
1231 status;
1232
1233 MagickOffsetType
1234 scene;
1235
1236 register const PixelPacket
1237 *p;
1238
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1239 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1240 x;
1241
1242 register unsigned char
1243 *q;
1244
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1245 ssize_t
1246 y;
1247
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1248 unsigned char
1249 *pixels;
1250
1251 /*
1252 Open output image file.
1253 */
1254 assert(image_info != (const ImageInfo *) NULL);
1255 assert(image_info-&gt;signature == MagickSignature);
1256 assert(image != (Image *) NULL);
1257 assert(image-&gt;signature == MagickSignature);
1258 if (image-&gt;debug != MagickFalse)
1259 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1260 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1261 if (status == MagickFalse)
1262 return(status);
1263 scene=0;
1264 do
1265 {
1266 /*
1267 Allocate memory for pixels.
1268 */
1269 if (image-&gt;colorspace != RGBColorspace)
1270 (void) SetImageColorspace(image,RGBColorspace);
1271 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1272 3UL*sizeof(*pixels));
1273 if (pixels == (unsigned char *) NULL)
1274 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1275 /*
1276 Initialize raster file header.
1277 */
1278 (void) WriteBlobString(image,"id=mgk\n");
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1279 (void) FormatLocaleString(buffer,MaxTextExtent,"%lu %lu\n",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1280 image-&gt;columns,image-&gt;rows);
1281 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1282 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1283 {
1284 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1285 if (p == (const PixelPacket *) NULL)
1286 break;
1287 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1288 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1289 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1290 *q++=ScaleQuantumToChar(GetPixelRed(p));
1291 *q++=ScaleQuantumToChar(GetPixelGreen(p));
1292 *q++=ScaleQuantumToChar(GetPixelBlue(p));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1293 p++;
1294 }
1295 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1296 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1297 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1298 break;
1299 }
1300 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1301 if (GetNextImageInList(image) == (Image *) NULL)
1302 break;
1303 image=SyncNextImageInList(image);
1304 status=SetImageProgress(image,SaveImagesTag,scene,
1305 GetImageListLength(image));
1306 if (status == MagickFalse)
1307 break;
1308 scene++;
1309 } while (image_info-&gt;adjoin != MagickFalse);
1310 (void) CloseBlob(image);
1311 return(MagickTrue);
1312}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1313</div>
1314
1315<p>To invoke the custom coder from the command line, use these commands:</p>
1316
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1317<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>
1318<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]1319
1320</div>
1321
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1322<h2><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1323<div class="doc-section">
1324
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1325<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]1326
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1327<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]1328
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1329<div class="viewport">#include &lt;stdio.h&gt;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1330#include &lt;stdlib.h&gt;
1331#include &lt;string.h&gt;
1332#include &lt;time.h&gt;
1333#include &lt;assert.h&gt;
1334#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1335#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1336
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1337/*
1338%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1339% %
1340% %
1341% %
1342% a n a l y z e I m a g e %
1343% %
1344% %
1345% %
1346%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1347%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1348% analyzeImage() computes the brightness and saturation mean, standard
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]1349% deviation, kurtosis and skewness and stores these values as attributes
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1350% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1351%
1352% The format of the analyzeImage method is:
1353%
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1354% size_t analyzeImage(Image *images,const int argc,char **argv,
1355% ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1356%
1357% A description of each parameter follows:
1358%
1359% o image: the address of a structure of type Image.
1360%
1361% o argc: Specifies a pointer to an integer describing the number of
1362% elements in the argument vector.
1363%
1364% o argv: Specifies a pointer to a text array containing the command line
1365% arguments.
1366%
1367% o exception: return any errors or warnings in this structure.
1368%
1369*/
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1370ModuleExport size_t analyzeImage(Image **images,const int argc,const char **argv,
1371 ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1372{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1373 char
1374 text[MaxTextExtent];
1375
1376 double
1377 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1378 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1379 brightness_mean,
1380 brightness_standard_deviation,
1381 brightness_kurtosis,
1382 brightness_skewness,
1383 brightness_sum_x,
1384 brightness_sum_x2,
1385 brightness_sum_x3,
1386 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1387 hue,
1388 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1389 saturation_mean,
1390 saturation_standard_deviation,
1391 saturation_kurtosis,
1392 saturation_skewness,
1393 saturation_sum_x,
1394 saturation_sum_x2,
1395 saturation_sum_x3,
1396 saturation_sum_x4;
1397
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1398 Image
1399 *image;
1400
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1401 assert(images != (Image **) NULL);
1402 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1403 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1404 (void) argc;
1405 (void) argv;
1406 image=(*images);
1407 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1408 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1409 CacheView
1410 *image_view;
1411
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1412 MagickBooleanType
1413 status;
1414
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1415 ssize_t
1416 y;
1417
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1418 brightness_sum_x=0.0;
1419 brightness_sum_x2=0.0;
1420 brightness_sum_x3=0.0;
1421 brightness_sum_x4=0.0;
1422 brightness_mean=0.0;
1423 brightness_standard_deviation=0.0;
1424 brightness_kurtosis=0.0;
1425 brightness_skewness=0.0;
1426 saturation_sum_x=0.0;
1427 saturation_sum_x2=0.0;
1428 saturation_sum_x3=0.0;
1429 saturation_sum_x4=0.0;
1430 saturation_mean=0.0;
1431 saturation_standard_deviation=0.0;
1432 saturation_kurtosis=0.0;
1433 saturation_skewness=0.0;
1434 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1435 status=MagickTrue;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1436 image_view=AcquireVirtualCacheView(image,exception);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1437#if defined(MAGICKCORE_OPENMP_SUPPORT)
1438 #pragma omp parallel for schedule(dynamic,4) shared(status)
1439#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1440 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1441 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1442 register const PixelPacket
1443 *p;
1444
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1445 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1446 x;
1447
1448 if (status == MagickFalse)
1449 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1450 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1451 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1452 {
1453 status=MagickFalse;
1454 continue;
1455 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1456 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1457 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1458 ConvertRGBToHSB(GetPixelRed(p),GetPixelGreen(p),GetPixelBue(p),&amp;hue,&amp;saturation,&amp;brightness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1459 brightness*=QuantumRange;
1460 brightness_sum_x+=brightness;
1461 brightness_sum_x2+=brightness*brightness;
1462 brightness_sum_x3+=brightness*brightness*brightness;
1463 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1464 saturation*=QuantumRange;
1465 saturation_sum_x+=saturation;
1466 saturation_sum_x2+=saturation*saturation;
1467 saturation_sum_x3+=saturation*saturation*saturation;
1468 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1469 area++;
1470 p++;
1471 }
1472 }
1473 image_view=DestroyCacheView(image_view);
1474 if (area &lt;= 0.0)
1475 break;
1476 brightness_mean=brightness_sum_x/area;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1477 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_mean);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1478 (void) SetImageProperty(image,"filter:brightness:mean",text);
1479 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1480 area*brightness_sum_x/area));
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1481 (void) FormatLocaleString(text,MaxTextExtent,"%g",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1482 brightness_standard_deviation);
1483 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1484 if (brightness_standard_deviation != 0)
1485 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1486 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1487 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1488 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1489 brightness_standard_deviation*brightness_standard_deviation*
1490 brightness_standard_deviation)-3.0;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1491 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_kurtosis);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1492 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1493 if (brightness_standard_deviation != 0)
1494 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1495 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1496 brightness_mean)/(brightness_standard_deviation*
1497 brightness_standard_deviation*brightness_standard_deviation);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1498 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_skewness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1499 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1500 saturation_mean=saturation_sum_x/area;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1501 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_mean);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1502 (void) SetImageProperty(image,"filter:saturation:mean",text);
1503 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1504 area*saturation_sum_x/area));
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1505 (void) FormatLocaleString(text,MaxTextExtent,"%g",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1506 saturation_standard_deviation);
1507 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1508 if (saturation_standard_deviation != 0)
1509 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1510 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1511 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1512 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1513 saturation_standard_deviation*saturation_standard_deviation*
1514 saturation_standard_deviation)-3.0;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1515 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_kurtosis);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1516 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1517 if (saturation_standard_deviation != 0)
1518 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1519 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1520 saturation_mean)/(saturation_standard_deviation*
1521 saturation_standard_deviation*saturation_standard_deviation);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1522 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_skewness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1523 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1524 }
1525 return(MagickImageFilterSignature);
1526}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1527</div>
1528
1529<p>To invoke the custom filter from the command line, use this command:</p>
1530
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1531<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/>
1532 Format: LOGO (ImageMagick Logo) <br/>
1533 Class: PseudoClass <br/>
1534 Geometry: 640x480 <br/>
1535 ... <br/>
1536 filter:brightness:kurtosis: 8.17947 <br/>
1537 filter:brightness:mean: 60632.1 <br/>
1538 filter:brightness:skewness: -2.97118 <br/>
1539 filter:brightness:standard-deviation: 13742.1 <br/>
1540 filter:saturation:kurtosis: 4.33554 <br/>
1541 filter:saturation:mean: 5951.55 <br/>
1542 filter:saturation:skewness: 2.42848 <br/>
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1543 filter:saturation:standard-deviation: 15575.9</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1544
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1545<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]1546
1547</div>
cristyad41c0c2012-10-31 00:49:28 +0000[diff] [blame]1548
1549</div>
1550
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cristy37b3d442015-02-28 14:00:30 +0000[diff] [blame^]1563 <span id="footer-west">© 1999-2014 ImageMagick Studio LLC</span>
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