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cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]7 <title>ImageMagick: Architecture</title>
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cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]54</div>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]55<div class="container">
56<div class="magick-header">
57<p class="text-center"><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]58
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]59<p class="lead magick-description">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>
60
61<h2 class="magick-header"><a id="overview"></a>Architecture Overview</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]62
63<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>
64
65<ul>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]66 <li>colorspace (e.g sRGB, linear RGB, linear GRAY, CMYK, YUV, Lab, etc.)</li>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]67 <li>bit depth (.e.g 1, 4, 8, 12, 16, etc.)</li>
68 <li>storage format (e.g. unsigned, signed, float, double, etc.)</li>
69 <li>compression (e.g. uncompressed, RLE, Zip, BZip, etc.)</li>
70 <li>orientation (i.e. top-to-bottom, right-to-left, etc.),</li>
71 <li>layout (.e.g. raw, interspersed with opcodes, etc.)</li>
72</ul>
73
74<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>
75
76<p>An efficient implementation of an image processing algorithm may require we get or set:</p>
77
78<ul>
79 <li>one pixel a time (e.g. pixel at location 10,3)</li>
80 <li>a single scanline (e.g. all pixels from row 4)</li>
81 <li>a few scanlines at once (e.g. pixel rows 4-7)</li>
82 <li>a single column or columns of pixels (e.g. all pixels from column 11)</li>
83 <li>an arbitrary region of pixels from the image (e.g. pixels defined at 10,7 to 10,19)</li>
84 <li>a pixel in random order (e.g. pixel at 14,15 and 640,480)</li>
85 <li>pixels from two different images (e.g. pixel at 5,1 from image 1 and pixel at 5,1 from image 2)</li>
86 <li>pixels outside the boundaries of the image (e.g. pixel at -1,-3)</li>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]87 <li>a pixel component that is unsigned (65311) or in a floating-point representation (e.g. 0.17836)</li>
88 <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]89 <li>one or more pixels simultaneously in different threads of execution</li>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]90 <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]91</ul>
92
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]93<p>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>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]94
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]95<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]96
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]97<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]98
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]99<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]100
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]101<h2 class="magick-header"><a id="cache"></a>The Pixel Cache</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]102
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]103<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]104
105<h3>Create the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]106
107<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>
108
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]109<dl>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]110<dt>Create an image canvas initialized to the background color:</dt><br>
111<dd><pre>image=AllocateImage(image_info);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]112if (SetImageExtent(image,640,480) == MagickFalse)
113 { /* an exception was thrown */ }
114(void) QueryMagickColor("red",&amp;image-&gt;background_color,&amp;image-&gt;exception);
115SetImageBackgroundColor(image);
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]116</pre></dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]117
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]118<dt>Create an image from a JPEG image on disk:</dt><br>
119<dd><pre>(void) strcpy(image_info-&gt;filename,"image.jpg"):
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]120image=ReadImage(image_info,exception);
121if (image == (Image *) NULL)
122 { /* an exception was thrown */ }
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]123</pre></dd>
124<dt>Create an image from a memory based image:</dt><br>
125<dd><pre>image=BlobToImage(blob_info,blob,extent,exception);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]126if (image == (Image *) NULL)
127 { /* an exception was thrown */ }
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]128</pre></dd>
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]129</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]130
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]131<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]132
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]133<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">‑version</a> option: </p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]134
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]135<p class="crt"><span class="crtprompt"> $magick&gt; </span><span class="crtin">identify -version</span><span class="crtout">Version: ImageMagick 6.9.1-2 2015-03-21 Q16 http://www.imagemagick.org</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]136<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]137
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]138<h3><a id="authentic-pixels"></a>Access the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]139
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]140<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]141<ul>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]142 <li><a href="http://www.imagemagick.org/ImageMagick-7.0.0/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>
143 <li><a href="http://www.imagemagick.org/ImageMagick-7.0.0/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a>: gets pixels that you intend to modify</li>
144 <li><a href="http://www.imagemagick.org/ImageMagick-7.0.0/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a>: queue pixels that you intend to set</li>
145 <li><a href="http://www.imagemagick.org/ImageMagick-7.0.0/api/cache.html#SyncAuthenticPixels">SyncAuthenticPixels()</a>: update the pixel cache with any modified pixels</li>
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]146</ul>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]147
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]148<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]149
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]150<pre class="pre-scrollable">const PixelPacket
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]151 *p;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]152
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]153PixelPacket
154 *q;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]155
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]156ssize_t
157 x,
158 y;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]159
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]160destination=CloneImage(source,source-&gt;columns,source-&gt;rows,MagickTrue,
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]161 exception);
162if (destination == (Image *) NULL)
163 { /* an exception was thrown */ }
164for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
165{
166 p=GetVirtualPixels(source,0,y,source-&gt;columns,1,exception);
167 q=GetAuthenticPixels(destination,0,y,destination-&gt;columns,1,exception);
168 if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL)
169 break;
170 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]171 {
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]172 SetPixelRed(q,90*p-&gt;red/100);
173 SetPixelGreen(q,90*p-&gt;green/100);
174 SetPixelBlue(q,90*p-&gt;blue/100);
175 SetPixelOpacity(q,90*p-&gt;opacity/100);
176 p++;
177 q++;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]178 }
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]179 if (SyncAuthenticPixels(destination,exception) == MagickFalse)
180 break;
181}
182if (y &lt; (ssize_t) source-&gt;rows)
183 { /* an exception was thrown */ }
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]184</pre>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]185
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]186<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="http://www.imagemagick.org/ImageMagick-7.0.0/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> or <a href="http://www.imagemagick.org/ImageMagick-7.0.0/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a>. Use <a href="http://www.imagemagick.org/ImageMagick-7.0.0/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="http://www.imagemagick.org/ImageMagick-7.0.0/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]187
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]188<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="http://www.imagemagick.org/ImageMagick-7.0.0/api/cache.html#GetVirtualIndexQueue">GetVirtualIndexQueue()</a> (to read the indexes) or <a href="http://www.imagemagick.org/ImageMagick-7.0.0/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]189
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]190<pre>const IndexPacket
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]191 *indexes;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]192
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]193for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
194{
195 p=GetVirtualPixels(source,0,y,source-&gt;columns,1);
196 if (p == (const PixelPacket *) NULL)
197 break;
198 indexes=GetVirtualIndexQueue(source);
199 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
200 (void) printf("%d\n",GetPixelIndex(indexes+x));
201}
202if (y &lt; (ssize_t) source-&gt;rows)
203 /* an exception was thrown */
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]204</pre>
205
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]206<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 <var>pushed</var> 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]207
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]208<pre>p=GetVirtualPixels(source,-3,-3,source-&gt;columns+3,6,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]209</pre>
210
211<p>gives you the pixels you asked for without complaint, even though some are not within the confines of the image region.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]212
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]213<h3><a id="virtual-pixels"></a>Virtual Pixels</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]214
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]215<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>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]216 <p>Access to the virtual pixels are controlled by the <a href="http://www.imagemagick.org/ImageMagick-7.0.0/api/cache.html#SetImageVirtualPixelMethod">SetImageVirtualPixelMethod()</a> method from the MagickCore API or the <a href="command-line-options.html#virtual-pixel">‑virtual‑pixel</a> option from the command line. The methods include:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]217
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]218<dl class="dl-horizontal">
219<dt>background</dt>
220<dd>the area surrounding the image is the background color</dd>
221<dt>black</dt>
222<dd>the area surrounding the image is black</dd>
223<dt>checker-tile</dt>
224<dd>alternate squares with image and background color</dd>
225<dt>dither</dt>
226<dd>non-random 32x32 dithered pattern</dd>
227<dt>edge</dt>
228<dd>extend the edge pixel toward infinity (default)</dd>
229<dt>gray</dt>
230<dd>the area surrounding the image is gray</dd>
231<dt>horizontal-tile</dt>
232<dd>horizontally tile the image, background color above/below</dd>
233<dt>horizontal-tile-edge</dt>
234<dd>horizontally tile the image and replicate the side edge pixels</dd>
235<dt>mirror</dt>
236<dd>mirror tile the image</dd>
237<dt>random</dt>
238<dd>choose a random pixel from the image</dd>
239<dt>tile</dt>
240<dd>tile the image</dd>
241<dt>transparent</dt>
242<dd>the area surrounding the image is transparent blackness</dd>
243<dt>vertical-tile</dt>
244<dd>vertically tile the image, sides are background color</dd>
245<dt>vertical-tile-edge</dt>
246<dd>vertically tile the image and replicate the side edge pixels</dd>
247<dt>white</dt>
248<dd>the area surrounding the image is white</dd>
249</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]250
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]251
252<h3>Cache Storage and Resource Requirements</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]253
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]254<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 <var>width * height * bit-depth / 8 * channels</var> 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 <var>automagically</var> by the pixel cache manager negotiating with the operating system. However, you can influence how the pixel cache manager allocates the pixel cache with <var>cache resource limits</var>. The limits include:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]255
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]256<dl class="dl-horizontal">
257 <dt>width</dt>
258 <dd>maximum width of an image. Exceed this limit and an exception is thrown and processing stops.</dd>
259 <dt>height</dt>
260 <dd>maximum height of an image. Exceed this limit and an exception is thrown and processing stops.</dd>
261 <dt>area</dt>
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]262 <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>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]263 <dt>memory</dt>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]264 <dd>maximum amount of memory in bytes to allocate for the pixel cache from the anonymous mapped memory or the heap.</dd>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]265 <dt>map</dt>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]266 <dd>maximum amount of memory map in bytes to allocate for the pixel cache.</dd>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]267 <dt>disk</dt>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]268 <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>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]269 <dt>files</dt>
270 <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>
271 <dt>thread</dt>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]272 <dd>maximum number of threads that are permitted to run in parallel.</dd>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]273 <dt>time</dt>
274 <dd>maximum number of seconds that the process is permitted to execute. Exceed this limit and an exception is thrown and processing stops.</dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]275</dl>
276
277<p>To determine the current setting of these limits, use this command:</p>
278
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]279<pre>
280-&gt; identify -list resource
cristy37b3d442015-02-28 14:00:30 +0000[diff] [blame]281Resource limits:
282 Width: 100MP
283 Height: 100MP
284 Area: 25.181GB
285 Memory: 11.726GiB
286 Map: 23.452GiB
287 Disk: unlimited
288 File: 768
289 Thread: 12
290 Throttle: 0
291 Time: unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]292</pre>
293
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]294<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="http://www.imagemagick.org/ImageMagick-7.0.0/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>
295<pre>
296&lt;policymap&gt;
297 &lt;policy domain="resource" name="temporary-path" value="/tmp"/&gt;
298 &lt;policy domain="resource" name="memory" value="256MiB"/&gt;
299 &lt;policy domain="resource" name="map" value="512MiB"/&gt;
300 &lt;policy domain="resource" name="width" value="8KP"/&gt;
301 &lt;policy domain="resource" name="height" value="8KP"/&gt;
302 &lt;policy domain="resource" name="area" value="128MB"/&gt;
303 &lt;policy domain="resource" name="disk" value="1GiB"/&gt;
304 &lt;policy domain="resource" name="file" value="768"/&gt;
305 &lt;policy domain="resource" name="thread" value="2"/&gt;
306 &lt;policy domain="resource" name="throttle" value="0"/&gt;
307 &lt;policy domain="resource" name="time" value="120"/&gt;
308 &lt;policy domain="system" name="precision" value="6"/&gt;
309 &lt;policy domain="cache" name="shared-secret" value="********"/&gt;
310&lt;/policymap&gt;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]311</pre>
312<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]313
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]314<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]315
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]316<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>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]317<pre>-&gt; convert -debug cache logo: -sharpen 3x2 null:
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]3182013-12-17T13:33:42-05:00 0:00.000 0.000u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]319 destroy
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]3202013-12-17T13:33:42-05:00 0:00.000 0.000u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]321 open LOGO[0] (Heap Memory, 640x480x4 4.688MiB)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]3222013-12-17T13:33:42-05:00 0:00.010 0.000u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]323 open LOGO[0] (Heap Memory, 640x480x3 3.516MiB)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]3242013-12-17T13:33:42-05:00 0:00.010 0.000u 7.0.0 Cache convert: cache.c/ClonePixelCachePixels/1044/Cache
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]325 Memory =&gt; Memory
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]3262013-12-17T13:33:42-05:00 0:00.020 0.010u 7.0.0 Cache convert: cache.c/ClonePixelCachePixels/1044/Cache
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]327 Memory =&gt; Memory
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]3282013-12-17T13:33:42-05:00 0:00.020 0.010u 7.0.0 Cache convert: cache.c/OpenPixelCache/3834/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]329 open LOGO[0] (Heap Memory, 640x480x3 3.516MiB)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]3302013-12-17T13:33:42-05:00 0:00.050 0.100u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]331 destroy LOGO[0]
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]3322013-12-17T13:33:42-05:00 0:00.050 0.100u 7.0.0 Cache convert: cache.c/DestroyPixelCache/1275/Cache
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]333 destroy LOGO[0]
334</pre>
335<p>This command utilizes a pixel cache in memory. The logo consumed 4.688MiB and after it was sharpened, 3.516MiB.</p>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]336
337
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame]338<h3>Distributed Pixel Cache</h3>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]339<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]340
341<h3>Cache Views</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]342
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]343<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 <var>cache view</var>. A cache view permits you to access as many areas simultaneously in the pixel cache as you require. The cache view <a href="http://www.imagemagick.org/ImageMagick-7.0.0/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]344
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]345<pre class="pre-scrollable">CacheView
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]346 *view_1,
347 *view_2;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]348
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]349view_1=AcquireVirtualCacheView(source,exception);
350view_2=AcquireVirtualCacheView(source,exception);
351for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
352{
353 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]354 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,exception);
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]355 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
356 break;
357 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]358 {
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]359 /* do something with u &amp; v here */
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]360 }
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]361}
362view_2=DestroyCacheView(view_2);
363view_1=DestroyCacheView(view_1);
364if (y &lt; (ssize_t) source-&gt;rows)
365 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]366</pre>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]367
368<h3>Magick Persistent Cache Format</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]369
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]370<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]371<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]372
373<h3>Best Practices</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]374
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]375<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]376
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]377<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>
378
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]379<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>
380
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]381<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]382
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]383<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]384
385<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>
386
387<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>
388
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]389<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]390
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]391<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]392
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]393<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 conserve memory with these options:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]394
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]395<pre>
396convert -limit memory 2GB -limit map 4GB -define registry:temporary-path=/data/tmp ...
397</pre>
398
399<p>Set global resource limits for your environment in the <code>policy.xml</code> configuration file.</p>
400
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]401<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>
402
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]403<pre>
404convert image.tif image.mpc
405convert image.mpc -crop 100x100+0+0 +repage 1.png
406convert image.mpc -crop 100x100+100+0 +repage 2.png
407convert image.mpc -crop 100x100+200+0 +repage 3.png
408</pre>
409
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]410<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>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]411
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]412<h2 class="magick-header"><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]413
414<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>
415
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]416<p>Use <a href="http://www.imagemagick.org/ImageMagick-7.0.0/api/stream.html#ReadStream">ReadStream()</a> or <a href="http://www.imagemagick.org/ImageMagick-7.0.0/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]417
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]418<pre class="pre-scrollable">static size_t StreamPixels(const Image *image,const void *pixels,const size_t columns)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]419{
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]420 register const PixelPacket
421 *p;
422
423 MyData
424 *my_data;
425
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]426 my_data=(MyData *) image-&gt;client_data;
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]427 p=(PixelPacket *) pixels;
428 if (p != (const PixelPacket *) NULL)
429 {
430 /* process pixels here */
431 }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]432 return(columns);
433}
434
435...
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]436
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]437/* invoke the pixel stream here */
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]438image_info-&gt;client_data=(void *) MyData;
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]439image=ReadStream(image_info,&amp;StreamPixels,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]440</pre>
441
cristy751980d2012-06-03 23:18:35 +0000[diff] [blame]442<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]443
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]444<h2 class="magick-header"><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]445
446<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>
447
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]448<pre>(void) printf("image width: %lu, height: %lu\n",image-&gt;columns,image-&gt;rows);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]449</pre>
450
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]451<p>For a great majority of image properties, such as an image comment or description, we use the <a href="http://www.imagemagick.org/ImageMagick-7.0.0/api/property.html#GetImageProperty">GetImageProperty()</a> and <a href="http://www.imagemagick.org/ImageMagick-7.0.0/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]452
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]453<pre>const char
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]454 *comment;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]455
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]456(void) SetImageProperty(image,"comment","This space for rent");
457comment=GetImageProperty(image,"comment");
458if (comment == (const char *) NULL)
459 (void) printf("Image comment: %s\n",comment);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]460</pre>
461
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]462<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]463
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]464<p>Image profiles are handled with <a href="http://www.imagemagick.org/ImageMagick-7.0.0/api/profile.html#GetImageProfile">GetImageProfile()</a>, <a href="http://www.imagemagick.org/ImageMagick-7.0.0/api/profile.html#SetImageProfile">SetImageProfile()</a>, and <a href="http://www.imagemagick.org/ImageMagick-7.0.0/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]465
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]466<pre>StringInfo
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]467 *profile;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]468
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]469profile=AcquireStringInfo(length);
470SetStringInfoDatum(profile,my_exif_profile);
471(void) SetImageProfile(image,"EXIF",profile);
472DestroyStringInfo(profile);
473profile=GetImageProfile(image,"EXIF");
474if (profile != (StringInfo *) NULL)
475 (void) PrintStringInfo(stdout,"EXIF",profile);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]476</pre>
477
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]478<h2 class="magick-header"><a id="tera-pixel"></a>Large Image Support</h2>
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]479<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]480
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]481<pre>
482convert logo: -resize 250000x250000 logo.miff
483</pre>
484
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]485<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]486
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]487<pre>
488convert -define registry:temporary-path=/data/tmp logo: \ <br> -resize 250000x250000 logo.miff
489</pre>
490
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]491<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>
492
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]493<pre>
494convert -define registry:temporary-path=/data/tmp -limit memory 16mb \
495 logo: -resize 250000x250000 logo.miff
496</pre>
497
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]498<p>Here we force all image pixels to disk:</p>
499
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]500<pre>
501convert -define registry:temporary-path=/data/tmp -limit area 0 \
502 logo: -resize 250000x250000 logo.miff
503</pre>
504
cristybac7a162010-06-15 19:57:29 +0000[diff] [blame]505<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]506
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]507<pre>convert -monitor -limit memory 2GiB -limit map 4GiB -define registry:temporary-path=/data/tmp \
508 logo: -resize 250000x250000 logo.miff
509</pre>
510
511<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>
512<pre>
cristyac1b4322013-07-28 13:58:06 +0000[diff] [blame]513convert -distribute-cache 6668 &amp; // start on 192.168.100.50
514convert -distribute-cache 6668 &amp; // start on 192.168.100.51
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]515convert -limit memory 2mb -limit map 2mb -limit disk 2gb \
516 -define registry:cache:hosts=192.168.100.50:6668,192.168.100.51:6668 \
517 myhugeimage.jpg -sharpen 5x2 myhugeimage.png
518</pre>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]519
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]520<h2 class="magick-header"><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]521
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]522<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="http://www.imagemagick.org/ImageMagick-7.0.0/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]523
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]524<p>Here is an MagickCore code snippet that takes advantage of threads of execution with the <a href="openmp.html">OpenMP</a> programming paradigm:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]525
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]526<pre class="pre-scrollable">CacheView
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]527 *image_view;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]528
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]529MagickBooleanType
530 status;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]531
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]532ssize_t
533 y;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]534
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]535status=MagickTrue;
536image_view=AcquireVirtualCacheView(image,exception);
537#pragma omp parallel for schedule(dynamic,4) shared(status)
538for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
539{
540 register IndexPacket
541 *indexes;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]542
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]543 register PixelPacket
544 *q;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]545
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]546 register ssize_t
547 x;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]548
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]549 if (status == MagickFalse)
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]550 continue;
551 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
552 if (q == (PixelPacket *) NULL)
553 {
554 status=MagickFalse;
555 continue;
556 }
557 indexes=GetCacheViewAuthenticIndexQueue(image_view);
558 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
559 {
560 SetPixelRed(q,...);
561 SetPixelGreen(q,...);
562 SetPixelBlue(q,...);
563 SetPixelOpacity(q,...);
564 if (indexes != (IndexPacket *) NULL)
565 SetPixelIndex(indexes+x,...);
566 q++;
567 }
568 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
569 status=MagickFalse;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]570}
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]571image_view=DestroyCacheView(image_view);
572if (status == MagickFalse)
573 perror("something went wrong");
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]574</pre>
575
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]576<p>This code snippet converts an uncompressed Windows bitmap to a Magick++ image:</p>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]577
578<pre class="pre-scrollable">#include "Magick++.h"
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]579#include &lt;assert.h&gt;
580#include "omp.h"
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]581
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]582void ConvertBMPToImage(const BITMAPINFOHEADER *bmp_info,
583 const unsigned char *restrict pixels,Magick::Image *image)
584{
585 /*
586 Prepare the image so that we can modify the pixels directly.
587 */
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]588 assert(bmp_info-&gt;biCompression == BI_RGB);
589 assert(bmp_info-&gt;biWidth == image-&gt;columns());
590 assert(abs(bmp_info-&gt;biHeight) == image-&gt;rows());
591 image-&gt;modifyImage();
592 if (bmp_info-&gt;biBitCount == 24)
593 image-&gt;type(MagickCore::TrueColorType);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]594 else
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]595 image-&gt;type(MagickCore::TrueColorMatteType);
596 register unsigned int bytes_per_row=bmp_info-&gt;biWidth*bmp_info-&gt;biBitCount/8;
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]597 if (bytes_per_row % 4 != 0) {
598 bytes_per_row=bytes_per_row+(4-bytes_per_row % 4); // divisible by 4.
599 }
600 /*
601 Copy all pixel data, row by row.
602 */
603 #pragma omp parallel for
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]604 for (int y=0; y &lt; int(image-&gt;rows()); y++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]605 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]606 int
607 row;
608
609 register const unsigned char
610 *restrict p;
611
612 register MagickCore::PixelPacket
613 *restrict q;
614
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]615 row=(bmp_info-&gt;biHeight &gt; 0) ? (image-&gt;rows()-y-1) : y;
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]616 p=pixels+row*bytes_per_row;
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]617 q=image-&gt;setPixels(0,y,image-&gt;columns(),1);
618 for (int x=0; x &lt; int(image-&gt;columns()); x++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]619 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]620 SetPixelBlue(q,p[0]);
621 SetPixelGreen(q,p[1]);
622 SetPixelRed(q,p[2]);
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]623 if (bmp_info-&gt;biBitCount == 32) {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]624 SetPixelOpacity(q,p[3]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]625 }
626 q++;
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]627 p+=bmp_info-&gt;biBitCount/8;
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]628 }
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]629 image-&gt;syncPixels(); // sync pixels to pixel cache.
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]630 }
631 return;
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]632}</pre>
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]633
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]634<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 <var>before</var> you call the API otherwise ImageMagick may fault.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]635
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]636<p><a href="http://www.imagemagick.org/ImageMagick-7.0.0/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="http://www.imagemagick.org/ImageMagick-7.0.0/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]637
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]638<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]639
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]640<pre>
641&lt;policy domain="resource" name="thread" value="2"/&gt;
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]642</pre>
643
644<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>
645
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]646<pre>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]647export MAGICK_THREAD_LIMIT=12
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]648</pre>
649
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]650<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]651
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]652<h4>Threading Performance</h4>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]653<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>
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]654<pre>
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]655convert -bench 10 model.png -sharpen 5x2 null:
656Performance[1]: 10i 1.135ips 1.000e 8.760u 0:08.810
657Performance[2]: 10i 2.020ips 0.640e 9.190u 0:04.950
658Performance[3]: 10i 2.786ips 0.710e 9.400u 0:03.590
659Performance[4]: 10i 3.378ips 0.749e 9.580u 0:02.960
660Performance[5]: 10i 4.032ips 0.780e 9.580u 0:02.480
661Performance[6]: 10i 4.566ips 0.801e 9.640u 0:02.190
662Performance[7]: 10i 3.788ips 0.769e 10.980u 0:02.640
663Performance[8]: 10i 4.115ips 0.784e 12.030u 0:02.430
664Performance[9]: 10i 4.484ips 0.798e 12.860u 0:02.230
665Performance[10]: 10i 4.274ips 0.790e 14.830u 0:02.340
666Performance[11]: 10i 4.348ips 0.793e 16.500u 0:02.300
667Performance[12]: 10i 4.525ips 0.799e 18.320u 0:02.210
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]668</pre>
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]669<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]670<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]671
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]672<h2 class="magick-header"><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]673<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>
674
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]675<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]676
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]677<pre>
678identify -version
679Features: OpenMP OpenCL
680</pre>
681
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]682<p>If so, run this command to realize a significant speed-up for image convolution:</p>
683
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]684<pre>
685convert image.png -convolve '-1, -1, -1, -1, 9, -1, -1, -1, -1' convolve.png
686</pre>
687
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]688<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
689
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]690<p>Here is an example OpenCL kernel that convolves an image:</p>
691
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]692<pre class="pre-scrollable">static inline long ClampToCanvas(const long offset,const ulong range)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]693{
694 if (offset &lt; 0L)
695 return(0L);
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]696 if (offset &gt;= range)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]697 return((long) (range-1L));
698 return(offset);
699}
700
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]701static inline CLQuantum ClampToQuantum(const float value)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]702{
703 if (value &lt; 0.0)
704 return((CLQuantum) 0);
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]705 if (value &gt;= (float) QuantumRange)
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]706 return((CLQuantum) QuantumRange);
707 return((CLQuantum) (value+0.5));
708}
709
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]710__kernel void Convolve(const __global CLPixelType *source,__constant float *filter,
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]711 const ulong width,const ulong height,__global CLPixelType *destination)
712{
713 const ulong columns = get_global_size(0);
714 const ulong rows = get_global_size(1);
715
716 const long x = get_global_id(0);
717 const long y = get_global_id(1);
718
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]719 const float scale = (1.0/QuantumRange);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]720 const long mid_width = (width-1)/2;
721 const long mid_height = (height-1)/2;
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]722 float4 sum = { 0.0, 0.0, 0.0, 0.0 };
723 float gamma = 0.0;
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]724 register ulong i = 0;
725
726 for (long v=(-mid_height); v &lt;= mid_height; v++)
727 {
728 for (long u=(-mid_width); u &lt;= mid_width; u++)
729 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]730 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
731 columns);
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]732 const float alpha=scale*(QuantumRange-source[index].w);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]733 sum.x+=alpha*filter[i]*source[index].x;
734 sum.y+=alpha*filter[i]*source[index].y;
735 sum.z+=alpha*filter[i]*source[index].z;
736 sum.w+=filter[i]*source[index].w;
737 gamma+=alpha*filter[i];
738 i++;
739 }
740 }
741
742 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
743 const ulong index=y*columns+x;
744 destination[index].x=ClampToQuantum(gamma*sum.x);
745 destination[index].y=ClampToQuantum(gamma*sum.y);
746 destination[index].z=ClampToQuantum(gamma*sum.z);
747 destination[index].w=ClampToQuantum(sum.w);
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]748};</pre>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]749
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]750<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]751
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]752<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>
753
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]754<h2 class="magick-header"><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]755
756<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>
757
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]758<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]759
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]760<pre class="pre-scrollable">/*
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]761 Include declarations.
762*/
763#include "magick/studio.h"
764#include "magick/blob.h"
765#include "magick/blob-private.h"
766#include "magick/colorspace.h"
767#include "magick/exception.h"
768#include "magick/exception-private.h"
769#include "magick/image.h"
770#include "magick/image-private.h"
771#include "magick/list.h"
772#include "magick/magick.h"
773#include "magick/memory_.h"
774#include "magick/monitor.h"
775#include "magick/monitor-private.h"
776#include "magick/quantum-private.h"
777#include "magick/static.h"
778#include "magick/string_.h"
779#include "magick/module.h"
780
781/*
782 Forward declarations.
783*/
784static MagickBooleanType
785 WriteMGKImage(const ImageInfo *,Image *);
786
787/*
788%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
789% %
790% %
791% %
792% I s M G K %
793% %
794% %
795% %
796%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
797%
798% IsMGK() returns MagickTrue if the image format type, identified by the
799% magick string, is MGK.
800%
801% The format of the IsMGK method is:
802%
803% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
804%
805% A description of each parameter follows:
806%
807% o magick: This string is generally the first few bytes of an image file
808% or blob.
809%
810% o length: Specifies the length of the magick string.
811%
812*/
813static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
814{
815 if (length &lt; 7)
816 return(MagickFalse);
817 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
818 return(MagickTrue);
819 return(MagickFalse);
820}
821
822/*
823%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
824% %
825% %
826% %
827% R e a d M G K I m a g e %
828% %
829% %
830% %
831%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
832%
833% ReadMGKImage() reads a MGK image file and returns it. It allocates
834% the memory necessary for the new Image structure and returns a pointer to
835% the new image.
836%
837% The format of the ReadMGKImage method is:
838%
839% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
840%
841% A description of each parameter follows:
842%
843% o image_info: the image info.
844%
845% o exception: return any errors or warnings in this structure.
846%
847*/
848static Image *ReadMGKImage(const ImageInfo *image_info,
849 ExceptionInfo *exception)
850{
851 char
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]852 buffer[MaxTextExtent];
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]853
854 Image
855 *image;
856
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]857 MagickBooleanType
858 status;
859
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]860 register PixelPacket
861 *q;
862
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]863 register size_t
864 x;
865
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]866 register unsigned char
867 *p;
868
869 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]870 count,
871 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]872
873 unsigned char
874 *pixels;
875
876 unsigned long
877 columns,
878 rows;
879
880 /*
881 Open image file.
882 */
883 assert(image_info != (const ImageInfo *) NULL);
884 assert(image_info-&gt;signature == MagickSignature);
885 if (image_info-&gt;debug != MagickFalse)
886 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
887 assert(exception != (ExceptionInfo *) NULL);
888 assert(exception-&gt;signature == MagickSignature);
889 image=AcquireImage(image_info);
890 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
891 if (status == MagickFalse)
892 {
893 image=DestroyImageList(image);
894 return((Image *) NULL);
895 }
896 /*
897 Read MGK image.
898 */
899 (void) ReadBlobString(image,buffer); /* read magic number */
900 if (IsMGK(buffer,7) == MagickFalse)
901 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
902 (void) ReadBlobString(image,buffer);
903 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
904 if (count &lt;= 0)
905 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
906 do
907 {
908 /*
909 Initialize image structure.
910 */
911 image-&gt;columns=columns;
912 image-&gt;rows=rows;
913 image-&gt;depth=8;
914 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]915 if (image-&gt;scene &gt;= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]916 break;
917 /*
918 Convert MGK raster image to pixel packets.
919 */
920 if (SetImageExtent(image,0,0) == MagickFalse)
921 {
922 InheritException(exception,&amp;image-&gt;exception);
923 return(DestroyImageList(image));
924 }
925 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
926 if (pixels == (unsigned char *) NULL)
927 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]928 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]929 {
930 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
931 if (count != (ssize_t) (3*image-&gt;columns))
932 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
933 p=pixels;
934 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
935 if (q == (PixelPacket *) NULL)
936 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]937 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]938 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]939 SetPixelRed(q,ScaleCharToQuantum(*p++));
940 SetPixelGreen(q,ScaleCharToQuantum(*p++));
941 SetPixelBlue(q,ScaleCharToQuantum(*p++));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]942 q++;
943 }
944 if (SyncAuthenticPixels(image,exception) == MagickFalse)
945 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]946 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]947 (SetImageProgress(image,LoadImageTag,y,image&gt;&gt;rows) == MagickFalse))
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]948 break;
949 }
950 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
951 if (EOFBlob(image) != MagickFalse)
952 {
953 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
954 break;
955 }
956 /*
957 Proceed to next image.
958 */
959 if (image_info-&gt;number_scenes != 0)
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]960 if (image-&gt;scene &gt;= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]961 break;
962 *buffer='\0';
963 (void) ReadBlobString(image,buffer);
964 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
965 if (count != 0)
966 {
967 /*
968 Allocate next image structure.
969 */
970 AcquireNextImage(image_info,image);
971 if (GetNextImageInList(image) == (Image *) NULL)
972 {
973 image=DestroyImageList(image);
974 return((Image *) NULL);
975 }
976 image=SyncNextImageInList(image);
977 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
978 if (status == MagickFalse)
979 break;
980 }
981 } while (count != 0);
982 (void) CloseBlob(image);
983 return(GetFirstImageInList(image));
984}
985
986/*
987%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
988% %
989% %
990% %
991% R e g i s t e r M G K I m a g e %
992% %
993% %
994% %
995%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
996%
997% RegisterMGKImage() adds attributes for the MGK image format to
998% the list of supported formats. The attributes include the image format
999% tag, a method to read and/or write the format, whether the format
1000% supports the saving of more than one frame to the same file or blob,
1001% whether the format supports native in-memory I/O, and a brief
1002% description of the format.
1003%
1004% The format of the RegisterMGKImage method is:
1005%
1006% unsigned long RegisterMGKImage(void)
1007%
1008*/
1009ModuleExport unsigned long RegisterMGKImage(void)
1010{
1011 MagickInfo
1012 *entry;
1013
1014 entry=SetMagickInfo("MGK");
1015 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
1016 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
1017 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
1018 entry-&gt;description=ConstantString("MGK");
1019 entry-&gt;module=ConstantString("MGK");
1020 (void) RegisterMagickInfo(entry);
1021 return(MagickImageCoderSignature);
1022}
1023
1024/*
1025%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1026% %
1027% %
1028% %
1029% U n r e g i s t e r M G K I m a g e %
1030% %
1031% %
1032% %
1033%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1034%
1035% UnregisterMGKImage() removes format registrations made by the
1036% MGK module from the list of supported formats.
1037%
1038% The format of the UnregisterMGKImage method is:
1039%
1040% UnregisterMGKImage(void)
1041%
1042*/
1043ModuleExport void UnregisterMGKImage(void)
1044{
1045 (void) UnregisterMagickInfo("MGK");
1046}
1047
1048/*
1049%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1050% %
1051% %
1052% %
1053% W r i t e M G K I m a g e %
1054% %
1055% %
1056% %
1057%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1058%
1059% WriteMGKImage() writes an image to a file in red, green, and blue
1060% MGK rasterfile format.
1061%
1062% The format of the WriteMGKImage method is:
1063%
1064% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1065%
1066% A description of each parameter follows.
1067%
1068% o image_info: the image info.
1069%
1070% o image: The image.
1071%
1072*/
1073static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1074{
1075 char
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1076 buffer[MaxTextExtent];
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1077
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1078 MagickBooleanType
1079 status;
1080
1081 MagickOffsetType
1082 scene;
1083
1084 register const PixelPacket
1085 *p;
1086
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1087 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1088 x;
1089
1090 register unsigned char
1091 *q;
1092
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1093 ssize_t
1094 y;
1095
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1096 unsigned char
1097 *pixels;
1098
1099 /*
1100 Open output image file.
1101 */
1102 assert(image_info != (const ImageInfo *) NULL);
1103 assert(image_info-&gt;signature == MagickSignature);
1104 assert(image != (Image *) NULL);
1105 assert(image-&gt;signature == MagickSignature);
1106 if (image-&gt;debug != MagickFalse)
1107 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1108 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1109 if (status == MagickFalse)
1110 return(status);
1111 scene=0;
1112 do
1113 {
1114 /*
1115 Allocate memory for pixels.
1116 */
1117 if (image-&gt;colorspace != RGBColorspace)
1118 (void) SetImageColorspace(image,RGBColorspace);
1119 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1120 3UL*sizeof(*pixels));
1121 if (pixels == (unsigned char *) NULL)
1122 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1123 /*
1124 Initialize raster file header.
1125 */
1126 (void) WriteBlobString(image,"id=mgk\n");
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1127 (void) FormatLocaleString(buffer,MaxTextExtent,"%lu %lu\n",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1128 image-&gt;columns,image-&gt;rows);
1129 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1130 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1131 {
1132 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1133 if (p == (const PixelPacket *) NULL)
1134 break;
1135 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1136 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1137 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1138 *q++=ScaleQuantumToChar(GetPixelRed(p));
1139 *q++=ScaleQuantumToChar(GetPixelGreen(p));
1140 *q++=ScaleQuantumToChar(GetPixelBlue(p));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1141 p++;
1142 }
1143 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1144 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1145 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1146 break;
1147 }
1148 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1149 if (GetNextImageInList(image) == (Image *) NULL)
1150 break;
1151 image=SyncNextImageInList(image);
1152 status=SetImageProgress(image,SaveImagesTag,scene,
1153 GetImageListLength(image));
1154 if (status == MagickFalse)
1155 break;
1156 scene++;
1157 } while (image_info-&gt;adjoin != MagickFalse);
1158 (void) CloseBlob(image);
1159 return(MagickTrue);
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1160}</pre>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1161
1162<p>To invoke the custom coder from the command line, use these commands:</p>
1163
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1164<pre>convert logo: logo.mgk
1165display logo.mgk
1166</pre>
1167
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1168<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]1169
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1170<h2 class="magick-header"><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1171
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1172<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="http://www.imagemagick.org/ImageMagick-7.0.0/api/module.html#ExecuteModuleProcess">ExecuteModuleProcess()</a>.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1173
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1174<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]1175
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1176<pre class="pre-scrollable">#include &lt;stdio.h&gt;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1177#include &lt;stdlib.h&gt;
1178#include &lt;string.h&gt;
1179#include &lt;time.h&gt;
1180#include &lt;assert.h&gt;
1181#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1182#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1183
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1184/*
1185%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1186% %
1187% %
1188% %
1189% a n a l y z e I m a g e %
1190% %
1191% %
1192% %
1193%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1194%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1195% analyzeImage() computes the brightness and saturation mean, standard
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]1196% deviation, kurtosis and skewness and stores these values as attributes
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1197% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1198%
1199% The format of the analyzeImage method is:
1200%
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1201% size_t analyzeImage(Image *images,const int argc,char **argv,
1202% ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1203%
1204% A description of each parameter follows:
1205%
1206% o image: the address of a structure of type Image.
1207%
1208% o argc: Specifies a pointer to an integer describing the number of
1209% elements in the argument vector.
1210%
1211% o argv: Specifies a pointer to a text array containing the command line
1212% arguments.
1213%
1214% o exception: return any errors or warnings in this structure.
1215%
1216*/
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1217ModuleExport size_t analyzeImage(Image **images,const int argc,const char **argv,
1218 ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1219{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1220 char
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1221 text[MaxTextExtent];
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1222
1223 double
1224 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1225 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1226 brightness_mean,
1227 brightness_standard_deviation,
1228 brightness_kurtosis,
1229 brightness_skewness,
1230 brightness_sum_x,
1231 brightness_sum_x2,
1232 brightness_sum_x3,
1233 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1234 hue,
1235 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1236 saturation_mean,
1237 saturation_standard_deviation,
1238 saturation_kurtosis,
1239 saturation_skewness,
1240 saturation_sum_x,
1241 saturation_sum_x2,
1242 saturation_sum_x3,
1243 saturation_sum_x4;
1244
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1245 Image
1246 *image;
1247
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1248 assert(images != (Image **) NULL);
1249 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1250 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1251 (void) argc;
1252 (void) argv;
1253 image=(*images);
1254 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1255 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1256 CacheView
1257 *image_view;
1258
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1259 MagickBooleanType
1260 status;
1261
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1262 ssize_t
1263 y;
1264
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1265 brightness_sum_x=0.0;
1266 brightness_sum_x2=0.0;
1267 brightness_sum_x3=0.0;
1268 brightness_sum_x4=0.0;
1269 brightness_mean=0.0;
1270 brightness_standard_deviation=0.0;
1271 brightness_kurtosis=0.0;
1272 brightness_skewness=0.0;
1273 saturation_sum_x=0.0;
1274 saturation_sum_x2=0.0;
1275 saturation_sum_x3=0.0;
1276 saturation_sum_x4=0.0;
1277 saturation_mean=0.0;
1278 saturation_standard_deviation=0.0;
1279 saturation_kurtosis=0.0;
1280 saturation_skewness=0.0;
1281 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1282 status=MagickTrue;
cristy8ee7f242013-06-20 16:08:44 +0000[diff] [blame]1283 image_view=AcquireVirtualCacheView(image,exception);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1284#if defined(MAGICKCORE_OPENMP_SUPPORT)
1285 #pragma omp parallel for schedule(dynamic,4) shared(status)
1286#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1287 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1288 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1289 register const PixelPacket
1290 *p;
1291
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1292 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1293 x;
1294
1295 if (status == MagickFalse)
1296 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1297 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1298 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1299 {
1300 status=MagickFalse;
1301 continue;
1302 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1303 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1304 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1305 ConvertRGBToHSB(GetPixelRed(p),GetPixelGreen(p),GetPixelBue(p),&amp;hue,&amp;saturation,&amp;brightness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1306 brightness*=QuantumRange;
1307 brightness_sum_x+=brightness;
1308 brightness_sum_x2+=brightness*brightness;
1309 brightness_sum_x3+=brightness*brightness*brightness;
1310 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1311 saturation*=QuantumRange;
1312 saturation_sum_x+=saturation;
1313 saturation_sum_x2+=saturation*saturation;
1314 saturation_sum_x3+=saturation*saturation*saturation;
1315 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1316 area++;
1317 p++;
1318 }
1319 }
1320 image_view=DestroyCacheView(image_view);
1321 if (area &lt;= 0.0)
1322 break;
1323 brightness_mean=brightness_sum_x/area;
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1324 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_mean);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1325 (void) SetImageProperty(image,"filter:brightness:mean",text);
1326 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1327 area*brightness_sum_x/area));
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1328 (void) FormatLocaleString(text,MaxTextExtent,"%g",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1329 brightness_standard_deviation);
1330 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1331 if (brightness_standard_deviation != 0)
1332 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1333 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1334 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1335 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1336 brightness_standard_deviation*brightness_standard_deviation*
1337 brightness_standard_deviation)-3.0;
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1338 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_kurtosis);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1339 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1340 if (brightness_standard_deviation != 0)
1341 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1342 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1343 brightness_mean)/(brightness_standard_deviation*
1344 brightness_standard_deviation*brightness_standard_deviation);
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1345 (void) FormatLocaleString(text,MaxTextExtent,"%g",brightness_skewness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1346 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1347 saturation_mean=saturation_sum_x/area;
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1348 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_mean);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1349 (void) SetImageProperty(image,"filter:saturation:mean",text);
1350 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1351 area*saturation_sum_x/area));
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1352 (void) FormatLocaleString(text,MaxTextExtent,"%g",
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1353 saturation_standard_deviation);
1354 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1355 if (saturation_standard_deviation != 0)
1356 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1357 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1358 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1359 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1360 saturation_standard_deviation*saturation_standard_deviation*
1361 saturation_standard_deviation)-3.0;
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1362 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_kurtosis);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1363 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1364 if (saturation_standard_deviation != 0)
1365 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1366 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1367 saturation_mean)/(saturation_standard_deviation*
1368 saturation_standard_deviation*saturation_standard_deviation);
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1369 (void) FormatLocaleString(text,MaxTextExtent,"%g",saturation_skewness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1370 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1371 }
1372 return(MagickImageFilterSignature);
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1373}</pre>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1374
1375<p>To invoke the custom filter from the command line, use this command:</p>
1376
cristyd2432012015-05-04 23:15:15 +0000[diff] [blame]1377<pre>convert logo: -process \"analyze\" -verbose info:
1378 Image: logo:
1379 Format: LOGO (ImageMagick Logo)
1380 Class: PseudoClass
1381 Geometry: 640x480
1382 ...
1383 filter:brightness:kurtosis: 8.17947
1384 filter:brightness:mean: 60632.1
1385 filter:brightness:skewness: -2.97118
1386 filter:brightness:standard-deviation: 13742.1
1387 filter:saturation:kurtosis: 4.33554
1388 filter:saturation:mean: 5951.55
1389 filter:saturation:skewness: 2.42848
1390 filter:saturation:standard-deviation: 15575.9
1391</pre>
1392
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1393
cristy91469932014-07-25 11:00:25 +0000[diff] [blame]1394<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]1395
1396</div>
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