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171
172<div class="main">
173
174
175
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]176<h1>The <em>Magick</em> Behind ImageMagick</h1>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]177<p class="navigation-index">[<a href="#overview">Architecture Overview</a> &bull; <a href="#cache">The Pixel Cache</a> &bull; <a href="#stream">Streaming Pixels</a> &bull; <a href="#properties">Image Properties and Profiles</a> &bull; <a href="#tera-pixel">Large Image Support</a> &bull; <a href="#threads">Threads of Execution</a> &bull; <a href="#distributed">Heterogeneous Distributed Processing</a> &bull; <a href="#coders">Custom Image Coders</a> &bull; <a href="#filters">Custom Image Filters</a>]</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]178
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]179
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]180<div class="doc-section">
181<p>The citizens of Oz were quite content with their benefactor, the all-powerful Wizard. They accepted his wisdom and benevolence without ever questioning the who, why, and where of his power. Like the citizens of Oz, if you feel comfortable that ImageMagick can help you convert, edit, or compose your images without knowing what goes on behind the curtain, feel free to skip this section. However, if you want to know more about the software and algorithms behind ImageMagick, read on. To fully benefit from this discussion, you should be comfortable with image nomenclature and be familiar with computer programming.</p>
182</div>
183
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]184<h2><a id="overview"></a>Architecture Overview</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]185<div class="doc-section">
186
187<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>
188
189<ul>
190 <li>colorspace (e.g RGB, CMYK, YUV, Lab, etc.)</li>
191 <li>bit depth (.e.g 1, 4, 8, 12, 16, etc.)</li>
192 <li>storage format (e.g. unsigned, signed, float, double, etc.)</li>
193 <li>compression (e.g. uncompressed, RLE, Zip, BZip, etc.)</li>
194 <li>orientation (i.e. top-to-bottom, right-to-left, etc.),</li>
195 <li>layout (.e.g. raw, interspersed with opcodes, etc.)</li>
196</ul>
197
198<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>
199
200<p>An efficient implementation of an image processing algorithm may require we get or set:</p>
201
202<ul>
203 <li>one pixel a time (e.g. pixel at location 10,3)</li>
204 <li>a single scanline (e.g. all pixels from row 4)</li>
205 <li>a few scanlines at once (e.g. pixel rows 4-7)</li>
206 <li>a single column or columns of pixels (e.g. all pixels from column 11)</li>
207 <li>an arbitrary region of pixels from the image (e.g. pixels defined at 10,7 to 10,19)</li>
208 <li>a pixel in random order (e.g. pixel at 14,15 and 640,480)</li>
209 <li>pixels from two different images (e.g. pixel at 5,1 from image 1 and pixel at 5,1 from image 2)</li>
210 <li>pixels outside the boundaries of the image (e.g. pixel at -1,-3)</li>
211 <li>a pixel component that is unsigned or in a floating-point representation (e.g. 0.17836)</li>
212 <li>a high-dynamic range pixel that can include negative values as well as values that exceed the quantum depth (e.g. -0.00716)</li>
213 <li>one or more pixels simultaneously in different threads of execution</li>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]214 <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]215</ul>
216
217<p>In addition, some images include a clip mask that define which pixels are eligible to be updated. Pixels outside the area defined by the clip mask remain untouched.</p>
218
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]219<p>Given the varied image formats and image processing requirements, we implemented the ImageMagick <a href="#cache">pixel cache</a> to provide convenient sequential or parallel access to any pixel on demand anywhere inside the image region (we call these <a href="#authentic-pixels">authentic pixels</a>) and from any image in a sequence. In addition, the pixel cache permits access to pixels outside the boundaries defined by the image (we call these <a href="#virtual-pixels">virtual pixels</a>).</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]220
cristy320dd6e2010-04-16 20:11:40 +0000[diff] [blame]221<p>In addition to pixels, images have a plethora of <a href="#properties">image properties and profiles</a>. Properties include the well known attributes such as width, height, depth, and colorspace. An image may have optional properties which might include the image author, a comment, a create date, and others. Some images also include profiles for color management, or EXIF, IPTC, 8BIM, or XMP informational profiles. ImageMagick provides command line options and programming methods to get, set, or view image properties or profiles or apply profiles.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]222
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]223<p>ImageMagick consists of more than 400,000 lines of C code and optionally depends on several million lines of code in dependent libraries (e.g. JPEG, PNG, TIFF libraries). Given that, one might expect a huge architecture document. However, a great majority of image processing is simply accessing pixels and its metadata and our simple and elegant implementation makes this easy for the ImageMagick developer. We discuss the implementation of the pixel cache and getting and setting image properties and profiles in the next few sections. Next, we discuss using ImageMagick within a <a href="#threads">thread</a> of execution. In the final sections, we discuss <a href="#coders">image coders</a> to read or write a particular image format followed by a few words on creating a <a href="#filters">filter</a> to access or update pixels based on your custom requirements.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]224
225</div>
226
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]227<h2><a id="cache"></a>The Pixel Cache</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]228<div class="doc-section">
229
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]230<p>The ImageMagick pixel cache is a repository for image pixels with up to 5 channels. The first 4 channels are stored contiguously and an optional second area follows with 1 channel. The channels are at the depth specified when ImageMagick was built. The channel depths are 8 bits-per-pixel component for the Q8 version of ImageMagick, 16 bits-per-pixel component for the Q16 version, and 32 bits-per-pixel component for the Q32 version. By default pixel components are unsigned quantities, however, if you use the <a href="../www/high-dynamic-range.html">high dynamic-range</a> version of ImageMagick, the components are 32-bit floating point. The primary 4 channels can hold any value but typically contain red, green, blue, and alpha intensities or cyan, magenta, yellow, and alpha intensities. The optional fifth channel contains the colormap indexes for colormapped images or the black channel for CMYK images. The pixel cache storage may be heap memory, anonymous memory mapped memory, disk-backed memory mapped, or on disk. The pixel cache is reference-counted. Only the cache properties are copied when the cache is cloned. The cache pixels are subsequently copied only when you signal your intention to update any of the pixels.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]231
232<h3>Create the Pixel Cache</h3>
233<div class="doc-section">
234
235<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>
236
237<h4>Create an image canvas initialized to the background color:</h4>
238<p class="code">
239 image=AllocateImage(image_info);
240 if (SetImageExtent(image,640,480) == MagickFalse)
241 { /* an exception was thrown */ }
242 (void) QueryMagickColor("red",&amp;image-&gt;background_color,&amp;image-&gt;exception);
243 SetImageBackgroundColor(image);
244</p>
245
246<h4>Create an image from a JPEG image on disk:</h4>
247<p class="code"> (void) strcpy(image_info-&gt;filename,"image.jpg"):
248 image=ReadImage(image_info,exception);
249 if (image == (Image *) NULL)
250 { /* an exception was thrown */ }
251</p>
252<h4>Create an image from a memory based image:</h4>
253<p class="code">
254 image=BlobToImage(blob_info,blob,extent,exception);
255 if (image == (Image *) NULL)
256 { /* an exception was thrown */ }
257</p>
258
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]259<p>In our discussion of the pixel cache, we use the <a href="../www/magick-core.html">MagickCore API</a> to illustrate our points, however, the principles are the same for other program interfaces to ImageMagick.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]260
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]261<p>When the pixel cache is initialized, pixels are scaled from whatever bit depth they originated from to that required by the pixel cache. For example, a 1-channel 1-bit monochrome PBM image is scaled to a 4 channel 8-bit RGBA image, if you are using the Q8 version of ImageMagick, and 16-bit RGBA for the Q16 version. You can determine which version you have with the <a href="../www/command-line-options.html#version">&#x2011;version</a> option: </p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]262
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]263<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Version: ImageMagick 6.6.6-8 2010-12-25 Q16 http://www.imagemagick.org</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]264<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]265</div>
266
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]267<h3><a id="authentic-pixels"></a>Access the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]268<div class="doc-section">
269
270<p>Once the pixel cache is associated with an image, you typically want to get, update, or put pixels into it. We refer to pixels inside the image region as <em>authentic pixels</em> and outside the region as <em>virtual pixels</em>. Use these methods to access the pixels in the cache:</p>
271<ul>
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]272 <li><a href="../www/api/cache.html#GetVirtualPixels">GetVirtualPixels()</a> gets pixels that you do not intend to modify or pixels that lie outside the image region (e.g. pixel @ -1,-3)</li>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]273 <li><a href="../www/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> gets pixels that you intend to modify</li>
274 <li><a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> queue pixels that you intend to modify</li>
275 <li><a href="../www/api/cache.html#SyncAuthenticPixels">SyncAuthenticPixels()</a> update the pixel cache with any modified pixels</li>
276</ul>
277
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]278<p>Here is a typical <a href="../www/magick-core.html">MagickCore</a> code snippet for manipulating pixels in the pixel cache. In our example, we copy pixels from the input image to the output image and decrease the intensity by 10%:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]279
280<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]281 const PixelPacket
282 *p;
283
284 PixelPacket
285 *q;
286
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]287 ssize_t
288 x,
289 y;
290
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]291 destination=CloneImage(source,source->columns,source->rows,MagickTrue,
292 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]293 if (destination == (Image *) NULL)
294 { /* an exception was thrown */ }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]295 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]296 {
297 p=GetVirtualPixels(source,0,y,source-&gt;columns,1,exception);
298 q=GetAuthenticPixels(destination,0,y,destination-&gt;columns,1,exception);
299 if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL)
300 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]301 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]302 {
303 q-&gt;red=90*p-&gt;red/100;
304 q-&gt;green=90*p-&gt;green/100;
305 q-&gt;blue=90*p-&gt;blue/100;
306 q-&gt;opacity=90*p-&gt;opacity/100;
307 p++;
308 q++;
309 }
310 if (SyncAuthenticPixels(destination,exception) == MagickFalse)
311 break;
312 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]313 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]314 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]315</div>
316
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]317<p>When we first create the destination image by cloning the source image, the pixel cache pixels are not copied. They are only copied when you signal your intentions to modify the pixel cache by calling <a href="../www/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> or <a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a>. Use <a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> if you want to set new pixel values rather than update existing ones. You could use GetAuthenticPixels() to set pixel values but it is slightly more efficient to use QueueAuthenticPixels() instead. Finally, use <a href="../www/api/cache.html#SyncAuthenticPixels">SyncAuthenticPixels()</a> to ensure any updated pixels are pushed to the pixel cache.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]318
319<p>Recall how we mentioned that the indexes of a colormapped image or the black channel of a CMYK image are stored separately. Use <a href="../www/api/cache.html#GetVirtualIndexes">GetVirtualIndexes()</a> (to read the indexes) or <a href="../www/api/cache.html#GetAuthenticIndexes">GetAuthenticIndexes()</a> (to update the indexes) to gain access to this channel. For example, to print the colormap indexes, use:</p>
320
321<pre class="code">
322 const IndexPacket
323 *indexes;
324
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]325 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]326 {
327 p=GetVirtualPixels(source,0,y,source-&gt;columns,1);
328 if (p == (const PixelPacket *) NULL)
329 break;
330 indexes=GetVirtualIndexes(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]331 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]332 (void) printf("%d\n",indexes[x];
333 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]334 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]335 /* an exception was thrown */
336</pre>
337
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]338<p>The pixel cache manager decides whether to give you direct or indirect access to the image pixels. In some cases the pixels are staged to an intermediate buffer-- and that is why you must call SyncAuthenticPixels() to ensure this buffer is <em>pushed</em> out to the pixel cache to guarantee the corresponding pixels in the cache are updated. For this reason we recommend that you only read or update a scanline or a few scanlines of pixels at a time. However, you can get any rectangular region of pixels you want. GetAuthenticPixels() requires that the region you request is within the bounds of the image area. For a 640 by 480 image, you can get a scanline of 640 pixels at row 479 but if you ask for a scanline at row 480, an exception is returned (rows are numbered starting at 0). GetVirtualPixels() does not have this constraint. For example,</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]339
340<pre class="code">
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]341 p=GetVirtualPixels(source,-3,-3,source-&gt;columns+3,6,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]342</pre>
343
344<p>gives you the pixels you asked for without complaint, even though some are not within the confines of the image region.</p>
345</div>
346
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]347<h3><a id="virtual-pixels"></a>Virtual Pixels</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]348<div class="doc-section">
349
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]350<p>There are a plethora of image processing algorithms that require a neighborhood of pixels about a pixel of interest. The algorithm typically includes a caveat concerning how to handle pixels around the image boundaries, known as edge pixels. With virtual pixels, you do not need to concern yourself about special edge processing other than choosing which virtual pixel method is most appropriate for your algorithm.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]351 <p>Access to the virtual pixels are controlled by the <a href="../www/api/cache.html#SetImageVirtualPixelMethod">SetImageVirtualPixelMethod()</a> method from the MagickCore API or the <a href="../www/command-line-options.html#virtual-pixel">&#x2011;virtual&#x2011;pixel</a> option from the command line. The methods include:</p>
352
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]353<pre class="text" style="font-size: 90%;">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]354 background: the area surrounding the image is the background color
355 black: the area surrounding the image is black
356 checker-tile: alternate squares with image and background color
357 dither: non-random 32x32 dithered pattern
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]358 edge: extend the edge pixel toward infinity (default)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]359 gray: the area surrounding the image is gray
360 horizontal-tile: horizontally tile the image, background color above/below
361 horizontal-tile-edge: horizontally tile the image and replicate the side edge pixels
362 mirror: mirror tile the image
363 random: choose a random pixel from the image
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]364 tile: tile the image
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]365 transparent: the area surrounding the image is transparent blackness
366 vertical-tile: vertically tile the image, sides are background color
367 vertical-tile-edge: vertically tile the image and replicate the side edge pixels
368 white: the area surrounding the image is white
369</pre>
370
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]371</div>
372
373<h3>Cache Storage and Resource Requirements</h3>
374<div class="doc-section">
375
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]376<p>Recall that this simple and elegant design of the ImageMagick pixel cache comes at a cost in terms of storage and processing speed. The pixel cache storage requirements scales with the area of the image and the bit depth of the pixel components. For example, if we have a 640 by 480 image and we are using the Q16 version of ImageMagick, the pixel cache consumes image <em>width * height * bit-depth / 8 * channels</em> bytes or approximately 2.3 mebibytes (i.e. 640 * 480 * 2 * 4). Not too bad, but what if your image is 25000 by 25000 pixels? The pixel cache requires approximately 4.7 gibibytes of storage. Ouch. ImageMagick accounts for possible huge storage requirements by caching large images to disk rather than memory. Typically the pixel cache is stored in memory using heap memory. If heap memory is exhausted, pixels are stored in in an anonymous map; if the anonymous memory map is exhausted, we create the pixel cache on disk and attempt to memory-map it; and if memory-map memory is exhausted, we simply use standard disk I/O. Disk storage is cheap but it is also very slow, upwards of 1000 times slower than memory. We can get some speed improvements, up to 5 times, if we use memory mapping to the disk-based cache. These decisions about storage are made <em>automagically</em> by the pixel cache manager negotiating with the operating system. However, you can influence how the pixel cache manager allocates the pixel cache with <em>cache resource limits</em>. The limits include:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]377
378<dl class="doc">
379 <dt class="doc">files</dt>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]380 <dd>maximum number of open pixel cache files. When this limit is exceeded, any subsequent pixels cached to disk are closed and reopened on demand. This behavior permits a large number of images to be accessed simultaneously on disk, but without a speed penalty due to repeated open/close calls.</dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]381 <dt class="doc">area</dt>
382 <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.</dd>
383 <dt class="doc">memory</dt>
384 <dd>maximum amount of memory in bytes to allocate for the pixel cache from the anonymous mapped memory or the heap.</dd>
385 <dt class="doc">map</dt>
386 <dd>maximum amount of memory map in bytes to allocate for the pixel cache.</dd>
387 <dt class="doc">disk</dt>
388 <dd>maximum amount of disk space in bytes permitted for use by the pixel cache. If this limit is exceeded, the pixel cache is not created and a fatal exception is thrown.</dd>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]389 <dt class="doc">thread</dt>
390 <dd>maximum number of threads that are permitted to run in parallel.</dd>
391 <dt class="doc">time</dt>
392 <dd>maximum number of seconds that the process is permitted to execute. When this limit is exceeded, an exception is thrown and processing stops.</dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]393</dl>
394
395<p>To determine the current setting of these limits, use this command:</p>
396
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]397<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -list resource</span></p><pre class="text">
398File Area Memory Map Disk Thread Time
cristy2c839602010-04-03 02:32:08 +0000[diff] [blame]399-------------------------------------------------------------------------------
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]400 768 1.0386GB 3.8692GiB 7.7384GiB unlimited 4 unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]401</pre>
402
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]403<p>You can set these limits either as a <a href="../www/resources.html#configure">policy</a> (see <a href="../www/source/policy.xml">policy.xml</a>), with an <a href="../www/resources.html#environment">environment variable</a>, with the <a href="../www/command-line-options.html#limit">-limit</a> command line option, or with the <a href="../www/api/resource.html#SetMagickResourceLimit">SetMagickResourceLimit()</a> MagickCore API method. As an example, our online web interface to ImageMagick, <a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">ImageMagick Studio</a>, has an area limit of 64 megabytes, a memory limit of 128 mebibytes and a map limit of 256 mebibytes and a disk limit of 1 gigabytes. Since we process multiple simultaneous sessions, we don't want any one session consuming all the available memory. Instead large images are cached to disk. If the image is too large and exceeds the pixel cache disk limit, the program exits. In addition, we place a 60 second time limit to prevent any run-away processing tasks.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]404
405<p>Note, the cache limits are global, meaning if you create several images, the combined resource requirements are compared to the limit to determine the pixel cache storage disposition.</p>
406</div>
407
408<h3>Cache Views</h3>
409<div class="doc-section">
410
411<p>GetVirtualPixels(), GetAuthenticPixels(), QueueAuthenticPixels(), and SyncAuthenticPixels() from the MagickCore API can only deal with one pixel cache area per image at a time. Suppose you want to access the first and last scanline from the same image at the same time? The solution is to use a <em>cache view</em>. A cache view permits you to access as many areas simultaneously in the pixel cache as you require. The cache view <a href="../www/api/cache-view.html">methods</a> behave like the previous methods except you must first open a view and close it when you are finished with it. Here is a snippet of MagickCore code that permits us to access two areas of an image simultaneously:</p>
412
413<pre class="code">
414 CacheView
415 *view_1,
416 *view_2;
417
418 view_1=OpenCacheView(source);
419 view_2=OpenCacheView(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]420 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]421 {
422 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]423 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,
424 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]425 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
426 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]427 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]428 {
429 /* do something with u &amp; v here */
430 }
431 }
432 view_1=CloseCacheView(view_1);
433 view_2=CloseCacheView(view_2);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]434 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]435 { /* an exception was thrown */ }
436</pre>
437</div>
438
439<h3>Magick Persistent Cache Format</h3>
440<div class="doc-section">
441
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]442<p>Recall that each image format is decoded by ImageMagick and the pixels are deposited in the pixel cache. If you write an image, the pixels are read from the pixel cache and encoded as required by the format you are writing (e.g. GIF, PNG, etc.). The Magick Persistent Cache (MPC) format is designed to eliminate the overhead of decoding and encoding pixels to and from an image format. MPC writes two files. One, with the extension <kbd>.mpc</kbd>, retains all the properties associated with the image or image sequence (e.g. width, height, colorspace, etc.) and the second, with the extension <kbd>.cache</kbd>, is the pixel cache in the native raw format. When reading an MPC image file, ImageMagick reads the image properties and memory maps the pixel cache on disk eliminating the need for decoding the image pixels. The tradeoff is in disk space. MPC is generally larger in file size than most other image formats.</p>
cristy5063d812010-10-19 16:28:10 +0000[diff] [blame]443<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]444</div>
445
446<h3>Best Practices</h3>
447<div class="doc-section">
448
449<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.</p>
450
451<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>
452
453<p>Use QueueAuthenticPixels() or QueueCacheViewAuthenticPixels() if you are setting an initial pixel value. The GetAuthenticPixels() or GetCacheViewAuthenticPixels() method reads pixels from the cache and if you are setting an initial pixel value, this read is unnecessary. Don't forget to call SyncAuthenticPixels() or SyncCacheViewAuthenticPixels() respectively to push your updates to the pixel cache.</p>
454
455<p>GetVirtualPixels(), GetAuthenticPixels(), QueueAuthenticPixels(), and SyncAuthenticPixels() are slightly more efficient than their cache view counter-parts. However, cache views are required if you need access to more than one region of the image simultaneously or if more than one <a href="#threads">thread of execution</a> is accessing the image.</p>
456
457<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>
458
459<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>
460
461<p>The ImageMagick Q16 version of ImageMagick permits you to read and write 16 bit images without scaling but the pixel cache consumes twice as much resources as the Q8 version. If your system has constrained memory or disk resources, consider the Q8 version of ImageMagick. In addition, the Q8 version typically executes faster than the Q16 version.</p>
462
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]463<p>A great majority of image formats and algorithms restrict themselves to a fixed range of pixel values from 0 to some maximum value, for example, the Q16 version of ImageMagick permit intensities from 0 to 65535. High dynamic-range imaging (HDRI), however, permits a far greater dynamic range of exposures (i.e. a large difference between light and dark areas) than standard digital imaging techniques. HDRI accurately represents the wide range of intensity levels found in real scenes ranging from the brightest direct sunlight to the deepest darkest shadows. Enable <a href="../www/high-dynamic-range.html">HDRI</a> at ImageMagick build time to deal with high dynamic-range images, but be mindful that each pixel component is a 32-bit floating point value. In addition, pixel values are not clamped by default so some algorithms may perform differently than the non-HDRI version.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]464
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]465<p>If you are dealing with large images, make sure the pixel cache is written to a disk area with plenty of free space. Under Unix, this is typically <kbd>/tmp</kbd> and for Windows, <kbd>c:/temp</kbd>. You can tell ImageMagick to write the pixel cache to an alternate location with the MAGICK_TEMPORARY_PATH environment variable. For example,</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]466
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]467<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>export MAGICK_TEMPORARY_PATH=/data/magick</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]468
469<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>
470
471<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.tif image.mpc</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.mpc -crop 100x100+0+0 +repage 1.png</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.mpc -crop 100x100+100+0 +repage 2.png</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.mpc -crop 100x100+200+0 +repage 3.png</span></p>
472<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>
473</div>
474
475</div>
476
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]477<h2><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]478<div class="doc-section">
479
480<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>
481
482<p>Use <a href="../www/api/stream.html#ReadStream">ReadStream()</a> or <a href="../www/api/stream.html#WriteStream">WriteStream()</a> with an appropriate callback method in your MagickCore program to consume the pixels as they are streaming. Here's an abbreviated example of using ReadStream:</p>
483
484<pre class="code">
485static size_t StreamHandler(const Image *image,const void *pixels,
486 const size_t columns)
487{
488 /* process pixels here */
489 return(columns);
490}
491
492...
493/* invoke the pixel stream here */
494image=ReadStream(image_info,&amp;StreamHandler,exception);
495</pre>
496
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]497<p>We also provide a lightweight tool, <a href="../www/stream.html">stream</a>, to stream one or more pixel components of the image or portion of the image to your choice of storage formats. It writes the pixel components as they are read from the input image a row at a time making <a href="../www/stream.html">stream</a> desirable when working with large images or when you require raw pixel components.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]498
499</div>
500
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]501<h2><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]502<div class="doc-section">
503
504<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>
505
506<pre class="code">
507 (void) printf("image width: %lu, height: %lu\n",image-&gt;columns,image-&gt;rows);
508</pre>
509
510<p>For a great majority of image properties, such as an image comment or description, we use the <a href="../www/api/property.html#GetImageProperty">GetImageProperty()</a> and <a href="../www/api/property.html#SetImageProperty">SetImageProperty()</a> methods. Here we set a property and fetch it right back:</p>
511
512<pre class="code">
513 const char
514 *comment;
515
516 (void) SetImageProperty(image,"comment","This space for rent");
517 comment=GetImageProperty(image,"comment");
518 if (comment == (const char *) NULL)
519 (void) printf("Image comment: %s\n",comment);
520</pre>
521
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]522<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]523
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]524<p>Image profiles are handled with <a href="../www/api/profile.html#GetImageProfile">GetImageProfile()</a>, <a href="../www/api/profile.html#SetImageProfile">SetImageProfile()</a>, and <a href="../www/api/profile.html#ProfileImage">ProfileImage()</a> methods. Here we set a profile and fetch it right back:</p>
525
526<pre class="code">
527 StringInfo
528 *profile;
529
530 profile=AcquireStringInfo(length);
531 SetStringInfoDatum(profile,my_exif_profile);
532 (void) SetImageProfile(image,"EXIF",profile);
533 DestroyStringInfo(profile);
534 profile=GetImageProfile(image,"EXIF");
535 if (profile != (StringInfo *) NULL)
536 (void) PrintStringInfo(stdout,"EXIF",profile);
537</pre>
538
539</div>
540
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]541<h2><a id="tera-pixel"></a>Large Image Support</h2>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]542<div class="doc-section">
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]543<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]544
545<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert logo: -resize 250000x250000 logo.miff</span></p>
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]546<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]547
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]548<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -define registry:temporary-path=/data/tmp logo: \ <br/> -resize 250000x250000 logo.miff</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]549<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>
550
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]551<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -define registry:temporary-path=/data/tmp -limit memory 16mb \ <br/> logo: -resize 250000x250000 logo.miff</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]552<p>Here we force all image pixels to disk:</p>
553
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]554<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -define registry:temporary-path=/data/tmp -limit area 0 \ <br/> logo: -resize 250000x250000 logo.miff</span></p>
cristybac7a162010-06-15 19:57:29 +0000[diff] [blame]555<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]556
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]557<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert -monitor -define registry:temporary-path=/data/tmp -limit area 0 \ <br/> logo: -resize 250000x250000 logo.miff</span></p></div>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]558
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]559<h2><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]560<div class="doc-section">
561
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]562<p>Many of ImageMagick's internal algorithms are threaded to take advantage of speed-ups offered by the multicore processor chips. However, you are welcome to use ImageMagick algorithms in your threads of execution with the exception of the MagickCore's GetVirtualPixels(), GetAuthenticPixels(), QueueAuthenticPixels(), or SyncAuthenticPixels() pixel cache methods. These methods are intended for one thread of execution only with the exception of an OpenMP parallel section. To access the pixel cache with more than one thread of execution, use a cache view. We do this for the <a href="../www/api/composite.html#CompositeImage">CompositeImage()</a> method, for example. Suppose we want to composite a single image over a different image in each thread of execution. If we use GetVirtualPixels(), the results are unpredictable because multiple threads would likely be asking for different areas of the pixel cache simultaneously. Instead we use GetCacheViewVirtualPixels() which creates a unique view for each thread of execution ensuring our program behaves properly regardless of how many threads are invoked. The other program interfaces, such as the <a href="../www/magick-wand.html">MagickWand API</a>, are completely thread safe so there are no special precautions for threads of execution.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]563
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]564<p>Here is an example of how ImageMagick can take advantage of threads of execution with the <a href="http://en.wikipedia.org/wiki/OpenMP">OpenMP</a> programming paradigm:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]565
566<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]567{
568 CacheView
569 *image_view;
570
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]571 MagickBooleanType
572 status;
573
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]574 ssize_t
575 y;
576
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]577 status=MagickTrue;
578 image_view=AcquireCacheView(image);
579 #pragma omp parallel for schedule(dynamic,4) shared(status)
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]580 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]581 {
582 register IndexPacket
583 *indexes;
584
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]585 register PixelPacket
586 *q;
587
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]588 register ssize_t
589 x;
590
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]591 if (status == MagickFalse)
592 continue;
593 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
594 if (q == (PixelPacket *) NULL)
595 {
596 status=MagickFalse;
597 continue;
598 }
599 indexes=GetCacheViewAuthenticIndexQueue(image_view);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]600 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]601 {
602 q-&gt;red= ...
603 q-&gt;green= ...
604 q-&gt;blue= ...
605 q-&gt;opacity= ...
606 if (indexes != (IndexPacket *) NULL)
607 indexes[x]= ...
608 q++;
609 }
610 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
611 status=MagickFalse;
612 }
613 image_view=DestroyCacheView(image_view);
614 if (status == MagickFalse)
615 perror("something went wrong");
616}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]617</div>
618
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]619
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]620<p>If you call the ImageMagick API from your OpenMP-enabled application and you intend to dynamically increase the number of threads available in subsequent parallel regions, be sure to perform the increase <em>before</em> you call the API otherwise ImageMagick may fault.</p>
621
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]622<p><a href="../www/api/wand-view.html">MagickWand</a> supports wand views. A view iterates over the entire, or portion, of the image in parallel and for each row of pixels, it invokes a callback method you provide. This limits most of your parallel programming activity to just that one module. There are similar methods in <a href="../www/api/image-view.html">MagickCore</a>. For an example, see the same sigmoidal contrast algorithm implemented in both <a href="../www/magick-wand.html#wand-view">MagickWand</a> and <a href="../www/magick-core.html#image-view">MagickCore</a>.</p>
cristyfe7ce342010-06-22 15:41:50 +0000[diff] [blame]623
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]624<p>In most circumstances, the default number of threads is set to the number of processor cores on your system for optimal performance. However, if your system is hyperthreaded or if you are running on a virtual host and only a subset of the processors are available to your server instance, you might get an increase in performance by setting the thread <a href="../www/resources.html#configure">policy</a> or the <a href="../www/resources.html#environment">MAGICK_THREAD_LIMIT</a> environment variable. For example, your virtual host has 8 processors but only 2 are assigned to your server instance. The default of 8 threads can cause severe performance problems. One solution is to limit the number of threads to the available processors in your <a href="../www/source/policy.xml">policy.xml</a> configuration file:</p>
cristyce66ab12010-10-21 23:36:32 +0000[diff] [blame]625
626<pre class="text">
627 &lt;policy domain="resource" name="thread" value="2"/>
628</pre>
629
630<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>
631
632<pre class="text">
633 export MAGICK_THREAD_LIMIT=12
634</pre>
635
636<p>The OpenMP committee has not defined the behavior of mixing OpenMP with other threading models such as Posix threads. However, using modern releases of Linux, OpenMP and Posix threads appear to interoperate without complaint. If you want to use Posix threads from a program module that calls one of the ImageMagick application programming interfaces (e.g. MagickCore, MagickWand, Magick++, etc.) from Mac OS X or an older Linux release, you may need to disable OpenMP support within ImageMagick. Add the <kbd>--disable-openmp</kbd> option to the configure script command line and rebuild and reinstall ImageMagick.</p>
637
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]638</div>
639
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]640<h2><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]641<div class="doc-section">
642<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>
643
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]644<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]645
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]646<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Features: OpenMP OpenCL</span></p>
647<p>If so, run this command to realize a significant speed-up for image convolution:</p>
648
cristy4949d522010-03-12 18:41:34 +0000[diff] [blame]649<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert image.png convolve '-1, -1, -1, -1, 9, -1, -1, -1, -1' \ <br/> convolve.png</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]650<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
651
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]652<p>Here is an example OpenCL kernel that convolves an image:</p>
653
654<div class="viewport">
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]655static inline long ClampToCanvas(const long offset,const ulong range)
656{
657 if (offset &lt; 0L)
658 return(0L);
659 if (offset >= range)
660 return((long) (range-1L));
661 return(offset);
662}
663
664static inline CLQuantum ClampToQuantum(const double value)
665{
666 if (value &lt; 0.0)
667 return((CLQuantum) 0);
668 if (value >= (double) QuantumRange)
669 return((CLQuantum) QuantumRange);
670 return((CLQuantum) (value+0.5));
671}
672
673__kernel void Convolve(const __global CLPixelType *source,__constant double *filter,
674 const ulong width,const ulong height,__global CLPixelType *destination)
675{
676 const ulong columns = get_global_size(0);
677 const ulong rows = get_global_size(1);
678
679 const long x = get_global_id(0);
680 const long y = get_global_id(1);
681
682 const double scale = (1.0/QuantumRange);
683 const long mid_width = (width-1)/2;
684 const long mid_height = (height-1)/2;
685 double4 sum = { 0.0, 0.0, 0.0, 0.0 };
686 double gamma = 0.0;
687 register ulong i = 0;
688
689 for (long v=(-mid_height); v &lt;= mid_height; v++)
690 {
691 for (long u=(-mid_width); u &lt;= mid_width; u++)
692 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]693 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
694 columns);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]695 const double alpha=scale*(QuantumRange-source[index].w);
696 sum.x+=alpha*filter[i]*source[index].x;
697 sum.y+=alpha*filter[i]*source[index].y;
698 sum.z+=alpha*filter[i]*source[index].z;
699 sum.w+=filter[i]*source[index].w;
700 gamma+=alpha*filter[i];
701 i++;
702 }
703 }
704
705 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
706 const ulong index=y*columns+x;
707 destination[index].x=ClampToQuantum(gamma*sum.x);
708 destination[index].y=ClampToQuantum(gamma*sum.y);
709 destination[index].z=ClampToQuantum(gamma*sum.z);
710 destination[index].w=ClampToQuantum(sum.w);
711};
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]712</div>
713
cristy37f02952010-03-24 19:47:41 +0000[diff] [blame]714<p>See <a href="http://trac.imagemagick.org/browser/ImageMagick/trunk/magick/accelerate.c">magick/accelerate.c</a> for a complete implementation of image convolution with an OpenCL kernel.</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]715
716</div>
717
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]718<h2><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]719<div class="doc-section">
720
721<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>
722
723<p>Here is a listing of a sample <a href="../www/source/mgk.c">custom coder</a>. It reads and writes images in the MGK image format which is simply an ID followed by the image width and height followed by the RGB pixel values.</p>
724
725<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]726/*
727 Include declarations.
728*/
729#include "magick/studio.h"
730#include "magick/blob.h"
731#include "magick/blob-private.h"
732#include "magick/colorspace.h"
733#include "magick/exception.h"
734#include "magick/exception-private.h"
735#include "magick/image.h"
736#include "magick/image-private.h"
737#include "magick/list.h"
738#include "magick/magick.h"
739#include "magick/memory_.h"
740#include "magick/monitor.h"
741#include "magick/monitor-private.h"
742#include "magick/quantum-private.h"
743#include "magick/static.h"
744#include "magick/string_.h"
745#include "magick/module.h"
746
747/*
748 Forward declarations.
749*/
750static MagickBooleanType
751 WriteMGKImage(const ImageInfo *,Image *);
752
753/*
754%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
755% %
756% %
757% %
758% I s M G K %
759% %
760% %
761% %
762%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
763%
764% IsMGK() returns MagickTrue if the image format type, identified by the
765% magick string, is MGK.
766%
767% The format of the IsMGK method is:
768%
769% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
770%
771% A description of each parameter follows:
772%
773% o magick: This string is generally the first few bytes of an image file
774% or blob.
775%
776% o length: Specifies the length of the magick string.
777%
778*/
779static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
780{
781 if (length &lt; 7)
782 return(MagickFalse);
783 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
784 return(MagickTrue);
785 return(MagickFalse);
786}
787
788/*
789%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
790% %
791% %
792% %
793% R e a d M G K I m a g e %
794% %
795% %
796% %
797%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
798%
799% ReadMGKImage() reads a MGK image file and returns it. It allocates
800% the memory necessary for the new Image structure and returns a pointer to
801% the new image.
802%
803% The format of the ReadMGKImage method is:
804%
805% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
806%
807% A description of each parameter follows:
808%
809% o image_info: the image info.
810%
811% o exception: return any errors or warnings in this structure.
812%
813*/
814static Image *ReadMGKImage(const ImageInfo *image_info,
815 ExceptionInfo *exception)
816{
817 char
818 buffer[MaxTextExtent];
819
820 Image
821 *image;
822
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]823 MagickBooleanType
824 status;
825
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]826 register PixelPacket
827 *q;
828
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]829 register size_t
830 x;
831
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]832 register unsigned char
833 *p;
834
835 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]836 count,
837 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]838
839 unsigned char
840 *pixels;
841
842 unsigned long
843 columns,
844 rows;
845
846 /*
847 Open image file.
848 */
849 assert(image_info != (const ImageInfo *) NULL);
850 assert(image_info-&gt;signature == MagickSignature);
851 if (image_info-&gt;debug != MagickFalse)
852 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
853 assert(exception != (ExceptionInfo *) NULL);
854 assert(exception-&gt;signature == MagickSignature);
855 image=AcquireImage(image_info);
856 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
857 if (status == MagickFalse)
858 {
859 image=DestroyImageList(image);
860 return((Image *) NULL);
861 }
862 /*
863 Read MGK image.
864 */
865 (void) ReadBlobString(image,buffer); /* read magic number */
866 if (IsMGK(buffer,7) == MagickFalse)
867 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
868 (void) ReadBlobString(image,buffer);
869 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
870 if (count &lt;= 0)
871 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
872 do
873 {
874 /*
875 Initialize image structure.
876 */
877 image-&gt;columns=columns;
878 image-&gt;rows=rows;
879 image-&gt;depth=8;
880 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
881 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
882 break;
883 /*
884 Convert MGK raster image to pixel packets.
885 */
886 if (SetImageExtent(image,0,0) == MagickFalse)
887 {
888 InheritException(exception,&amp;image-&gt;exception);
889 return(DestroyImageList(image));
890 }
891 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
892 if (pixels == (unsigned char *) NULL)
893 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]894 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]895 {
896 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
897 if (count != (ssize_t) (3*image-&gt;columns))
898 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
899 p=pixels;
900 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
901 if (q == (PixelPacket *) NULL)
902 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]903 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]904 {
905 q-&gt;red=ScaleCharToQuantum(*p++);
906 q-&gt;green=ScaleCharToQuantum(*p++);
907 q-&gt;blue=ScaleCharToQuantum(*p++);
908 q++;
909 }
910 if (SyncAuthenticPixels(image,exception) == MagickFalse)
911 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]912 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]913 (SetImageProgress(image,LoadImageTag,y,image&gt;>rows) == MagickFalse))
914 break;
915 }
916 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
917 if (EOFBlob(image) != MagickFalse)
918 {
919 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
920 break;
921 }
922 /*
923 Proceed to next image.
924 */
925 if (image_info-&gt;number_scenes != 0)
926 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
927 break;
928 *buffer='\0';
929 (void) ReadBlobString(image,buffer);
930 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
931 if (count != 0)
932 {
933 /*
934 Allocate next image structure.
935 */
936 AcquireNextImage(image_info,image);
937 if (GetNextImageInList(image) == (Image *) NULL)
938 {
939 image=DestroyImageList(image);
940 return((Image *) NULL);
941 }
942 image=SyncNextImageInList(image);
943 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
944 if (status == MagickFalse)
945 break;
946 }
947 } while (count != 0);
948 (void) CloseBlob(image);
949 return(GetFirstImageInList(image));
950}
951
952/*
953%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
954% %
955% %
956% %
957% R e g i s t e r M G K I m a g e %
958% %
959% %
960% %
961%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
962%
963% RegisterMGKImage() adds attributes for the MGK image format to
964% the list of supported formats. The attributes include the image format
965% tag, a method to read and/or write the format, whether the format
966% supports the saving of more than one frame to the same file or blob,
967% whether the format supports native in-memory I/O, and a brief
968% description of the format.
969%
970% The format of the RegisterMGKImage method is:
971%
972% unsigned long RegisterMGKImage(void)
973%
974*/
975ModuleExport unsigned long RegisterMGKImage(void)
976{
977 MagickInfo
978 *entry;
979
980 entry=SetMagickInfo("MGK");
981 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
982 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
983 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
984 entry-&gt;description=ConstantString("MGK");
985 entry-&gt;module=ConstantString("MGK");
986 (void) RegisterMagickInfo(entry);
987 return(MagickImageCoderSignature);
988}
989
990/*
991%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
992% %
993% %
994% %
995% U n r e g i s t e r M G K I m a g e %
996% %
997% %
998% %
999%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1000%
1001% UnregisterMGKImage() removes format registrations made by the
1002% MGK module from the list of supported formats.
1003%
1004% The format of the UnregisterMGKImage method is:
1005%
1006% UnregisterMGKImage(void)
1007%
1008*/
1009ModuleExport void UnregisterMGKImage(void)
1010{
1011 (void) UnregisterMagickInfo("MGK");
1012}
1013
1014/*
1015%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1016% %
1017% %
1018% %
1019% W r i t e M G K I m a g e %
1020% %
1021% %
1022% %
1023%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1024%
1025% WriteMGKImage() writes an image to a file in red, green, and blue
1026% MGK rasterfile format.
1027%
1028% The format of the WriteMGKImage method is:
1029%
1030% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1031%
1032% A description of each parameter follows.
1033%
1034% o image_info: the image info.
1035%
1036% o image: The image.
1037%
1038*/
1039static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1040{
1041 char
1042 buffer[MaxTextExtent];
1043
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1044 MagickBooleanType
1045 status;
1046
1047 MagickOffsetType
1048 scene;
1049
1050 register const PixelPacket
1051 *p;
1052
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1053 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1054 x;
1055
1056 register unsigned char
1057 *q;
1058
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1059 ssize_t
1060 y;
1061
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1062 unsigned char
1063 *pixels;
1064
1065 /*
1066 Open output image file.
1067 */
1068 assert(image_info != (const ImageInfo *) NULL);
1069 assert(image_info-&gt;signature == MagickSignature);
1070 assert(image != (Image *) NULL);
1071 assert(image-&gt;signature == MagickSignature);
1072 if (image-&gt;debug != MagickFalse)
1073 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1074 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1075 if (status == MagickFalse)
1076 return(status);
1077 scene=0;
1078 do
1079 {
1080 /*
1081 Allocate memory for pixels.
1082 */
1083 if (image-&gt;colorspace != RGBColorspace)
1084 (void) SetImageColorspace(image,RGBColorspace);
1085 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1086 3UL*sizeof(*pixels));
1087 if (pixels == (unsigned char *) NULL)
1088 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1089 /*
1090 Initialize raster file header.
1091 */
1092 (void) WriteBlobString(image,"id=mgk\n");
1093 (void) FormatMagickString(buffer,MaxTextExtent,"%lu %lu\n",
1094 image-&gt;columns,image-&gt;rows);
1095 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1096 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1097 {
1098 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1099 if (p == (const PixelPacket *) NULL)
1100 break;
1101 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1102 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1103 {
1104 *q++=ScaleQuantumToChar(p-&gt;red);
1105 *q++=ScaleQuantumToChar(p-&gt;green);
1106 *q++=ScaleQuantumToChar(p-&gt;blue);
1107 p++;
1108 }
1109 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]1110 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1111 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1112 break;
1113 }
1114 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1115 if (GetNextImageInList(image) == (Image *) NULL)
1116 break;
1117 image=SyncNextImageInList(image);
1118 status=SetImageProgress(image,SaveImagesTag,scene,
1119 GetImageListLength(image));
1120 if (status == MagickFalse)
1121 break;
1122 scene++;
1123 } while (image_info-&gt;adjoin != MagickFalse);
1124 (void) CloseBlob(image);
1125 return(MagickTrue);
1126}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1127</div>
1128
1129<p>To invoke the custom coder from the command line, use these commands:</p>
1130
1131<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert logo: logo.mgk</span><span class='crtout'></span><span class="crtprompt"> $magick&gt; </span><span class='crtin'>display logo.mgk</span></p>
1132<p>We provide the <a href="ftp://ftp.imagemagick.org/pub/ImageMagick/kits/MagickCoderKit-1.0.0.tar.gz">Magick Coder Kit</a> to help you get started writing your own custom coder.</p>
1133
1134</div>
1135
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]1136<h2><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1137<div class="doc-section">
1138
1139<p>ImageMagick provides a convenient mechanism for adding your own custom image processing algorithms. We call these image filters and they are invoked from the command line with the <a href="../www/command-line-options.html#process">-process</a> option or from the MagickCore API method <a href="../www/api/module.html#ExecuteModuleProcess">ExecuteModuleProcess()</a>.</p>
1140
1141<p>Here is a listing of a sample <a href="../www/source/analyze.c">custom image filter</a>. It computes a few statistics such as the pixel brightness and saturation mean and standard-deviation.</p>
1142
1143<div class="viewport">
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1144#include &lt;stdio.h&gt;
1145#include &lt;stdlib.h&gt;
1146#include &lt;string.h&gt;
1147#include &lt;time.h&gt;
1148#include &lt;assert.h&gt;
1149#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1150#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame^]1151
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1152/*
1153%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1154% %
1155% %
1156% %
1157% a n a l y z e I m a g e %
1158% %
1159% %
1160% %
1161%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1162%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1163% analyzeImage() computes the brightness and saturation mean, standard
1164% deviation, kurtosis and skewness and stores these values as attributes
1165% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1166%
1167% The format of the analyzeImage method is:
1168%
1169% unsigned long analyzeImage(Image *images,const int argc,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1170% char **argv,ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1171%
1172% A description of each parameter follows:
1173%
1174% o image: the address of a structure of type Image.
1175%
1176% o argc: Specifies a pointer to an integer describing the number of
1177% elements in the argument vector.
1178%
1179% o argv: Specifies a pointer to a text array containing the command line
1180% arguments.
1181%
1182% o exception: return any errors or warnings in this structure.
1183%
1184*/
1185ModuleExport unsigned long analyzeImage(Image **images,const int argc,
1186 const char **argv,ExceptionInfo *exception)
1187{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1188 char
1189 text[MaxTextExtent];
1190
1191 double
1192 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1193 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1194 brightness_mean,
1195 brightness_standard_deviation,
1196 brightness_kurtosis,
1197 brightness_skewness,
1198 brightness_sum_x,
1199 brightness_sum_x2,
1200 brightness_sum_x3,
1201 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1202 hue,
1203 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1204 saturation_mean,
1205 saturation_standard_deviation,
1206 saturation_kurtosis,
1207 saturation_skewness,
1208 saturation_sum_x,
1209 saturation_sum_x2,
1210 saturation_sum_x3,
1211 saturation_sum_x4;
1212
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1213 Image
1214 *image;
1215
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1216 assert(images != (Image **) NULL);
1217 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1218 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1219 (void) argc;
1220 (void) argv;
1221 image=(*images);
1222 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1223 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1224 CacheView
1225 *image_view;
1226
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1227 MagickBooleanType
1228 status;
1229
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1230 ssize_t
1231 y;
1232
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1233 brightness_sum_x=0.0;
1234 brightness_sum_x2=0.0;
1235 brightness_sum_x3=0.0;
1236 brightness_sum_x4=0.0;
1237 brightness_mean=0.0;
1238 brightness_standard_deviation=0.0;
1239 brightness_kurtosis=0.0;
1240 brightness_skewness=0.0;
1241 saturation_sum_x=0.0;
1242 saturation_sum_x2=0.0;
1243 saturation_sum_x3=0.0;
1244 saturation_sum_x4=0.0;
1245 saturation_mean=0.0;
1246 saturation_standard_deviation=0.0;
1247 saturation_kurtosis=0.0;
1248 saturation_skewness=0.0;
1249 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1250 status=MagickTrue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1251 image_view=AcquireCacheView(image);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1252#if defined(MAGICKCORE_OPENMP_SUPPORT)
1253 #pragma omp parallel for schedule(dynamic,4) shared(status)
1254#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1255 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1256 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1257 register const PixelPacket
1258 *p;
1259
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1260 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1261 x;
1262
1263 if (status == MagickFalse)
1264 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1265 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1266 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1267 {
1268 status=MagickFalse;
1269 continue;
1270 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1271 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1272 {
1273 ConvertRGBToHSB(p-&gt;red,p-&gt;green,p-&gt;blue,&amp;hue,&amp;saturation,&amp;brightness);
1274 brightness*=QuantumRange;
1275 brightness_sum_x+=brightness;
1276 brightness_sum_x2+=brightness*brightness;
1277 brightness_sum_x3+=brightness*brightness*brightness;
1278 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1279 saturation*=QuantumRange;
1280 saturation_sum_x+=saturation;
1281 saturation_sum_x2+=saturation*saturation;
1282 saturation_sum_x3+=saturation*saturation*saturation;
1283 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1284 area++;
1285 p++;
1286 }
1287 }
1288 image_view=DestroyCacheView(image_view);
1289 if (area &lt;= 0.0)
1290 break;
1291 brightness_mean=brightness_sum_x/area;
1292 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_mean);
1293 (void) SetImageProperty(image,"filter:brightness:mean",text);
1294 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1295 area*brightness_sum_x/area));
1296 (void) FormatMagickString(text,MaxTextExtent,"%g",
1297 brightness_standard_deviation);
1298 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1299 if (brightness_standard_deviation != 0)
1300 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1301 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1302 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1303 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1304 brightness_standard_deviation*brightness_standard_deviation*
1305 brightness_standard_deviation)-3.0;
1306 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_kurtosis);
1307 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1308 if (brightness_standard_deviation != 0)
1309 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1310 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1311 brightness_mean)/(brightness_standard_deviation*
1312 brightness_standard_deviation*brightness_standard_deviation);
1313 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_skewness);
1314 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1315 saturation_mean=saturation_sum_x/area;
1316 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_mean);
1317 (void) SetImageProperty(image,"filter:saturation:mean",text);
1318 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1319 area*saturation_sum_x/area));
1320 (void) FormatMagickString(text,MaxTextExtent,"%g",
1321 saturation_standard_deviation);
1322 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1323 if (saturation_standard_deviation != 0)
1324 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1325 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1326 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1327 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1328 saturation_standard_deviation*saturation_standard_deviation*
1329 saturation_standard_deviation)-3.0;
1330 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_kurtosis);
1331 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1332 if (saturation_standard_deviation != 0)
1333 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1334 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1335 saturation_mean)/(saturation_standard_deviation*
1336 saturation_standard_deviation*saturation_standard_deviation);
1337 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_skewness);
1338 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1339 }
1340 return(MagickImageFilterSignature);
1341}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1342</div>
1343
1344<p>To invoke the custom filter from the command line, use this command:</p>
1345
1346<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert logo: -process analyze -verbose info:</span><span class='crtout'>Image: logo: <br/>
1347 Format: LOGO (ImageMagick Logo) <br/>
1348 Class: PseudoClass <br/>
1349 Geometry: 640x480 <br/>
1350 ... <br/>
1351 filter:brightness:kurtosis: 8.98864 <br/>
1352 filter:brightness:mean: 238.096 <br/>
1353 filter:brightness:skewness: -3.04519 <br/>
1354 filter:brightness:standard-deviation: 46.3286 <br/>
1355 filter:saturation:kurtosis: 5.9137 <br/>
1356 filter:saturation:mean: 23.4635 <br/>
1357 filter:saturation:skewness: 2.71874 <br/>
1358 filter:saturation:standard-deviation: 64.7734</span></p>
1359
1360<p>We provide the <a href="ftp://ftp.imagemagick.org/pub/ImageMagick/kits/MagickFilterKit-1.0.0.tar.gz">Magick Filter Kit</a> to help you get started writing your own custom image filter.</p>
1361
1362</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1363
1364</div>
1365
1366<div id="linkbar">
cristyce69bb02010-07-27 19:49:46 +0000[diff] [blame]1367 <span id="linkbar-west">&nbsp;</span>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1368 <span id="linkbar-center">
1369 <a href="http://www.imagemagick.org/discourse-server/">Discourse Server</a> &bull;
cristya8902942010-07-30 00:49:52 +0000[diff] [blame]1370 <a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">Studio</a>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1371 </span>
1372 <span id="linkbar-east">&nbsp;</span>
1373 </div>
1374 <div class="footer">
cristy7e41fe82010-12-04 23:12:08 +0000[diff] [blame]1375 <span id="footer-west">&copy; 1999-2011 ImageMagick Studio LLC</span>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1376 <span id="footer-east"> <a href="http://www.imagemagick.org/script/contact.php">Contact the Wizards</a></span>
1377 </div>
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