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213<div class="main">
214
215
216
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]217<h1>The <em>Magick</em> Behind ImageMagick</h1>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]218<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]219
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cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]221<div class="doc-section">
222<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>
223</div>
224
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]225<h2><a id="overview"></a>Architecture Overview</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]226<div class="doc-section">
227
228<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>
229
230<ul>
231 <li>colorspace (e.g RGB, CMYK, YUV, Lab, etc.)</li>
232 <li>bit depth (.e.g 1, 4, 8, 12, 16, etc.)</li>
233 <li>storage format (e.g. unsigned, signed, float, double, etc.)</li>
234 <li>compression (e.g. uncompressed, RLE, Zip, BZip, etc.)</li>
235 <li>orientation (i.e. top-to-bottom, right-to-left, etc.),</li>
236 <li>layout (.e.g. raw, interspersed with opcodes, etc.)</li>
237</ul>
238
239<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>
240
241<p>An efficient implementation of an image processing algorithm may require we get or set:</p>
242
243<ul>
244 <li>one pixel a time (e.g. pixel at location 10,3)</li>
245 <li>a single scanline (e.g. all pixels from row 4)</li>
246 <li>a few scanlines at once (e.g. pixel rows 4-7)</li>
247 <li>a single column or columns of pixels (e.g. all pixels from column 11)</li>
248 <li>an arbitrary region of pixels from the image (e.g. pixels defined at 10,7 to 10,19)</li>
249 <li>a pixel in random order (e.g. pixel at 14,15 and 640,480)</li>
250 <li>pixels from two different images (e.g. pixel at 5,1 from image 1 and pixel at 5,1 from image 2)</li>
251 <li>pixels outside the boundaries of the image (e.g. pixel at -1,-3)</li>
252 <li>a pixel component that is unsigned or in a floating-point representation (e.g. 0.17836)</li>
253 <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>
254 <li>one or more pixels simultaneously in different threads of execution</li>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]255 <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]256</ul>
257
258<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>
259
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]260<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]261
cristy320dd6e2010-04-16 20:11:40 +0000[diff] [blame]262<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]263
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]264<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]265
266</div>
267
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]268<h2><a id="cache"></a>The Pixel Cache</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]269<div class="doc-section">
270
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]271<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]272
273<h3>Create the Pixel Cache</h3>
274<div class="doc-section">
275
276<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>
277
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]278<dl>
279<dt>Create an image canvas initialized to the background color:</dt>
280<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]281 image=AllocateImage(image_info);
282 if (SetImageExtent(image,640,480) == MagickFalse)
283 { /* an exception was thrown */ }
284 (void) QueryMagickColor("red",&amp;image-&gt;background_color,&amp;image-&gt;exception);
285 SetImageBackgroundColor(image);
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]286</p></dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]287
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]288<dt>Create an image from a JPEG image on disk:</dt>
289<dd><p class="code">
290 (void) strcpy(image_info-&gt;filename,"image.jpg"):
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]291 image=ReadImage(image_info,exception);
292 if (image == (Image *) NULL)
293 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]294</p></dd>
295<dt>Create an image from a memory based image:</dt>
296<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]297 image=BlobToImage(blob_info,blob,extent,exception);
298 if (image == (Image *) NULL)
299 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]300</p></dd>
301</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]302
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]303<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]304
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]305<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]306
cristy1efc1ab2011-08-01 14:47:02 +0000[diff] [blame^]307<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Version: ImageMagick 6.7.1-1 2011-07-01 Q16 http://www.imagemagick.org</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]308<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]309</div>
310
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]311<h3><a id="authentic-pixels"></a>Access the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]312<div class="doc-section">
313
314<p>Once the pixel cache is associated with an image, you typically want to get, update, or put pixels into it. We refer to pixels inside the image region as <em>authentic pixels</em> and outside the region as <em>virtual pixels</em>. Use these methods to access the pixels in the cache:</p>
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]315<ul>
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]316 <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]317 <li><a href="../www/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> gets pixels that you intend to modify</li>
318 <li><a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> queue pixels that you intend to modify</li>
319 <li><a href="../www/api/cache.html#SyncAuthenticPixels">SyncAuthenticPixels()</a> update the pixel cache with any modified pixels</li>
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]320</ul>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]321
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]322<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]323
324<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]325 const PixelPacket
326 *p;
327
328 PixelPacket
329 *q;
330
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]331 ssize_t
332 x,
333 y;
334
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]335 destination=CloneImage(source,source->columns,source->rows,MagickTrue,
336 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]337 if (destination == (Image *) NULL)
338 { /* an exception was thrown */ }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]339 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]340 {
341 p=GetVirtualPixels(source,0,y,source-&gt;columns,1,exception);
342 q=GetAuthenticPixels(destination,0,y,destination-&gt;columns,1,exception);
343 if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL)
344 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]345 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]346 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]347 SetPixelRed(q,90*p-&gt;red/100);
348 SetPixelGreen(q,90*p-&gt;green/100);
349 SetPixelBlue(q,90*p-&gt;blue/100);
350 SetPixelOpacity(q,90*p-&gt;opacity/100);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]351 p++;
352 q++;
353 }
354 if (SyncAuthenticPixels(destination,exception) == MagickFalse)
355 break;
356 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]357 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]358 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]359</div>
360
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]361<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]362
cristy84134182011-06-15 22:59:00 +0000[diff] [blame]363<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#GetVirtualIndexQueue">GetVirtualIndexQueue()</a> (to read the indexes) or <a href="../www/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]364
365<pre class="code">
366 const IndexPacket
367 *indexes;
368
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]369 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]370 {
371 p=GetVirtualPixels(source,0,y,source-&gt;columns,1);
372 if (p == (const PixelPacket *) NULL)
373 break;
cristy84134182011-06-15 22:59:00 +0000[diff] [blame]374 indexes=GetVirtualIndexQueue(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]375 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]376 (void) printf("%d\n",GetPixelIndex(indexes+x));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]377 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]378 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]379 /* an exception was thrown */
380</pre>
381
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]382<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]383
384<pre class="code">
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]385 p=GetVirtualPixels(source,-3,-3,source-&gt;columns+3,6,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]386</pre>
387
388<p>gives you the pixels you asked for without complaint, even though some are not within the confines of the image region.</p>
389</div>
390
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]391<h3><a id="virtual-pixels"></a>Virtual Pixels</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]392<div class="doc-section">
393
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]394<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]395 <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>
396
cristy4c54bbb2011-03-17 13:53:13 +0000[diff] [blame]397<pre class="text" style="font-size: 83.3333%;">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]398 background: the area surrounding the image is the background color
399 black: the area surrounding the image is black
400 checker-tile: alternate squares with image and background color
401 dither: non-random 32x32 dithered pattern
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]402 edge: extend the edge pixel toward infinity (default)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]403 gray: the area surrounding the image is gray
404 horizontal-tile: horizontally tile the image, background color above/below
405 horizontal-tile-edge: horizontally tile the image and replicate the side edge pixels
406 mirror: mirror tile the image
407 random: choose a random pixel from the image
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]408 tile: tile the image
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]409 transparent: the area surrounding the image is transparent blackness
410 vertical-tile: vertically tile the image, sides are background color
411 vertical-tile-edge: vertically tile the image and replicate the side edge pixels
412 white: the area surrounding the image is white
413</pre>
414
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]415</div>
416
417<h3>Cache Storage and Resource Requirements</h3>
418<div class="doc-section">
419
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]420<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]421
422<dl class="doc">
423 <dt class="doc">files</dt>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]424 <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]425 <dt class="doc">area</dt>
426 <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>
427 <dt class="doc">memory</dt>
428 <dd>maximum amount of memory in bytes to allocate for the pixel cache from the anonymous mapped memory or the heap.</dd>
429 <dt class="doc">map</dt>
430 <dd>maximum amount of memory map in bytes to allocate for the pixel cache.</dd>
431 <dt class="doc">disk</dt>
432 <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]433 <dt class="doc">thread</dt>
434 <dd>maximum number of threads that are permitted to run in parallel.</dd>
435 <dt class="doc">time</dt>
436 <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]437</dl>
438
439<p>To determine the current setting of these limits, use this command:</p>
440
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]441<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -list resource</span></p><pre class="text">
442File Area Memory Map Disk Thread Time
cristy2c839602010-04-03 02:32:08 +0000[diff] [blame]443-------------------------------------------------------------------------------
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]444 768 1.0386GB 3.8692GiB 7.7384GiB unlimited 4 unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]445</pre>
446
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]447<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]448
449<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>
450</div>
451
452<h3>Cache Views</h3>
453<div class="doc-section">
454
455<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>
456
457<pre class="code">
458 CacheView
459 *view_1,
460 *view_2;
461
cristye9a32c32011-04-07 01:11:05 +0000[diff] [blame]462 view_1=AcquireCacheView(source);
463 view_2=AcquireCacheView(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]464 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]465 {
466 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]467 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,
468 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]469 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
470 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]471 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]472 {
473 /* do something with u &amp; v here */
474 }
475 }
cristye9a32c32011-04-07 01:11:05 +0000[diff] [blame]476 view_2=DestroyCacheView(view_2);
477 view_1=DestroyCacheView(view_1);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]478 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]479 { /* an exception was thrown */ }
480</pre>
481</div>
482
483<h3>Magick Persistent Cache Format</h3>
484<div class="doc-section">
485
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]486<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]487<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]488</div>
489
490<h3>Best Practices</h3>
491<div class="doc-section">
492
cristy30092792011-02-22 02:06:14 +0000[diff] [blame]493<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 perfomance 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]494
495<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>
496
497<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>
498
499<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>
500
501<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>
502
503<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>
504
505<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>
506
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]507<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]508
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]509<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]510
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]511<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]512
513<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>
514
515<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>
516<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>
517</div>
518
519</div>
520
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]521<h2><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]522<div class="doc-section">
523
524<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>
525
526<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>
527
528<pre class="code">
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]529static size_t StreamPixels(const Image *image,const void *pixels,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]530 const size_t columns)
531{
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]532 register const PixelPacket
533 *p;
534
535 MyData
536 *my_data;
537
538 my_data=(MyData *) image->client_data;
539 p=(PixelPacket *) pixels;
540 if (p != (const PixelPacket *) NULL)
541 {
542 /* process pixels here */
543 }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]544 return(columns);
545}
546
547...
548/* invoke the pixel stream here */
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]549image_info->client_data=(void *) MyData;
550image=ReadStream(image_info,&amp;StreamPixels,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]551</pre>
552
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]553<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. 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]554
555</div>
556
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]557<h2><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]558<div class="doc-section">
559
560<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>
561
562<pre class="code">
563 (void) printf("image width: %lu, height: %lu\n",image-&gt;columns,image-&gt;rows);
564</pre>
565
566<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>
567
568<pre class="code">
569 const char
570 *comment;
571
572 (void) SetImageProperty(image,"comment","This space for rent");
573 comment=GetImageProperty(image,"comment");
574 if (comment == (const char *) NULL)
575 (void) printf("Image comment: %s\n",comment);
576</pre>
577
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]578<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]579
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]580<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>
581
582<pre class="code">
583 StringInfo
584 *profile;
585
586 profile=AcquireStringInfo(length);
587 SetStringInfoDatum(profile,my_exif_profile);
588 (void) SetImageProfile(image,"EXIF",profile);
589 DestroyStringInfo(profile);
590 profile=GetImageProfile(image,"EXIF");
591 if (profile != (StringInfo *) NULL)
592 (void) PrintStringInfo(stdout,"EXIF",profile);
593</pre>
594
595</div>
596
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]597<h2><a id="tera-pixel"></a>Large Image Support</h2>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]598<div class="doc-section">
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]599<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]600
601<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]602<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]603
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]604<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]605<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>
606
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]607<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]608<p>Here we force all image pixels to disk:</p>
609
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]610<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]611<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]612
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]613<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]614
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]615<h2><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]616<div class="doc-section">
617
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]618<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]619
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]620<p>Here is an MagickCore code snippet that takes 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]621
622<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]623{
624 CacheView
625 *image_view;
626
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]627 MagickBooleanType
628 status;
629
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]630 ssize_t
631 y;
632
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]633 status=MagickTrue;
634 image_view=AcquireCacheView(image);
635 #pragma omp parallel for schedule(dynamic,4) shared(status)
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]636 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]637 {
638 register IndexPacket
639 *indexes;
640
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]641 register PixelPacket
642 *q;
643
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]644 register ssize_t
645 x;
646
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]647 if (status == MagickFalse)
648 continue;
649 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
650 if (q == (PixelPacket *) NULL)
651 {
652 status=MagickFalse;
653 continue;
654 }
655 indexes=GetCacheViewAuthenticIndexQueue(image_view);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]656 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]657 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]658 SetPixelRed(q,...);
659 SetPixelGreen(q,...);
660 SetPixelBlue(q,...);
661 SetPixelOpacity(q,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]662 if (indexes != (IndexPacket *) NULL)
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]663 SetPixelIndex(indexes+x,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]664 q++;
665 }
666 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
667 status=MagickFalse;
668 }
669 image_view=DestroyCacheView(image_view);
670 if (status == MagickFalse)
671 perror("something went wrong");
672}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]673</div>
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]674<p>This code snippet converts an uncompressed Windows bitmap to a Magick++ image:</p>
675<div class="viewport">
676#include "Magick++.h"
677#include &lt;assert.h&gt;
678#include "omp.h"
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]679
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]680void ConvertBMPToImage(const BITMAPINFOHEADER *bmp_info,
681 const unsigned char *restrict pixels,Magick::Image *image)
682{
683 /*
684 Prepare the image so that we can modify the pixels directly.
685 */
686 assert(bmp_info->biCompression == BI_RGB);
687 assert(bmp_info->biWidth == image->columns());
688 assert(abs(bmp_info->biHeight) == image->rows());
689 image->modifyImage();
690 if (bmp_info->biBitCount == 24)
691 image->type(MagickCore::TrueColorType);
692 else
693 image->type(MagickCore::TrueColorMatteType);
694 register unsigned int bytes_per_row=bmp_info->biWidth*bmp_info->biBitCount/8;
695 if (bytes_per_row % 4 != 0) {
696 bytes_per_row=bytes_per_row+(4-bytes_per_row % 4); // divisible by 4.
697 }
698 /*
699 Copy all pixel data, row by row.
700 */
701 #pragma omp parallel for
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]702 for (int y=0; y &lt; int(image->rows()); y++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]703 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]704 int
705 row;
706
707 register const unsigned char
708 *restrict p;
709
710 register MagickCore::PixelPacket
711 *restrict q;
712
713 row=(bmp_info->biHeight > 0) ? (image->rows()-y-1) : y;
714 p=pixels+row*bytes_per_row;
715 q=image->setPixels(0,y,image->columns(),1);
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]716 for (int x=0; x &lt; int(image->columns()); x++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]717 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]718 SetPixelBlue(q,p[0]);
719 SetPixelGreen(q,p[1]);
720 SetPixelRed(q,p[2]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]721 if (bmp_info->biBitCount == 32) {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]722 SetPixelOpacity(q,p[3]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]723 }
724 q++;
725 p+=bmp_info->biBitCount/8;
726 }
727 image->syncPixels(); // sync pixels to pixel cache.
728 }
729 return;
730}
731</div>
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]732
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]733<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>
734
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]735<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]736
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]737<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]738
739<pre class="text">
740 &lt;policy domain="resource" name="thread" value="2"/>
741</pre>
742
743<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>
744
745<pre class="text">
746 export MAGICK_THREAD_LIMIT=12
747</pre>
748
749<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>
750
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]751</div>
752
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]753<h2><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]754<div class="doc-section">
755<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>
756
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]757<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]758
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]759<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Features: OpenMP OpenCL</span></p>
760<p>If so, run this command to realize a significant speed-up for image convolution:</p>
761
cristy4949d522010-03-12 18:41:34 +0000[diff] [blame]762<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]763<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
764
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]765<p>Here is an example OpenCL kernel that convolves an image:</p>
766
767<div class="viewport">
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]768static inline long ClampToCanvas(const long offset,const ulong range)
769{
770 if (offset &lt; 0L)
771 return(0L);
772 if (offset >= range)
773 return((long) (range-1L));
774 return(offset);
775}
776
777static inline CLQuantum ClampToQuantum(const double value)
778{
779 if (value &lt; 0.0)
780 return((CLQuantum) 0);
781 if (value >= (double) QuantumRange)
782 return((CLQuantum) QuantumRange);
783 return((CLQuantum) (value+0.5));
784}
785
786__kernel void Convolve(const __global CLPixelType *source,__constant double *filter,
787 const ulong width,const ulong height,__global CLPixelType *destination)
788{
789 const ulong columns = get_global_size(0);
790 const ulong rows = get_global_size(1);
791
792 const long x = get_global_id(0);
793 const long y = get_global_id(1);
794
795 const double scale = (1.0/QuantumRange);
796 const long mid_width = (width-1)/2;
797 const long mid_height = (height-1)/2;
798 double4 sum = { 0.0, 0.0, 0.0, 0.0 };
799 double gamma = 0.0;
800 register ulong i = 0;
801
802 for (long v=(-mid_height); v &lt;= mid_height; v++)
803 {
804 for (long u=(-mid_width); u &lt;= mid_width; u++)
805 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]806 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
807 columns);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]808 const double alpha=scale*(QuantumRange-source[index].w);
809 sum.x+=alpha*filter[i]*source[index].x;
810 sum.y+=alpha*filter[i]*source[index].y;
811 sum.z+=alpha*filter[i]*source[index].z;
812 sum.w+=filter[i]*source[index].w;
813 gamma+=alpha*filter[i];
814 i++;
815 }
816 }
817
818 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
819 const ulong index=y*columns+x;
820 destination[index].x=ClampToQuantum(gamma*sum.x);
821 destination[index].y=ClampToQuantum(gamma*sum.y);
822 destination[index].z=ClampToQuantum(gamma*sum.z);
823 destination[index].w=ClampToQuantum(sum.w);
824};
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]825</div>
826
cristy37f02952010-03-24 19:47:41 +0000[diff] [blame]827<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]828
829</div>
830
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]831<h2><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]832<div class="doc-section">
833
834<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>
835
836<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>
837
838<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]839/*
840 Include declarations.
841*/
842#include "magick/studio.h"
843#include "magick/blob.h"
844#include "magick/blob-private.h"
845#include "magick/colorspace.h"
846#include "magick/exception.h"
847#include "magick/exception-private.h"
848#include "magick/image.h"
849#include "magick/image-private.h"
850#include "magick/list.h"
851#include "magick/magick.h"
852#include "magick/memory_.h"
853#include "magick/monitor.h"
854#include "magick/monitor-private.h"
855#include "magick/quantum-private.h"
856#include "magick/static.h"
857#include "magick/string_.h"
858#include "magick/module.h"
859
860/*
861 Forward declarations.
862*/
863static MagickBooleanType
864 WriteMGKImage(const ImageInfo *,Image *);
865
866/*
867%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
868% %
869% %
870% %
871% I s M G K %
872% %
873% %
874% %
875%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
876%
877% IsMGK() returns MagickTrue if the image format type, identified by the
878% magick string, is MGK.
879%
880% The format of the IsMGK method is:
881%
882% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
883%
884% A description of each parameter follows:
885%
886% o magick: This string is generally the first few bytes of an image file
887% or blob.
888%
889% o length: Specifies the length of the magick string.
890%
891*/
892static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
893{
894 if (length &lt; 7)
895 return(MagickFalse);
896 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
897 return(MagickTrue);
898 return(MagickFalse);
899}
900
901/*
902%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
903% %
904% %
905% %
906% R e a d M G K I m a g e %
907% %
908% %
909% %
910%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
911%
912% ReadMGKImage() reads a MGK image file and returns it. It allocates
913% the memory necessary for the new Image structure and returns a pointer to
914% the new image.
915%
916% The format of the ReadMGKImage method is:
917%
918% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
919%
920% A description of each parameter follows:
921%
922% o image_info: the image info.
923%
924% o exception: return any errors or warnings in this structure.
925%
926*/
927static Image *ReadMGKImage(const ImageInfo *image_info,
928 ExceptionInfo *exception)
929{
930 char
931 buffer[MaxTextExtent];
932
933 Image
934 *image;
935
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]936 MagickBooleanType
937 status;
938
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]939 register PixelPacket
940 *q;
941
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]942 register size_t
943 x;
944
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]945 register unsigned char
946 *p;
947
948 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]949 count,
950 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]951
952 unsigned char
953 *pixels;
954
955 unsigned long
956 columns,
957 rows;
958
959 /*
960 Open image file.
961 */
962 assert(image_info != (const ImageInfo *) NULL);
963 assert(image_info-&gt;signature == MagickSignature);
964 if (image_info-&gt;debug != MagickFalse)
965 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
966 assert(exception != (ExceptionInfo *) NULL);
967 assert(exception-&gt;signature == MagickSignature);
968 image=AcquireImage(image_info);
969 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
970 if (status == MagickFalse)
971 {
972 image=DestroyImageList(image);
973 return((Image *) NULL);
974 }
975 /*
976 Read MGK image.
977 */
978 (void) ReadBlobString(image,buffer); /* read magic number */
979 if (IsMGK(buffer,7) == MagickFalse)
980 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
981 (void) ReadBlobString(image,buffer);
982 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
983 if (count &lt;= 0)
984 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
985 do
986 {
987 /*
988 Initialize image structure.
989 */
990 image-&gt;columns=columns;
991 image-&gt;rows=rows;
992 image-&gt;depth=8;
993 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
994 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
995 break;
996 /*
997 Convert MGK raster image to pixel packets.
998 */
999 if (SetImageExtent(image,0,0) == MagickFalse)
1000 {
1001 InheritException(exception,&amp;image-&gt;exception);
1002 return(DestroyImageList(image));
1003 }
1004 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
1005 if (pixels == (unsigned char *) NULL)
1006 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1007 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1008 {
1009 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
1010 if (count != (ssize_t) (3*image-&gt;columns))
1011 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
1012 p=pixels;
1013 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
1014 if (q == (PixelPacket *) NULL)
1015 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1016 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1017 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1018 SetPixelRed(q,ScaleCharToQuantum(*p++));
1019 SetPixelGreen(q,ScaleCharToQuantum(*p++));
1020 SetPixelBlue(q,ScaleCharToQuantum(*p++));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1021 q++;
1022 }
1023 if (SyncAuthenticPixels(image,exception) == MagickFalse)
1024 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1025 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1026 (SetImageProgress(image,LoadImageTag,y,image&gt;>rows) == MagickFalse))
1027 break;
1028 }
1029 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1030 if (EOFBlob(image) != MagickFalse)
1031 {
1032 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
1033 break;
1034 }
1035 /*
1036 Proceed to next image.
1037 */
1038 if (image_info-&gt;number_scenes != 0)
1039 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
1040 break;
1041 *buffer='\0';
1042 (void) ReadBlobString(image,buffer);
1043 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1044 if (count != 0)
1045 {
1046 /*
1047 Allocate next image structure.
1048 */
1049 AcquireNextImage(image_info,image);
1050 if (GetNextImageInList(image) == (Image *) NULL)
1051 {
1052 image=DestroyImageList(image);
1053 return((Image *) NULL);
1054 }
1055 image=SyncNextImageInList(image);
1056 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
1057 if (status == MagickFalse)
1058 break;
1059 }
1060 } while (count != 0);
1061 (void) CloseBlob(image);
1062 return(GetFirstImageInList(image));
1063}
1064
1065/*
1066%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1067% %
1068% %
1069% %
1070% R e g i s t e r M G K I m a g e %
1071% %
1072% %
1073% %
1074%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1075%
1076% RegisterMGKImage() adds attributes for the MGK image format to
1077% the list of supported formats. The attributes include the image format
1078% tag, a method to read and/or write the format, whether the format
1079% supports the saving of more than one frame to the same file or blob,
1080% whether the format supports native in-memory I/O, and a brief
1081% description of the format.
1082%
1083% The format of the RegisterMGKImage method is:
1084%
1085% unsigned long RegisterMGKImage(void)
1086%
1087*/
1088ModuleExport unsigned long RegisterMGKImage(void)
1089{
1090 MagickInfo
1091 *entry;
1092
1093 entry=SetMagickInfo("MGK");
1094 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
1095 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
1096 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
1097 entry-&gt;description=ConstantString("MGK");
1098 entry-&gt;module=ConstantString("MGK");
1099 (void) RegisterMagickInfo(entry);
1100 return(MagickImageCoderSignature);
1101}
1102
1103/*
1104%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1105% %
1106% %
1107% %
1108% U n r e g i s t e r M G K I m a g e %
1109% %
1110% %
1111% %
1112%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1113%
1114% UnregisterMGKImage() removes format registrations made by the
1115% MGK module from the list of supported formats.
1116%
1117% The format of the UnregisterMGKImage method is:
1118%
1119% UnregisterMGKImage(void)
1120%
1121*/
1122ModuleExport void UnregisterMGKImage(void)
1123{
1124 (void) UnregisterMagickInfo("MGK");
1125}
1126
1127/*
1128%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1129% %
1130% %
1131% %
1132% W r i t e M G K I m a g e %
1133% %
1134% %
1135% %
1136%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1137%
1138% WriteMGKImage() writes an image to a file in red, green, and blue
1139% MGK rasterfile format.
1140%
1141% The format of the WriteMGKImage method is:
1142%
1143% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1144%
1145% A description of each parameter follows.
1146%
1147% o image_info: the image info.
1148%
1149% o image: The image.
1150%
1151*/
1152static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1153{
1154 char
1155 buffer[MaxTextExtent];
1156
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1157 MagickBooleanType
1158 status;
1159
1160 MagickOffsetType
1161 scene;
1162
1163 register const PixelPacket
1164 *p;
1165
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1166 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1167 x;
1168
1169 register unsigned char
1170 *q;
1171
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1172 ssize_t
1173 y;
1174
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1175 unsigned char
1176 *pixels;
1177
1178 /*
1179 Open output image file.
1180 */
1181 assert(image_info != (const ImageInfo *) NULL);
1182 assert(image_info-&gt;signature == MagickSignature);
1183 assert(image != (Image *) NULL);
1184 assert(image-&gt;signature == MagickSignature);
1185 if (image-&gt;debug != MagickFalse)
1186 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1187 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1188 if (status == MagickFalse)
1189 return(status);
1190 scene=0;
1191 do
1192 {
1193 /*
1194 Allocate memory for pixels.
1195 */
1196 if (image-&gt;colorspace != RGBColorspace)
1197 (void) SetImageColorspace(image,RGBColorspace);
1198 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1199 3UL*sizeof(*pixels));
1200 if (pixels == (unsigned char *) NULL)
1201 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1202 /*
1203 Initialize raster file header.
1204 */
1205 (void) WriteBlobString(image,"id=mgk\n");
1206 (void) FormatMagickString(buffer,MaxTextExtent,"%lu %lu\n",
1207 image-&gt;columns,image-&gt;rows);
1208 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1209 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1210 {
1211 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1212 if (p == (const PixelPacket *) NULL)
1213 break;
1214 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1215 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1216 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1217 *q++=ScaleQuantumToChar(GetPixelRed(p));
1218 *q++=ScaleQuantumToChar(GetPixelGreen(p));
1219 *q++=ScaleQuantumToChar(GetPixelBlue(p));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1220 p++;
1221 }
1222 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1223 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1224 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1225 break;
1226 }
1227 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1228 if (GetNextImageInList(image) == (Image *) NULL)
1229 break;
1230 image=SyncNextImageInList(image);
1231 status=SetImageProgress(image,SaveImagesTag,scene,
1232 GetImageListLength(image));
1233 if (status == MagickFalse)
1234 break;
1235 scene++;
1236 } while (image_info-&gt;adjoin != MagickFalse);
1237 (void) CloseBlob(image);
1238 return(MagickTrue);
1239}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1240</div>
1241
1242<p>To invoke the custom coder from the command line, use these commands:</p>
1243
1244<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>
1245<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>
1246
1247</div>
1248
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1249<h2><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1250<div class="doc-section">
1251
1252<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>
1253
1254<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>
1255
1256<div class="viewport">
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1257#include &lt;stdio.h&gt;
1258#include &lt;stdlib.h&gt;
1259#include &lt;string.h&gt;
1260#include &lt;time.h&gt;
1261#include &lt;assert.h&gt;
1262#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1263#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1264
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1265/*
1266%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1267% %
1268% %
1269% %
1270% a n a l y z e I m a g e %
1271% %
1272% %
1273% %
1274%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1275%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1276% analyzeImage() computes the brightness and saturation mean, standard
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]1277% deviation, kurtosis and skewness and stores these values as attributes
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1278% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1279%
1280% The format of the analyzeImage method is:
1281%
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1282% size_t analyzeImage(Image *images,const int argc,char **argv,
1283% ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1284%
1285% A description of each parameter follows:
1286%
1287% o image: the address of a structure of type Image.
1288%
1289% o argc: Specifies a pointer to an integer describing the number of
1290% elements in the argument vector.
1291%
1292% o argv: Specifies a pointer to a text array containing the command line
1293% arguments.
1294%
1295% o exception: return any errors or warnings in this structure.
1296%
1297*/
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1298ModuleExport size_t analyzeImage(Image **images,const int argc,const char **argv,
1299 ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1300{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1301 char
1302 text[MaxTextExtent];
1303
1304 double
1305 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1306 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1307 brightness_mean,
1308 brightness_standard_deviation,
1309 brightness_kurtosis,
1310 brightness_skewness,
1311 brightness_sum_x,
1312 brightness_sum_x2,
1313 brightness_sum_x3,
1314 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1315 hue,
1316 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1317 saturation_mean,
1318 saturation_standard_deviation,
1319 saturation_kurtosis,
1320 saturation_skewness,
1321 saturation_sum_x,
1322 saturation_sum_x2,
1323 saturation_sum_x3,
1324 saturation_sum_x4;
1325
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1326 Image
1327 *image;
1328
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1329 assert(images != (Image **) NULL);
1330 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1331 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1332 (void) argc;
1333 (void) argv;
1334 image=(*images);
1335 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1336 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1337 CacheView
1338 *image_view;
1339
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1340 MagickBooleanType
1341 status;
1342
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1343 ssize_t
1344 y;
1345
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1346 brightness_sum_x=0.0;
1347 brightness_sum_x2=0.0;
1348 brightness_sum_x3=0.0;
1349 brightness_sum_x4=0.0;
1350 brightness_mean=0.0;
1351 brightness_standard_deviation=0.0;
1352 brightness_kurtosis=0.0;
1353 brightness_skewness=0.0;
1354 saturation_sum_x=0.0;
1355 saturation_sum_x2=0.0;
1356 saturation_sum_x3=0.0;
1357 saturation_sum_x4=0.0;
1358 saturation_mean=0.0;
1359 saturation_standard_deviation=0.0;
1360 saturation_kurtosis=0.0;
1361 saturation_skewness=0.0;
1362 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1363 status=MagickTrue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1364 image_view=AcquireCacheView(image);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1365#if defined(MAGICKCORE_OPENMP_SUPPORT)
1366 #pragma omp parallel for schedule(dynamic,4) shared(status)
1367#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1368 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1369 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1370 register const PixelPacket
1371 *p;
1372
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1373 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1374 x;
1375
1376 if (status == MagickFalse)
1377 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1378 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1379 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1380 {
1381 status=MagickFalse;
1382 continue;
1383 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1384 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1385 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1386 ConvertRGBToHSB(GetPixelRed(p),GetPixelGreen(p),GetPixelBue(p),&amp;hue,&amp;saturation,&amp;brightness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1387 brightness*=QuantumRange;
1388 brightness_sum_x+=brightness;
1389 brightness_sum_x2+=brightness*brightness;
1390 brightness_sum_x3+=brightness*brightness*brightness;
1391 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1392 saturation*=QuantumRange;
1393 saturation_sum_x+=saturation;
1394 saturation_sum_x2+=saturation*saturation;
1395 saturation_sum_x3+=saturation*saturation*saturation;
1396 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1397 area++;
1398 p++;
1399 }
1400 }
1401 image_view=DestroyCacheView(image_view);
1402 if (area &lt;= 0.0)
1403 break;
1404 brightness_mean=brightness_sum_x/area;
1405 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_mean);
1406 (void) SetImageProperty(image,"filter:brightness:mean",text);
1407 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1408 area*brightness_sum_x/area));
1409 (void) FormatMagickString(text,MaxTextExtent,"%g",
1410 brightness_standard_deviation);
1411 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1412 if (brightness_standard_deviation != 0)
1413 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1414 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1415 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1416 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1417 brightness_standard_deviation*brightness_standard_deviation*
1418 brightness_standard_deviation)-3.0;
1419 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_kurtosis);
1420 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1421 if (brightness_standard_deviation != 0)
1422 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1423 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1424 brightness_mean)/(brightness_standard_deviation*
1425 brightness_standard_deviation*brightness_standard_deviation);
1426 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_skewness);
1427 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1428 saturation_mean=saturation_sum_x/area;
1429 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_mean);
1430 (void) SetImageProperty(image,"filter:saturation:mean",text);
1431 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1432 area*saturation_sum_x/area));
1433 (void) FormatMagickString(text,MaxTextExtent,"%g",
1434 saturation_standard_deviation);
1435 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1436 if (saturation_standard_deviation != 0)
1437 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1438 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1439 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1440 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1441 saturation_standard_deviation*saturation_standard_deviation*
1442 saturation_standard_deviation)-3.0;
1443 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_kurtosis);
1444 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1445 if (saturation_standard_deviation != 0)
1446 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1447 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1448 saturation_mean)/(saturation_standard_deviation*
1449 saturation_standard_deviation*saturation_standard_deviation);
1450 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_skewness);
1451 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1452 }
1453 return(MagickImageFilterSignature);
1454}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1455</div>
1456
1457<p>To invoke the custom filter from the command line, use this command:</p>
1458
cristy323f35b2011-03-24 23:05:13 +0000[diff] [blame]1459<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/>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1460 Format: LOGO (ImageMagick Logo) <br/>
1461 Class: PseudoClass <br/>
1462 Geometry: 640x480 <br/>
1463 ... <br/>
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1464 filter:brightness:kurtosis: 8.17947 <br/>
1465 filter:brightness:mean: 60632.1 <br/>
1466 filter:brightness:skewness: -2.97118 <br/>
1467 filter:brightness:standard-deviation: 13742.1 <br/>
1468 filter:saturation:kurtosis: 4.33554 <br/>
1469 filter:saturation:mean: 5951.55 <br/>
1470 filter:saturation:skewness: 2.42848 <br/>
1471 filter:saturation:standard-deviation: 15575.9</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1472
1473<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>
1474
1475</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1476
1477</div>
1478
1479<div id="linkbar">
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1487 <div class="footer">
cristy7e41fe82010-12-04 23:12:08 +0000[diff] [blame]1488 <span id="footer-west">&copy; 1999-2011 ImageMagick Studio LLC</span>
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