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215<div class="main">
216
217
218
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]219<h1>The <em>Magick</em> Behind ImageMagick</h1>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]220<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]221
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]222
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]223<div class="doc-section">
224<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>
225</div>
226
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]227<h2><a id="overview"></a>Architecture Overview</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]228<div class="doc-section">
229
230<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>
231
232<ul>
233 <li>colorspace (e.g RGB, CMYK, YUV, Lab, etc.)</li>
234 <li>bit depth (.e.g 1, 4, 8, 12, 16, etc.)</li>
235 <li>storage format (e.g. unsigned, signed, float, double, etc.)</li>
236 <li>compression (e.g. uncompressed, RLE, Zip, BZip, etc.)</li>
237 <li>orientation (i.e. top-to-bottom, right-to-left, etc.),</li>
238 <li>layout (.e.g. raw, interspersed with opcodes, etc.)</li>
239</ul>
240
241<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>
242
243<p>An efficient implementation of an image processing algorithm may require we get or set:</p>
244
245<ul>
246 <li>one pixel a time (e.g. pixel at location 10,3)</li>
247 <li>a single scanline (e.g. all pixels from row 4)</li>
248 <li>a few scanlines at once (e.g. pixel rows 4-7)</li>
249 <li>a single column or columns of pixels (e.g. all pixels from column 11)</li>
250 <li>an arbitrary region of pixels from the image (e.g. pixels defined at 10,7 to 10,19)</li>
251 <li>a pixel in random order (e.g. pixel at 14,15 and 640,480)</li>
252 <li>pixels from two different images (e.g. pixel at 5,1 from image 1 and pixel at 5,1 from image 2)</li>
253 <li>pixels outside the boundaries of the image (e.g. pixel at -1,-3)</li>
254 <li>a pixel component that is unsigned or in a floating-point representation (e.g. 0.17836)</li>
255 <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>
256 <li>one or more pixels simultaneously in different threads of execution</li>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]257 <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]258</ul>
259
260<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>
261
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]262<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]263
cristy320dd6e2010-04-16 20:11:40 +0000[diff] [blame]264<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]265
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]266<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]267
268</div>
269
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]270<h2><a id="cache"></a>The Pixel Cache</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]271<div class="doc-section">
272
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]273<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]274
275<h3>Create the Pixel Cache</h3>
276<div class="doc-section">
277
278<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>
279
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]280<dl>
281<dt>Create an image canvas initialized to the background color:</dt>
282<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]283 image=AllocateImage(image_info);
284 if (SetImageExtent(image,640,480) == MagickFalse)
285 { /* an exception was thrown */ }
286 (void) QueryMagickColor("red",&amp;image-&gt;background_color,&amp;image-&gt;exception);
287 SetImageBackgroundColor(image);
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]288</p></dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]289
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]290<dt>Create an image from a JPEG image on disk:</dt>
291<dd><p class="code">
292 (void) strcpy(image_info-&gt;filename,"image.jpg"):
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]293 image=ReadImage(image_info,exception);
294 if (image == (Image *) NULL)
295 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]296</p></dd>
297<dt>Create an image from a memory based image:</dt>
298<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]299 image=BlobToImage(blob_info,blob,extent,exception);
300 if (image == (Image *) NULL)
301 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]302</p></dd>
303</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]304
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]305<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]306
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]307<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]308
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]309<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Version: ImageMagick 6.7.0-9 2011-06-03 Q16 http://www.imagemagick.org</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]310<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]311</div>
312
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]313<h3><a id="authentic-pixels"></a>Access the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]314<div class="doc-section">
315
316<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]317<ul>
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]318 <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]319 <li><a href="../www/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> gets pixels that you intend to modify</li>
320 <li><a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> queue pixels that you intend to modify</li>
321 <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]322</ul>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]323
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]324<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]325
326<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]327 const PixelPacket
328 *p;
329
330 PixelPacket
331 *q;
332
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]333 ssize_t
334 x,
335 y;
336
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]337 destination=CloneImage(source,source->columns,source->rows,MagickTrue,
338 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]339 if (destination == (Image *) NULL)
340 { /* an exception was thrown */ }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]341 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]342 {
343 p=GetVirtualPixels(source,0,y,source-&gt;columns,1,exception);
344 q=GetAuthenticPixels(destination,0,y,destination-&gt;columns,1,exception);
345 if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL)
346 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]347 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]348 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]349 SetPixelRed(q,90*p-&gt;red/100);
350 SetPixelGreen(q,90*p-&gt;green/100);
351 SetPixelBlue(q,90*p-&gt;blue/100);
352 SetPixelOpacity(q,90*p-&gt;opacity/100);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]353 p++;
354 q++;
355 }
356 if (SyncAuthenticPixels(destination,exception) == MagickFalse)
357 break;
358 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]359 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]360 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]361</div>
362
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]363<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]364
cristy84134182011-06-15 22:59:00 +0000[diff] [blame]365<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]366
367<pre class="code">
368 const IndexPacket
369 *indexes;
370
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]371 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]372 {
373 p=GetVirtualPixels(source,0,y,source-&gt;columns,1);
374 if (p == (const PixelPacket *) NULL)
375 break;
cristy84134182011-06-15 22:59:00 +0000[diff] [blame]376 indexes=GetVirtualIndexQueue(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]377 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]378 (void) printf("%d\n",GetPixelIndex(indexes+x));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]379 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]380 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]381 /* an exception was thrown */
382</pre>
383
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]384<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]385
386<pre class="code">
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]387 p=GetVirtualPixels(source,-3,-3,source-&gt;columns+3,6,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]388</pre>
389
390<p>gives you the pixels you asked for without complaint, even though some are not within the confines of the image region.</p>
391</div>
392
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]393<h3><a id="virtual-pixels"></a>Virtual Pixels</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]394<div class="doc-section">
395
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]396<p>There are a plethora of image processing algorithms that require a neighborhood of pixels about a pixel of interest. The algorithm typically includes a caveat concerning how to handle pixels around the image boundaries, known as edge pixels. With virtual pixels, you do not need to concern yourself about special edge processing other than choosing which virtual pixel method is most appropriate for your algorithm.</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]397 <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>
398
cristy4c54bbb2011-03-17 13:53:13 +0000[diff] [blame]399<pre class="text" style="font-size: 83.3333%;">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]400 background: the area surrounding the image is the background color
401 black: the area surrounding the image is black
402 checker-tile: alternate squares with image and background color
403 dither: non-random 32x32 dithered pattern
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]404 edge: extend the edge pixel toward infinity (default)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]405 gray: the area surrounding the image is gray
406 horizontal-tile: horizontally tile the image, background color above/below
407 horizontal-tile-edge: horizontally tile the image and replicate the side edge pixels
408 mirror: mirror tile the image
409 random: choose a random pixel from the image
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]410 tile: tile the image
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]411 transparent: the area surrounding the image is transparent blackness
412 vertical-tile: vertically tile the image, sides are background color
413 vertical-tile-edge: vertically tile the image and replicate the side edge pixels
414 white: the area surrounding the image is white
415</pre>
416
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]417</div>
418
419<h3>Cache Storage and Resource Requirements</h3>
420<div class="doc-section">
421
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]422<p>Recall that this simple and elegant design of the ImageMagick pixel cache comes at a cost in terms of storage and processing speed. The pixel cache storage requirements scales with the area of the image and the bit depth of the pixel components. For example, if we have a 640 by 480 image and we are using the Q16 version of ImageMagick, the pixel cache consumes image <em>width * height * bit-depth / 8 * channels</em> bytes or approximately 2.3 mebibytes (i.e. 640 * 480 * 2 * 4). Not too bad, but what if your image is 25000 by 25000 pixels? The pixel cache requires approximately 4.7 gibibytes of storage. Ouch. ImageMagick accounts for possible huge storage requirements by caching large images to disk rather than memory. Typically the pixel cache is stored in memory using heap memory. If heap memory is exhausted, pixels are stored in in an anonymous map; if the anonymous memory map is exhausted, we create the pixel cache on disk and attempt to memory-map it; and if memory-map memory is exhausted, we simply use standard disk I/O. Disk storage is cheap but it is also very slow, upwards of 1000 times slower than memory. We can get some speed improvements, up to 5 times, if we use memory mapping to the disk-based cache. These decisions about storage are made <em>automagically</em> by the pixel cache manager negotiating with the operating system. However, you can influence how the pixel cache manager allocates the pixel cache with <em>cache resource limits</em>. The limits include:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]423
424<dl class="doc">
425 <dt class="doc">files</dt>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]426 <dd>maximum number of open pixel cache files. When this limit is exceeded, any subsequent pixels cached to disk are closed and reopened on demand. This behavior permits a large number of images to be accessed simultaneously on disk, but without a speed penalty due to repeated open/close calls.</dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]427 <dt class="doc">area</dt>
428 <dd>maximum area in bytes of any one image that can reside in the pixel cache memory. If this limit is exceeded, the image is automagically cached to disk.</dd>
429 <dt class="doc">memory</dt>
430 <dd>maximum amount of memory in bytes to allocate for the pixel cache from the anonymous mapped memory or the heap.</dd>
431 <dt class="doc">map</dt>
432 <dd>maximum amount of memory map in bytes to allocate for the pixel cache.</dd>
433 <dt class="doc">disk</dt>
434 <dd>maximum amount of disk space in bytes permitted for use by the pixel cache. If this limit is exceeded, the pixel cache is not created and a fatal exception is thrown.</dd>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]435 <dt class="doc">thread</dt>
436 <dd>maximum number of threads that are permitted to run in parallel.</dd>
437 <dt class="doc">time</dt>
438 <dd>maximum number of seconds that the process is permitted to execute. When this limit is exceeded, an exception is thrown and processing stops.</dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]439</dl>
440
441<p>To determine the current setting of these limits, use this command:</p>
442
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]443<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -list resource</span></p><pre class="text">
444File Area Memory Map Disk Thread Time
cristy2c839602010-04-03 02:32:08 +0000[diff] [blame]445-------------------------------------------------------------------------------
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]446 768 1.0386GB 3.8692GiB 7.7384GiB unlimited 4 unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]447</pre>
448
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]449<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]450
451<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>
452</div>
453
454<h3>Cache Views</h3>
455<div class="doc-section">
456
457<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>
458
459<pre class="code">
460 CacheView
461 *view_1,
462 *view_2;
463
cristye9a32c32011-04-07 01:11:05 +0000[diff] [blame]464 view_1=AcquireCacheView(source);
465 view_2=AcquireCacheView(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]466 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]467 {
468 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]469 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,
470 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]471 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
472 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]473 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]474 {
475 /* do something with u &amp; v here */
476 }
477 }
cristye9a32c32011-04-07 01:11:05 +0000[diff] [blame]478 view_2=DestroyCacheView(view_2);
479 view_1=DestroyCacheView(view_1);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]480 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]481 { /* an exception was thrown */ }
482</pre>
483</div>
484
485<h3>Magick Persistent Cache Format</h3>
486<div class="doc-section">
487
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]488<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]489<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]490</div>
491
492<h3>Best Practices</h3>
493<div class="doc-section">
494
cristy30092792011-02-22 02:06:14 +0000[diff] [blame]495<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]496
497<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>
498
499<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>
500
501<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>
502
503<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>
504
505<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>
506
507<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>
508
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]509<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]510
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]511<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]512
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]513<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]514
515<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>
516
517<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>
518<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>
519</div>
520
521</div>
522
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]523<h2><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]524<div class="doc-section">
525
526<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>
527
528<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>
529
530<pre class="code">
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]531static size_t StreamPixels(const Image *image,const void *pixels,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]532 const size_t columns)
533{
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]534 register const PixelPacket
535 *p;
536
537 MyData
538 *my_data;
539
540 my_data=(MyData *) image->client_data;
541 p=(PixelPacket *) pixels;
542 if (p != (const PixelPacket *) NULL)
543 {
544 /* process pixels here */
545 }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]546 return(columns);
547}
548
549...
550/* invoke the pixel stream here */
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]551image_info->client_data=(void *) MyData;
552image=ReadStream(image_info,&amp;StreamPixels,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]553</pre>
554
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]555<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]556
557</div>
558
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]559<h2><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]560<div class="doc-section">
561
562<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>
563
564<pre class="code">
565 (void) printf("image width: %lu, height: %lu\n",image-&gt;columns,image-&gt;rows);
566</pre>
567
568<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>
569
570<pre class="code">
571 const char
572 *comment;
573
574 (void) SetImageProperty(image,"comment","This space for rent");
575 comment=GetImageProperty(image,"comment");
576 if (comment == (const char *) NULL)
577 (void) printf("Image comment: %s\n",comment);
578</pre>
579
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]580<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]581
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]582<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>
583
584<pre class="code">
585 StringInfo
586 *profile;
587
588 profile=AcquireStringInfo(length);
589 SetStringInfoDatum(profile,my_exif_profile);
590 (void) SetImageProfile(image,"EXIF",profile);
591 DestroyStringInfo(profile);
592 profile=GetImageProfile(image,"EXIF");
593 if (profile != (StringInfo *) NULL)
594 (void) PrintStringInfo(stdout,"EXIF",profile);
595</pre>
596
597</div>
598
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]599<h2><a id="tera-pixel"></a>Large Image Support</h2>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]600<div class="doc-section">
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]601<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]602
603<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]604<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]605
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]606<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]607<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>
608
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]609<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]610<p>Here we force all image pixels to disk:</p>
611
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]612<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]613<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]614
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]615<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]616
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]617<h2><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]618<div class="doc-section">
619
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]620<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]621
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]622<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]623
624<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]625{
626 CacheView
627 *image_view;
628
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]629 MagickBooleanType
630 status;
631
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]632 ssize_t
633 y;
634
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]635 status=MagickTrue;
636 image_view=AcquireCacheView(image);
637 #pragma omp parallel for schedule(dynamic,4) shared(status)
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]638 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]639 {
640 register IndexPacket
641 *indexes;
642
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]643 register PixelPacket
644 *q;
645
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]646 register ssize_t
647 x;
648
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]649 if (status == MagickFalse)
650 continue;
651 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
652 if (q == (PixelPacket *) NULL)
653 {
654 status=MagickFalse;
655 continue;
656 }
657 indexes=GetCacheViewAuthenticIndexQueue(image_view);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]658 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]659 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]660 SetPixelRed(q,...);
661 SetPixelGreen(q,...);
662 SetPixelBlue(q,...);
663 SetPixelOpacity(q,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]664 if (indexes != (IndexPacket *) NULL)
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]665 SetPixelIndex(indexes+x,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]666 q++;
667 }
668 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
669 status=MagickFalse;
670 }
671 image_view=DestroyCacheView(image_view);
672 if (status == MagickFalse)
673 perror("something went wrong");
674}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]675</div>
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]676<p>This code snippet converts an uncompressed Windows bitmap to a Magick++ image:</p>
677<div class="viewport">
678#include "Magick++.h"
679#include &lt;assert.h&gt;
680#include "omp.h"
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]681
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]682void ConvertBMPToImage(const BITMAPINFOHEADER *bmp_info,
683 const unsigned char *restrict pixels,Magick::Image *image)
684{
685 /*
686 Prepare the image so that we can modify the pixels directly.
687 */
688 assert(bmp_info->biCompression == BI_RGB);
689 assert(bmp_info->biWidth == image->columns());
690 assert(abs(bmp_info->biHeight) == image->rows());
691 image->modifyImage();
692 if (bmp_info->biBitCount == 24)
693 image->type(MagickCore::TrueColorType);
694 else
695 image->type(MagickCore::TrueColorMatteType);
696 register unsigned int bytes_per_row=bmp_info->biWidth*bmp_info->biBitCount/8;
697 if (bytes_per_row % 4 != 0) {
698 bytes_per_row=bytes_per_row+(4-bytes_per_row % 4); // divisible by 4.
699 }
700 /*
701 Copy all pixel data, row by row.
702 */
703 #pragma omp parallel for
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]704 for (int y=0; y &lt; int(image->rows()); y++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]705 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]706 int
707 row;
708
709 register const unsigned char
710 *restrict p;
711
712 register MagickCore::PixelPacket
713 *restrict q;
714
715 row=(bmp_info->biHeight > 0) ? (image->rows()-y-1) : y;
716 p=pixels+row*bytes_per_row;
717 q=image->setPixels(0,y,image->columns(),1);
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]718 for (int x=0; x &lt; int(image->columns()); x++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]719 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]720 SetPixelBlue(q,p[0]);
721 SetPixelGreen(q,p[1]);
722 SetPixelRed(q,p[2]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]723 if (bmp_info->biBitCount == 32) {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]724 SetPixelOpacity(q,p[3]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]725 }
726 q++;
727 p+=bmp_info->biBitCount/8;
728 }
729 image->syncPixels(); // sync pixels to pixel cache.
730 }
731 return;
732}
733</div>
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]734
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]735<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>
736
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]737<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]738
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]739<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]740
741<pre class="text">
742 &lt;policy domain="resource" name="thread" value="2"/>
743</pre>
744
745<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>
746
747<pre class="text">
748 export MAGICK_THREAD_LIMIT=12
749</pre>
750
751<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>
752
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]753</div>
754
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]755<h2><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]756<div class="doc-section">
757<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>
758
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]759<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]760
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]761<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Features: OpenMP OpenCL</span></p>
762<p>If so, run this command to realize a significant speed-up for image convolution:</p>
763
cristy4949d522010-03-12 18:41:34 +0000[diff] [blame]764<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]765<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
766
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]767<p>Here is an example OpenCL kernel that convolves an image:</p>
768
769<div class="viewport">
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]770static inline long ClampToCanvas(const long offset,const ulong range)
771{
772 if (offset &lt; 0L)
773 return(0L);
774 if (offset >= range)
775 return((long) (range-1L));
776 return(offset);
777}
778
779static inline CLQuantum ClampToQuantum(const double value)
780{
781 if (value &lt; 0.0)
782 return((CLQuantum) 0);
783 if (value >= (double) QuantumRange)
784 return((CLQuantum) QuantumRange);
785 return((CLQuantum) (value+0.5));
786}
787
788__kernel void Convolve(const __global CLPixelType *source,__constant double *filter,
789 const ulong width,const ulong height,__global CLPixelType *destination)
790{
791 const ulong columns = get_global_size(0);
792 const ulong rows = get_global_size(1);
793
794 const long x = get_global_id(0);
795 const long y = get_global_id(1);
796
797 const double scale = (1.0/QuantumRange);
798 const long mid_width = (width-1)/2;
799 const long mid_height = (height-1)/2;
800 double4 sum = { 0.0, 0.0, 0.0, 0.0 };
801 double gamma = 0.0;
802 register ulong i = 0;
803
804 for (long v=(-mid_height); v &lt;= mid_height; v++)
805 {
806 for (long u=(-mid_width); u &lt;= mid_width; u++)
807 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]808 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
809 columns);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]810 const double alpha=scale*(QuantumRange-source[index].w);
811 sum.x+=alpha*filter[i]*source[index].x;
812 sum.y+=alpha*filter[i]*source[index].y;
813 sum.z+=alpha*filter[i]*source[index].z;
814 sum.w+=filter[i]*source[index].w;
815 gamma+=alpha*filter[i];
816 i++;
817 }
818 }
819
820 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
821 const ulong index=y*columns+x;
822 destination[index].x=ClampToQuantum(gamma*sum.x);
823 destination[index].y=ClampToQuantum(gamma*sum.y);
824 destination[index].z=ClampToQuantum(gamma*sum.z);
825 destination[index].w=ClampToQuantum(sum.w);
826};
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]827</div>
828
cristy37f02952010-03-24 19:47:41 +0000[diff] [blame]829<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]830
831</div>
832
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]833<h2><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]834<div class="doc-section">
835
836<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>
837
838<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>
839
840<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]841/*
842 Include declarations.
843*/
844#include "magick/studio.h"
845#include "magick/blob.h"
846#include "magick/blob-private.h"
847#include "magick/colorspace.h"
848#include "magick/exception.h"
849#include "magick/exception-private.h"
850#include "magick/image.h"
851#include "magick/image-private.h"
852#include "magick/list.h"
853#include "magick/magick.h"
854#include "magick/memory_.h"
855#include "magick/monitor.h"
856#include "magick/monitor-private.h"
857#include "magick/quantum-private.h"
858#include "magick/static.h"
859#include "magick/string_.h"
860#include "magick/module.h"
861
862/*
863 Forward declarations.
864*/
865static MagickBooleanType
866 WriteMGKImage(const ImageInfo *,Image *);
867
868/*
869%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
870% %
871% %
872% %
873% I s M G K %
874% %
875% %
876% %
877%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
878%
879% IsMGK() returns MagickTrue if the image format type, identified by the
880% magick string, is MGK.
881%
882% The format of the IsMGK method is:
883%
884% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
885%
886% A description of each parameter follows:
887%
888% o magick: This string is generally the first few bytes of an image file
889% or blob.
890%
891% o length: Specifies the length of the magick string.
892%
893*/
894static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
895{
896 if (length &lt; 7)
897 return(MagickFalse);
898 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
899 return(MagickTrue);
900 return(MagickFalse);
901}
902
903/*
904%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
905% %
906% %
907% %
908% R e a d M G K I m a g e %
909% %
910% %
911% %
912%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
913%
914% ReadMGKImage() reads a MGK image file and returns it. It allocates
915% the memory necessary for the new Image structure and returns a pointer to
916% the new image.
917%
918% The format of the ReadMGKImage method is:
919%
920% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
921%
922% A description of each parameter follows:
923%
924% o image_info: the image info.
925%
926% o exception: return any errors or warnings in this structure.
927%
928*/
929static Image *ReadMGKImage(const ImageInfo *image_info,
930 ExceptionInfo *exception)
931{
932 char
933 buffer[MaxTextExtent];
934
935 Image
936 *image;
937
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]938 MagickBooleanType
939 status;
940
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]941 register PixelPacket
942 *q;
943
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]944 register size_t
945 x;
946
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]947 register unsigned char
948 *p;
949
950 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]951 count,
952 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]953
954 unsigned char
955 *pixels;
956
957 unsigned long
958 columns,
959 rows;
960
961 /*
962 Open image file.
963 */
964 assert(image_info != (const ImageInfo *) NULL);
965 assert(image_info-&gt;signature == MagickSignature);
966 if (image_info-&gt;debug != MagickFalse)
967 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
968 assert(exception != (ExceptionInfo *) NULL);
969 assert(exception-&gt;signature == MagickSignature);
970 image=AcquireImage(image_info);
971 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
972 if (status == MagickFalse)
973 {
974 image=DestroyImageList(image);
975 return((Image *) NULL);
976 }
977 /*
978 Read MGK image.
979 */
980 (void) ReadBlobString(image,buffer); /* read magic number */
981 if (IsMGK(buffer,7) == MagickFalse)
982 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
983 (void) ReadBlobString(image,buffer);
984 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
985 if (count &lt;= 0)
986 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
987 do
988 {
989 /*
990 Initialize image structure.
991 */
992 image-&gt;columns=columns;
993 image-&gt;rows=rows;
994 image-&gt;depth=8;
995 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
996 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
997 break;
998 /*
999 Convert MGK raster image to pixel packets.
1000 */
1001 if (SetImageExtent(image,0,0) == MagickFalse)
1002 {
1003 InheritException(exception,&amp;image-&gt;exception);
1004 return(DestroyImageList(image));
1005 }
1006 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
1007 if (pixels == (unsigned char *) NULL)
1008 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1009 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1010 {
1011 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
1012 if (count != (ssize_t) (3*image-&gt;columns))
1013 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
1014 p=pixels;
1015 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
1016 if (q == (PixelPacket *) NULL)
1017 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1018 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1019 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]1020 SetPixelRed(q,ScaleCharToQuantum(*p++));
1021 SetPixelGreen(q,ScaleCharToQuantum(*p++));
1022 SetPixelBlue(q,ScaleCharToQuantum(*p++));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1023 q++;
1024 }
1025 if (SyncAuthenticPixels(image,exception) == MagickFalse)
1026 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1027 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1028 (SetImageProgress(image,LoadImageTag,y,image&gt;>rows) == MagickFalse))
1029 break;
1030 }
1031 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1032 if (EOFBlob(image) != MagickFalse)
1033 {
1034 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
1035 break;
1036 }
1037 /*
1038 Proceed to next image.
1039 */
1040 if (image_info-&gt;number_scenes != 0)
1041 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
1042 break;
1043 *buffer='\0';
1044 (void) ReadBlobString(image,buffer);
1045 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1046 if (count != 0)
1047 {
1048 /*
1049 Allocate next image structure.
1050 */
1051 AcquireNextImage(image_info,image);
1052 if (GetNextImageInList(image) == (Image *) NULL)
1053 {
1054 image=DestroyImageList(image);
1055 return((Image *) NULL);
1056 }
1057 image=SyncNextImageInList(image);
1058 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
1059 if (status == MagickFalse)
1060 break;
1061 }
1062 } while (count != 0);
1063 (void) CloseBlob(image);
1064 return(GetFirstImageInList(image));
1065}
1066
1067/*
1068%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1069% %
1070% %
1071% %
1072% R e g i s t e r M G K I m a g e %
1073% %
1074% %
1075% %
1076%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1077%
1078% RegisterMGKImage() adds attributes for the MGK image format to
1079% the list of supported formats. The attributes include the image format
1080% tag, a method to read and/or write the format, whether the format
1081% supports the saving of more than one frame to the same file or blob,
1082% whether the format supports native in-memory I/O, and a brief
1083% description of the format.
1084%
1085% The format of the RegisterMGKImage method is:
1086%
1087% unsigned long RegisterMGKImage(void)
1088%
1089*/
1090ModuleExport unsigned long RegisterMGKImage(void)
1091{
1092 MagickInfo
1093 *entry;
1094
1095 entry=SetMagickInfo("MGK");
1096 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
1097 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
1098 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
1099 entry-&gt;description=ConstantString("MGK");
1100 entry-&gt;module=ConstantString("MGK");
1101 (void) RegisterMagickInfo(entry);
1102 return(MagickImageCoderSignature);
1103}
1104
1105/*
1106%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1107% %
1108% %
1109% %
1110% U n r e g i s t e r M G K I m a g e %
1111% %
1112% %
1113% %
1114%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1115%
1116% UnregisterMGKImage() removes format registrations made by the
1117% MGK module from the list of supported formats.
1118%
1119% The format of the UnregisterMGKImage method is:
1120%
1121% UnregisterMGKImage(void)
1122%
1123*/
1124ModuleExport void UnregisterMGKImage(void)
1125{
1126 (void) UnregisterMagickInfo("MGK");
1127}
1128
1129/*
1130%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1131% %
1132% %
1133% %
1134% W r i t e M G K I m a g e %
1135% %
1136% %
1137% %
1138%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1139%
1140% WriteMGKImage() writes an image to a file in red, green, and blue
1141% MGK rasterfile format.
1142%
1143% The format of the WriteMGKImage method is:
1144%
1145% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1146%
1147% A description of each parameter follows.
1148%
1149% o image_info: the image info.
1150%
1151% o image: The image.
1152%
1153*/
1154static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1155{
1156 char
1157 buffer[MaxTextExtent];
1158
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1159 MagickBooleanType
1160 status;
1161
1162 MagickOffsetType
1163 scene;
1164
1165 register const PixelPacket
1166 *p;
1167
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1168 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1169 x;
1170
1171 register unsigned char
1172 *q;
1173
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1174 ssize_t
1175 y;
1176
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1177 unsigned char
1178 *pixels;
1179
1180 /*
1181 Open output image file.
1182 */
1183 assert(image_info != (const ImageInfo *) NULL);
1184 assert(image_info-&gt;signature == MagickSignature);
1185 assert(image != (Image *) NULL);
1186 assert(image-&gt;signature == MagickSignature);
1187 if (image-&gt;debug != MagickFalse)
1188 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1189 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1190 if (status == MagickFalse)
1191 return(status);
1192 scene=0;
1193 do
1194 {
1195 /*
1196 Allocate memory for pixels.
1197 */
1198 if (image-&gt;colorspace != RGBColorspace)
1199 (void) SetImageColorspace(image,RGBColorspace);
1200 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1201 3UL*sizeof(*pixels));
1202 if (pixels == (unsigned char *) NULL)
1203 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1204 /*
1205 Initialize raster file header.
1206 */
1207 (void) WriteBlobString(image,"id=mgk\n");
1208 (void) FormatMagickString(buffer,MaxTextExtent,"%lu %lu\n",
1209 image-&gt;columns,image-&gt;rows);
1210 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1211 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1212 {
1213 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1214 if (p == (const PixelPacket *) NULL)
1215 break;
1216 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1217 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1218 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]1219 *q++=ScaleQuantumToChar(GetPixelRed(p));
1220 *q++=ScaleQuantumToChar(GetPixelGreen(p));
1221 *q++=ScaleQuantumToChar(GetPixelBlue(p));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1222 p++;
1223 }
1224 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1225 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1226 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1227 break;
1228 }
1229 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1230 if (GetNextImageInList(image) == (Image *) NULL)
1231 break;
1232 image=SyncNextImageInList(image);
1233 status=SetImageProgress(image,SaveImagesTag,scene,
1234 GetImageListLength(image));
1235 if (status == MagickFalse)
1236 break;
1237 scene++;
1238 } while (image_info-&gt;adjoin != MagickFalse);
1239 (void) CloseBlob(image);
1240 return(MagickTrue);
1241}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1242</div>
1243
1244<p>To invoke the custom coder from the command line, use these commands:</p>
1245
1246<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>
1247<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>
1248
1249</div>
1250
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1251<h2><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1252<div class="doc-section">
1253
1254<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>
1255
1256<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>
1257
1258<div class="viewport">
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1259#include &lt;stdio.h&gt;
1260#include &lt;stdlib.h&gt;
1261#include &lt;string.h&gt;
1262#include &lt;time.h&gt;
1263#include &lt;assert.h&gt;
1264#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1265#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1266
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1267/*
1268%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1269% %
1270% %
1271% %
1272% a n a l y z e I m a g e %
1273% %
1274% %
1275% %
1276%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1277%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1278% analyzeImage() computes the brightness and saturation mean, standard
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]1279% deviation, kurtosis and skewness and stores these values as attributes
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1280% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1281%
1282% The format of the analyzeImage method is:
1283%
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1284% size_t analyzeImage(Image *images,const int argc,char **argv,
1285% ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1286%
1287% A description of each parameter follows:
1288%
1289% o image: the address of a structure of type Image.
1290%
1291% o argc: Specifies a pointer to an integer describing the number of
1292% elements in the argument vector.
1293%
1294% o argv: Specifies a pointer to a text array containing the command line
1295% arguments.
1296%
1297% o exception: return any errors or warnings in this structure.
1298%
1299*/
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1300ModuleExport size_t analyzeImage(Image **images,const int argc,const char **argv,
1301 ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1302{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1303 char
1304 text[MaxTextExtent];
1305
1306 double
1307 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1308 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1309 brightness_mean,
1310 brightness_standard_deviation,
1311 brightness_kurtosis,
1312 brightness_skewness,
1313 brightness_sum_x,
1314 brightness_sum_x2,
1315 brightness_sum_x3,
1316 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1317 hue,
1318 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1319 saturation_mean,
1320 saturation_standard_deviation,
1321 saturation_kurtosis,
1322 saturation_skewness,
1323 saturation_sum_x,
1324 saturation_sum_x2,
1325 saturation_sum_x3,
1326 saturation_sum_x4;
1327
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1328 Image
1329 *image;
1330
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1331 assert(images != (Image **) NULL);
1332 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1333 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1334 (void) argc;
1335 (void) argv;
1336 image=(*images);
1337 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1338 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1339 CacheView
1340 *image_view;
1341
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1342 MagickBooleanType
1343 status;
1344
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1345 ssize_t
1346 y;
1347
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1348 brightness_sum_x=0.0;
1349 brightness_sum_x2=0.0;
1350 brightness_sum_x3=0.0;
1351 brightness_sum_x4=0.0;
1352 brightness_mean=0.0;
1353 brightness_standard_deviation=0.0;
1354 brightness_kurtosis=0.0;
1355 brightness_skewness=0.0;
1356 saturation_sum_x=0.0;
1357 saturation_sum_x2=0.0;
1358 saturation_sum_x3=0.0;
1359 saturation_sum_x4=0.0;
1360 saturation_mean=0.0;
1361 saturation_standard_deviation=0.0;
1362 saturation_kurtosis=0.0;
1363 saturation_skewness=0.0;
1364 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1365 status=MagickTrue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1366 image_view=AcquireCacheView(image);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1367#if defined(MAGICKCORE_OPENMP_SUPPORT)
1368 #pragma omp parallel for schedule(dynamic,4) shared(status)
1369#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1370 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1371 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1372 register const PixelPacket
1373 *p;
1374
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1375 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1376 x;
1377
1378 if (status == MagickFalse)
1379 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1380 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1381 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1382 {
1383 status=MagickFalse;
1384 continue;
1385 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1386 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1387 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame^]1388 ConvertRGBToHSB(GetPixelRed(p),GetPixelGreen(p),GetPixelBue(p),&amp;hue,&amp;saturation,&amp;brightness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1389 brightness*=QuantumRange;
1390 brightness_sum_x+=brightness;
1391 brightness_sum_x2+=brightness*brightness;
1392 brightness_sum_x3+=brightness*brightness*brightness;
1393 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1394 saturation*=QuantumRange;
1395 saturation_sum_x+=saturation;
1396 saturation_sum_x2+=saturation*saturation;
1397 saturation_sum_x3+=saturation*saturation*saturation;
1398 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1399 area++;
1400 p++;
1401 }
1402 }
1403 image_view=DestroyCacheView(image_view);
1404 if (area &lt;= 0.0)
1405 break;
1406 brightness_mean=brightness_sum_x/area;
1407 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_mean);
1408 (void) SetImageProperty(image,"filter:brightness:mean",text);
1409 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1410 area*brightness_sum_x/area));
1411 (void) FormatMagickString(text,MaxTextExtent,"%g",
1412 brightness_standard_deviation);
1413 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1414 if (brightness_standard_deviation != 0)
1415 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1416 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1417 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1418 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1419 brightness_standard_deviation*brightness_standard_deviation*
1420 brightness_standard_deviation)-3.0;
1421 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_kurtosis);
1422 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1423 if (brightness_standard_deviation != 0)
1424 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1425 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1426 brightness_mean)/(brightness_standard_deviation*
1427 brightness_standard_deviation*brightness_standard_deviation);
1428 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_skewness);
1429 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1430 saturation_mean=saturation_sum_x/area;
1431 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_mean);
1432 (void) SetImageProperty(image,"filter:saturation:mean",text);
1433 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1434 area*saturation_sum_x/area));
1435 (void) FormatMagickString(text,MaxTextExtent,"%g",
1436 saturation_standard_deviation);
1437 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1438 if (saturation_standard_deviation != 0)
1439 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1440 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1441 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1442 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1443 saturation_standard_deviation*saturation_standard_deviation*
1444 saturation_standard_deviation)-3.0;
1445 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_kurtosis);
1446 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1447 if (saturation_standard_deviation != 0)
1448 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1449 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1450 saturation_mean)/(saturation_standard_deviation*
1451 saturation_standard_deviation*saturation_standard_deviation);
1452 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_skewness);
1453 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1454 }
1455 return(MagickImageFilterSignature);
1456}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1457</div>
1458
1459<p>To invoke the custom filter from the command line, use this command:</p>
1460
cristy323f35b2011-03-24 23:05:13 +0000[diff] [blame]1461<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]1462 Format: LOGO (ImageMagick Logo) <br/>
1463 Class: PseudoClass <br/>
1464 Geometry: 640x480 <br/>
1465 ... <br/>
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1466 filter:brightness:kurtosis: 8.17947 <br/>
1467 filter:brightness:mean: 60632.1 <br/>
1468 filter:brightness:skewness: -2.97118 <br/>
1469 filter:brightness:standard-deviation: 13742.1 <br/>
1470 filter:saturation:kurtosis: 4.33554 <br/>
1471 filter:saturation:mean: 5951.55 <br/>
1472 filter:saturation:skewness: 2.42848 <br/>
1473 filter:saturation:standard-deviation: 15575.9</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1474
1475<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>
1476
1477</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1478
1479</div>
1480
1481<div id="linkbar">
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1488 </div>
1489 <div class="footer">
cristy7e41fe82010-12-04 23:12:08 +0000[diff] [blame]1490 <span id="footer-west">&copy; 1999-2011 ImageMagick Studio LLC</span>
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