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212<div class="main">
213
214
215
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]216<h1>The <em>Magick</em> Behind ImageMagick</h1>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]217<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]218
cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]219
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]220<div class="doc-section">
221<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>
222</div>
223
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]224<h2><a id="overview"></a>Architecture Overview</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]225<div class="doc-section">
226
227<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>
228
229<ul>
230 <li>colorspace (e.g RGB, CMYK, YUV, Lab, etc.)</li>
231 <li>bit depth (.e.g 1, 4, 8, 12, 16, etc.)</li>
232 <li>storage format (e.g. unsigned, signed, float, double, etc.)</li>
233 <li>compression (e.g. uncompressed, RLE, Zip, BZip, etc.)</li>
234 <li>orientation (i.e. top-to-bottom, right-to-left, etc.),</li>
235 <li>layout (.e.g. raw, interspersed with opcodes, etc.)</li>
236</ul>
237
238<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>
239
240<p>An efficient implementation of an image processing algorithm may require we get or set:</p>
241
242<ul>
243 <li>one pixel a time (e.g. pixel at location 10,3)</li>
244 <li>a single scanline (e.g. all pixels from row 4)</li>
245 <li>a few scanlines at once (e.g. pixel rows 4-7)</li>
246 <li>a single column or columns of pixels (e.g. all pixels from column 11)</li>
247 <li>an arbitrary region of pixels from the image (e.g. pixels defined at 10,7 to 10,19)</li>
248 <li>a pixel in random order (e.g. pixel at 14,15 and 640,480)</li>
249 <li>pixels from two different images (e.g. pixel at 5,1 from image 1 and pixel at 5,1 from image 2)</li>
250 <li>pixels outside the boundaries of the image (e.g. pixel at -1,-3)</li>
251 <li>a pixel component that is unsigned or in a floating-point representation (e.g. 0.17836)</li>
252 <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>
253 <li>one or more pixels simultaneously in different threads of execution</li>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]254 <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]255</ul>
256
257<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>
258
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]259<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]260
cristy320dd6e2010-04-16 20:11:40 +0000[diff] [blame]261<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]262
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]263<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]264
265</div>
266
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]267<h2><a id="cache"></a>The Pixel Cache</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]268<div class="doc-section">
269
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]270<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]271
272<h3>Create the Pixel Cache</h3>
273<div class="doc-section">
274
275<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>
276
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]277<dl>
278<dt>Create an image canvas initialized to the background color:</dt>
279<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]280 image=AllocateImage(image_info);
281 if (SetImageExtent(image,640,480) == MagickFalse)
282 { /* an exception was thrown */ }
283 (void) QueryMagickColor("red",&amp;image-&gt;background_color,&amp;image-&gt;exception);
284 SetImageBackgroundColor(image);
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]285</p></dd>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]286
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]287<dt>Create an image from a JPEG image on disk:</dt>
288<dd><p class="code">
289 (void) strcpy(image_info-&gt;filename,"image.jpg"):
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]290 image=ReadImage(image_info,exception);
291 if (image == (Image *) NULL)
292 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]293</p></dd>
294<dt>Create an image from a memory based image:</dt>
295<dd><p class="code">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]296 image=BlobToImage(blob_info,blob,extent,exception);
297 if (image == (Image *) NULL)
298 { /* an exception was thrown */ }
cristyec6b4752011-01-08 03:16:23 +0000[diff] [blame]299</p></dd>
300</dl>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]301
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]302<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]303
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]304<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]305
cristyd48f07c2011-07-09 23:09:26 +0000[diff] [blame]306<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Version: ImageMagick 6.7.1-0 2011-07-01 Q16 http://www.imagemagick.org</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]307<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]308</div>
309
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]310<h3><a id="authentic-pixels"></a>Access the Pixel Cache</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]311<div class="doc-section">
312
313<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]314<ul>
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]315 <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]316 <li><a href="../www/api/cache.html#GetAuthenticPixels">GetAuthenticPixels()</a> gets pixels that you intend to modify</li>
317 <li><a href="../www/api/cache.html#QueueAuthenticPixels">QueueAuthenticPixels()</a> queue pixels that you intend to modify</li>
318 <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]319</ul>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]320
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]321<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]322
323<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]324 const PixelPacket
325 *p;
326
327 PixelPacket
328 *q;
329
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]330 ssize_t
331 x,
332 y;
333
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]334 destination=CloneImage(source,source->columns,source->rows,MagickTrue,
335 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]336 if (destination == (Image *) NULL)
337 { /* an exception was thrown */ }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]338 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]339 {
340 p=GetVirtualPixels(source,0,y,source-&gt;columns,1,exception);
341 q=GetAuthenticPixels(destination,0,y,destination-&gt;columns,1,exception);
342 if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL)
343 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]344 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]345 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]346 SetPixelRed(q,90*p-&gt;red/100);
347 SetPixelGreen(q,90*p-&gt;green/100);
348 SetPixelBlue(q,90*p-&gt;blue/100);
349 SetPixelOpacity(q,90*p-&gt;opacity/100);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]350 p++;
351 q++;
352 }
353 if (SyncAuthenticPixels(destination,exception) == MagickFalse)
354 break;
355 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]356 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]357 { /* an exception was thrown */ }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]358</div>
359
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]360<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]361
cristy84134182011-06-15 22:59:00 +0000[diff] [blame]362<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]363
364<pre class="code">
365 const IndexPacket
366 *indexes;
367
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]368 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]369 {
370 p=GetVirtualPixels(source,0,y,source-&gt;columns,1);
371 if (p == (const PixelPacket *) NULL)
372 break;
cristy84134182011-06-15 22:59:00 +0000[diff] [blame]373 indexes=GetVirtualIndexQueue(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]374 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]375 (void) printf("%d\n",GetPixelIndex(indexes+x));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]376 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]377 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]378 /* an exception was thrown */
379</pre>
380
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]381<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]382
383<pre class="code">
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]384 p=GetVirtualPixels(source,-3,-3,source-&gt;columns+3,6,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]385</pre>
386
387<p>gives you the pixels you asked for without complaint, even though some are not within the confines of the image region.</p>
388</div>
389
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]390<h3><a id="virtual-pixels"></a>Virtual Pixels</h3>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]391<div class="doc-section">
392
cristyc3186d52010-06-04 13:55:23 +0000[diff] [blame]393<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]394 <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>
395
cristy4c54bbb2011-03-17 13:53:13 +0000[diff] [blame]396<pre class="text" style="font-size: 83.3333%;">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]397 background: the area surrounding the image is the background color
398 black: the area surrounding the image is black
399 checker-tile: alternate squares with image and background color
400 dither: non-random 32x32 dithered pattern
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]401 edge: extend the edge pixel toward infinity (default)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]402 gray: the area surrounding the image is gray
403 horizontal-tile: horizontally tile the image, background color above/below
404 horizontal-tile-edge: horizontally tile the image and replicate the side edge pixels
405 mirror: mirror tile the image
406 random: choose a random pixel from the image
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]407 tile: tile the image
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]408 transparent: the area surrounding the image is transparent blackness
409 vertical-tile: vertically tile the image, sides are background color
410 vertical-tile-edge: vertically tile the image and replicate the side edge pixels
411 white: the area surrounding the image is white
412</pre>
413
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]414</div>
415
416<h3>Cache Storage and Resource Requirements</h3>
417<div class="doc-section">
418
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]419<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]420
421<dl class="doc">
422 <dt class="doc">files</dt>
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]423 <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]424 <dt class="doc">area</dt>
425 <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>
426 <dt class="doc">memory</dt>
427 <dd>maximum amount of memory in bytes to allocate for the pixel cache from the anonymous mapped memory or the heap.</dd>
428 <dt class="doc">map</dt>
429 <dd>maximum amount of memory map in bytes to allocate for the pixel cache.</dd>
430 <dt class="doc">disk</dt>
431 <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]432 <dt class="doc">thread</dt>
433 <dd>maximum number of threads that are permitted to run in parallel.</dd>
434 <dt class="doc">time</dt>
435 <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]436</dl>
437
438<p>To determine the current setting of these limits, use this command:</p>
439
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]440<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -list resource</span></p><pre class="text">
441File Area Memory Map Disk Thread Time
cristy2c839602010-04-03 02:32:08 +0000[diff] [blame]442-------------------------------------------------------------------------------
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]443 768 1.0386GB 3.8692GiB 7.7384GiB unlimited 4 unlimited
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]444</pre>
445
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]446<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]447
448<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>
449</div>
450
451<h3>Cache Views</h3>
452<div class="doc-section">
453
454<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>
455
456<pre class="code">
457 CacheView
458 *view_1,
459 *view_2;
460
cristye9a32c32011-04-07 01:11:05 +0000[diff] [blame]461 view_1=AcquireCacheView(source);
462 view_2=AcquireCacheView(source);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]463 for (y=0; y &lt; (ssize_t) source-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]464 {
465 u=GetCacheViewVirtualPixels(view_1,0,y,source-&gt;columns,1,exception);
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]466 v=GetCacheViewVirtualPixels(view_2,0,source-&gt;rows-y-1,source-&gt;columns,1,
467 exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]468 if ((u == (const PixelPacket *) NULL) || (v == (const PixelPacket *) NULL))
469 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]470 for (x=0; x &lt; (ssize_t) source-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]471 {
472 /* do something with u &amp; v here */
473 }
474 }
cristye9a32c32011-04-07 01:11:05 +0000[diff] [blame]475 view_2=DestroyCacheView(view_2);
476 view_1=DestroyCacheView(view_1);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]477 if (y &lt; (ssize_t) source-&gt;rows)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]478 { /* an exception was thrown */ }
479</pre>
480</div>
481
482<h3>Magick Persistent Cache Format</h3>
483<div class="doc-section">
484
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]485<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]486<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]487</div>
488
489<h3>Best Practices</h3>
490<div class="doc-section">
491
cristy30092792011-02-22 02:06:14 +0000[diff] [blame]492<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]493
494<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>
495
496<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>
497
498<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>
499
500<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>
501
502<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>
503
504<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>
505
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]506<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]507
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]508<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]509
cristy739df912009-10-24 16:10:18 +0000[diff] [blame]510<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]511
512<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>
513
514<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>
515<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>
516</div>
517
518</div>
519
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]520<h2><a id="stream"></a>Streaming Pixels</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]521<div class="doc-section">
522
523<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>
524
525<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>
526
527<pre class="code">
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]528static size_t StreamPixels(const Image *image,const void *pixels,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]529 const size_t columns)
530{
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]531 register const PixelPacket
532 *p;
533
534 MyData
535 *my_data;
536
537 my_data=(MyData *) image->client_data;
538 p=(PixelPacket *) pixels;
539 if (p != (const PixelPacket *) NULL)
540 {
541 /* process pixels here */
542 }
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]543 return(columns);
544}
545
546...
547/* invoke the pixel stream here */
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]548image_info->client_data=(void *) MyData;
549image=ReadStream(image_info,&amp;StreamPixels,exception);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]550</pre>
551
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]552<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]553
554</div>
555
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]556<h2><a id="properties"></a>Image Properties and Profiles</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]557<div class="doc-section">
558
559<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>
560
561<pre class="code">
562 (void) printf("image width: %lu, height: %lu\n",image-&gt;columns,image-&gt;rows);
563</pre>
564
565<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>
566
567<pre class="code">
568 const char
569 *comment;
570
571 (void) SetImageProperty(image,"comment","This space for rent");
572 comment=GetImageProperty(image,"comment");
573 if (comment == (const char *) NULL)
574 (void) printf("Image comment: %s\n",comment);
575</pre>
576
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]577<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]578
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]579<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>
580
581<pre class="code">
582 StringInfo
583 *profile;
584
585 profile=AcquireStringInfo(length);
586 SetStringInfoDatum(profile,my_exif_profile);
587 (void) SetImageProfile(image,"EXIF",profile);
588 DestroyStringInfo(profile);
589 profile=GetImageProfile(image,"EXIF");
590 if (profile != (StringInfo *) NULL)
591 (void) PrintStringInfo(stdout,"EXIF",profile);
592</pre>
593
594</div>
595
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]596<h2><a id="tera-pixel"></a>Large Image Support</h2>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]597<div class="doc-section">
cristy94fb0312010-06-09 16:06:13 +0000[diff] [blame]598<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]599
600<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]601<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]602
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]603<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]604<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>
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 -limit memory 16mb \ <br/> logo: -resize 250000x250000 logo.miff</span></p>
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]607<p>Here we force all image pixels to disk:</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 area 0 \ <br/> logo: -resize 250000x250000 logo.miff</span></p>
cristybac7a162010-06-15 19:57:29 +0000[diff] [blame]610<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]611
cristyfe0019b2010-06-07 02:23:32 +0000[diff] [blame]612<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]613
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]614<h2><a id="threads"></a>Threads of Execution</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]615<div class="doc-section">
616
cristy5c4585b2010-11-11 00:13:57 +0000[diff] [blame]617<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]618
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]619<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]620
621<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]622{
623 CacheView
624 *image_view;
625
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]626 MagickBooleanType
627 status;
628
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]629 ssize_t
630 y;
631
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]632 status=MagickTrue;
633 image_view=AcquireCacheView(image);
634 #pragma omp parallel for schedule(dynamic,4) shared(status)
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]635 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]636 {
637 register IndexPacket
638 *indexes;
639
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]640 register PixelPacket
641 *q;
642
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]643 register ssize_t
644 x;
645
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]646 if (status == MagickFalse)
647 continue;
648 q=GetCacheViewAuthenticPixels(image_view,0,y,image-&gt;columns,1,exception);
649 if (q == (PixelPacket *) NULL)
650 {
651 status=MagickFalse;
652 continue;
653 }
654 indexes=GetCacheViewAuthenticIndexQueue(image_view);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]655 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]656 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]657 SetPixelRed(q,...);
658 SetPixelGreen(q,...);
659 SetPixelBlue(q,...);
660 SetPixelOpacity(q,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]661 if (indexes != (IndexPacket *) NULL)
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]662 SetPixelIndex(indexes+x,...);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]663 q++;
664 }
665 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
666 status=MagickFalse;
667 }
668 image_view=DestroyCacheView(image_view);
669 if (status == MagickFalse)
670 perror("something went wrong");
671}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]672</div>
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]673<p>This code snippet converts an uncompressed Windows bitmap to a Magick++ image:</p>
674<div class="viewport">
675#include "Magick++.h"
676#include &lt;assert.h&gt;
677#include "omp.h"
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]678
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]679void ConvertBMPToImage(const BITMAPINFOHEADER *bmp_info,
680 const unsigned char *restrict pixels,Magick::Image *image)
681{
682 /*
683 Prepare the image so that we can modify the pixels directly.
684 */
685 assert(bmp_info->biCompression == BI_RGB);
686 assert(bmp_info->biWidth == image->columns());
687 assert(abs(bmp_info->biHeight) == image->rows());
688 image->modifyImage();
689 if (bmp_info->biBitCount == 24)
690 image->type(MagickCore::TrueColorType);
691 else
692 image->type(MagickCore::TrueColorMatteType);
693 register unsigned int bytes_per_row=bmp_info->biWidth*bmp_info->biBitCount/8;
694 if (bytes_per_row % 4 != 0) {
695 bytes_per_row=bytes_per_row+(4-bytes_per_row % 4); // divisible by 4.
696 }
697 /*
698 Copy all pixel data, row by row.
699 */
700 #pragma omp parallel for
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]701 for (int y=0; y &lt; int(image->rows()); y++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]702 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]703 int
704 row;
705
706 register const unsigned char
707 *restrict p;
708
709 register MagickCore::PixelPacket
710 *restrict q;
711
712 row=(bmp_info->biHeight > 0) ? (image->rows()-y-1) : y;
713 p=pixels+row*bytes_per_row;
714 q=image->setPixels(0,y,image->columns(),1);
cristy2bd2a982011-02-15 00:52:58 +0000[diff] [blame]715 for (int x=0; x &lt; int(image->columns()); x++)
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]716 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]717 SetPixelBlue(q,p[0]);
718 SetPixelGreen(q,p[1]);
719 SetPixelRed(q,p[2]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]720 if (bmp_info->biBitCount == 32) {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]721 SetPixelOpacity(q,p[3]);
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]722 }
723 q++;
724 p+=bmp_info->biBitCount/8;
725 }
726 image->syncPixels(); // sync pixels to pixel cache.
727 }
728 return;
729}
730</div>
cristyfbb4a972010-06-30 17:42:22 +0000[diff] [blame]731
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]732<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>
733
cristy8030a5b2010-09-17 18:31:49 +0000[diff] [blame]734<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]735
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]736<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]737
738<pre class="text">
739 &lt;policy domain="resource" name="thread" value="2"/>
740</pre>
741
742<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>
743
744<pre class="text">
745 export MAGICK_THREAD_LIMIT=12
746</pre>
747
748<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>
749
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]750</div>
751
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]752<h2><a id="distributed"></a>Heterogeneous Distributed Processing</h2>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]753<div class="doc-section">
754<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>
755
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]756<p>First verify that your version of ImageMagick includes support for the OpenCL feature:</p>
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]757
cristyd43a46b2010-01-21 02:13:41 +0000[diff] [blame]758<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>identify -version</span><span class='crtout'>Features: OpenMP OpenCL</span></p>
759<p>If so, run this command to realize a significant speed-up for image convolution:</p>
760
cristy4949d522010-03-12 18:41:34 +0000[diff] [blame]761<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]762<p>If an accelerator is not available or if the accelerator fails to respond, ImageMagick reverts to the non-accelerated convolution algorithm.</p>
763
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]764<p>Here is an example OpenCL kernel that convolves an image:</p>
765
766<div class="viewport">
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]767static inline long ClampToCanvas(const long offset,const ulong range)
768{
769 if (offset &lt; 0L)
770 return(0L);
771 if (offset >= range)
772 return((long) (range-1L));
773 return(offset);
774}
775
776static inline CLQuantum ClampToQuantum(const double value)
777{
778 if (value &lt; 0.0)
779 return((CLQuantum) 0);
780 if (value >= (double) QuantumRange)
781 return((CLQuantum) QuantumRange);
782 return((CLQuantum) (value+0.5));
783}
784
785__kernel void Convolve(const __global CLPixelType *source,__constant double *filter,
786 const ulong width,const ulong height,__global CLPixelType *destination)
787{
788 const ulong columns = get_global_size(0);
789 const ulong rows = get_global_size(1);
790
791 const long x = get_global_id(0);
792 const long y = get_global_id(1);
793
794 const double scale = (1.0/QuantumRange);
795 const long mid_width = (width-1)/2;
796 const long mid_height = (height-1)/2;
797 double4 sum = { 0.0, 0.0, 0.0, 0.0 };
798 double gamma = 0.0;
799 register ulong i = 0;
800
801 for (long v=(-mid_height); v &lt;= mid_height; v++)
802 {
803 for (long u=(-mid_width); u &lt;= mid_width; u++)
804 {
cristy4103d562010-12-10 01:38:54 +0000[diff] [blame]805 register const ulong index=ClampToCanvas(y+v,rows)*columns+ClampToCanvas(x+u,
806 columns);
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]807 const double alpha=scale*(QuantumRange-source[index].w);
808 sum.x+=alpha*filter[i]*source[index].x;
809 sum.y+=alpha*filter[i]*source[index].y;
810 sum.z+=alpha*filter[i]*source[index].z;
811 sum.w+=filter[i]*source[index].w;
812 gamma+=alpha*filter[i];
813 i++;
814 }
815 }
816
817 gamma=1.0/(fabs(gamma) &lt;= MagickEpsilon ? 1.0 : gamma);
818 const ulong index=y*columns+x;
819 destination[index].x=ClampToQuantum(gamma*sum.x);
820 destination[index].y=ClampToQuantum(gamma*sum.y);
821 destination[index].z=ClampToQuantum(gamma*sum.z);
822 destination[index].w=ClampToQuantum(sum.w);
823};
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]824</div>
825
cristy37f02952010-03-24 19:47:41 +0000[diff] [blame]826<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]827
828</div>
829
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]830<h2><a id="coders"></a>Custom Image Coders</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]831<div class="doc-section">
832
833<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>
834
835<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>
836
837<div class="viewport">
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]838/*
839 Include declarations.
840*/
841#include "magick/studio.h"
842#include "magick/blob.h"
843#include "magick/blob-private.h"
844#include "magick/colorspace.h"
845#include "magick/exception.h"
846#include "magick/exception-private.h"
847#include "magick/image.h"
848#include "magick/image-private.h"
849#include "magick/list.h"
850#include "magick/magick.h"
851#include "magick/memory_.h"
852#include "magick/monitor.h"
853#include "magick/monitor-private.h"
854#include "magick/quantum-private.h"
855#include "magick/static.h"
856#include "magick/string_.h"
857#include "magick/module.h"
858
859/*
860 Forward declarations.
861*/
862static MagickBooleanType
863 WriteMGKImage(const ImageInfo *,Image *);
864
865/*
866%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
867% %
868% %
869% %
870% I s M G K %
871% %
872% %
873% %
874%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
875%
876% IsMGK() returns MagickTrue if the image format type, identified by the
877% magick string, is MGK.
878%
879% The format of the IsMGK method is:
880%
881% MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
882%
883% A description of each parameter follows:
884%
885% o magick: This string is generally the first few bytes of an image file
886% or blob.
887%
888% o length: Specifies the length of the magick string.
889%
890*/
891static MagickBooleanType IsMGK(const unsigned char *magick,const size_t length)
892{
893 if (length &lt; 7)
894 return(MagickFalse);
895 if (LocaleNCompare((char *) magick,"id=mgk",7) == 0)
896 return(MagickTrue);
897 return(MagickFalse);
898}
899
900/*
901%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
902% %
903% %
904% %
905% R e a d M G K I m a g e %
906% %
907% %
908% %
909%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
910%
911% ReadMGKImage() reads a MGK image file and returns it. It allocates
912% the memory necessary for the new Image structure and returns a pointer to
913% the new image.
914%
915% The format of the ReadMGKImage method is:
916%
917% Image *ReadMGKImage(const ImageInfo *image_info,ExceptionInfo *exception)
918%
919% A description of each parameter follows:
920%
921% o image_info: the image info.
922%
923% o exception: return any errors or warnings in this structure.
924%
925*/
926static Image *ReadMGKImage(const ImageInfo *image_info,
927 ExceptionInfo *exception)
928{
929 char
930 buffer[MaxTextExtent];
931
932 Image
933 *image;
934
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]935 MagickBooleanType
936 status;
937
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]938 register PixelPacket
939 *q;
940
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]941 register size_t
942 x;
943
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]944 register unsigned char
945 *p;
946
947 ssize_t
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]948 count,
949 y;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]950
951 unsigned char
952 *pixels;
953
954 unsigned long
955 columns,
956 rows;
957
958 /*
959 Open image file.
960 */
961 assert(image_info != (const ImageInfo *) NULL);
962 assert(image_info-&gt;signature == MagickSignature);
963 if (image_info-&gt;debug != MagickFalse)
964 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image_info-&gt;filename);
965 assert(exception != (ExceptionInfo *) NULL);
966 assert(exception-&gt;signature == MagickSignature);
967 image=AcquireImage(image_info);
968 status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
969 if (status == MagickFalse)
970 {
971 image=DestroyImageList(image);
972 return((Image *) NULL);
973 }
974 /*
975 Read MGK image.
976 */
977 (void) ReadBlobString(image,buffer); /* read magic number */
978 if (IsMGK(buffer,7) == MagickFalse)
979 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
980 (void) ReadBlobString(image,buffer);
981 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
982 if (count &lt;= 0)
983 ThrowReaderException(CorruptImageError,"ImproperImageHeader");
984 do
985 {
986 /*
987 Initialize image structure.
988 */
989 image-&gt;columns=columns;
990 image-&gt;rows=rows;
991 image-&gt;depth=8;
992 if ((image_info-&gt;ping != MagickFalse) &amp;&amp; (image_info-&gt;number_scenes != 0))
993 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
994 break;
995 /*
996 Convert MGK raster image to pixel packets.
997 */
998 if (SetImageExtent(image,0,0) == MagickFalse)
999 {
1000 InheritException(exception,&amp;image-&gt;exception);
1001 return(DestroyImageList(image));
1002 }
1003 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,3UL*sizeof(*pixels));
1004 if (pixels == (unsigned char *) NULL)
1005 ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1006 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1007 {
1008 count=(ssize_t) ReadBlob(image,(size_t) (3*image-&gt;columns),pixels);
1009 if (count != (ssize_t) (3*image-&gt;columns))
1010 ThrowReaderException(CorruptImageError,"UnableToReadImageData");
1011 p=pixels;
1012 q=QueueAuthenticPixels(image,0,y,image-&gt;columns,1,exception);
1013 if (q == (PixelPacket *) NULL)
1014 break;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1015 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1016 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1017 SetPixelRed(q,ScaleCharToQuantum(*p++));
1018 SetPixelGreen(q,ScaleCharToQuantum(*p++));
1019 SetPixelBlue(q,ScaleCharToQuantum(*p++));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1020 q++;
1021 }
1022 if (SyncAuthenticPixels(image,exception) == MagickFalse)
1023 break;
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1024 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1025 (SetImageProgress(image,LoadImageTag,y,image&gt;>rows) == MagickFalse))
1026 break;
1027 }
1028 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1029 if (EOFBlob(image) != MagickFalse)
1030 {
1031 ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",image-&gt;filename);
1032 break;
1033 }
1034 /*
1035 Proceed to next image.
1036 */
1037 if (image_info-&gt;number_scenes != 0)
1038 if (image-&gt;scene >= (image_info-&gt;scene+image_info-&gt;number_scenes-1))
1039 break;
1040 *buffer='\0';
1041 (void) ReadBlobString(image,buffer);
1042 count=(ssize_t) sscanf(buffer,"%lu %lu\n",&amp;columns,&amp;rows);
1043 if (count != 0)
1044 {
1045 /*
1046 Allocate next image structure.
1047 */
1048 AcquireNextImage(image_info,image);
1049 if (GetNextImageInList(image) == (Image *) NULL)
1050 {
1051 image=DestroyImageList(image);
1052 return((Image *) NULL);
1053 }
1054 image=SyncNextImageInList(image);
1055 status=SetImageProgress(image,LoadImageTag,TellBlob(image),GetBlobSize(image));
1056 if (status == MagickFalse)
1057 break;
1058 }
1059 } while (count != 0);
1060 (void) CloseBlob(image);
1061 return(GetFirstImageInList(image));
1062}
1063
1064/*
1065%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1066% %
1067% %
1068% %
1069% R e g i s t e r M G K I m a g e %
1070% %
1071% %
1072% %
1073%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1074%
1075% RegisterMGKImage() adds attributes for the MGK image format to
1076% the list of supported formats. The attributes include the image format
1077% tag, a method to read and/or write the format, whether the format
1078% supports the saving of more than one frame to the same file or blob,
1079% whether the format supports native in-memory I/O, and a brief
1080% description of the format.
1081%
1082% The format of the RegisterMGKImage method is:
1083%
1084% unsigned long RegisterMGKImage(void)
1085%
1086*/
1087ModuleExport unsigned long RegisterMGKImage(void)
1088{
1089 MagickInfo
1090 *entry;
1091
1092 entry=SetMagickInfo("MGK");
1093 entry-&gt;decoder=(DecodeImageHandler *) ReadMGKImage;
1094 entry-&gt;encoder=(EncodeImageHandler *) WriteMGKImage;
1095 entry-&gt;magick=(IsImageFormatHandler *) IsMGK;
1096 entry-&gt;description=ConstantString("MGK");
1097 entry-&gt;module=ConstantString("MGK");
1098 (void) RegisterMagickInfo(entry);
1099 return(MagickImageCoderSignature);
1100}
1101
1102/*
1103%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1104% %
1105% %
1106% %
1107% U n r e g i s t e r M G K I m a g e %
1108% %
1109% %
1110% %
1111%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1112%
1113% UnregisterMGKImage() removes format registrations made by the
1114% MGK module from the list of supported formats.
1115%
1116% The format of the UnregisterMGKImage method is:
1117%
1118% UnregisterMGKImage(void)
1119%
1120*/
1121ModuleExport void UnregisterMGKImage(void)
1122{
1123 (void) UnregisterMagickInfo("MGK");
1124}
1125
1126/*
1127%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1128% %
1129% %
1130% %
1131% W r i t e M G K I m a g e %
1132% %
1133% %
1134% %
1135%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1136%
1137% WriteMGKImage() writes an image to a file in red, green, and blue
1138% MGK rasterfile format.
1139%
1140% The format of the WriteMGKImage method is:
1141%
1142% MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1143%
1144% A description of each parameter follows.
1145%
1146% o image_info: the image info.
1147%
1148% o image: The image.
1149%
1150*/
1151static MagickBooleanType WriteMGKImage(const ImageInfo *image_info,Image *image)
1152{
1153 char
1154 buffer[MaxTextExtent];
1155
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1156 MagickBooleanType
1157 status;
1158
1159 MagickOffsetType
1160 scene;
1161
1162 register const PixelPacket
1163 *p;
1164
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1165 register ssize_t
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1166 x;
1167
1168 register unsigned char
1169 *q;
1170
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1171 ssize_t
1172 y;
1173
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1174 unsigned char
1175 *pixels;
1176
1177 /*
1178 Open output image file.
1179 */
1180 assert(image_info != (const ImageInfo *) NULL);
1181 assert(image_info-&gt;signature == MagickSignature);
1182 assert(image != (Image *) NULL);
1183 assert(image-&gt;signature == MagickSignature);
1184 if (image-&gt;debug != MagickFalse)
1185 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image-&gt;filename);
1186 status=OpenBlob(image_info,image,WriteBinaryBlobMode,&amp;image-&gt;exception);
1187 if (status == MagickFalse)
1188 return(status);
1189 scene=0;
1190 do
1191 {
1192 /*
1193 Allocate memory for pixels.
1194 */
1195 if (image-&gt;colorspace != RGBColorspace)
1196 (void) SetImageColorspace(image,RGBColorspace);
1197 pixels=(unsigned char *) AcquireQuantumMemory((size_t) image-&gt;columns,
1198 3UL*sizeof(*pixels));
1199 if (pixels == (unsigned char *) NULL)
1200 ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1201 /*
1202 Initialize raster file header.
1203 */
1204 (void) WriteBlobString(image,"id=mgk\n");
1205 (void) FormatMagickString(buffer,MaxTextExtent,"%lu %lu\n",
1206 image-&gt;columns,image-&gt;rows);
1207 (void) WriteBlobString(image,buffer);
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1208 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1209 {
1210 p=GetVirtualPixels(image,0,y,image-&gt;columns,1,&amp;image-&gt;exception);
1211 if (p == (const PixelPacket *) NULL)
1212 break;
1213 q=pixels;
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1214 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1215 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1216 *q++=ScaleQuantumToChar(GetPixelRed(p));
1217 *q++=ScaleQuantumToChar(GetPixelGreen(p));
1218 *q++=ScaleQuantumToChar(GetPixelBlue(p));
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1219 p++;
1220 }
1221 (void) WriteBlob(image,(size_t) (q-pixels),pixels);
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1222 if ((image-&gt;previous == (Image *) NULL) &amp;&amp;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1223 (SetImageProgress(image,SaveImageTag,y,image-&gt;rows) == MagickFalse))
1224 break;
1225 }
1226 pixels=(unsigned char *) RelinquishMagickMemory(pixels);
1227 if (GetNextImageInList(image) == (Image *) NULL)
1228 break;
1229 image=SyncNextImageInList(image);
1230 status=SetImageProgress(image,SaveImagesTag,scene,
1231 GetImageListLength(image));
1232 if (status == MagickFalse)
1233 break;
1234 scene++;
1235 } while (image_info-&gt;adjoin != MagickFalse);
1236 (void) CloseBlob(image);
1237 return(MagickTrue);
1238}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1239</div>
1240
1241<p>To invoke the custom coder from the command line, use these commands:</p>
1242
1243<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>
1244<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>
1245
1246</div>
1247
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1248<h2><a id="filters"></a>Custom Image Filters</h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1249<div class="doc-section">
1250
1251<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>
1252
1253<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>
1254
1255<div class="viewport">
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1256#include &lt;stdio.h&gt;
1257#include &lt;stdlib.h&gt;
1258#include &lt;string.h&gt;
1259#include &lt;time.h&gt;
1260#include &lt;assert.h&gt;
1261#include &lt;math.h&gt;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1262#include "magick/MagickCore.h"
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]1263
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1264/*
1265%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1266% %
1267% %
1268% %
1269% a n a l y z e I m a g e %
1270% %
1271% %
1272% %
1273%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1274%
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1275% analyzeImage() computes the brightness and saturation mean, standard
cristy52923442011-01-15 22:54:31 +0000[diff] [blame]1276% deviation, kurtosis and skewness and stores these values as attributes
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1277% of the image.
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1278%
1279% The format of the analyzeImage method is:
1280%
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1281% size_t analyzeImage(Image *images,const int argc,char **argv,
1282% ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1283%
1284% A description of each parameter follows:
1285%
1286% o image: the address of a structure of type Image.
1287%
1288% o argc: Specifies a pointer to an integer describing the number of
1289% elements in the argument vector.
1290%
1291% o argv: Specifies a pointer to a text array containing the command line
1292% arguments.
1293%
1294% o exception: return any errors or warnings in this structure.
1295%
1296*/
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1297ModuleExport size_t analyzeImage(Image **images,const int argc,const char **argv,
1298 ExceptionInfo *exception)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1299{
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1300 char
1301 text[MaxTextExtent];
1302
1303 double
1304 area,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1305 brightness,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1306 brightness_mean,
1307 brightness_standard_deviation,
1308 brightness_kurtosis,
1309 brightness_skewness,
1310 brightness_sum_x,
1311 brightness_sum_x2,
1312 brightness_sum_x3,
1313 brightness_sum_x4,
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1314 hue,
1315 saturation,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1316 saturation_mean,
1317 saturation_standard_deviation,
1318 saturation_kurtosis,
1319 saturation_skewness,
1320 saturation_sum_x,
1321 saturation_sum_x2,
1322 saturation_sum_x3,
1323 saturation_sum_x4;
1324
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1325 Image
1326 *image;
1327
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1328 assert(images != (Image **) NULL);
1329 assert(*images != (Image *) NULL);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1330 assert((*images)-&gt;signature == MagickSignature);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1331 (void) argc;
1332 (void) argv;
1333 image=(*images);
1334 for ( ; image != (Image *) NULL; image=GetNextImageInList(image))
1335 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1336 CacheView
1337 *image_view;
1338
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1339 MagickBooleanType
1340 status;
1341
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1342 ssize_t
1343 y;
1344
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1345 brightness_sum_x=0.0;
1346 brightness_sum_x2=0.0;
1347 brightness_sum_x3=0.0;
1348 brightness_sum_x4=0.0;
1349 brightness_mean=0.0;
1350 brightness_standard_deviation=0.0;
1351 brightness_kurtosis=0.0;
1352 brightness_skewness=0.0;
1353 saturation_sum_x=0.0;
1354 saturation_sum_x2=0.0;
1355 saturation_sum_x3=0.0;
1356 saturation_sum_x4=0.0;
1357 saturation_mean=0.0;
1358 saturation_standard_deviation=0.0;
1359 saturation_kurtosis=0.0;
1360 saturation_skewness=0.0;
1361 area=0.0;
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1362 status=MagickTrue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1363 image_view=AcquireCacheView(image);
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1364#if defined(MAGICKCORE_OPENMP_SUPPORT)
1365 #pragma omp parallel for schedule(dynamic,4) shared(status)
1366#endif
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1367 for (y=0; y &lt; (ssize_t) image-&gt;rows; y++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1368 {
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1369 register const PixelPacket
1370 *p;
1371
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1372 register ssize_t
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1373 x;
1374
1375 if (status == MagickFalse)
1376 continue;
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1377 p=GetCacheViewVirtualPixels(image_view,0,y,image-&gt;columns,1,exception);
1378 if (p == (const PixelPacket *) NULL)
cristy76e378e2009-12-21 18:20:04 +0000[diff] [blame]1379 {
1380 status=MagickFalse;
1381 continue;
1382 }
cristyde368992010-11-05 14:32:14 +0000[diff] [blame]1383 for (x=0; x &lt; (ssize_t) image-&gt;columns; x++)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1384 {
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]1385 ConvertRGBToHSB(GetPixelRed(p),GetPixelGreen(p),GetPixelBue(p),&amp;hue,&amp;saturation,&amp;brightness);
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1386 brightness*=QuantumRange;
1387 brightness_sum_x+=brightness;
1388 brightness_sum_x2+=brightness*brightness;
1389 brightness_sum_x3+=brightness*brightness*brightness;
1390 brightness_sum_x4+=brightness*brightness*brightness*brightness;
1391 saturation*=QuantumRange;
1392 saturation_sum_x+=saturation;
1393 saturation_sum_x2+=saturation*saturation;
1394 saturation_sum_x3+=saturation*saturation*saturation;
1395 saturation_sum_x4+=saturation*saturation*saturation*saturation;
1396 area++;
1397 p++;
1398 }
1399 }
1400 image_view=DestroyCacheView(image_view);
1401 if (area &lt;= 0.0)
1402 break;
1403 brightness_mean=brightness_sum_x/area;
1404 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_mean);
1405 (void) SetImageProperty(image,"filter:brightness:mean",text);
1406 brightness_standard_deviation=sqrt(brightness_sum_x2/area-(brightness_sum_x/
1407 area*brightness_sum_x/area));
1408 (void) FormatMagickString(text,MaxTextExtent,"%g",
1409 brightness_standard_deviation);
1410 (void) SetImageProperty(image,"filter:brightness:standard-deviation",text);
1411 if (brightness_standard_deviation != 0)
1412 brightness_kurtosis=(brightness_sum_x4/area-4.0*brightness_mean*
1413 brightness_sum_x3/area+6.0*brightness_mean*brightness_mean*
1414 brightness_sum_x2/area-3.0*brightness_mean*brightness_mean*
1415 brightness_mean*brightness_mean)/(brightness_standard_deviation*
1416 brightness_standard_deviation*brightness_standard_deviation*
1417 brightness_standard_deviation)-3.0;
1418 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_kurtosis);
1419 (void) SetImageProperty(image,"filter:brightness:kurtosis",text);
1420 if (brightness_standard_deviation != 0)
1421 brightness_skewness=(brightness_sum_x3/area-3.0*brightness_mean*
1422 brightness_sum_x2/area+2.0*brightness_mean*brightness_mean*
1423 brightness_mean)/(brightness_standard_deviation*
1424 brightness_standard_deviation*brightness_standard_deviation);
1425 (void) FormatMagickString(text,MaxTextExtent,"%g",brightness_skewness);
1426 (void) SetImageProperty(image,"filter:brightness:skewness",text);
1427 saturation_mean=saturation_sum_x/area;
1428 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_mean);
1429 (void) SetImageProperty(image,"filter:saturation:mean",text);
1430 saturation_standard_deviation=sqrt(saturation_sum_x2/area-(saturation_sum_x/
1431 area*saturation_sum_x/area));
1432 (void) FormatMagickString(text,MaxTextExtent,"%g",
1433 saturation_standard_deviation);
1434 (void) SetImageProperty(image,"filter:saturation:standard-deviation",text);
1435 if (saturation_standard_deviation != 0)
1436 saturation_kurtosis=(saturation_sum_x4/area-4.0*saturation_mean*
1437 saturation_sum_x3/area+6.0*saturation_mean*saturation_mean*
1438 saturation_sum_x2/area-3.0*saturation_mean*saturation_mean*
1439 saturation_mean*saturation_mean)/(saturation_standard_deviation*
1440 saturation_standard_deviation*saturation_standard_deviation*
1441 saturation_standard_deviation)-3.0;
1442 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_kurtosis);
1443 (void) SetImageProperty(image,"filter:saturation:kurtosis",text);
1444 if (saturation_standard_deviation != 0)
1445 saturation_skewness=(saturation_sum_x3/area-3.0*saturation_mean*
1446 saturation_sum_x2/area+2.0*saturation_mean*saturation_mean*
1447 saturation_mean)/(saturation_standard_deviation*
1448 saturation_standard_deviation*saturation_standard_deviation);
1449 (void) FormatMagickString(text,MaxTextExtent,"%g",saturation_skewness);
1450 (void) SetImageProperty(image,"filter:saturation:skewness",text);
1451 }
1452 return(MagickImageFilterSignature);
1453}
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1454</div>
1455
1456<p>To invoke the custom filter from the command line, use this command:</p>
1457
cristy323f35b2011-03-24 23:05:13 +0000[diff] [blame]1458<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]1459 Format: LOGO (ImageMagick Logo) <br/>
1460 Class: PseudoClass <br/>
1461 Geometry: 640x480 <br/>
1462 ... <br/>
cristy178edaf2011-01-23 03:42:39 +0000[diff] [blame]1463 filter:brightness:kurtosis: 8.17947 <br/>
1464 filter:brightness:mean: 60632.1 <br/>
1465 filter:brightness:skewness: -2.97118 <br/>
1466 filter:brightness:standard-deviation: 13742.1 <br/>
1467 filter:saturation:kurtosis: 4.33554 <br/>
1468 filter:saturation:mean: 5951.55 <br/>
1469 filter:saturation:skewness: 2.42848 <br/>
1470 filter:saturation:standard-deviation: 15575.9</span></p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]1471
1472<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>
1473
1474</div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]1475
1476</div>
1477
1478<div id="linkbar">
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1486 <div class="footer">
cristy7e41fe82010-12-04 23:12:08 +0000[diff] [blame]1487 <span id="footer-west">&copy; 1999-2011 ImageMagick Studio LLC</span>
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