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209<p class="navigation-index">[<a href="#headers">Header Files</a> &bull; <a href="#channels">Pixel Channels</a> &bull; <a href="#alpha">Alpha</a> &bull; <a href="#depecate">Deprecated Features Removed</a> &bull; <a href="#summary">Version 7 Change Summary</a> ]</p>
210
211<h1>ImageMagick Version 7 Porting Guide</h1>
212
213<p>ImageMagick was originally designed to display RGB images to an X Windows server. Over time we extended support to RGBA images and then to the CMYK and CMYKA image format. With ImageMagick version 7, we extend support to arbitrary colorspaces with an arbitrary number of pixel channels.
214
215<h2><a id="headers"></a>Header Files</h2>
216<div class="doc-section">
217<p>Prior versions of ImageMagick (4-6) references the ImageMagick header files as <kbd>magick/</kbd> and <kbd>wand/</kbd>. ImageMagick 7 instead uses <kbd>MagickCore/</kbd> and <kbd>MagickWand/</kbd> respectively. For example,</p>
218<pre class="code">
219#include &lt;MagickCore/MagickCore.h>
220#include &lt;MagickWand/MagickWand.h>
221</pre>
222</div>
223
224<h2><a id="channels"></a>Pixel Channels</h2>
225<div class="doc-section">
226<p>Prior versions of ImageMagick (4-6), supports 4 to 5 pixel channels (RGBA or CMYKA). The first 4 channels are accessed with the PixelPacket data structure. The structure includes 4 members of type Quantum (typically 16-bits) of red, green, blue, and opacity. The black channel or colormap indexes are supported by a separate method and structure, IndexPacket. As an example, here is a code snippet from ImageMagick version 6 that negates image pixels:</p>
227
228<pre class="code">
229 for (y=0; y &lt; (ssize_t) image->rows; y++)
230 {
231 register IndexPacket
232 *indexes;
233
234 register PixelPacket
235 *q;
236
237 q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,exception);
238 if (q == (PixelPacket *) NULL)
239 {
240 status=MagickFalse;
241 continue;
242 }
243 indexes=GetCacheViewAuthenticIndexQueue(image_view);
244 for (x=0; x &lt; (ssize_t) image->columns; x++)
245 {
246 if ((channels & RedChannel) != 0)
247 q->red=(Quantum) QuantumRange-q->red;
248 if ((channels & GreenChannel) != 0)
249 q->green=(Quantum) QuantumRange-q->green;
250 if ((channels & BlueChannel) != 0)
251 q->blue=(Quantum) QuantumRange-q->blue;
252 if ((channels & OpacityChannel) != 0)
253 q->opacity=(Quantum) QuantumRange-q->opacity;
254 if (((channels & IndexChannel) != 0) &&
255 (image->colorspace == CMYKColorspace))
256 indexes[x]=(IndexPacket) QuantumRange-indexes[x];
257 q++;
258 }
259 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
260 status=MagickFalse;
261 }
262</pre>
263
264<p>ImageMagick version 7 supports any number of channels from 1 to 100 (and beyond) and simplifies access with a single method that returns an array of channels of type Quantum. Source code that compiles against prior versions of ImageMagick will require refactoring to work with ImageMagick version 7. We illustrate with an example. Let's refactor the version 6 code snippet from above so it works with the ImageMagick version 7 API:</p>
265
266<pre class="code">
267 for (y=0; y &lt; (ssize_t) image->rows; y++)
268 {
269 register Quantum
270 *q;
271
272 q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,exception);
273 if (q == (Quantum *) NULL)
274 {
275 status=MagickFalse;
276 continue;
277 }
278 for (x=0; x &lt; (ssize_t) image->columns; x++)
279 for (channel=0; channel &lt; GetCacheViewChannels(image_view); channel++)
280 {
281 if ((channels & (1 &lt;&lt; channel)) != 0)
282 *q=(Quantum) QuantumRange-(*q);
283 q++;
284 }
285 if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
286 status=MagickFalse;
287 }
288</pre>
289
290<p>In addition to supporting any number of channels, version 7 simplifies working with channels and provides opportunity for compiler optimiziations that were previously not possible. Our benchmarking shows version 7 has increased performance for virtually all image operations.</p>
291</div>
292
293<h2><a id="alpha"></a>Alpha</h2>
294<div class="doc-section">
295<p>We support alpha now, previously opacity. With alpha, a value of 0 means that the pixel does not have any coverage information and is transparent; i.e. there was no color contribution from any geometry because the geometry did not overlap this pixel. A value of QuantumRange means that the pixel is opaque because the geometry completely overlapped the pixel.</p>
296<p>In version 7, the PixelPacket structure member alpha has replaced the previous opacity member.</p>
297</div>
298
299<h2><a id="deprecate"></a>Deprecated Features Removed</h2>
300<div class="doc-section">
301<p>All deprecated features from ImageMagick version 1-6 are removed in version 7. These include the <kbd>Magick-config<kbd> and <kbd>Wand-config<kbd> configuration utilities. Instead use:</p>
302
303<pre class="code">
304 MagickCore-config
305 MagickWand-config
306</pre>
307
308<p>In addition, all deprecated <a href="http://magick.imagemagick.org/api/deprecate.html">MagickCore</a> and <a href="http://magick.imagemagick.org/api/magick-deprecate.html">MagickWand</a> methods are no longer available in version 7.</p>
309</div>
310<h2><a id="summary"></a>Version 7 Change Summary</h2>
311<div class="doc-section">
312<p>Changes from ImageMagick version 1-6 to version 7 are summarized here:</p>
313<h5>Pixels</h5>
314<dl>
315<li>Pixels are no longer addressed with PixelPacket structure members (e.g. red, green, blue, opacity) but as an array of channels (e.g. p[RedPixelComponent]).</li>
316<li>Use convenience macros to access pixel components (e.g. GetRedPixelComponent(p), SetRedPixelComponent(q,red)).</li>
317<li>The black channel for the CMYK colorspace is no longer stored in the index channel, previously accessed with GetAuthenticIndexQueue() and GetCacheViewAuthenticIndexQueue((). Instead its now a pixel channel and accessed with the convenience pixel macros GetBlackPixelComponent(p) and SetBlackPixelComponent(q).</li>
318<li>Use the index channel to address colormapped indexes. It no longer hosts the black channel for CMYK and CMYKA images.</li>
319</dl>
320<h5>Alpha</h5>
321<dl>
322<li>We support alpha rather than opacity (0 transparent; QuantumRange opaque).</li>
323<li>The PixelPacket structure member alpha has replaced the previous opacity member.</li>
324</dl>
325<h5>Deprecated Methods</h5>
326<dl>
327<li>All MagickCore and MagickWand deprecated methods are removed and no longer available in ImageMagick version 7.</li>
328</dl>
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