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60 <p class="text-center"><a href="porting.html#imv7">ImageMagick Version 7</a> ? <a href="porting.html#hdri">High Dynamic Range Imaging</a> ? <a href="porting.html#channels">Pixel Channels</a> ? <a href="porting.html#alpha">Alpha</a> ? <a href="porting.html#grayscale">Grayscale</a> ? <a href="porting.html#mask">Masks</a> ? <a href="porting.html#core">MagickCore API</a> ? <a href="porting.html#headers">Header Files</a> ? <a href="porting.html#deprecate">Deprecated Features Removed</a> ? <a href="porting.html#cli">Command-line Interface</a> ? <a href="porting.html#summary">Version 7 Change Summary</a> </p>
87 <p>Prior versions of ImageMagick (4-6), support 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 the color components (but not the alpha component) of the image pixels:</p>
241 <dd>blend this pixel channel with the alpha mask if it's enabled</dd>
264 <p>Previously MagickCore methods had channel analogs, for example, NegateImage() and NegateImageChannels(). The channel analog methods are no longer necessary because the pixel channel traits specify whether to act on a particular pixel channel or whether to blend with the alpha mask. For example, instead of</p>
276 <p>In version 7, we introduce pixel user channels. Traditionally we utilize 4 channels, red, green, blue, and alpha. For CMYK we also have a black channel. User channels are designed to contain whatever additional channel information that makes sense for your application. Some examples include extra channels in TIFF or PSD images or perhaps you require a channel with infrared information for the pixel. You can associate traits with the user channels so that they when they are acted upon by an image processing algorithm (e.g. blur) the pixels are copied, acted upon by the algorithm, or even blended with the alpha channel if that makes sense.</p>
288 <h2 class="magick-header"><a id="alpha"></a>Alpha</h2>
289 <p>We support alpha now, previously opacity. With alpha, a value of <kbd>0</kbd> 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 <code>QuantumRange</code> means that the pixel is opaque because the geometry completely overlapped the pixel. As a consequence, in version 7, the PixelInfo structure member alpha has replaced the previous opacity member. Another consequence is the alpha part of a sRGB value in hexadecimal notation is now reversed (e.g. #0000 is fully transparent).</p>
304 <p>Previously, grayscale images were Rec601Luminance and consumed 4 channels: red, green, blue, and alpha. With version 7, grayscale consumes only 1 channel requiring far less resources as a result.</p>
380 <p>Most algorithms update the red, green, blue, black (for CMYK), and alpha
381 channels. Most operators will blend alpha the other color channels, but other
383 currently done by removing alpha from teh active channels via
422 <p>By default, image operations such as convolution blends alpha with each channel. To convolve each channel independently, deactivate the alpha channel as follows:</p>
424 convert ... -alpha discrete -blur 0x1 ...
426 <p>To remove the alpha values from your image, use <code>-alpha off</code>.</p>
451 secondary image reads (for use in things like alpha composition) from
458 <dt>-alpha discrete</dt>
459 <dd>treat the alpha channel independently (do not blend).</dd>
473 | move to the next input image for the source of channel data (e.g. | gray=>alpha)
484 <p>Here we take an sRGB image and a grayscale image and inject the grayscale image into the alpha channel:</p>
486 convert wizard.png mask.pgm -channel-fx '| gray=>alpha' wizard-alpha.png
538 <dd>The <code>matte</code> primitive is now <code>alpha</code> (e.g. <code>-draw 'alpha 0,0 floodfill'</code>).</dd>
540 <dd>currently negates all channels, including alpha if present. As such you
541 may need to use the -channel option to prevent alpha negation. </dd>
561 <dd>Replaced by <code>-alpha Set/Off</code>.</dd>
612 <h4>Alpha</h4>
614 <li>We support alpha rather than opacity (0 transparent; QuantumRange opaque).</li>
615 <li>Use GetPixelAlpha() or SetPixelAlpha() to get or set the alpha pixel channel value.</li>
