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<h1 class="refname">Imagick::sigmoidalContrastImage</h1>
<p class="verinfo">(PECL imagick 2.0.0)</p><p class="refpurpose"><span class="refname">Imagick::sigmoidalContrastImage</span> — <span class="dc-title">Adjusts the contrast of an image</span></p>
</div>
<div class="refsect1 description" id="refsect1-imagick.sigmoidalcontrastimage-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">bool</span> <span class="methodname"><strong>Imagick::sigmoidalContrastImage</strong></span>
( <span class="methodparam"><span class="type">bool</span> <code class="parameter">$sharpen</code></span>
, <span class="methodparam"><span class="type">float</span> <code class="parameter">$alpha</code></span>
, <span class="methodparam"><span class="type">float</span> <code class="parameter">$beta</code></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$channel</code><span class="initializer"> = Imagick::CHANNEL_DEFAULT</span></span>
] )</div>
<p class="para rdfs-comment">
Adjusts the contrast of an image with a non-linear sigmoidal contrast
algorithm. Increase the contrast of the image using a sigmoidal transfer
function without saturating highlights or shadows. Contrast indicates
how much to increase the contrast (0 is none; 3 is typical; 20 is
pushing it); mid-point indicates where midtones fall in the resultant
image (0 is white; 50 is middle-gray; 100 is black). Set sharpen to
<strong><code>TRUE</code></strong> to increase the image contrast otherwise the contrast is reduced.
</p>
<p class="para">
See also <a href="url.imagemagick.usage.color_mods.sigmoidal" class="link external">» ImageMagick
v6 Examples - Image Transformations — Sigmoidal Non-linearity Contrast</a>
</p>
</div>
<div class="refsect1 parameters" id="refsect1-imagick.sigmoidalcontrastimage-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">sharpen</code></dt>
<dd>
<p class="para">
If true increase the contrast, if false decrease the contrast.
</p>
</dd>
<dt>
<code class="parameter">alpha</code></dt>
<dd>
<p class="para">
The amount of contrast to apply. 1 is very little, 5 is a significant amount, 20 is extreme.
</p>
</dd>
<dt>
<code class="parameter">beta</code></dt>
<dd>
<p class="para">
Where the midpoint of the gradient will be. This value should be in the range 0 to 1 - mutliplied by the quantum value for ImageMagick.
</p>
</dd>
<dt>
<code class="parameter">channel</code></dt>
<dd>
<p class="para">
Which color channels the contrast will be applied to.
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-imagick.sigmoidalcontrastimage-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns <strong><code>TRUE</code></strong> on success.
</p>
</div>
<div class="refsect1 examples" id="refsect1-imagick.sigmoidalcontrastimage-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-4029">
<p><strong>Example #1
Create a gradient image using <span class="function"><strong>Imagick::sigmoidalContrastImage()</strong></span>
suitable for blending two images together smoothly, with the blending
defined by $contrast and $the midpoint
</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">function </span><span style="color: #0000BB">generateBlendImage</span><span style="color: #007700">(</span><span style="color: #0000BB">$width</span><span style="color: #007700">, </span><span style="color: #0000BB">$height</span><span style="color: #007700">, </span><span style="color: #0000BB">$contrast </span><span style="color: #007700">= </span><span style="color: #0000BB">10</span><span style="color: #007700">, </span><span style="color: #0000BB">$midpoint </span><span style="color: #007700">= </span><span style="color: #0000BB">0.5</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">$imagick </span><span style="color: #007700">= new </span><span style="color: #0000BB">Imagick</span><span style="color: #007700">();<br /> </span><span style="color: #0000BB">$imagick</span><span style="color: #007700">-></span><span style="color: #0000BB">newPseudoImage</span><span style="color: #007700">(</span><span style="color: #0000BB">$width</span><span style="color: #007700">, </span><span style="color: #0000BB">$height</span><span style="color: #007700">, </span><span style="color: #DD0000">'gradient:black-white'</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">$quanta </span><span style="color: #007700">= </span><span style="color: #0000BB">$imagick</span><span style="color: #007700">-></span><span style="color: #0000BB">getQuantumRange</span><span style="color: #007700">();<br /> </span><span style="color: #0000BB">$imagick</span><span style="color: #007700">-></span><span style="color: #0000BB">sigmoidalContrastImage</span><span style="color: #007700">(</span><span style="color: #0000BB">true</span><span style="color: #007700">, </span><span style="color: #0000BB">$contrast</span><span style="color: #007700">, </span><span style="color: #0000BB">$midpoint </span><span style="color: #007700">* </span><span style="color: #0000BB">$quanta</span><span style="color: #007700">[</span><span style="color: #DD0000">"quantumRangeLong"</span><span style="color: #007700">]);<br /><br /> return </span><span style="color: #0000BB">$imagick</span><span style="color: #007700">; <br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 errors" id="refsect1-imagick.sigmoidalcontrastimage-errors">
<h3 class="title">Errors/Exceptions</h3>
<p class="para">
Throws ImagickException on error.
</p>
</div>
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