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<title>Get the index of the color of a pixel</title>
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<div class="refnamediv">
<h1 class="refname">imagecolorat</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">imagecolorat</span> — <span class="dc-title">Get the index of the color of a pixel</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.imagecolorat-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">int</span> <span class="methodname"><strong>imagecolorat</strong></span>
( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$image</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$x</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$y</code></span>
)</div>
<p class="para rdfs-comment">
Returns the index of the color of the pixel at the
specified location in the image specified by <em><code class="parameter">image</code></em>.
</p>
<p class="para">
If PHP is compiled against GD library 2.0 or higher and the image is a
truecolor image, this function returns the RGB value of that pixel as
integer. Use bitshifting and masking to access the distinct red, green and blue
component values:
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.imagecolorat-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">
image</code></em></span><dd>
<p class="para">An image resource, returned by one of the image creation functions,
such as <span class="function"><a href="function.imagecreatetruecolor.html" class="function">imagecreatetruecolor()</a></span>.</p></dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">x</code></em></span>
<dd>
<p class="para">
x-coordinate of the point.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">y</code></em></span>
<dd>
<p class="para">
y-coordinate of the point.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.imagecolorat-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the index of the color.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.imagecolorat-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-3185">
<p><strong>Example #1 Access distinct RGB values</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$im </span><span style="color: #007700">= </span><span style="color: #0000BB">imagecreatefrompng</span><span style="color: #007700">(</span><span style="color: #DD0000">"php.png"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$rgb </span><span style="color: #007700">= </span><span style="color: #0000BB">imagecolorat</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">, </span><span style="color: #0000BB">10</span><span style="color: #007700">, </span><span style="color: #0000BB">15</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$r </span><span style="color: #007700">= (</span><span style="color: #0000BB">$rgb </span><span style="color: #007700">>> </span><span style="color: #0000BB">16</span><span style="color: #007700">) & </span><span style="color: #0000BB">0xFF</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$g </span><span style="color: #007700">= (</span><span style="color: #0000BB">$rgb </span><span style="color: #007700">>> </span><span style="color: #0000BB">8</span><span style="color: #007700">) & </span><span style="color: #0000BB">0xFF</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= </span><span style="color: #0000BB">$rgb </span><span style="color: #007700">& </span><span style="color: #0000BB">0xFF</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$r</span><span style="color: #007700">, </span><span style="color: #0000BB">$g</span><span style="color: #007700">, </span><span style="color: #0000BB">$b</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
int(119)
int(123)
int(180)
</pre></div>
</div>
</div>
<div class="example" id="example-3186">
<p><strong>Example #2 Human-readable RGB values using <span class="function"><a href="function.imagecolorsforindex.html" class="function">imagecolorsforindex()</a></span></strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$im </span><span style="color: #007700">= </span><span style="color: #0000BB">imagecreatefrompng</span><span style="color: #007700">(</span><span style="color: #DD0000">"php.png"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$rgb </span><span style="color: #007700">= </span><span style="color: #0000BB">imagecolorat</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">, </span><span style="color: #0000BB">10</span><span style="color: #007700">, </span><span style="color: #0000BB">15</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$colors </span><span style="color: #007700">= </span><span style="color: #0000BB">imagecolorsforindex</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">, </span><span style="color: #0000BB">$rgb</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$colors</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(4) {
["red"]=>
int(119)
["green"]=>
int(123)
["blue"]=>
int(180)
["alpha"]=>
int(127)
}
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.imagecolorat-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.imagecolorset.html" class="function" rel="rdfs-seeAlso">imagecolorset()</a> - Set the color for the specified palette index</span></li>
<li class="member"> <span class="function"><a href="function.imagecolorsforindex.html" class="function" rel="rdfs-seeAlso">imagecolorsforindex()</a> - Get the colors for an index</span></li>
<li class="member"> <span class="function"><a href="function.imagesetpixel.html" class="function" rel="rdfs-seeAlso">imagesetpixel()</a> - Set a single pixel</span></li>
</ul>
</p>
</div>
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