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<title>Adding watermarks to images using alpha channels</title>
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<h2 class="title">Adding watermarks to images using alpha channels</h2>
<p class="para">
<div class="example" id="example-3167">
<p><strong>Example #1 Adding watermarks to images using alpha channels</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// Load the stamp and the photo to apply the watermark to<br /></span><span style="color: #0000BB">$stamp </span><span style="color: #007700">= </span><span style="color: #0000BB">imagecreatefrompng</span><span style="color: #007700">(</span><span style="color: #DD0000">'stamp.png'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$im </span><span style="color: #007700">= </span><span style="color: #0000BB">imagecreatefromjpeg</span><span style="color: #007700">(</span><span style="color: #DD0000">'photo.jpeg'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Set the margins for the stamp and get the height/width of the stamp image<br /></span><span style="color: #0000BB">$marge_right </span><span style="color: #007700">= </span><span style="color: #0000BB">10</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$marge_bottom </span><span style="color: #007700">= </span><span style="color: #0000BB">10</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$sx </span><span style="color: #007700">= </span><span style="color: #0000BB">imagesx</span><span style="color: #007700">(</span><span style="color: #0000BB">$stamp</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$sy </span><span style="color: #007700">= </span><span style="color: #0000BB">imagesy</span><span style="color: #007700">(</span><span style="color: #0000BB">$stamp</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Copy the stamp image onto our photo using the margin offsets and the photo <br />// width to calculate positioning of the stamp. <br /></span><span style="color: #0000BB">imagecopy</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">, </span><span style="color: #0000BB">$stamp</span><span style="color: #007700">, </span><span style="color: #0000BB">imagesx</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">) - </span><span style="color: #0000BB">$sx </span><span style="color: #007700">- </span><span style="color: #0000BB">$marge_right</span><span style="color: #007700">, </span><span style="color: #0000BB">imagesy</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">) - </span><span style="color: #0000BB">$sy </span><span style="color: #007700">- </span><span style="color: #0000BB">$marge_bottom</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">imagesx</span><span style="color: #007700">(</span><span style="color: #0000BB">$stamp</span><span style="color: #007700">), </span><span style="color: #0000BB">imagesy</span><span style="color: #007700">(</span><span style="color: #0000BB">$stamp</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">// Output and free memory<br /></span><span style="color: #0000BB">header</span><span style="color: #007700">(</span><span style="color: #DD0000">'Content-type: image/png'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">imagepng</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">imagedestroy</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="mediaobject">
<div class="imageobject">
<img src="images/21009b70229598c6a80eef8b45bf282b-watermarks.png" alt="Adding watermarks to images using alpha channels" width="320" height="240" />
</div>
</div>
</div>
This example is a common way to add watermarks and stamps to photos and
copyrighted images. Note that the presence of an alpha channel in the
stamp image as the text is anti-aliased. This is preserved during copying.
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