php-doc-en/reference/image/examples.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->

<chapter xml:id="image.examples" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 &reftitle.examples;
 <section xml:id="image.examples-png">
  <para>
   <example>
    <title>PNG creation with PHP</title>
    <programlisting role="php">
<![CDATA[
<?php

header("Content-type: image/png");
$string = $_GET['text'];
$im     = imagecreatefrompng("images/button1.png");
$orange = imagecolorallocate($im, 220, 210, 60);
$px     = (imagesx($im) - 7.5 * strlen($string)) / 2;
imagestring($im, 3, $px, 9, $string, $orange);
imagepng($im);
imagedestroy($im);

?>
]]>
    </programlisting>
   </example>
   This example would be called from a page with a tag like: <literal>&lt;img
   src=&quot;button.php?text=text&quot;&gt;</literal>. The above <filename>button.php</filename> script
   then takes this <literal>&quot;text&quot;</literal> string and overlays it on top of a
   base image which in this case is <literal>&quot;images/button1.png&quot;</literal>
   and outputs the resulting image. This is a very convenient way to
   avoid having to draw new button images every time you want to
   change the text of a button. With this method they are
   dynamically generated.
  </para>
 </section>
 <section xml:id="image.examples-watermark">
  <para>
   <example>
    <title>Adding watermarks to images using alpha channels</title>
    <programlisting role="php">
<![CDATA[
<?php
// Load the stamp and the photo to apply the watermark to
$stamp = imagecreatefrompng('stamp.png');
$im = imagecreatefromjpeg('photo.jpeg');

// Set the margins for the stamp and get the height/width of the stamp image
$marge_right = 10;
$marge_bottom = 10;
$sx = imagesx($stamp);
$sy = imagesy($stamp);

// Copy the stamp image onto our photo using the margin offsets and the photo 
// width to calculate positioning of the stamp. 
imagecopy($im, $stamp, imagesx($im) - $sx - $marge_right, imagesy($im) - $sy - $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp));

// Output and free memory
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
?>
]]>
    </programlisting>
    <mediaobject>
     <imageobject>
      <imagedata fileref="en/reference/image/figures/watermarks.png" />
     </imageobject>
    </mediaobject>
   </example>
   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.
  </para>
 </section>
 <section xml:id="image.examples.merged-watermark">
  <para>
   <example>
    <title>Using <function>imagecopymerge</function> to create a translucent watermark</title>
    <programlisting role="php">
<![CDATA[
<?php
// Load the stamp and the photo to apply the watermark to
$im = imagecreatefromjpeg('photo.jpeg');

// First we create our stamp image manually from GD
$stamp = imagecreatetruecolor(100, 70);
imagefilledrectangle($stamp, 0, 0, 99, 69, 0x0000FF);
imagefilledrectangle($stamp, 9, 9, 90, 60, 0xFFFFFF);
$im = imagecreatefromjpeg('photo.jpeg');
imagestring($stamp, 5, 20, 20, 'libGD', 0x0000FF);
imagestring($stamp, 3, 20, 40, '(c) 2007-9', 0x0000FF);

// Set the margins for the stamp and get the height/width of the stamp image
$marge_right = 10;
$marge_bottom = 10;
$sx = imagesx($stamp);
$sy = imagesy($stamp);

// Merge the stamp onto our photo with an opacity (transparency) of 50%
imagecopymerge($im, $stamp, imagesx($im) - $sx - $marge_right, imagesy($im) - $sy - $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp), 50);

// Save the image to file and free memory
imagepng($im, 'photo_stamp.png');
imagedestroy($im);

?>
]]>
    </programlisting>
    <mediaobject>
     <imageobject>
      <imagedata fileref="en/reference/image/figures/watermark-merged.png" />
     </imageobject>
    </mediaobject>
   </example>
   This example uses <function>imagecopymerge</function> to merge the stamp
   with our original image. Using this we can set the opacity of our stamp - 
   in our example we've set it to 50% opacity (another term for transparency).
   In practice this would be useful in copyright protection as semi-transparent
   watermarks are hard to remove yet allow viewers to see the image.
  </para>
 </section>
</chapter>

<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
indent-tabs-mode:nil
sgml-parent-document:nil
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim600: syn=xml fen fdm=syntax fdl=2 si
vim: et tw=78 syn=sgml
vi: ts=1 sw=1
-->