&reftitle.examples;

## PNG creation with PHP

    <?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);

    ?>

This example would be called from a page with a tag like: `<img src="button.php?text=text">`. The above `button.php` script then takes this `"text"` string and overlays it on top of a base image which in this case is `"images/button1.png"` 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.

## Adding watermarks to images using alpha channels

    <?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);
    ?>

Adding watermarks to images using alpha channels
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.

## Using `imagecopymerge` to create a translucent watermark

    <?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 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);

    ?>

Using imagecopymerge() to create a translucent watermark
This example uses `imagecopymerge` 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. In practice this would be useful in copyright protection as semi-transparent watermarks are hard to remove yet allow viewers to see the image.