Commands we will use:

header()
 imagefrompng()
 imagefromjpeg()
 imagecopymerge()
 imagejpeg()
 imagedestroy()
 getimagesize()

The method:

1. send your browser an image header, because you will create a new image:

header("content-type: image/jpeg");

2. get your watermark image, and the other image what your want to get watermarked too:

$wm = imagecreatefrompng("watermark.png");
 $img = imagecreatefromjpeg("myimage.jpg");

4. if you want to center your watermark on your image, you should calculate it's position:

$wmsize = getimagesize("watermark.png");
 $imgsize = getimagesize("myimage.jpg");
 $destx = ($imgsize[0] - $wmsize[0]) / 2;
 $desty = ($imgsize[1] - $wmsize[1]) / 2;

3.use the imagecopymerge() function to copy your watermark to your image:

imagecopymerge($img,$wm,$destx,$desty, 0, 0, $wmsize[0], $wmsize[1], 75);

- the last parameter of the above function is the alpha transparency

4. send the new image to the browser:

imagejpeg($img);

5. finally, destroy your sources:

imagedestroy($img);
 imagejpeg($img);

The full source:

<?php
 header("content-type: image/jpeg");
 $wm = imagecreatefrompng("watermark.png");
 $img = imagecreatefromjpeg("myimage.jpg");
 $wmsize = getimagesize("watermark.png");
 $imgsize = getimagesize("myimage.jpg");
 $destx = ($imgsize[0] - $wmsize[0]) / 2;
 $desty = ($imgsize[1] - $wmsize[1] / 2;
 imagecopymerge($img,$wm,$destx,$desty, 0, 0, $wmsize[0], $wmsize[1], 75);
 imagejpeg($img);
 imagedestroy($img);
 imagedestroy($wm);
 ?>

By Peter Radics web design - cleanweb.hu