<?php
class ImageDecorator extends DataObjectDecorator {

/**
* Put on uploaded images watermark
*/
function onAfterWrite(){
parent::onAfterWrite();

//absolute path to watermark in mycase is watermark located in http://localhost/ak/mysite/code/images/watermark.png
$watermark = imagecreatefrompng(Director::absoluteBaseURL().'mysite/code/images/watermark.png');

//get watermark width
$watermark_width = imagesx($watermark);

//get watermark height
$watermark_height = imagesy($watermark);

//imagecreatetruecolor() returns an image identifier representing a black image of the specified size. http://si.php.net/manual/en/function.imagecreatetruecolor.php
$image = imagecreatetruecolor($watermark_width, $watermark_height);

//imagecreatefromjpeg() returns an image identifier representing the image obtained from the given filename. http://si.php.net/manual/en/function.imagecreatefromjpeg.php
$image = imagecreatefromjpeg(str_replace('/','\\',Director::baseFolder().'/'.$this->owner->Filename));

//array getimagesize ( string $filename [, array &$imageinfo ] ) http://si.php.net/manual/en/function.getimagesize.php
$size = getimagesize(str_replace('/','\\',Director::baseFolder().'/'.$this->owner->Filename));

//x-coordinate of destination point.
$dest_x = $size[0] - $watermark_width - 5;

//y-coordinate of destination point.
$dest_y = $size[1] - $watermark_height - 5;

//imagecopymerge — Copy and merge part of an image http://si.php.net/manual/en/function.imagecopymerge.php
imagecopymerge($image, $watermark, $dest_x, $dest_y, 0, 0, $watermark_width, $watermark_height, 100);

//imagejpeg — Output image to browser or file , I override uploaded image with the watermarked image http://si.php.net/manual/en/function.imagejpeg.php
imagejpeg($image,str_replace('/','\\',Director::baseFolder().'/'.$this->owner->Filename));

//imagedestroy — Destroy an image http://si.php.net/manual/en/function.imagedestroy.php
imagedestroy($image);
imagedestroy($watermark);
}
}
?>

Object::add_extension('Image','ImageDecorator');