<?
   $input = "bild.jpg";
   $watermark_file = "sign.png";

   $size = getimagesize($input);
   $width = $size[0];
   $height = $size[1];
   $img = imagecreatetruecolor($width, $height);
   $image = imagecreatefromjpeg($input);
   imagecopy($img, $image, 0, 0, 0, 0, $width, $height);

   $size2 = getimagesize($watermark_file);
   $width2 = $size2[0];
   $height2 = $size2[1];
   $posx = ($width/2) - ($width2 / 2);
   $posy = ($height/2) - ($height2 / 2);
   $watermark = imagecreatefrompng($watermark_file);
   imagecopy($img, $watermark, $posx, $posy, 0, 0, $width2, $height2);

   header("Content-type: image/jpeg");
   imagejpeg($img , "", 100);
   imagedestroy($img);
?>