<?php
    $bg = imagecreatefrompng('bg.png');
    $over = imagecreatefrompng('over.png');
    imagecopymerge($bg, $over, 0,0,0,0,32,32,100);
    imagecopymerge($bg, $over, 16,0,0,0,32,32,50);
    imagepng($bg, 'imagecopymerge.png');
?>