zlucenie 2 obrazkov pomocou php

function watermark($im){
//$im je obrazok pre ktory nahravame watermark
$watermark = imagecreatefrompng('temp_small.png');
$watermark_width = imagesx($watermark);
$watermark_height = imagesy($watermark);
$image = imagecreatetruecolor($watermark_width, $watermark_height);
$image = imagecreatefromjpeg($im);
$size = getimagesize($im);
//vypocitame polohu watermarku
$dest_x = $size[0] - $watermark_width; $placementX =  round($dest_x / 2);
//-5 znamena posun o 5 pixelov po osi x a y
$dest_y = $size[1] - $watermark_height;$placementY =  round($dest_y / 2);

imagecopymerge_alpha($image, $watermark, $placementX, $placementY, 0, 0, $watermark_width, $watermark_height, 0);

imagejpeg($image,$im,100);
imagedestroy($image);
imagedestroy($watermark);

function imagecopymerge_alpha($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $pct){
$opacity=$pct;
// getting the watermark width
$w = imagesx($src_im);
// getting the watermark height
$h = imagesy($src_im);

// creating a cut resource
$cut = imagecreatetruecolor($src_w, $src_h);
// copying that section of the background to the cut
imagecopy($cut, $dst_im, 0, 0, $dst_x, $dst_y, $src_w, $src_h);
// inverting the opacity
$opacity = 100 - $opacity;

// placing the watermark now
imagecopy($cut, $src_im, 0, 0, $src_x, $src_y, $src_w, $src_h);
imagecopymerge($dst_im, $cut, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $opacity);
}

}