if(!function_exists('imageconvolution')){
function imageconvolution($src, $filter, $filter_div, $offset){
	if ($src==NULL) {
		return false;
	}
	$pxl=array(0,0);
	$sx = imagesx($src);
	$sy = imagesy($src);
	$srcback = ImageCreateTrueColor ($sx, $sy);
	ImageCopy($srcback, $src,0,0,0,0,$sx,$sy);
 
	if($srcback==NULL){
		return 0;
	}
 
	for ($y=0; $y<$sy; ++$y){
		for($x=0; $x<$sx; ++$x){
			$new_r = $new_g = $new_b = 0;
			$alpha = imagecolorat($srcback, $pxl[0], $pxl[1]);
			$new_a = $alpha >> 24;
 
			for ($j=0; $j<3; ++$j) {
				$yv = min(max($y - 1 + $j, 0), $sy - 1);
				for ($i=0; $i<3; ++$i) {
				        $pxl = array(min(max($x - 1 + $i, 0), $sx - 1), $yv);
				    $rgb = imagecolorat($srcback, $pxl[0], $pxl[1]);
					$new_r += (($rgb >> 16) & 0xFF) * $filter[$j][$i];
					$new_g += (($rgb >> 8) & 0xFF) * $filter[$j][$i];
					$new_b += ($rgb & 0xFF) * $filter[$j][$i];
				}
			}
 
			$new_r = ($new_r/$filter_div)+$offset;
			$new_g = ($new_g/$filter_div)+$offset;
			$new_b = ($new_b/$filter_div)+$offset;
 
			$new_r = ($new_r > 255)? 255 : (($new_r < 0)? 0:$new_r);
			$new_g = ($new_g > 255)? 255 : (($new_g < 0)? 0:$new_g);
			$new_b = ($new_b > 255)? 255 : (($new_b < 0)? 0:$new_b);
 
			$new_pxl = ImageColorAllocateAlpha($src, (int)$new_r, (int)$new_g, (int)$new_b, $new_a);
			if ($new_pxl == -1) {
				$new_pxl = ImageColorClosestAlpha($src, (int)$new_r, (int)$new_g, (int)$new_b, $new_a);
			}
			if (($y >= 0) && ($y < $sy)) {
				imagesetpixel($src, $x, $y, $new_pxl);
			}
		}
	}
	imagedestroy($srcback);
	return true;
}
}