function ImageConvolution($src, $filter, $filter_div, $offset){
    if ($src==NULL) {
        return 0;
    }
 
    $sx = imagesx($src);
    $sy = imagesy($src);
    $srcback = ImageCreateTrueColor ($sx, $sy);
    ImageAlphaBlending($srcback, false);
    ImageAlphaBlending($src, false);
    ImageCopy($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_a += ((0x7F000000 & $rgb) >> 24) * $filter[$j][$i];
                }
            }
 
            $new_r = ($new_r/$filter_div)+$offset;
            $new_g = ($new_g/$filter_div)+$offset;
            $new_b = ($new_b/$filter_div)+$offset;
            $new_a = ($new_a/$filter_div)+$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);
            $new_a = ($new_a > 127)? 127 : (($new_a < 0)? 0:$new_a);
 
            $new_pxl = ImageColorAllocateAlpha($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 1;
}