SimpleImage::imagecopymerge_alpha PHP Method

    protected function imagecopymerge_alpha($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $pct)
    {
        // Get image width and height and percentage
        $pct /= 100;
        $w = imagesx($src_im);
        $h = imagesy($src_im);
        // Turn alpha blending off
        imagealphablending($src_im, false);
        // Find the most opaque pixel in the image (the one with the smallest alpha value)
        $minalpha = 127;
        for ($x = 0; $x < $w; $x++) {
            for ($y = 0; $y < $h; $y++) {
                $alpha = imagecolorat($src_im, $x, $y) >> 24 & 0xff;
                if ($alpha < $minalpha) {
                    $minalpha = $alpha;
                }
            }
        }
        // Loop through image pixels and modify alpha for each
        for ($x = 0; $x < $w; $x++) {
            for ($y = 0; $y < $h; $y++) {
                // Get current alpha value (represents the TANSPARENCY!)
                $colorxy = imagecolorat($src_im, $x, $y);
                $alpha = $colorxy >> 24 & 0xff;
                // Calculate new alpha
                if ($minalpha !== 127) {
                    $alpha = 127 + 127 * $pct * ($alpha - 127) / (127 - $minalpha);
                } else {
                    $alpha += 127 * $pct;
                }
                // Get the color index with new alpha
                $alphacolorxy = imagecolorallocatealpha($src_im, $colorxy >> 16 & 0xff, $colorxy >> 8 & 0xff, $colorxy & 0xff, $alpha);
                // Set pixel with the new color + opacity
                if (!imagesetpixel($src_im, $x, $y, $alphacolorxy)) {
                    return;
                }
            }
        }
        // Copy it
        imagesavealpha($dst_im, true);
        imagealphablending($dst_im, true);
        imagesavealpha($src_im, true);
        imagealphablending($src_im, true);
        imagecopy($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h);
    }