ManaPHP\Image\Adapter\Gd::watermark PHP Method

    public function watermark($file, $offsetX = 0, $offsetY = 0, $opacity = 1.0)
    {
        $file = $this->alias->resolve($file);
        $maskImageInfo = getimagesize($file);
        $maskWidth = $maskImageInfo[0];
        /** @noinspection MultiAssignmentUsageInspection */
        $maskHeight = $maskImageInfo[1];
        /** @noinspection MultiAssignmentUsageInspection */
        $maskType = $maskImageInfo[2];
        if ($maskType === IMAGETYPE_GIF) {
            $maskImage = imagecreatefromgif($file);
        } elseif ($maskType === IMAGETYPE_JPEG) {
            $maskImage = imagecreatefromjpeg($file);
        } elseif ($maskType === IMAGETYPE_PNG) {
            $maskImage = imagecreatefrompng($file);
        } else {
            throw new GdException('Installed GD does not support such images');
        }
        imagesavealpha($maskImage, true);
        $image = imagecreatetruecolor($this->_width, $this->_height);
        imagealphablending($image, false);
        imagesavealpha($image, true);
        if ($maskType !== IMAGETYPE_PNG) {
            $filedColor = imagecolorallocatealpha($image, 127, 127, 127, (1 - $opacity) * 127);
        } else {
            $filedColor = imagecolorallocate($image, 127, 127, 127);
        }
        imagelayereffect($maskImage, IMG_EFFECT_OVERLAY);
        imagefilledrectangle($maskImage, 0, 0, $maskWidth, $maskHeight, $filedColor);
        imagealphablending($this->_image, true);
        imagecopy($this->_image, $maskImage, $offsetX, $offsetY, 0, 0, $maskWidth, $maskHeight);
        return $this;
    }