protected function gifAddHeader()
    {
        $cmap = 0;
        if (ord($this->sources[ 0 ]{10}) & 0x80) {

            $cmap = 3 * (2 << (ord($this->sources[ 0 ]{10}) & 0x07));
            $this->gif .= substr($this->sources[ 0 ], 6, 7);
            $this->gif .= substr($this->sources[ 0 ], 13, $cmap);
            $this->gif .= "!\377\13NETSCAPE2.0\3\1".$this->word2bin($this->config[ 'loop' ])."\0";
        }
    }