private function allocateColors()
    {

        $this->ink['red'] = imagecolorallocate($this->im, 0xff, 0x00, 0x00);
        $this->ink['orange'] = imagecolorallocate($this->im, 0xd2, 0x8a, 0x00);
        $this->ink['yellow'] = imagecolorallocate($this->im, 0xff, 0xff, 0x00);
        $this->ink['green'] = imagecolorallocate($this->im, 0x00, 0xff, 0x00);
        $this->ink['blue'] = imagecolorallocate($this->im, 0x00, 0x00, 0xff);

        $this->ink['purple'] = imagecolorallocate($this->im, 0x70, 0x70, 0xf9);
        $this->ink['white'] = imagecolorallocate($this->im, 0xff, 0xff, 0xff);
        $this->ink['black'] = imagecolorallocate($this->im, 0x00, 0x00, 0x00);
        $this->ink['gray'] = imagecolorallocate($this->im, 0xaf, 0xaf, 0xaf);

        $this->ink['axis'] = imagecolorallocate($this->im, 95, 95, 95);

        $this->ink['line'] = imagecolorallocate($this->im, 0xff, 0xff, 0x00);
        $this->ink['background'] = imagecolorallocate($this->im, 0x00, 0x00,
            0x00);
        $this->ink['text'] = imagecolorallocate($this->im, 0xff, 0xff, 0xff);
        $this->ink['point'] = imagecolorallocate($this->im, 0xff, 0xff, 0xff);
    }