php 自动生成后缀图片

   public function icon()
    {
        $suffix = $this->request->request("suffix");
        $suffix = $suffix ? $suffix : "FILE";
        $data = build_suffix_image($suffix);
        $header = ['Content-Type' => 'image/svg+xml'];
        $offset = 30 * 60 * 60 * 24; // 缓存一个月
        $header['Cache-Control'] = 'public';
        $header['Pragma'] = 'cache';
        $header['Expires'] = gmdate("D, d M Y H:i:s", time() + $offset) . " GMT";
        $response = Response::create($data, '', 200, $header);
        return $response;
    }


 /**
     * 生成文件后缀图片
     * @param string $suffix 后缀
     * @param null   $background
     * @return string
     */
    function build_suffix_image($suffix, $background = null)
    {
        $suffix = mb_substr(strtoupper($suffix), 0, 4);
        $total = unpack('L', hash('adler32', $suffix, true))[1];
        $hue = $total % 360;
        list($r, $g, $b) = hsv2rgb($hue / 360, 0.3, 0.9);

        $background = $background ? $background : "rgb({$r},{$g},{$b})";

        $icon = <<<EOT
        <svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewBox="0 0 512 512" style="enable-background:new 0 0 512 512;" xml:space="preserve">
            <path style="fill:#E2E5E7;" d="M128,0c-17.6,0-32,14.4-32,32v448c0,17.6,14.4,32,32,32h320c17.6,0,32-14.4,32-32V128L352,0H128z"/>
            <path style="fill:#B0B7BD;" d="M384,128h96L352,0v96C352,113.6,366.4,128,384,128z"/>
            <polygon style="fill:#CAD1D8;" points="480,224 384,128 480,128 "/>
            <path style="fill:{$background};" d="M416,416c0,8.8-7.2,16-16,16H48c-8.8,0-16-7.2-16-16V256c0-8.8,7.2-16,16-16h352c8.8,0,16,7.2,16,16 V416z"/>
            <path style="fill:#CAD1D8;" d="M400,432H96v16h304c8.8,0,16-7.2,16-16v-16C416,424.8,408.8,432,400,432z"/>
            <g><text><tspan x="220" y="380" font-size="124" font-family="Verdana, Helvetica, Arial, sans-serif" fill="white" text-anchor="middle">{$suffix}</tspan></text></g>
        </svg>
EOT;
        return $icon;
    }