PHP生成Gif图片验证码

/**
  说明: 验证码生成类,支持生成Gif图片验证码(带噪点，干扰线，网格，随机色背景，随机自定义字体，倾斜，Gif动画）

服务端：
  $mod = strtolower(isset($_REQUEST["mod"]) ? $_REQUEST["mod"] : "");
  if($mod == "code"){
  echo SecurityCode::Draw(4, 1, 120, 30, 5, 10, 100, "secode");
  die();
  }
  调用: <img src="https://www.jb51.net/getcode.php?mod=code">
  验证:
  $reqCode = strtolower(isset($_REQUEST["secode"]) ? $_REQUEST["secode"] : "");  //请求的验证码
  $sessionCode = strtolower(isset($_SESSION["secode"]) ? $_SESSION["secode"] : ""); //会话生成的验证码
  if($reqCode != $sessionCode){
  echo "安全验证码错误！";
  die();
  }
 */
$mod = strtolower(isset($_REQUEST["mod"]) ? $_REQUEST["mod"] : "");
if ($mod == "code") {
    echo SecurityCode::Draw(4, 15, 100, 27, 10, 2, 100, "secode");
    die();
}

//安全验证码类
class SecurityCode {

private static $Debug = 0;
    private static $Code = '';
    private static $Chars = 'bcdefhkmnrstuvwxyABCDEFGHKMNPRSTUVWXY34568';
    //private static $Chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890';
    private static $TextGap = 20;
    private static $TextMargin = 5;
    private static $FontFilePath = "static/font/"; //相对地本代码文件的位置
    private static $FontFileName =array("3.ttf");// array("1.ttf", "2.ttf", "3.ttf", "4.ttf", "5.ttf", "6.ttf", "7.ttf", "8.ttf"); //
    private static $Img = 'GIF89a'; //GIF header 6 bytes   
    private static $BUF = Array();
    private static $LOP = 0;
    private static $DIS = 2;
    private static $COL = -1;
    private static $IMG = -1;

/**
      生成GIF图片验证
      @param int $L 验证码长度
      @param int $F 生成Gif图的帧数
      @param int $W 宽度
      @param int $H 高度
      @param int $MixCnt 干扰线数
      @param int $lineGap 网格线间隔
      @param int $noisyCnt 澡点数
      @param int $sessionName 验证码Session名称
     */
    public static function Draw($L = 4, $F = 1, $W = 150, $H = 30, $MixCnt = 2, $lineGap = 0, $noisyCnt = 10, $sessionName = "Code") {
        ob_start();
        ob_clean();

for ($i = 0; $i < $L; $i++) {
            self::$Code .= SubStr(self::$Chars, mt_rand(0, strlen(self::$Chars) - 1), 1);
        }

if (!isset($_SESSION))
            session_start();
        $_SESSION[$sessionName] = strtolower(self::$Code);

$bgRGB = array(rand(0, 255), rand(0, 255), rand(0, 255));
        //生成一个多帧的GIF动画
        for ($i = 0; $i < $F; $i++) {
            $img = ImageCreate($W, $H);

//背景色
            $bgColor = imagecolorallocate($img, $bgRGB[0], $bgRGB[1], $bgRGB[2]);
            ImageColorTransparent($img, $bgColor);
            unset($bgColor);

//添加噪点
            $maxNoisy = rand(0, $noisyCnt);
            $noisyColor = imagecolorallocate($img, rand(0, 255), rand(0, 255), rand(0, 255));
            for ($k = 0; $k <= $maxNoisy; $k++) {
                imagesetpixel($img, rand(0, $W), rand(0, $H), $noisyColor);
            }

//添加网格
            if ($lineGap > 0) {
                for ($m = 0; $m < ($W / $lineGap); $m++) { //竖线
                    imageline($img, $m * $lineGap, 0, $m * $lineGap, $H, $noisyColor);
                }
                for ($n = 0; $n < ($H / $lineGap); $n++) { //横线
                    imageline($img, 0, $n * $lineGap, $W, $n * $lineGap, $noisyColor);
                }
            }
            unset($noisyColor);