/**
* 显示验证码图片
* @param $width 宽
* @param $height 高
* @param $length 字符串长度
* @param $format 图片格式(默认png)
* <p>可选项：
* <br>PNG
* <br>JPG
* <br>GIF
*/
public static final function show($width = null, $height = null, $length = 4, $format = PNG)
{
$width = intval($width);
$height = intval($height);
if ($width > 0) {
self::$width = $width;
}
if ($height > 0) {
self::$height = $height;
}
self::create();
self::create_disturb_points();
self::create_disturb_lines();
self::create_code($length);
self::create_picture(self::$code);
$method = 'get_' . $format;
self::$method();
imagedestroy(self::$im);
}
