/application/libraries/Captcha.php

<?php

if (!defined('BASEPATH'))

    exit('No direct script access allowed');



class Captcha

{

    private $charset = 'abcdefghkmnprstuvwxyzABCDEFGHKMNPRSTUVWXYZ23456789'; //随机因子

    private $code; //验证码

    private $codelen = 4; //验证码长度

    private $width = 300; //宽度

    private $height = 50; //高度

    private $img; //图形资源句柄

    private $font; //指定的字体

    private $fontsize = 30; //指定字体大小

    private $fontcolor; //指定字体颜色

    //构造方法初始化

    public function __construct($config)

    {

        $this->font = empty($config['font_file']) ? './css/fonts/elephant.ttf' : $config['font_file'];

        $this->createBg();

        $this->createCode();

    }



    //生成随机码

    private function createCode()

    {

        $_len = strlen($this->charset) - 1;

        for ($i = 0; $i < $this->codelen; $i++) {

            $this->code .= $this->charset[mt_rand(0, $_len)];

        }

    }



    //生成背景

    private function createBg()

    {

        $this->img = imagecreatetruecolor($this->width, $this->height);

        $color = imagecolorallocate($this->img, mt_rand(157, 255), mt_rand(157, 255), mt_rand(157, 255));

        imagefilledrectangle($this->img, 0, $this->height, $this->width, 0, $color);

    }



    //生成文字

    private function createFont()

    {

        $_x = $this->width / $this->codelen;

        for ($i = 0; $i < $this->codelen; $i++) {

            $this->fontcolor = imagecolorallocate($this->img, mt_rand(0, 156), mt_rand(0, 156), mt_rand(0, 156));

            imagettftext($this->img, $this->fontsize, mt_rand(-30, 30), $_x * $i + mt_rand(1, 5), $this->height / 1.4, $this->fontcolor, $this->font, $this->code[$i]);

        }

    }



    //生成线条、雪花

    private function createLine()

    {

        //线条

        for ($i = 0; $i < 6; $i++) {

            $color = imagecolorallocate($this->img, mt_rand(0, 156), mt_rand(0, 156), mt_rand(0, 156));

            imageline($this->img, mt_rand(0, $this->width), mt_rand(0, $this->height), mt_rand(0, $this->width), mt_rand(0, $this->height), $color);

        }

        //雪花

        for ($i = 0; $i < 100; $i++) {

            $color = imagecolorallocate($this->img, mt_rand(200, 255), mt_rand(200, 255), mt_rand(200, 255));

            imagestring($this->img, mt_rand(1, 5), mt_rand(0, $this->width), mt_rand(0, $this->height), '*', $color);

        }

    }



    //输出

    private function outPut()

    {

        header('Content-type:image/png');

        imagepng($this->img);

        imagedestroy($this->img);

    }



    //对外生成

    public function doimg()

    {

        $this->createLine();

        $this->createFont();

        $this->outPut();

    }



    //获取验证码

    public function getCode()

    {

        return strtolower($this->code);

    }

}