php图片验证码类

<?php
/**
 * 图片验证码类
 * 生成图片类型验证码，验证码包含数字和大写字母，session中存放md5加密后的验证码
 * 
 * 使用方法：
 * $captcha = new Catpcha();
 * $captcha->buildAndExportImage();
 * 
 * 作          者: luojing
 * 创建时间: 2013-3-27 上午11:42:12
 */
class Captcha {
	
	private $width;//宽度
	private $height; //高度
	private $codeNum;//验证码字符数量
	private $image;//验证码图像资源
	private $sessionKey;//session中保存的名字
	private $captcha;//验证码字符串
	const charWidth = 10;//单个字符宽度,根据输出字符大小而变
	
	/**
	 * 创建验证码类，初始化相关参数
	 * @param  $width 图片宽度
	 * @param  $height 图片高度
	 * @param  $codeNum 验证码字符数量
	 * @param  $sessionKey session中保存的名字
	 */
	function __construct($width = 50, $height = 20, $codeNum = 4, $sessionKey = 'captcha') {
		$this->width = $width;
		$this->height = $height;
		$this->codeNum = $codeNum;
		$this->sessionKey = $sessionKey;
		
		//保证最小高度和宽度
		if($height < 20) {
			$this->height = 20;
		}
		if($width < ($codeNum * self::charWidth + 10)) {//左右各保留5像素空隙
			$this->width = $codeNum * self::charWidth + 10;
		}
	}
	
	/**
	 * 构造并输出验证码图片
	 */
	public  function buildAndExportImage() {
		$this->createImage();
		$this->setDisturb();
		$this->setCaptcha();
		$this->exportImage();
	}
	
	/**
	 * 构造图像，设置底色
	 */
	private function createImage() {
		//创建图像
		$this->image = imagecreatetruecolor($this->width, $this->height);  
		//创建背景色
		$bg = imagecolorallocate($this->image, mt_rand(220, 255), mt_rand(220, 255), mt_rand(220, 255));  
		//填充背景色
		imagefilledrectangle($this->image, 0, 0, $this->width - 1, $this->height - 1, $bg);
	}
	
	/**
	 * 设置干扰元素
	 */
	private function setDisturb() {
		
		//设置干扰点
		for($i = 0; $i < 150; $i++) {
			$color = imagecolorallocate($this->image, mt_rand(150, 200),  mt_rand(150, 200),  mt_rand(150, 200));
			imagesetpixel($this->image, mt_rand(5, $this->width - 10), mt_rand(5, $this->height - 3), $color);
		}
		
		//设置干扰线
		for($i = 0; $i < 10; $i++) {
			$color = imagecolorallocate($this->image, mt_rand(150, 220), mt_rand(150, 220), mt_rand(150, 220));
			imagearc($this->image, mt_rand(-10, $this->width), mt_rand(-10, $this->height), mt_rand(30, 300), mt_rand(20, 200), 55, 44, $color);
		}
		
		//创建边框色
		$border = imagecolorallocate($this->image, mt_rand(0, 50), mt_rand(0, 50), mt_rand(0, 50));
		//画边框
		imagerectangle($this->image, 0, 0, $this->width - 1, $this->height - 1, $border);
	}
	
	/**
	 * 产生并绘制验证码
	 */
	private function setCaptcha() {
		$str = '23456789ABCDEFGHJKLMNPQRSTUVWXYZ';
		//生成验证码字符
		for($i = 0; $i < $this->codeNum; $i++) {
			$this->captcha .= $str{mt_rand(0, strlen($str) - 1)};
		}
		//绘制验证码
		for($i = 0; $i < strlen($this->captcha); $i++) {
			$color = imagecolorallocate($this->image, mt_rand(0, 200), mt_rand(0, 200), mt_rand(0, 200));
			$x = floor(($this->width - 10)/$this->codeNum);
			$x = $x*$i + floor(($x-self::charWidth)/2) + 5;
			$y = mt_rand(2, $this->height - 20);
			imagechar($this->image, 5, $x, $y, $this->captcha{$i}, $color);
		}
	}
	
	/*
	 * 输出图像,验证码保存到session中
	 */
	private function exportImage() {
		if(imagetypes() & IMG_GIF){
			header('Content-type:image/gif');
			imagegif($this->image);
		} else if(imagetypes() & IMG_PNG){
			header('Content-type:image/png');  
         	imagepng($this->iamge);
		} else if(imagetypes() & IMG_JPEG) {
			header('Content-type:image/jpeg');  
         	imagepng($this->iamge);
		} else {
			imagedestroy($this->image);
			die("Don't support image type!");
		}
		//将验证码信息保存到session中，md5加密
		if(!isset($_SESSION)){
    		session_start();
		} 
		$_SESSION[$this->sessionKey] = md5($this->captcha);
		
        imagedestroy($this->image);  
	}
	
	function __destruct() {
		unset($this->width, $this->height, $this->codeNum,$this->captcha);
	}
}