适用于自定义的验证码类！

<?php

/* 
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
Class Image{

private $img;
public $width = 85;
public $height = 25;
public $code;
public $code_len = 4;
public $code_str = "329832983DSDSKDSLKQWEWQ2lkfDSFSDjfdsfdsjwlkfj93290KFDSKJFDSOIDSLK";
public $bg_color = '#DCDCDC';
public $font_size = 16;
public $font = 'font.ttf';
public $font_color = '#000000';

//创建验证码饿字符创
public function create_code(){
$code = '';
for( $i=0;$i<$this->code_len;$i++ ){
$code .= $this->code_str[mt_rand(0, strlen($this->code_str)-1)];
}
return $this->code = $code;
}

//输出图像
public function getImage(){
$w = $this->width;
$h = $this->height;
$bg_color = $this->bg_color;
$img = imagecreatetruecolor($w, $h);
$bg_color = imagecolorallocate($img, 
hexdec(substr($bg_color, 1,2)), hexdec(substr($bg_color, 3,2)), hexdec(substr($bg_color, 5,2)));
imagefill($img, 0, 0, $bg_color);
$this->img = $img;
$this->create_font();
$this->create_pix();
$this->show_code();
}


//写入验证码
public function create_font(){
$this->create_code();
$color = $this->font_color;
$font_color = imagecolorallocate($this->img, hexdec(substr($color,1,2)), hexdec(substr($color, 3,2)), hexdec(substr($color,5,2)));
$x = $this->width/$this->code_len;
for( $i=0;$i<$this->code_len;$i++ ){
$txt_color = imagecolorallocate($this->img, mt_rand(0,100), mt_rand(0, 150), mt_rand(0, 200));
imagettftext($this->img, $this->font_size, mt_rand(-30, 30), $x*$i+mt_rand(3, 6), mt_rand($this->height/1.2, $this->height), $txt_color, $this->font , $this->code[$i]); 
//imagestring($this->img, $this->font_size, $x*$i+mt_rand(3, 6),mt_rand(0, $this->height/4) , $this->code[$i], $font_color);
}
$this->font_color = $font_color;
}

//画干扰线
public function create_pix(){
$pix_color= $this->font_color;
for($i=0;$i<100;$i++){
imagesetpixel($this->img, mt_rand(0, $this->width),mt_rand(0, $this->height), $pix_color);
}
for($j=0;$j<4;$j++){
imagesetthickness($this->img, mt_rand(1, 2));
imageline($this->img, mt_rand(0, $this->width), mt_rand(0, $this->height), mt_rand(0, $this->width), mt_rand(0, $this->height), $pix_color);
}
}

//得到验证码
public function getCode(){
return strtoupper($this->code);
}


//输出验证码
private function show_code(){
header("Content-type:image/png");
imagepng($this->img);
imagedestroy($this->img);
}
}

我们再来看一例代码：

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

<?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);
}
}

例三：

<?php
class ValidationCode {
private $width;
private $height;
private $codeNum;
private $image; //图像资源
private $disturbColorNum;
private $checkCode;
function __construct($width=80, $height=20, $codeNum=4){
$this->width=$width;
$this->height=$height;
$this->codeNum=$codeNum;
$this->checkCode=$this->createCheckCode();
$number=floor($width*$height/15);

if($number > 240-$codeNum){
$this->disturbColorNum= 240-$codeNum;
}else{
$this->disturbColorNum=$number;
}

}
//通过访问该方法向浏览器中输出图像
function showImage($fontFace=""){
//第一步：创建图像背景
$this->createImage();
//第二步：设置干扰元素
$this->setDisturbColor();
//第三步：向图像中随机画出文本
$this->outputText($fontFace);
//第四步：输出图像
$this->outputImage();
}

//通过调用该方法获取随机创建的验证码字符串
function getCheckCode(){
return $this->checkCode;
}
private function createImage(){
//创建图像资源
$this->image=imagecreatetruecolor($this->width, $this->height);
//随机背景色
$backColor=imagecolorallocate($this->image, rand(225, 255), rand(225,255), rand(225, 255));
//为背景添充颜色
imagefill($this->image, 0, 0, $backColor);
//设置边框颜色
$border=imagecolorallocate($this->image, 0, 0, 0);
//画出矩形边框
imagerectangle($this->image, 0, 0, $this->width-1, $this->height-1, $border);
}
private function setDisturbColor(){
for($i=0; $i<$this->disturbColorNum; $i++){
$color=imagecolorallocate($this->image, rand(0, 255), rand(0, 255), rand(0, 255));
imagesetpixel($this->image, rand(1, $this->width-2), rand(1, $this->height-2), $color);
}
for($i=0; $i<10; $i++){
$color=imagecolorallocate($this->image, rand(200, 255), rand(200, 255), rand(200, 255));
imagearc($this->image, rand(-10, $this->width), rand(-10, $this->height), rand(30, 300), rand(20, 200), 55, 44, $color);
}
}