<?php
/**
* @version 1.0
* @author  bolted snail
* @date 2011-10-15
* @PHP驗證碼類
* 使用方法：
* $image=new Captcha();
* $image->config('寬度','高度','字符個數(shù)','驗證碼session索引');
* $image->create();//這樣就會向瀏覽器輸出一張圖片
* //所有參數(shù)都可以省略，
* 默認(rèn)是：寬80 高20 字符數(shù)4 驗證碼session索引captcha_code
* 第四個參數(shù)即把驗證碼存到$_SESSION['captcha_code']
* 最簡單使用示例:
* $image=new Captcha();
* $image->create();//這樣就會向瀏覽器輸出一張圖片
*/
class Captcha
{
private $width=80,$height=20,$codenum=4;
public $checkcode;   //產(chǎn)生的驗證碼
private $checkimage;  //驗證碼圖片 
private $disturbColor = ''; //干擾像素
private $session_flag='captcha_code';//存到session中的索引
//嘗試開始session
function __construct(){
  @session_start();
}
/*
* 參數(shù)：（寬度，高度，字符個數(shù)）
*/
function config($width='80',$height='20',$codenum='4',$session_flag='captcha_code')
{ 
  $this->width=$width;
  $this->height=$height;
  $this->codenum=$codenum;
  $this->session_flag=$session_flag;
}
function create()
{
  //輸出頭
  $this->outFileHeader();
  //產(chǎn)生驗證碼
  $this->createCode();
  //產(chǎn)生圖片
  $this->createImage();
  //設(shè)置干擾像素
  $this->setDisturbColor();
  //往圖片上寫驗證碼
  $this->writeCheckCodeToImage();
  imagepng($this->checkimage);
  imagedestroy($this->checkimage);
  $_SESSION[$this->session_flag]=$this->checkcode;
}
/*
  * @brief 輸出頭
  */
private function outFileHeader()
{
  header ("Content-type: image/png");
}
/**
  * 產(chǎn)生驗證碼
  */
private function createCode()
{
  $this->checkcode = strtoupper(substr(md5(rand()),0,$this->codenum));
}
/**
  * 產(chǎn)生驗證碼圖片
  */
private function createImage()
{
  $this->checkimage = @imagecreate($this->width,$this->height);
  $back = imagecolorallocate($this->checkimage,255,255,255); 
  $border = imagecolorallocate($this->checkimage,0,0,0); 
  imagefilledrectangle($this->checkimage,0,0,$this->width - 1,$this->height - 1,$back); // 白色底
  imagerectangle($this->checkimage,0,0,$this->width - 1,$this->height - 1,$border);  // 黑色邊框
}
/**
  * 設(shè)置圖片的干擾像素 
  */
private function setDisturbColor()
{
  for ($i=0;$i<=200;$i++)
  {
  $this->disturbColor = imagecolorallocate($this->checkimage, rand(0,255), rand(0,255), rand(0,255));
  imagesetpixel($this->checkimage,rand(2,128),rand(2,38),$this->disturbColor);
  }
}
/**
  *
  * 在驗證碼圖片上逐個畫上驗證碼
  *
  */
private function writeCheckCodeToImage()
{
  for ($i=0;$i<$this->codenum;$i++)
  {
  $bg_color = imagecolorallocate ($this->checkimage, rand(0,255), rand(0,128), rand(0,255));
  $x = floor($this->width/$this->codenum)*$i;
  $y = rand(0,$this->height-15);
  imagechar ($this->checkimage, rand(5,8), $x+5, $y, $this->checkcode[$i], $bg_color);
  }
}
function __destruct()
{
  unset($this->width,$this->height,$this->codenum,$this->session_flag);
}
}
?>