简述php设计验证码的过程

简述php设计验证码的过程

php使用GD库生成验证码

一、绘图步骤:

1.创建画布，分配颜色,使用以下两个函数(可以在php手册GD库函数中找到)：

imagecreatetruecolor()

imagecolorallocate()

2.绘画过程：

imagefill()

imagettftext()

imagesetpixel()

imageline()

3. 输出图像：

header(“Content-Type:image/png”);

imagepng();

imagejpeg();

4.销毁图片（释放内存）

imagedestroy();

二、绘图具体步骤

生成验证码字符串

private function getCode(){
   $str="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
   $t='';
   for($i=0;$i<$this->m;$i++){
  $t.=$str[rand(0,$this->type['letter'])];
   }
   return $t;
    } 

画出验证码

function drawCode(){
   $code=$this->getCode();//获取验证码字符串
   imagefill($this->im, 0, 0, $this->bg);
   for ($i=0; $i <200 ; $i++) { 
  imagesetpixel($this->im, rand(0,$this->width), rand(0,$this->height), rand(0,255));
   }
   imageline($this->im, rand(0,$this->width), rand(0,$this->height), rand(0,$this->width), rand(0,$this->height), rand(0,255));
   $c=imagecolorallocate($this->im, rand(0,200), rand(0,200), rand(0,200));
   for($i=0;$i<$this->m;$i++){
  imagettftext($this->im, 18, rand(-40,40), 8+(18*$i), 24, $c, "georgia.ttf",$code[$i] );
   }
    } 

输出图像

function printImage(){
   $this->drawCode();
   header("Content-Type:image/jpeg");
   imagepng($this->im);
   $this->destroy();
    }
    function destroy(){
   imagedestroy($this->im);
    } 

三、代码演示

<?php
/**
* 验证码画图类
*/
class Image 
{
    private $width;
    private $height;
    private $im;
    private $bg;
    private $m;
    private $type=array('num' => 9,'letter' => 61 );
    function __construct($width,$height,$m)
    {
   $this->width=$width;
   $this->height=$height;
   $this->m=$m;
   $this->im=imagecreatetruecolor($this->width, $this->height);
   $this->bg=imagecolorallocate($this->im, 220, 220, 220);
    }
    private function getCode(){
   $str="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
   $t='';
   for($i=0;$i<$this->m;$i++){
  $t.=$str[rand(0,$this->type['letter'])];
   }
   return $t;
    }
    function drawCode(){
   $code=$this->getCode();//获取验证码字符串
   imagefill($this->im, 0, 0, $this->bg);
   //加干扰点
   for ($i=0; $i <200 ; $i++) { 
  imagesetpixel($this->im, rand(0,$this->width), rand(0,$this->height), rand(0,255));
   }
   //加干扰线
   imageline($this->im, rand(0,$this->width), rand(0,$this->height), rand(0,$this->width), rand(0,$this->height), rand(0,255));
   $c=imagecolorallocate($this->im, rand(0,200), rand(0,200), rand(0,200));
   for($i=0;$i<$this->m;$i++){
  imagettftext($this->im, 18, rand(-40,40), 8+(18*$i), 24, $c, "georgia.ttf",$code[$i] );
   }
    }
    function printImage(){
   $this->drawCode();
   header("Content-Type:image/jpeg");
   imagepng($this->im);
   $this->destroy();
    }
    function destroy(){
   imagedestroy($this->im);
    }
}
function unit_test(){
    $obj=new Image(20*4,30,4);
    $obj->printImage();
}
unit_test();
?> 

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