php 绘制验证码 示例

<?php
header("content-type:image/jpeg");

session_start();//开启session

//宽高 字体大小
$width=120;
$height=40;
$fontsize=20;

//给画布宽高
$img=imagecreatetruecolor($width,$height);

//画布背景色
$bgcolor=imagecolorallocate($img,rand(200,255),rand(200,255),rand(200,255));

 //画布边框背景
$bordercolor=imagecolorallocate($img,rand(0,155),rand(0,155),rand(0,155));

//内容字体颜色
$fontcolor=imagecolorallocate($img,rand(30,100),rand(30,100),rand(30,100));

//填充背景色
imagefill($img,0,0,$bgcolor);

//填充边框
imagerectangle($img,0,0,$width-1,$height-1,$bordercolor);

//干扰点
for($a=0;$a<100;$a++){
    imagesetpixel($img,rand(1,$width-2),rand(1,$height-2),$bordercolor);
}

//创建数组
$shuzi=range(0,9);

//随机数
$suiji=$shuzi[rand(0,count($shuzi)-1)].$shuzi[rand(0,count($shuzi)-1)]
    .$shuzi[rand(0,count($shuzi)-1)].$shuzi[rand(0,count($shuzi)-1)];

//输出内容
imagettftext($img,$fontsize,rand(-5,5),rand(15,25),rand(28,33),$fontcolor,'ziti.ttf',$suiji);$_SESSION['yzm_b']=$suiji;

//获取‘验证码输入框的内容’



//输出画布
imagejpeg($img);
?>