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);
?>