php 生成随机验证码图片代码

一个最简单的生成随机验证码图片的例子

<?php 
/** 默认首页 **/ 
class DefaultController extends AppController 
{ 
public function index() { 
$len = 5; 
$str = "ABCDEFGHIJKLNMPQRSTUVWXYZ123456789"; 

$im = imagecreatetruecolor ( 70, 20 ); 
$bgc = imagecolorallocate($im, 255, 255, 255); 
$bgtxt = imagecolorallocate($im, 220, 220, 220); 

//随机调色板 
$colors = array( 
imagecolorallocate($im, 255, 0, 0), 
imagecolorallocate($im, 0, 200, 0), 
imagecolorallocate($im, 0, 0, 255), 
imagecolorallocate($im, 0, 0, 0), 
imagecolorallocate($im, 255, 128, 0), 
imagecolorallocate($im, 255, 208, 0), 
imagecolorallocate($im, 98, 186, 245), 
); 

//填充背景色 
imagefill($im, 0, 0, $bgc); 

//随机获取数字 
$verify = ""; 
while (strlen($verify) < $len) { 
$i = strlen($verify); 
$random = $str[rand(0, strlen($str))]; 
$verify .= $random; 

//绘制背景文字 
imagestring($im, 6, ($i*10)+3, rand(0,6), $random, $bgtxt); 
//绘制主文字信息 
imagestring($im, 6, ($i*10)+3, rand(0,6), $random, $colors[rand(0, count($colors)-1)]); 
} 

//添加随机杂色 
for($i=0; $i<100; $i++) { 
$color = imagecolorallocate($im, rand(50,220), rand(50,220), rand(50,220)); 
imagesetpixel($im, rand(0,70), rand(0,20), $color); 
} 

//将验证码存入$_SESSION中 
sess("verify", $verify); 

//输出图片并释放缓存 
header('Content-type: image/png'); 
imagepng($im); 
imagedestroy($im); 
} 
}; 
?>