PHP运用GD库实现一个简单的验证码

<?php$img=imagecreatetruecolor(100, 40);$red=imagecolorallocate($img, 255, 0, 0);$green=imagecolorallocate($img, 0, 255, 0);$blue=imagecolorallocate($img, 0, 0, 255);$white=imagecolorallocate($img, 255, 255, 255);$black=imagecolorallocate($img, 0, 0, 0);//生成图片imagefill($img, 0, 0, $black);//设置验证码$code="";for($i=0;$i<5;$i++){$code.=rand(0,9);}//验证码写到图片中imagestring($img, 5, 20, 15, $code, $white);//加点儿干扰for($i=0;$i<10;$i++){imagesetpixel($img, rand(0,100), rand(0,40), $red);imagesetpixel($img, rand(0,100), rand(0,40), $green);imagesetpixel($img, rand(0,100), rand(0,40), $blue);}//再加点儿干扰for($i=0;$i<1;$i++){imageline($img, rand(0,50), rand(0,20), rand(50,100), rand(20,40), $red);imageline($img, rand(0,50), rand(0,20), rand(50,100), rand(20,40), $green);imageline($img, rand(0,50), rand(0,20), rand(50,100), rand(20,40), $blue);}header("Content-type:image/png");imagepng($img);imagedestroy($img);?>