算数验证码

<?php

session_start();

getCode(100, 24);

function getCode($w, $h) {

$im = imagecreate($w, $h);

//imagecolorallocate($im, 14, 114, 180); // background color

$red = imagecolorallocate($im, 255, 0, 0);

$white = imagecolorallocate($im, 255, 255, 255);

$num1 = rand(1, 20);

$num2 = rand(1, 20);

$_SESSION['helloweba_math'] = $num1 + $num2;

$gray = imagecolorallocate($im, 118, 151, 199);

$black = imagecolorallocate($im, mt_rand(0, 100), mt_rand(0, 100), mt_rand(0, 100));

//画背景

imagefilledrectangle($im, 0, 0, 100, 24, $black);

//在画布上随机生成大量点，起干扰作用;

for ($i = 0; $i < 80; $i++) {

imagesetpixel($im, rand(0, $w), rand(0, $h), $gray);

}

imagestring($im, 5, 5, 4, $num1, $red);

imagestring($im, 5, 30, 3, "+", $red);

imagestring($im, 5, 45, 4, $num2, $red);

imagestring($im, 5, 70, 3, "=", $red);

imagestring($im, 5, 80, 2, "?", $white);

header("Content-type: image/png");

imagepng($im);

imagedestroy($im);

}

?>