<?php
/**
 * =======================================
 * Created by WeiBang Technology.
 * User: Wei ZhiHua
 * Date: 2016/10/12 0020
 * Time: 下午 4:14
 * Power: 实现验证码功能
 * =======================================
 */
 
//开启session
session_start();
//创建一个大小为 100*30 的验证码
$image = imagecreatetruecolor(100, 30);
$bgcolor = imagecolorallocate($image, 255, 255, 255);
imagefill($image, 0, 0, $bgcolor);
 
$captch_code = '';
for ($i = 0; $i < 4; $i++) {
    $fontsize = 6;
    $fontcolor = imagecolorallocate($image, rand(0, 120), rand(0, 120), rand(0, 120));
    $data = 'abcdefghijkmnpqrstuvwxy3456789';
    $fontcontent = substr($data, rand(0, strlen($data) - 1), 1);
    $captch_code .= $fontcontent;
    $x = ($i * 100 / 4) + rand(5, 10);
    $y = rand(5, 10);
    imagestring($image, $fontsize, $x, $y, $fontcontent, $fontcolor);
}
//就生成的验证码保存到session
$_SESSION['authcode'] = $captch_code;
 
//在图片上增加点干扰元素
for ($i = 0; $i < 200; $i++) {
    $pointcolor = imagecolorallocate($image, rand(50, 200), rand(50, 200), rand(50, 200));
    imagesetpixel($image, rand(1, 99), rand(1, 29), $pointcolor);
}
 
//在图片上增加线干扰元素
for ($i = 0; $i < 3; $i++) {
    $linecolor = imagecolorallocate($image, rand(80, 220), rand(80, 220), rand(80, 220));
    imageline($image, rand(1, 99), rand(1, 29), rand(1, 99), rand(1, 29), $linecolor);
}
//设置头
header('content-type:image/png');
imagepng($image);
imagedestroy($image);
 
?>
