How to generate verification code in PHP graphics and image processing?

The content of this article is to introduce how to generate verification code in PHP graphics and image processing? It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Nowadays, verification codes are increasingly indispensable on the Internet. I wonder if you guys know that you can use the GD library of php to generate verification codes.

First introduce a few functions that need to be used.

1.imagesetpixel()

This function can draw pixels. In the verification code, we call it "noise", it is simply an artifact. I don’t know if you guys have remembered that the dots on the verification code are generated using this function.

2.str_shuffle()

Use this to scramble the string, and then use substr() to intercept a given number of digits to generate a random string.

Example:

<?php

$img = imagecreatetruecolor(100, 50);
$black = imagecolorallocate($img, 0x00, 0x00, 0x00);
$green = imagecolorallocate($img, 0x00, 0xFF, 0x00);
$white = imagecolorallocate($img, 0xFF, 0xFF, 0xFF);
imagefill($img, 0, 0, $white);
//生成随机的验证码
$code = make(5);
imagestring($img, 5, 10, 10, $code, $black);
//加入噪点干扰
for ($i = 0; $i < 300; $i++) {
    imagesetpixel($img, rand(0, 100), rand(0, 100), $black);
    imagesetpixel($img, rand(0, 100), rand(0, 100), $green);
}
//加入线段干扰
for ($n = 0; $n <= 1; $n++) {
    imageline($img, 0, rand(0, 40), 100, rand(0, 40), $black);
    imageline($img, 0, rand(0, 40), 100, rand(0, 40), $white);
}
//输出验证码
header("content-type: image/png");
imagepng($img);
//销毁图片
imagedestroy($img);
//生产随机验证码的函数
function make($length)
{
    $code = &#39;abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789&#39;;
    return substr(str_shuffle($code), 0, $length);
}

Rendering: