Use image processing technology to generate verification codes (Typical application tutorial of PHP graphics images 3)

Using image processing technology to generate verification codes (Typical application tutorial of PHP graphics and images 3)

There are many ways to implement the verification code function, including digital verification codes , graphic verification code and text verification code, etc. In this section, a verification code generated using image processing technology is introduced.

In the previous article "How to use the GD2 function to add text to pictures (Typical application tutorial of PHP graphics images 2)", we introduced how to add text to pictures Introduction, then today we will continue to introduce to you how to use image technology to generate verification codes.

The following introduces the use of image processing technology to generate verification codes. The specific code is as follows:

<?php
session_start();
// 告诉浏览器，这个文件，是一个png图片
header(&#39;Content-type: image/png&#39;);
// 创建图像
$image = imagecreatetruecolor(50,20);
// 填充颜色 - ps里的点击画布填色
imagefill($image,0,0,imagecolorallocate($image,149,188,205));
//加入干扰象素 ， 循环100次
for ($i = 0; $i < 100; $i++) {
    $randcolor = imagecolorallocate($image, rand(0, 255), rand(0, 255), rand(0, 255));
//画像素点函数
    imagesetpixel($image, rand(1, 55), rand(1,18), $randcolor);
}
// 设置颜色
$red = imagecolorallocate($image, 255,255,255);
$code = "";
for( $i=1; $i <=4; $i++){
    $rand_code = rand(1,9); // 生成1-9的随机数
    imagestring($image, 5, 5+($i-1)*10, 2, $rand_code,$red); // 将文字写入图片
    $code .= $rand_code;
}
// 生成图片
imagepng($image);
// 销毁图片， 释放内存
imagedestroy($image);
?>

The output result is:

The above is the simplest An example of generating a verification code. Below we introduce an example that is important in daily development. The specific steps are as follows:

(1) Create a checks.php file, use the GD2 function to create a 4-digit verification code in the file, and save the generated verification code in the Session variable. The code is as follows:

<?php
session_start();          //初始化Session变量
header("content-type:image/png");        //设置创建图像的格式
$image_width=70;                          //设置图像宽度
$image_height=18;                          //设置图像高度
srand(microtime()*100000);                //设置随机数的种子
for($i=0;$i<4;$i++){                      //循环输出一个4位的随机数
    $new_number.=dechex(rand(0,15));
}
$_SESSION[check_checks]=$new_number;       //将获取的随机数验
证码写入到Session变量中
$num_image=imagecreate($image_width,$image_height);    //创建一个画布
imagecolorallocate($num_image,255,255,255);         //设置画布的颜色
for($i=0;$i<strlen($_SESSION[check_checks]);$i++){     //循环读取
    Session变量中的验证码
$font=mt_rand(3,5);                                //设置随机的字体
$x=mt_rand(1,8)+$image_width*$i/4;               //设置随机字符所在位置的X坐标
$y=mt_rand(1,$image_height/4);                   //设置随机字符所在位置的Y坐标
$color=imagecolorallocate($num_image,mt_rand(0,100),
    mt_rand(0,150),mt_rand(0,200)); //设置字符的颜色
imagestring($num_image,$font,$x,$y,$_SESSION
[check_checks][$i],$color);   //水平输出字符
}
imagepng($num_image);              //生成PNG格式的图像
imagedestroy($num_image);          //释放图像资源
?>

In the above code, when outputting the verification code, the position, color and font of each character are obtained through random numbers, and various verifications can be generated in the browser Code can also prevent malicious users from attacking the website system.

(2) Create a user login form, and call the checks.php file, output the content of the image in the form page, submit the form information, and use if conditional statements to determine whether the entered verification code is correct. If the verification code filled in by the user is equal to the randomly generated verification code, it will prompt "User login successfully!", the code is as follows:

<?php
session_start();           //初始化Session
if($_POST["Submit"]!=""){
    $checks=$_POST["checks"];        //获取验证码文本框的值
    if($checks==""){           //如果验证码的值为空，则弹出提示信息
        echo "<script> alert(&#39;验证码不能为空&#39;);window.location.
href=&#39;index.php&#39;;</script>";
    }
//如果用户输入验证码的值与随机生成的验证码的值相等，则弹出登录成功提示
    if($checks==$_SESSION[check_checks]){
        echo "<script> alert(&#39;用户登录成功!&#39;);window.location.
href=&#39;index.php&#39;;</script>";
    }else{            //否则弹出验证码不正确的提示信息
        echo "<script> alert(&#39;您输入的验证码不正确!&#39;);window.
location.href=&#39;index.php&#39;;</script>";
    }
}
?>

You can try it on your own computer, and I will not post the picture here. Okay, that’s all about using image processing technology to generate verification codes. Below we will introduce to you "Using GD2 function to draw geometric figures (PHP graphics and images typical application tutorial 4)"!

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