Detailed explanation of the latest and most complete PHP code to generate verification code (recommended), detailed explanation of verification code_PHP tutorial

Detailed explanation of the latest and most complete PHP verification code generation code (recommended), detailed explanation of verification code

1.0 First, look at the code

<&#63;php
header("Content-Type:text/html;Charset=UTF-");// 设置页面的编码风格
header("Content-Type:image/jpeg");// 通知浏览器输出的是jpeg格式的图像
$img = imagecreatetruecolor(,);//创建画布并设置大小 x轴 y轴
$bgcolor = imagecolorallocate($img, mt_rand(,), mt_rand(,), mt_rand(,));//分配背景颜色
imagefill($img, , , $bgcolor); ////把背景填充到图像
imagejpeg($img); // 输出图像
imagedestroy($img); // 销毁图像
&#63;> 

Okay, now combine the above code to analyze the functions used above:

① Imagecreatetruecolor();

imagecreatetruecolor — Create a new true color image (it feels so long, but it’s actually easy to remember if you look carefully image/create/true/color, what is a true color image? Read on)

resource imagecreatetruecolor ( int $width , int $height )

Both functions imagecreatetruecolor() and imagecreate() can create canvases

resource imagecreate ( int $x_size , int $y_size ) 

imagecreatetruecolor() creates a black image with sizes x and y (the default is black [even if it is called a true color image]), if you want to change the background color, you need to

Use the fill color function imagefill($img,0,0,$color);

imagecreate creates a new blank image resource and uses imagecolorAllocate() to add a background color

The above two functions are just two methods of the same function

②　imagecolorallocate();

imagecolorallocate — Assign a color to an image

int imagecolorallocate ( resource $image , int $red , int $green , int $blue )

The colors are a combination of red, green and blue. These parameters are integers from 0 to 255 or hexadecimal 0x00 to 0xFF.

③　mt_rand();

mt_rand — generate better random numbers

int mt_rand ( int $min , int $max )

$min Optional, the minimum value returned (default: 0) $max Optional, the maximum value returned (default: mt_getrandmax())
This is used to randomly generate the background color, with any value from 0-255. Therefore, the canvas background color is different even if the page is refreshed. Rendering:

2.0 Start making interference lines and interference points inside. Prevent verification images from being recognized in seconds

<&#63;php
header("Content-Type:text/html;Charset=UTF-");// 设置页面的编码风格
header("Content-Type:image/jpeg");// 通知浏览器输出的是jpeg格式的图像
$img = imagecreatetruecolor(,);//创建画布并设置大小 x轴 y轴
$bgcolor = imagecolorallocate($img, mt_rand(,), mt_rand(,), mt_rand(,));//分配背景颜色
//添加干扰线，并循环次，背景颜色随机
for($i=;$i<;$i++){
$linecolor = imagecolorallocate($img,mt_rand(,),mt_rand(,),mt_rand(,));
imageline($img, mt_rand(,), mt_rand(,), mt_rand(,), mt_rand(,), $linecolor);
}
//添加干扰点，并循环次，背景颜色随机
for($i=;$i<;$i++){
$dotcolor = imagecolorallocate($img, mt_rand(,), mt_rand(,), mt_rand(,));
imagesetpixel($img, mt_rand(,), mt_rand(,), $dotcolor);
}
imagefill($img, , , $bgcolor); ////把背景填充到图像
imagejpeg($img); // 输出图像
imagedestroy($img); // 销毁图像
&#63;> 

Function analysis:

① imageline();

imageline — draw a line segment

bool imageline ( resource $image , int $x1 , int $y1 , int $x2 , int $y2 , int $color ) 

imageline() draws a line segment in the image image from coordinates x1, y1 to x2, y2 (the upper left corner of the image is 0, 0) using color color.

imageline($img, mt_rand(0,150), mt_rand(0,50), mt_rand(0,150), mt_rand(0,50), $linecolor); This means from coordinates x1, y1 to x2 in canvas $img ,y2random

②　imagesetpixel();

imagesetpixel—draw a single pixel

bool imagesetpixel ( resource $image , int $x , int $y , int $color )

imagesetpixel() draws a point in the image image at the x, y coordinates (the upper left corner of the image is 0, 0) using the color color.

imagesetpixel($img, mt_rand(0,150), mt_rand(0,60), $dotcolor);具体含义同上 

Rendering:

3.0 Add verification alphanumeric

<&#63;php
header("Content-Type:text/html;Charset=UTF-");// 设置页面的编码风格
header("Content-Type:image/jpeg");// 通知浏览器输出的是jpeg格式的图像
$img = imagecreatetruecolor(,);//创建画布并设置大小 x轴 y轴
$bgcolor = imagecolorallocate($img, mt_rand(,), mt_rand(,), mt_rand(,));//分配背景颜色
//添加干扰线，并循环次，背景颜色随机
for($i=;$i<;$i++){
$linecolor = imagecolorallocate($img,mt_rand(,),mt_rand(,),mt_rand(,));
imageline($img, mt_rand(,), mt_rand(,), mt_rand(,), mt_rand(,), $linecolor);
}
//添加干扰点，并循环次，背景颜色随机
for($i=;$i<;$i++){
$dotcolor = imagecolorallocate($img, mt_rand(,), mt_rand(,), mt_rand(,));
imagesetpixel($img, mt_rand(,), mt_rand(,), $dotcolor);
}
//添加需要验证的字母或者数字
$rand_str = "qwertyuiopasdfghjklzxcvbnm";//需要使用到验证的一些字母和数字
$str_arr = array(); //命名一个数组
for($i = ;$i<;$i++){ //循环次，就是有四个随机的字母或者数字 
$pos = mt_rand(,strlen($rand_str)-);
$str_arr[] = $rand_str[$pos];//临时交换
}
$x_start=/;//单个字符X轴位置
foreach ($str_arr as $key) {
$fontcolor = imagecolorallocate($img, mt_rand(,), mt_rand(,), mt_rand(,));
imagettftext($img, , mt_rand(-,), $x_start, /, $fontcolor, "C:/Windows/Fonts/Verdana.TTF", $key);
$x_start +=;//遍历后单个字符沿X轴 +
}
imagefill($img, , , $bgcolor); ////把背景填充到图像
imagejpeg($img); // 输出图像
imagedestroy($img); // 销毁图像
&#63;> 

Function:

imagettftext();

imagettftext — Write text to an image using TrueType fonts

array imagettftext ( resource $image , float $size , float $angle , int $x , int $y , int $color , string $fontfile , string $text ) 

Analyze the code below:

imagettftext($img, 25, mt_rand(-15,15), $x_start, 50/2, $fontcolor, "C:/Windows/Fonts/Verdana.TTF", $key); 

$img----------canvas

25----------The size of the font.

mt_rand(-15,15)----------The angle expressed in the angle system, 0 degrees means text read from left to right. Higher values ​​indicate counterclockwise rotation. For example, 90 degrees represents text that reads from bottom to top. (It’s just a matter of font angle,)

$x_start----------In simple terms, it is the X-axis position of the character

50/2----------Character height

$fontcolor----------Character color

"C:/Windows/Fonts/Verdana.TTF"----------Character font style path

$key----------traverse the following characters

Effect:

The above content is the entire description of the latest and most complete PHP code generation and production verification code detailed (recommended) introduced in this article. I hope it will be helpful to everyone!

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