A simple example of generating verification code with PHP, php verification code example_PHP tutorial

A simple example of PHP generating verification code, PHP verification code example

You will know it after reading it, you won’t hit me, don’t talk much, let’s do it ( People don’t talk much)

1.0 First look at the code

<&#63;php
header("Content-Type:text/html;Charset=UTF-8");// 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(150,50);//创建画布并设置大小 x轴150 y轴50

$bgcolor = imagecolorallocate($img, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255));//分配背景颜色
imagefill($img, 0, 0, $bgcolor); ////把背景填充到图像
imagejpeg($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 size 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-8");// 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(150,50);//创建画布并设置大小 x轴150 y轴50

$bgcolor = imagecolorallocate($img, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255));//分配背景颜色

//添加干扰线，并循环3次，背景颜色随机
for($i=0;$i<3;$i++){

  $linecolor = imagecolorallocate($img,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));
  imageline($img, mt_rand(0,150), mt_rand(0,50), mt_rand(0,150), mt_rand(0,50), $linecolor);

}
//添加干扰点，并循环25次，背景颜色随机
for($i=0;$i<25;$i++){

  $dotcolor = imagecolorallocate($img, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255));
  imagesetpixel($img, mt_rand(0,150), mt_rand(0,60), $dotcolor);

}

imagefill($img, 0, 0, $bgcolor); ////把背景填充到图像
imagejpeg($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() uses the color color in the image image to draw a point on the x, y coordinates (the upper left corner of the image is 0, 0) .

imagesetpixel($img, mt_rand(0,150), mt_rand(0,60), $dotcolor); The specific meaning is the same as above. Rendering:

3.0 Add verification alphanumeric

<&#63;php
header("Content-Type:text/html;Charset=UTF-8");// 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(150,50);//创建画布并设置大小 x轴150 y轴50

$bgcolor = imagecolorallocate($img, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255));//分配背景颜色

//添加干扰线，并循环3次，背景颜色随机
for($i=0;$i<3;$i++){

  $linecolor = imagecolorallocate($img,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));
  imageline($img, mt_rand(0,150), mt_rand(0,50), mt_rand(0,150), mt_rand(0,50), $linecolor);

}
//添加干扰点，并循环25次，背景颜色随机
for($i=0;$i<25;$i++){

  $dotcolor = imagecolorallocate($img, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255));
  imagesetpixel($img, mt_rand(0,150), mt_rand(0,60), $dotcolor);

}

//添加需要验证的字母或者数字
$rand_str = "qwertyuiopasdfghjklzxcvbnm1234567890";//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 = 0;$i<4;$i++){  //循环4次，就是有四个随机的字母或者数字              
  $pos = mt_rand(0,strlen($rand_str)-1);
  $str_arr[] = $rand_str[$pos];//临时交换
}

$x_start=150/4;//单个字符X轴位置

foreach ($str_arr as $key) {
  $fontcolor = imagecolorallocate($img, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255));
  imagettftext($img, 25, mt_rand(-15,15), $x_start, 50/2, $fontcolor, "C:/Windows/Fonts/Verdana.TTF", $key);
  $x_start +=20;//遍历后单个字符沿X轴 +20
}

imagefill($img, 0, 0, $bgcolor); ////把背景填充到图像
imagejpeg($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 following code:

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:

Looks pretty cute.

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