PHP realizes the function of generating graphic verification code with background

The example of this article describes the PHP function of generating a graphical verification code with a background. I share it with you for your reference. The details are as follows:

In the past, we used PHP to generate verification codes without background or with the same color background. However, this kind of verification is easy for machines to recognize. Here are some introductions. Generate a graphic verification code example with a background.

1. Generate a png picture,
2. Set the background color for the picture,
3. Set the font color and style,
4 , Generate a 4-digit random verification code,
5. Adjust the rotation angle and position of each generated character and draw it on the png image,
6. Add noise and interference lines to prevent the registration machine from analyzing the original image. Malicious registration,
7. Output pictures,
8. Release the memory occupied by pictures

authcode.php file, the code is as follows:

<?php
    session_start ();
    header ( &#39;Content-type: image/png&#39; );
    //创建图片
    $im = imagecreate($x=130,$y=45 );
    $bg = imagecolorallocate($im,rand(50,200),rand(0,155),rand(0,155)); //第一次对 imagecolorallocate() 的调用会给基于调色板的图像填充背景色
    $fontColor = imageColorAllocate ( $im, 255, 255, 255 );  //字体颜色
    $fontstyle = &#39;rock.ttf&#39;;          //字体样式，这个可以从c:windowsFonts文件夹下找到，我把它放到和authcode.php文件同一个目录，这里可以替换其他的字体样式
    //产生随机字符
    for($i = 0; $i < 4; $i ++) {
        $randAsciiNumArray     = array (rand(48,57),rand(65,90));
        $randAsciiNum         = $randAsciiNumArray [rand ( 0, 1 )];
        $randStr             = chr ( $randAsciiNum );
        imagettftext($im,30,rand(0,20)-rand(0,25),5+$i*30,rand(30,35),$fontColor,$fontstyle,$randStr);
        $authcode            .= $randStr;
    }
    $_SESSION[&#39;authcode&#39;]    = $randFourStr;//用户和用户输入的验证码做比较
    //干扰线
    for ($i=0;$i<8;$i++){
        $lineColor    = imagecolorallocate($im,rand(0,255),rand(0,255),rand(0,255));
        imageline ($im,rand(0,$x),0,rand(0,$x),$y,$lineColor);
    }
    //干扰点
    for ($i=0;$i<250;$i++){
        imagesetpixel($im,rand(0,$x),rand(0,$y),$fontColor);
    }
    imagepng($im);
    imagedestroy($im);
?>

Example 2, create a new PHP file captcha_code_file .php, the code is as follows:

//首先开启session
session_start();
//定义前台显示验证码长&宽
$image_width = 120;
$image_height = 40;
$characters_on_image = 6;
$font = './monofont.ttf';
//The characters that can be used in the CAPTCHA code.
//avoid confusing characters (l 1 and i for example)
$possible_letters = '23456789bcdfghjkmnpqrstvwxyz';
$random_dots = 10;
$random_lines = 30;
$captcha_text_color="0x142864";
$captcha_noice_color = "0x142864";
//定义要生成验证码的字符串
$code = '';
$i = 0;
while ($i < $characters_on_image) {
$code .= substr($possible_letters, mt_rand(0, strlen($possible_letters)-1), 1);
$i++;
}
$font_size = $image_height * 0.75;
$image = @imagecreate($image_width, $image_height);
/* setting the background, text and noise colours here */
$background_color = imagecolorallocate($image, 255, 255, 255);
$arr_text_color = hexrgb($captcha_text_color);
$text_color = imagecolorallocate($image, $arr_text_color[&#39;red&#39;],
    $arr_text_color[&#39;green&#39;], $arr_text_color[&#39;blue&#39;]);
$arr_noice_color = hexrgb($captcha_noice_color);
$image_noise_color = imagecolorallocate($image, $arr_noice_color[&#39;red&#39;],
    $arr_noice_color[&#39;green&#39;], $arr_noice_color[&#39;blue&#39;]);
/* generating the dots randomly in background */
for( $i=0; $i<$random_dots; $i++ ) {
imagefilledellipse($image, mt_rand(0,$image_width),
 mt_rand(0,$image_height), 2, 3, $image_noise_color);
}
/* generating lines randomly in background of image */
for( $i=0; $i<$random_lines; $i++ ) {
imageline($image, mt_rand(0,$image_width), mt_rand(0,$image_height),
 mt_rand(0,$image_width), mt_rand(0,$image_height), $image_noise_color);
}
/* create a text box and add 6 letters code in it */
$textbox = imagettfbbox($font_size, 0, $font, $code);
$x = ($image_width - $textbox[4])/2;
$y = ($image_height - $textbox[5])/2;
imagettftext($image, $font_size, 0, $x, $y, $text_color, $font , $code);
/* Show captcha image in the page html page */
header(&#39;Content-Type: image/jpeg&#39;);// defining the image type to be shown in browser widow
imagejpeg($image);//showing the image
imagedestroy($image);//destroying the image instance
//设置session，做验证
$_SESSION[&#39;6_letters_code&#39;] = $code;
function hexrgb ($hexstr)
{
 $int = hexdec($hexstr);
 return array("red" => 0xFF & ($int >> 0x10),
        "green" => 0xFF & ($int >> 0x8),
        "blue" => 0xFF & $int);
}

Display the verification code page index.php, the example code is as follows:

<?php
session_start();
if(isset($_REQUEST[&#39;Submit&#39;])){
  // code for check server side validation
  if(emptyempty($_SESSION[&#39;6_letters_code&#39;] ) ||
    strcasecmp($_SESSION[&#39;6_letters_code&#39;], $_POST[&#39;6_letters_code&#39;]) != 0)
  {
    $msg="您输入的验证码有误，请重新输入!";
  }else{
    echo "您输入的是正确的!";
    // Captcha verification is Correct. Final Code Execute here!
  }
}
?>
<style type="text/css">
.table{
  font-family:Arial, Helvetica, sans-serif;
  font-size:12px;
  color:#333;
  background-color:#E4E4E4;
}
.table td{
  background-color:#F8F8F8;
}
</style>
<form action="" method="post" name="form1" id="form1" >
 <table width="400" border="0" align="center" cellpadding="5" cellspacing="1">
<?php if(isset($msg)){?>
  <tr>
   <td colspan="2" align="center" valign="top"><?php echo $msg;?></td>
  </tr>
<?php } ?>
  <tr>
   <td align="right" valign="top"> 验证码Demo:</td>
   <td><img src="captcha_code_file.php?rand=<?php echo rand(0,20);?>" id=&#39;captchaimg&#39; onclick="refreshCaptcha();" ><br>
    <label for=&#39;message&#39;>请输入验证码:</label>
    <br>
    <input id="6_letters_code" name="6_letters_code" type="text">
    <br>
    如果看不到，请 <a href=&#39;javascript： refreshCaptcha();&#39;>点我</a> 刷新一下!
    </p></td>
  </tr>
  <tr>
   <td> </td>
   <td><input name="Submit" type="submit" onclick="return validate();" value="Submit"></td>
  </tr>
 </table>
</form>
<script type=&#39;text/javascript&#39;>
//定义的刷新请求
function refreshCaptcha()
{
  var img = document.images[&#39;captchaimg&#39;];
  img.src = img.src.substring(0,img.src.lastIndexOf("?"))+"?rand="+Math.random()*1000;
}
</script>

Example 3, verification code with snowflake background, the code is as follows:

<?session_start();?>
<FORM METHOD=POST ACTION="">
<input type=text name=number maxlength=4><img src="YanZhengMa.php?act=init">
<INPUT TYPE="submit" name="sub">
</FORM>
<?
//检验校验码
if(isset($HTTP_POST_VARS["sub"])):
if($HTTP_POST_VARS["number"] != $HTTP_SESSION_VARS[login_check_number] || emptyempty($HTTP_POST_VARS["number"])){
  echo "校验码不正确!" ;
}else{
  echo"验证码通过！";
}
endif;
show_source(&#39;test.php&#39;);
//以上本页的源码
//以下是生成验证码的源码
show_source(&#39;YanZhengMa.php&#39;);
?>
<?php
session_start();
session_register("login_check_number");
//昨晚看到了chianren上的验证码效果，就考虑了一下，用PHP的GD库完成了类似功能
//先成生背景，再把生成的验证码放上去
$img_height=120;  //先定义图片的长、宽
$img_width=40;
if($HTTP_GET_VARS["act"]== "init"){
  //srand(microtime() * 100000);//PHP420后，srand不是必须的
  for($Tmpa=0;$Tmpa<4;$Tmpa++){
    $nmsg.=dechex(rand(0,15));
  }//by sports98
  $HTTP_SESSION_VARS[login_check_number] = $nmsg;
  //$HTTP_SESSION_VARS[login_check_number] = strval(mt_rand("1111","9999"));  //生成4位的随机数，放入session中
  //谁能做下补充，可以同时生成字母和数字啊？？----由sports98完成了
  $aimg = imageCreate($img_height,$img_width);  //生成图片
  ImageColorAllocate($aimg, 255,255,255);      //图片底色，ImageColorAllocate第1次定义颜色PHP就认为是底色了
  $black = ImageColorAllocate($aimg, 0,0,0);    //定义需要的黑色
  ImageRectangle($aimg,0,0,$img_height-1,$img_width-1,$black);//先成一黑色的矩形把图片包围
  //下面该生成雪花背景了，其实就是在图片上生成一些符号
  for ($i=1; $i<=100; $i++) {  //先用100个做测试
    imageString($aimg,1,mt_rand(1,$img_height),mt_rand(1,$img_width),"*",imageColorAllocate($aimg,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255)));
    //哈，看到了吧，其实也不是雪花，就是生成＊号而已。为了使它们看起来"杂乱无章、5颜6色"，就得在1个1个生成它们的时候，让它们的位置、颜色，甚至大小都用随机数，rand()或mt_rand都可以完成。
  }
  //上面生成了背景，现在就该把已经生成的随机数放上来了。道理和上面差不多，随机数1个1个地放，同时让他们的位置、大小、颜色都用成随机数~~
  //为了区别于背景，这里的颜色不超过200，上面的不小于200
  for ($i=0;$i<strlen($HTTP_SESSION_VARS[login_check_number]);$i++){
    imageString($aimg, mt_rand(3,5),$i*$img_height/4+mt_rand(1,10),mt_rand(1,$img_width/2), $HTTP_SESSION_VARS[login_check_number][$i],imageColorAllocate($aimg,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200)));
  }
  Header("Content-type: image/png");  //告诉浏览器，下面的数据是图片，而不要按文字显示
  ImagePng($aimg);          //生成png格式。。。嘿嘿效果蛮像回事的嘛。。。
  ImageDestroy($aimg);
}
?>

I hope this article will be helpful to everyone in PHP programming.

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