//1.生成100*30大小的圖片,默認(rèn)為黑色
$image = imagecreatetruecolor(100,30);
//創(chuàng)建白色底圖
$bgcolor = imagecolorallocate($image,255,255,255);
//用白色填充黑色
imagefill ($image,0,0,$bgcolor);

//2.隨機(jī)顯示數(shù)字或字母
$captch_code = "";
for($i=0;$i<4;$i++){
 $fontsize=6;
 $fontcolor=imagecolorallocate($image,rand(0,120),rand(0,120),rand(0,120));
 $data = "abcdefghijkmnpqrstuvwxy3456789";
 $fontcontent =substr($data,rand(0,strlen($data)),1);
 $captch_code .=$fontcontent;
 $x = ($i*100/4)+rand(5,10);
 $y = rand(5,10);

 imagestring($image, $fontsize, $x, $y, $fontcontent,$fontcolor);
}
$_SESSION["authcode"] = $captch_code;

//3.增加干擾
//干擾點(diǎn)
for($i=0;$i<100;$i++){
 $pointcolor=imagecolorallocate($image,rand(50,200),rand(50,200),rand(50,200));
 imagesetpixel($image,rand(1,99),rand(1,29),$pointcolor);
}

//干擾線
for($i=0;$i<2;$i++){
 $linecolor=imagecolorallocate($image,rand(80,220),rand(80,220),rand(80,220));
 imageline($image,rand(1,99),rand(1,29),rand(1,99),rand(1,29),$linecolor);
}


header("content-type:image/png");
imagepng($image);

2.頁面實(shí)現(xiàn)驗(yàn)證碼功能
form.php

<?php
if(isset($_POST["authcode"])){
 session_start();
 if(strtolower($_POST["authcode"])==$_SESSION["authcode"]){
  echo "OK";
 }else{
  echo "NO";
 }
}

?>


<!doctype html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>Document</title>
</head>
<body>
<form action="form.php" method="post">
 <p>驗(yàn)證碼圖片: <img id="img" border="1" src="captcha.php?r=<?php echo rand()?>" alt="">
 <a href="javascript:void(0)" onclick="document.getElementById('img').src='captcha.php?r'+Math.random() ">換一個(gè)</a>
 </p>
 <p><input type="text" name="authcode"></p>
 <p><input type="submit" value="提交"></p>

</form>
</body>
</html>

以上就是本文的全部?jī)?nèi)容，幫助大家輕松實(shí)現(xiàn)php圖片驗(yàn)證碼。

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