<?php
      session_start();

      $image=imagecreatetruecolor(200, 60);
      $bgcolor=imagecolorallocate($image, 255, 255, 255);
      imagefill($image, 0, 0, $bgcolor);
      
      $fontface='FZYTK.TTF'; //字体一定要命名为英文
      
      $str = "的一是在了不和有大这主中人上为们地个用工时要动国产以
           走议县兵固除般引齿千胜细影济白格效置推空配刀叶率述今选养德话";

      //$strdb=array('慕' , '课' ,'网' ,'赞' );
      $strdb=str_split($str,3);
      //header('content-type:text/html; charset=gb2312');
      //var_dump($strdb);
      //die();
     $captch_code='';
     for($i=0;$i<4;$i++)//写汉字       
     {
         $fontcolor=imagecolorallocate($image,rand(0,120), rand(0,120), rand(0,120));//字体颜色
        
         $index=rand(0,count($strdb));
         $cn=$strdb[$index];
         $captch_code.=$cn;

         imagettftext($image, mt_rand(20,24), mt_rand(-60,60),(40*$i+20), mt_rand(30,35),  $fontcolor, $fontface, $cn);
         //imagettftext(image, size, angle, x, y, color, fontfile, text)
       }
      

      $_SESSION['authcode']=$captch_code;

      for ($i=0; $i < 200; $i++) //干扰点
      {
          $pointcolor=imagecolorallocate($image, rand(50,200), rand(50,200), rand(50,200));
          imagesetpixel($image, rand(1,199), rand(1,59), $pointcolor);
      }
      
       for ($i=0; $i < 3; $i++) //干扰线
      {
          $linecolor=imagecolorallocate($image, rand(80,220), rand(80,220), rand(80,220));
          imageline($image, rand(1,199), rand(1,59),rand(1,199), rand(1,59), $linecolor);
      }

      header('content-type: image/png; charset=gb2312');
      imagepng($image);

      imagedestroy($image);
      
?>