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【www.bbyears.com--图像处理】

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session_start();

$enablegd = 1;
//判断图像处理函数是否存在
$funcs = array("imagecreatetruecolor","imagecolorallocate","imagefill","imagestring","imageline","imagerotate","imagedestroy","imagecolorallocatealpha","imageellips教程e","imagepng");
foreach($funcs as $func)
{
 if(!function_exists($func))
 {
  $enablegd = 0;
  break;
 }
}

ob_clean(); //清理缓冲

if($enablegd)
{
 //create captcha
 $consts = "cdfgkmnpqrstwxyz23456";
 $vowels = "aek23456789";
 for ($x = 0; $x < 6; $x++)
 {
  $const[$x] = substr($consts, mt_rand(0,strlen($consts)-1),1); //获取$consts中的一个随机数
  $vow[$x] = substr($vowels, mt_rand(0,strlen($vowels)-1),1); //获取$vowels中的一个随机数
 }
 $radomstring = $const[0] . $vow[0] .$const[2] . $const[1] . $vow[1] . $const[3] . $vow[3] . $const[4];
 $_SESSION["checkcode"] = $string = substr($radomstring,0,4); //显示4个字符

 $imageX = strlen($radomstring)*8; //图像的宽
 $imageY = 20;      //图像的高
 $im = imagecreatetruecolor($imageX,$imageY); //新建一个真彩色图像

 //creates two variables to store color
 $background = imagecolorallocate($im, rand(180, 250), rand(180, 250), rand(180, 250)); //背景色
 $foregroundArr = array(imagecolorallocate($im, rand(0, 20), rand(0, 20), rand(0, 20)),
  imagecolorallocate($im, rand(0, 20), rand(0, 10), rand(245, 255)),
  imagecolorallocate($im, rand(245, 255), rand(0, 20), rand(0, 10)),
  imagecolorallocate($im, rand(245, 255), rand(0, 20), rand(245, 255))
 );
 $foreground2 = imagecolorallocatealpha($im, rand(20, 100), rand(20, 100), rand(20, 100),80); //分配颜色并说明透明度
 $middleground = imagecolorallocate($im, rand(200, 160), rand(200, 160), rand(200, 160)); //中间背景
 $middleground2 = imagecolorallocatealpha($im, rand(180, 140), rand(180, 140), rand(180, 140),80); //中间背景2

 //与左上角的颜色相同的都会被填充
 imagefill($im, 0, 0, imagecolorallocate($im, 250, 253, 254));
 //往图像上写入文字
 imagettftext($im, 12, rand(30, -30), 5, rand(14, 16), $foregroundArr[rand(0,3)], "C:WindowsFontsArial.ttf", $string[0]);
 imagettftext($im, 12, rand(50, -50), 20, rand(14, 16), $foregroundArr[rand(0,3)], "C:WindowsFontsArial.ttf", $string[1]);
 imagettftext($im, 12, rand(50, -50), 35, rand(14, 16), $foregroundArr[rand(0,3)],"C:WindowsFontsArial.ttf", $string[2]);
 imagettftext($im, 12, rand(30, -30), 50, rand(14, 16), $foregroundArr[rand(0,3)],"C:WindowsFontsArial.ttf", $string[3]);

 //画边框
 $border = imagecolorallocate($im, 133, 153, 193);
 imagerectangle($im, 0, 0, $imageX - 1, $imageY - 1, $border);

 //画一些随机出现的点
 $pointcol = imagecolorallocate($im, rand(0,255), rand(0,255), rand(0,255));
 for ($i=0;$i<80;$i++)
 {
  imagesetpixel($im,rand(2,$imageX-2),rand(2,$imageX-2),$pointcol);
 }
 //画随机出现的线
 for ($x=0; $x<9;$x++)
 {
  if(mt_rand(0,$x)%2==0)
  {
   imageline($im, rand(0, 120), rand(0, 120), rand(0, 120), rand(0, 120), rand(0, 999999)); //画线
   imageellipse($im, rand(0, 120), rand(0, 120), rand(0, 120), rand(0, 120), $middleground2); //画椭圆
  }
  else
  {
   imageline($im, rand(0, 120), rand(0, 120), rand(0, 120), rand(0, 120), rand(0, 999999));
   imageellipse($im, rand(0, 120), rand(0, 120), rand(0, 120), rand(0, 120), $middleground);
  }
 }
 //output to browser
 header("content-type:image/pngrn");
 imagepng($im);
 imagedestroy($im);
}
else
{
 $files = glob(XINCHENG_ROOT."images/checkcode/*.jpg");
 if(!is_array($files)) die("请检查文件目录完整性:/images/checkcode/");

 $checkcodefile = $files[rand(0, count($files)-1)]; //随机其中一个文件
 $_SESSION["checkcode"] = substr(basename($checkcodefile), 0, 4); //获得文件名

 header("content-type:image/jpegrn");
 include $checkcodefile;
}
?>

本文来源：http://www.bbyears.com/jiaocheng/31810.html