โค๊ด Chaptcha ครับ แสดงผลแปลกๆๆ ครับ รบกวนพี่ๆๆช่วยหน่อยครับ

<?php 
error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED);
header('Content-Type: image/png'); // เอามาไว้ตรงนี้แทน
$img = imagecreate(130, 50);
$bg = imagecolorallocate($img,0,0,0);
$gray = imagecolorallocate($img,150,150,150); 
$red = imagecolorallocate($img,255,0,0);
$width = imagesx($img);
$hight = imagesy($img);

 $x1=0;$y1=0;
 $x2=0;$y2= $hight;
 $num_vr_lines = ceil($width/10);
 for($i=0;$i<$num_vr_lines;$i++){
	 imageline($img,$x1,$y1,$x2,$y2,$gray);
	 $x1 += 10;$x2 +=10;
	 }
 
  $x1=0;$y1=0;
  $x2=$width;$y2=0;
  $num_hr_lines = ceil($hight/10);
  for($i=0;$i<$num_hr_lines;$i++){
	  imageline($img,$x1,$y1,$x2,$y2,$gray);
	  $y1 += 10;$y2 += 10;
	  }
  $font = "tahoma.ttf";
  $fontsize =20;
  $str = md5(crypt("captcha"));
  $captcha = strtoupper(substr($str,0,4));
  $x = 10; $y = 30;
  $deg = array(0,30,-30);
  for($i = 0; $i < strlen($str);$i++){
	  $d = rand(0,2);
	  imagettftext($img,$fontsize,$deg[$d],$x,$y,$red,$font,$captcha[$i]);
	  $x += 30;
	  }
  //header("Content-type:img/png");
  imagepng($img);
  imagedestroy($img);

?>