รบกวนครับ.. โค้ช crop รูป ใช้งานแล้วไม่ชัดแก้ยังไงครับ

<?
header ("Content-type: image/jpeg");
$file_name=$_GET['f'];
$crop_height=$_GET['h'];
$crop_width=$_GET['w'];
$file_type= explode('.', $file_name);
$file_type = $file_type[count($file_type) -1];
$file_type=strtolower($file_type);

$original_image_size = getimagesize($file_name);
$original_width = $original_image_size[0];
$original_height = $original_image_size[1];

if($file_type=='jpg')
{
$original_image_gd = imagecreatefromjpeg($file_name);
}

if($file_type=='jpeg')
{
$original_image_gd = imagecreatefromjpeg($file_name);
}

if($file_type=='gif')
{ $original_image_gd = imagecreatefromgif($file_name);
}

if($file_type=='png')
{
$original_image_gd = imagecreatefrompng($file_name);
}

$cropped_image_gd = imagecreatetruecolor($crop_width, $crop_height);
$wm = $original_width /$crop_width;
$hm = $original_height /$crop_height;
$h_height = $crop_height/2;
$w_height = $crop_width/2;

if($original_width > $original_height )
{
$adjusted_width =$original_width / $hm;
$half_width = $adjusted_width / 2;
$int_width = $half_width - $w_height;

imagecopyresampled($cropped_image_gd ,$original_image_gd ,-$int_width,0,0,0, $adjusted_width, $crop_height, $original_width , $original_height );
}
elseif(($original_width < $original_height ) || ($original_width == $original_height ))
{
$adjusted_height = $original_height / $wm;
$half_height = $adjusted_height / 2;
$int_height = $half_height - $h_height;

imagecopyresampled($cropped_image_gd , $original_image_gd ,0,-$int_height,0,0, $crop_width, $adjusted_height, $original_width , $original_height );
}
else {

imagecopyresampled($cropped_image_gd , $original_image_gd ,0,0,0,0, $crop_width, $crop_height, $original_width , $original_height );
}
imagejpeg($cropped_image_gd);

?>