图片出现裂痕不正常打开？求解
session_start();
$table=array(
'pic0'=>'虎',
'pic1'=>'鼠',
'pic2'=>'牛',
'pic3'=>'兔',
);
$index=rand(0,3);
$value=$table['pic'.$index];
$_SESSION['authcode']=$value;
$filename=dirname(__FILE__).'\\pic'.$index.'.jpg'; $contents=file_get_contents($filename);
header('content-type:image/jpg');
echo $contents;
？？？