我把慕课完整代码复制过来　　还有自己对照手写　都不行

<?php
$filename="./des_big.jpg";
$src_image=imagecreatefromjpeg($filename);
list($src_w,$src_h)=getimagesize($filename);
$scale=0.5;
$dst_w=ceil($src_w*$scale);
$dst_h=ceil($src_h*$scale);
$dst_image=imagecreatetruecolor($dst_w, $dst_h);
imagecopyresampled($dst_image, $src_image,0,0,0,0, $dst_w, $dst_h, $src_w, $src_h);
header("content-type:image/jpeg");
imagejpeg($dst_image,"uploads/".$filename);
imagedestroy($src_image);
imagedestroy($dst_image);

图片路径也是对的　就是ｔｅｓｔ下面