php 图片下载程序

function displayimg($image)
{
$image = './upload/'.imgdecode($image);
//echo $image;exit;
if (file_exists($image))
{
$info = getimagesize($image);
header("Content-type:$info[mime]");
switch ($info[2])
{
case 1: $cimage = imagecreatefromgif($image);
imagegif($cimage);
imagedestroy($cimage);
break;
case 2: $cimage = imagecreatefromjpeg($image);
imagejpeg($cimage);
imagedestroy($cimage);
break;
case 3: $cimage = imagecreatefrompng($image);
imagepng($cimage);
imagedestroy($cimage);
break;
case 6: $cimage = imagecreatefromwbmp($image);
imagewbmp($cimage);
imagedestroy($cimage);
break;
}
echo $simage;
}
else
{
header("HTTP/1.0 404 Not Found");
}
}