php生成縮略圖代碼

/**
@filename - path to the image@tmpname - temporary path to thumbnail
@xmax - max width@ymax - max height
*/
function resize_image($filename, $tmpname, $xmax, $ymax)
{
    $ext = explode(".", $filename);
    $ext = $ext[count($ext)-1];


if($ext == "jpg" || $ext == "jpeg")
    $im = imagecreatefromjpeg($tmpname);
elseif($ext == "png")
    $im = imagecreatefrompng($tmpname);
elseif($ext == "gif")
    $im = imagecreatefromgif($tmpname);  

$x = imagesx($im);
$y = imagesy($im);  

if($x <= $xmax && $y <= $ymax)
    return $im;  

if($x >= $y) {
    $newx = $xmax;
    $newy = $newx * $y / $x;
}
else {
    $newy = $ymax;
    $newx = $x / $y * $newy;
}  

$im2 = imagecreatetruecolor($newx, $newy);
imagecopyresized($im2, $im, 0, 0, 0, 0, floor($newx), floor($newy), $x, $y);
return $im2;

}
</pre>