图片上传质量会变得很差

<input type="file" size="30" name="upload_image" id="team-create-image" class="f-input" />



function upload_image($inputname, $image=null, $type='team', $width=440) {
    $year = date('Y'); $day = date('md'); $n = time().rand(1000,9999).'.jpg';
    $z = $_FILES[$inputname];
    if ($z && strpos($z['type'], 'image')===0 && $z['error']==0) {
        if (!$image) {
            RecursiveMkdir( IMG_ROOT . '/' . "{$type}/{$year}/{$day}" );
            $image = "{$type}/{$year}/{$day}/{$n}";
            $path = IMG_ROOT . '/' . $image;
        } else {
            RecursiveMkdir( dirname(IMG_ROOT .'/' .$image) );
            $path = IMG_ROOT . '/' .$image;
        }
        if ($type=='user') {
            Image::Convert($z['tmp_name'], $path, 48, 48, Image::MODE_CUT);
        }
        else if($type=='team') {
            Image::Convert($z['tmp_name'], $path, $width,0,Image::MODE_SCALE);
        }
        return $image;
    }
    return $image;
}

上传图片的时候 图片质量会变得非常的差 这个要怎么修改？