thinkphp5.1生成缩略图很模糊

缩略图一定要从大分辨率往小生成

$image->thumb(400,400,\think\Image::THUMB_CENTER)->save(Env::get('root_path').$path.$SP.$fileDatePath.$SP.'400_400_'.$fileNameWithoutPath);
$image->thumb(200,200,\think\Image::THUMB_CENTER)->save(Env::get('root_path').$path.$SP.$fileDatePath.$SP.'200_200_'.$fileNameWithoutPath);