Converting images to greyscale using intervention

I am trying to convert my images into greyscale and then downloading it in Laravel but each and every time I am getting this error

The file "" does not exist

Dont' know why it giving this error here is my code.

$file = public_path() . "/large/s/" . $sheet[0]->sheet_f_id . '-s.jpg';
$image = Image::make($file);
$grayScale = $image->greyscale();
return Response::download($grayScale);

When I dump my $file variable I got the response something like this.

"D:\xampp\htdocs\wikistaging\public/large/s/03-02-05-025-s.jpg"

But still it is giving me the sam error why is that happening. Any help would be great.

via Chebli Mohamed