Python OpenCV - 将图像裁剪为灰色背景区域

Question

It is quite hard to explain what I want in the title. I'll show what I need with an example or input/output. I have an image called 'image.jpg' that'll be an image with random strokes of different shades of black and dark-blackish gray on a white background and on one area it'll be a light grey background

I want to use python's opencv and maybe PIL if it's useful and crop the image so I'll only see the gray area. So after whatever code I'll do it'll look like this image here

That's it, appreciate all help here. I don't seem to know where to start here so I can't include whatever code I tried.