the grayscale works not well with rotation

[mahengrui1]

hello, with the brightness config the result goes to dark and gray, however the rotation let corners keep white. then, it is easy to see the virtual attribute.

Edit: typo

[rwv]

Can you give a example screenshot?

[mahengrui1]

like this. the real scanner devices will not produce an image like this, pure white at corners but suddenly dark at centre