[sane-devel] Why is the background of the scanned image not a constant grayscale

[Peter Chen]

Hi,

I set up the tl_x, tl_y, br_x and br_y, scanned one image and found that
there was another layer between the real image and the dark background. It
was a rectangle, not of constant grayscale. The scanner is Fujitsu fi-4120c.

Could somebody pls tell me how to get rid of this layer? Since when I scan
images using Twain, there is not such a layer.

The reason that I want to get rid of the layer is I need to do some edge
detection and deskewing. If the background is a constant black (or white),
then it would be much easier to implement the algorithm.

Thanks,

Peter