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We are looking for a flatbed A4 scanner with those capabilities, but at the moment we haven’t found anyone.
Is that usual? do you know anyone?
If not, how do you programme those functionalities in your applications? do you use any image treatment libraries? Our target application is developed in Java.
Thanks in advance.
My Agfa scanner (e42 with a black background) has this function in the TWAIN driver, not sure it is exposed as a capability. Usually flatbeds scanners have limited capability concerning deskew and auto-crop, because it is based on the image itself, any application can do that. In the feeder you can have additional sensors to help you, and it is more efficient and useful.
This functionality is based on extraction of the border of the image assuming that the foreground is black, and the border of the image is white. Extracting all the borders points (transition from black to white) gives you 4 lines approximated (to have a minimal distance between the approximated line and the points). Then you have to choose two skews (top or bottom and left or right, or a mean value …) and rotate the image, then crop.
You should find many papers to implement this function whit a lot a of different approaches.