How to reproduce this digital document scan effect using python?

Question

I want to reproduce the quality to scan of an APP, that app get images like this one: RGB image and produce good results, like this: image procesed. I have already used adaptiveThreshold, adaptative_thresholding, otsu filter, etc, but they all just throw me in binary. I do not get the effect of removing noise from paper and obtaining the lines of the image in gray scale. Any idea about to solve this problem?