Sounds like local contrast adjustment. There are several different ways of solving it, here's a couple that look like they work pretty well: https://stackoverf

Sounds like local contrast adjustment. There are several different ways of solving it, here's a couple that look like they work pretty well: https://stackoverflow.com/questions/63251089/how-to-do-a-localized-contrast-enhancement-in-a-scanned-image-using-opencv-pytho https://stackoverflow.com/questions/63251089/how-to-do-a-loc... https://stackoverflow.com/questions/65666507/local-contrast-enhancement-for-digit-recognition-with-cv2-pytesseract https://stackoverflow.com/questions/65666507/local-contrast-... One possible preprocessing step could be to do a high pass filter on it, if the shadows vary slowly over the image. There are also more specialized techniques specifically for removing shadows from documents, like these: http://civc.ucsb.edu/graphics/Papers/ACCV2016_DocShadow/ http://civc.ucsb.edu/graphics/Papers/ACCV2016_DocShadow/ https://faculty.iiit.ac.in/~vgandhi/papers/shadow_removal_camera_ready.pdf https://faculty.iiit.ac.in/~vgandhi/papers/shadow_removal_ca... I also found this, an image editor based approach if you just want to do a few images manually: https://janithl.github.io/2021/12/remove-shadows-and-uneven-lighting/ https://janithl.github.io/2021/12/remove-shadows-and-uneven-...