[cooper12]

I love well-illustrated writeups. Even a reader without mathematics or programming knowledge can understand what steps the author took. His model actually seems to better represent the warped paper than a cylinder would. (though I don't know the actual specifics of the CTM model)

I wish he went into more details on the steps taken after dewarping. You can tweak the image levels to get good contrast, but surprisingly there aren't any shadows from underleveling or loss of detail from overleveling. I wonder if the author ran OCR on the scans after, and speaking of OCR, IIRC Leptonica is one of the dependencies of Tesseract so it must do some similar pre-processing.

Edit: reading more carefully, he mentions that he used adaptive thresholding from OpenCV.