  In this paper, we propose a novel algorithm to rectify illumination of the
digitized documents by eliminating shading artifacts. Firstly, a topographic
surface of an input digitized document is created using luminance value of each
pixel. Then the shading artifact on the document is estimated by simulating an
immersion process. The simulation of the immersion process is modeled using a
novel diffusion equation with an iterative update rule. After estimating the
shading artifacts, the digitized document is reconstructed using the Lambertian
surface model. In order to evaluate the performance of the proposed algorithm,
we conduct rigorous experiments on a set of digitized documents which is
generated using smartphones under challenging lighting conditions. According to
the experimental results, it is found that the proposed method produces
promising illumination correction results and outperforms the results of the
state-of-the-art methods.
