M J Taylor, Chris Dance
"Enhancement of Document Images from Cameras." M.Taylor and C. Dance.
Proceedings of IS&T/SPIE Electronic Imaging 1998: Document Recognition V, pp230-
As digital cameras become cheaper and more powerful, driven by the consumer
digital photography market, we anticipate significant value in extending their
utility as a general office peripheral by adding a paper scanning capability.
The main technical challenges in realizing this new scanning interface are
insufficient resolution, blur and lighting variations. We have developed an
efficient technique for the recovery of text from digital camera images, which
simultaneously treats these three problems, unlike other local thresholding
algorithms which do not cope with blur and resolution enhancement.

The technique first performs deblurring by deconvolution, and then resolution
enhancement by linear interpolation. We compare the performance of a threshold
derived from the local mean and variance of all pixel values within a
neighborhood with a threshold derived from the local mean of just those pixels
with high gradient. We assess performance using OCR error scores.
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