Document Image Enhancement

The first part of this chapter describes a method for correcting scanned pages of thick bound documents, including books and thick journals. Images of pages can contain various types of degradation effects, such as page skew, page warping and the presence of a shadow near the spine area. The correction procedure described herein is capable of detecting whether part of the page is outside the scanning area and would not appear in the image and will make the correction procedure accordingly. The second part of this chapter proposes a method for the correction of document images captured with a mobile device. The method applies document boundary detection, uneven lighting compensation and distortion correction, including image cropping. The methods that are proposed for document restoration are based exclusively on image processing and do not involve any additional information related to the scanning system. The methods can help in the correction of images acquired by flatbed scanners, digital cameras and Smartphones and other devices. Numerical examples show the high-quality restoration of skewed documents with a skew angle of up to 45°. This can significantly improve the results of text recognition.

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