Improving Degraded Ancient Document Images Using Phase-based Binarization Model

Here presenting a phase-based binarization model for ancient document images, and also a post processing method which can improve any binarization method and a ground truth generation tool. Three feature maps derived from the phase information of an input document image form the core of this binarization model. These features are the maximum moment of phase corresponding to covariance, a locally weighted mean phase angle, and a phase preserved denoised image. The proposed model consists of three standard steps: 1) preprocessing; 2) main binarization; and 3) post processing. In the preprocessing and main binarization steps, the features used are mainly phase derived, while in the post processing step, specialized adaptive Gaussian and median filters are considered. One of the outputs of the binarization step, which shows high recall performance, is used in a proposed post processing method to improve the performance of other binarization methodologies. Finally, we develop a ground truth generation tool, called Phase ground truth, to simplify and speed up the ground truth generation process for ancient document images. The comprehensive experimental results on the DIBCO’09, H-DIBCO’10, DIBCO’11, H-DIBCO’12, DIBCO’13, PHIBD’12, and BICKLEY DIARY data sets show the robustness of the proposed binarization method on various types of degradation and document images. Key words—Binarization Model; Phase-Derived Features, Phase Ground Truthing, Document Enhancement.