A Performance Evaluation Methodology for Historical Document Image Binarization

Document image binarization is of great importance in the document image analysis and recognition pipeline since it affects further stages of the recognition process. The evaluation of a binarization method aids in studying its algorithmic behaviour and verifying its effectiveness by providing qualitative and quantitative indication of its performance. This work concerns a pixel-based binarization evaluation methodology for historical handwritten/machine-printed document images. In the proposed evaluation scheme, the Recall and Precision evaluation measures are properly modified using a weighting scheme that diminishes any potential evaluation bias. Additional performance metrics of the proposed evaluation scheme consist of the percentage rates of broken and missed text, false alarms, background noise, character enlargement and merging. Several experiments conducted in comparison with other pixel-based evaluation measures, demonstrate the validity of the proposed evaluation scheme.