Binarization of pre-filtered historical manuscripts images

Abstract

Purpose – The purpose of this paper is to introduce an innovative procedure for digital historical documents image binarization based on image pre-processing and image condition classification. The estimated results for each class of images and each method have shown improved image quality for the six categories of document images described by their separate characteristics. Design/methodology/approach – The applied technique consists of five stages, i.e. text image acquisition, image preparation, denoising, image type classification in six categories according to image condition, image thresholding and final refinement, a very effective approach to binarize document images. The results achieved by the authors’ method require minimal pre-processing steps for best quality of the image and increased text readability. This methodology performs better compared to current state-of-the-art adaptive thresholding techniques. Findings – An innovative procedure for digital historical documents image binarization based on image pre-processing, image type classification in categories according to image condition and further enhancement. This methodology is robust and simple, with minimal pre-processing steps for best quality of the image, increased text readability and it performs better compared to available thresholding techniques. Research limitations/implications – The technique consists of limited but optimized pre-processing sequential steps, and attention should be given in document image preparation and denoising, and on image condition classification for thresholding and refinement, since bad results in a single stage corrupt the final document image quality and text readability. Originality/value – The paper contributes in digital image binarization of text images suggesting a procedure based on image preparation, image type classification and thresholding and image refinement with applicability on Byzantine historical documents.