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Entropy in Image Analysis
Open AccessArticle

Improvement of Image Binarization Methods Using Image Preprocessing with Local Entropy Filtering for Alphanumerical Character Recognition Purposes

Faculty of Electrical Engineering, West Pomeranian University of Technology, Szczecin, 70-313 Szczecin, Poland
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Entropy 2019, 21(6), 562; https://doi.org/10.3390/e21060562
Received: 26 May 2019 / Revised: 2 June 2019 / Accepted: 2 June 2019 / Published: 4 June 2019
(This article belongs to the Special Issue Entropy in Image Analysis II)
Automatic text recognition from the natural images acquired in uncontrolled lighting conditions is a challenging task due to the presence of shadows hindering the shape analysis and classification of individual characters. Since the optical character recognition methods require prior image binarization, the application of classical global thresholding methods in such case makes it impossible to preserve the visibility of all characters. Nevertheless, the use of adaptive binarization does not always lead to satisfactory results for heavily unevenly illuminated document images. In this paper, the image preprocessing methodology with the use of local image entropy filtering is proposed, allowing for the improvement of various commonly used image thresholding methods, which can be useful also for text recognition purposes. The proposed approach was verified using a dataset of 140 differently illuminated document images subjected to further text recognition. Experimental results, expressed as Levenshtein distances and F-Measure values for obtained text strings, are promising and confirm the usefulness of the proposed approach. View Full-Text
Keywords: image binarization; optical character recognition; local entropy filter; thresholding; image preprocessing; image entropy image binarization; optical character recognition; local entropy filter; thresholding; image preprocessing; image entropy
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Michalak, H.; Okarma, K. Improvement of Image Binarization Methods Using Image Preprocessing with Local Entropy Filtering for Alphanumerical Character Recognition Purposes. Entropy 2019, 21, 562.

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