The purpose of this paper is to propose a procedure that automatically extracts color halftones from a document image and then converts them into continuous-tone images. An extraction method of color halftones is proposed, which is based on analysis of the Fourier spectrum of the color halftones. The characteristics of color halftone patterns in the Fourier spectrum are used to determine halftone regions in the document image. Particularly, this method is designed not to extract the background-halftone region that consists of text and simple halftones. This method is also applicable to extract arbitrarily shaped halftone regions. The extracted halftone regions are then converted into continuous-tone images by using the color inverse halftoning that is proposed in our previous work. A new color-channel separation method for the color inverse halftoning is proposed in this paper. Additionally, an enhancing method for inverse halftoned images is also presented in order to reduce various distortions in printing or scanning process. The proposed methods can be effectively used in the field of digital library, World Wide Web (WWW), and content-based image retrieval.

Date Published: 21 December 2000
PDF: 11 pages
Proc. SPIE 4307, Document Recognition and Retrieval VIII, (21 December 2000); doi: 10.1117/12.410831

Published in SPIE Proceedings Vol. 4307:
Document Recognition and Retrieval VIII
Paul B. Kantor; Daniel P. Lopresti; Jiangying Zhou, Editor(s)