A Use of Magnitude-Only Images for Privacy- and Copyright-Protected Image Trading Systems

摘要

This paper introduces magnitude-only images to image trading systems in which not only the copyright of images but also the privacy of purchasers are protected. In such systems, an image is segmented into two pieces for copyright protection; one is sent to a trusted third party (TTP) and the other is directly sent to a purchaser. The TTP watermarks the received piece and it sends the watermarked piece to the purchaser, and here, the room for a privacy violation exists. Whereas conventional schemes divide an image in the spatial domain, the proposed scheme divides an image in the discrete Fourier transformed domain; two pieces are amplitude and phase spectra. An amplitude-only image which is the inversely transformed amplitude spectra almost completely protects its content, so the privacy of purchasers are protected against the TTP. In addition, any image watermarking technique which watermarks the magnitude of images can be used in the proposed scheme. Experimental results show the effectiveness of the proposed scheme.