Real Perfect Contrast Visual Secret Sharing Schemes with Reversing

The visual secret sharing (VSS for short) scheme is a secret image sharing scheme. A secret image is visually revealed from overlapping shadow images without additional computations. However, the contrast of reconstructed image is much lost. By means of the reversing operation (reverse black and white), Viet and Kurosawa used the traditional VSS scheme to design a VSS scheme which the secret image is almost perfectly reconstructed. Two drawbacks of the Viet-Kurosawa scheme are: (1) one can only reconstruct an almost ideal-contrast image but not an ideal-contrast image (2) the used traditional VSS scheme must be a perfect black scheme. This paper shows a real perfect contrast VSS scheme such that black and white pixels are all perfectly reconstructed within finite runs, no matter what type (perfect black or non-perfect black) of the traditional VSS scheme is.