A 8-bit-grey-level image embedding its 512 color palette

In this paper, we propose a method to embed the high resolution color information of an image in its corresponding grey-level image. The objective of this work is to allow free access to the grey-level image and give high resolution color image access to secret key owners. This method is made of two steps which are the color image decomposition (in a grey-level image and its associated color information) and the color-information hiding. The main contribution of this paper is to consider the decomposition into 512 colors and to apply a reversible embedding of a bitplane plus a color palette. The resultant watermarked grey-level image is then a 8-bit coded image. With this watermarked image and the extraction secret key, a user is able to rebuild a color image composed of 512 colors. Considering the previous work, the two important consequences of this approach are the improvement of the security and a better color image quality.