An Improved Reversible Data Hiding Scheme Using Extra Space Modulation for Color Palette Image

In this paper, a reversible data hiding scheme for color palette image is proposed. The technique of data embedding is used to hide the secret data into multimedia such as text contents, audio, video, and images. The reversibility of data hiding is an important requirement in some applications such as distance medical treatment and military industrial applications. In recent years, many researchers have proposed reversible techniques that work on grayscale images, but these methods cannot be applied directly to color images, which have increased in popularity and have more redundant space available for embedding the secret data. Moreover, the size of color image can be reduced by sorting the stored palette based format. Some researchers have proposed data hiding techniques for palette based images. While their methods successfully achieve the purpose of secret data delivery, they do not achieve reversibility. In our scheme, we make use of the differences between a center index and its neighboring indexes in each sub-blocks of indexed table by using a palette color replacement. The proposed scheme can enhance the embedding capacity for color palette images and recover the embedded data from the stego image without causing perceptible distortions to the cover image. Moreover, we can embed up to bytes into a color image, which provides much more embedding capacity than the existing reversible data hiding schemes. The experimental results confirm the effectiveness of our scheme in term of hiding capacity of embedding data and visual quality of stego image.