A fast and efficient method to protect color images In this paper, we propose a method to embed the color information of an image in a corresponding greylevel image. The objective of this work is to allow free access to the greylevel image and give color image access only if you own a secret key. This method is made of three major steps which are a fast color quantization, an optimized ordering and an adapted data hiding. The principle is to build an index image which is, in the same time, a semantically intelligible greylevel image. In order to obtain this particular index image, which should be robust to data hiding, a layer running algorithm is proceeded to sort the K colors of the palette. The major contributions of this paper are the fast color quantization, the optimized layer running algorithm, the color palette compression and the adapted data hiding.

A Novel Approach to Image Steganography Based on the Image Colorization This paper proposes a novel image steganography algorithm for color image. Recently, colorizationbased image coding technique has been studied. In order to compress the color image effectively, this technique transform the chrominance image to a vector in a lowdimensional subspace via the colorization matrix. This paper utilizes the colorizationbased image coding for steganography algorithm, where the secret data is embedded into the null space of the colorization matrix. Because the null space is high dimension enough, a large capacity data can be embedded. Numerical examples show that the proposed algorithm embeds large capacity secret data such as grayscale image into color image effectively.