Capacity-Raising Steganography Using Multi-Pixel Differencing and Pixel-Value Shifting Operations

In order to provide large embedding capacity and to minimize distortion for the stegoimage, a steganographic method using multi-pixel differencing is presented in this paper. It takes into consideration four pixels of a block, and the differences between the lowest gray-value pixel and its surrounding pixels are used to determine the degree of smoothness and sharpness for embedding the secret data. If the difference values are large in a block, and the block is located in the sharp area then more data can be embedded. On the other hand, if the block is located in the smooth area less data can be embedded. The multi-pixel differencing method is employed in our scheme. We also propose the pixel-value shifting method to increase the image quality. The experimental results show that our scheme has a large embedding capacity without creating a noticeable distortion.