OPTIMAL PIXEL ADJUSTMENT BASED REVERSIBLE STEGANOGRAPHY

A novel prediction-based reversible steganographic scheme based on image in-painting is used to embed the secret information. First, reference pixels are chosen adaptively according to the distribution characteristics of the image content. Then, the image in-painting technique based on partial differential equations (PDE) was introduced to generate a prediction image that has similar structural and geometric information as the cover image. Finally, by using the two selected groups of peak points and zero points, the histogram of the prediction error is shifted to embed the secret bits reversibly[1]. Since the same reference pixels can be exploited in the extraction procedure, the embedded secret bits can be extracted from the stego image correctly, and the restoration of the cover image is lossless. Through, the use of the adaptive strategy for choosing reference pixels and the in-painting predictor, the more embeddable pixels are acquired.However, PDE based in-painting algorithm is computationally complex and requires more execution time. Also, the quality of the stego image is not considered in the in-painting algorithm. To improve the visual quality of the stego image Optimal Pixel Adjustment algorithm (OPA) can be used. The OPA is applied after embedding the message. The frequency domain is employed to increase the robustness of the steganography method. OPA algorithm is to minimize the error difference between the original coefficient value and the altered value by checking the right next bit to the modified LSBs so that the resulted change will be minimal. This research work uses OPA to obtain an optimal mapping function to reduce the difference error between the cover and the stego-image which increases the hiding capacity with low distortions and Peak Signal to Noise Ratio (PSNR)