Modification in contrast mapping: Reversible watermarking with performance improvement

Reversible watermarking, a special form of information hiding, becomes appealing for certain applications (for example, medical or military data) where reconstruction of original data is essential from the watermarked one after serving the intended purpose. Among various methods, reversible contrast mapping (RCM) is a flexible integer transform for pixel pairs that offers high embedding rate at low mathematical complexity and without requiring additional data compression. Mathematically, RCM may be interpreted as a form of intercept in straight line that controls distortion and leads to retention of structural information of the watermarked image. A simple yet effective modification over previously proposed RCM is suggested here that offers a better trade-off in visual quality-embedding rate-security of the hidden data. Simulation results validate the above claims.