International Journal of Computer Theory and Engineering

Abstract

The proposed scheme combines the advantages of cryptographic concept and imperceptibility feature of digital image watermarking in spatial domain. The watermark is first generated based on one-way hash function with the help of user key. Each bit of this new generated watermark is then embedded into respective blocks of the original image, in raster scan order. The embedding is performed by modifying the average value of pixel intensity of each block within a range specified by the contrast value for a given block. This reduces the effects of the modification as perceived by the human eye. The extraction procedure computes and compares the sum of the pixels values for the blocks of the original and watermarked image. The results demonstrates the robustness of scheme against common image processing operations like cropping, modification, low pass filter, median pass filter, scaled down and lossy JPEG compression with various quality index factor. Results also illustrate that the watermark is secure, recoverable and recognizable even after the watermarked image has been tampered, forged and modified by common image processing operations. The comparative study of proposed scheme with existing scheme has also been performed to observe the strength of the scheme.