Reversible Image Watermarking Scheme Based on Contrast Identification

Abstract

Protection of images nowadays is very difficult due to uncontrolled spread of images over internet and other various applications. Copy right protection and authentication of origin is very important. Images can be secured using secure watermarking algorithms by adding distinctive identification in them. Extraction of actual image without any noise for certain sensitive sector like military, medical and low enforcement is very important [1]. Confidential data needs to be protected and in order to reduce forgery, tampering, attacks and fake/illegal copies of original image, watermarking algorithms should be used so that authenticity and integrity of the images can be ensured. In this research, an efficient image watermarking technique has been proposed in which image is interpolated and segmented using quadtree decomposition and labelled. Nature of each labelled segment is determined by calculating contrast value for that segment and on the basis of this value, watermark bits are embedded in the image using a proposed modified version of predictive error expansion technique. Furthermore, decoder of this watermark technique detects if the watermarked image is attacked/tampered and takes corrective actions if the attack was a form of geometric attack i.e. rotational attack at angles 90,180,270 and 360.