A fuzzy logic based contrast and edge sensitive digital image watermarking technique

Abstract

In this paper, a fuzzy logic based digital image watermarking technique is proposed. The contrast and edge values of the host image are analyzed by the fuzzy inference system (FIS) against fuzzy rules and then the FIS evaluates the output which is proposed as the watermarking strength (α) of the image. By varying the contrast and edge values of the host image, the fuzzy logic adjusts the watermarking strength to keep the system performance unchanged which helps to improve imperceptibility of the watermarked image. DWT is performed to divide the cover image and watermark image into sub-bands and the maximum entropy region among the sub-bands is calculated for selecting the embedding location because it is less affected by the image processing attacks. Hence, it makes the scheme more robust than other fuzzy based methods. In the extraction phase, the watermark is recovered from the sub-band where it was embedded. The effectiveness of the algorithm is measured in terms of performance parameters like peak signal to noise ratio and normalized correlation. Experimental results indicate that the fuzzy logic adjusts the watermarking strength to keep the performance parameters unchanged irrespective of the contrast and edge values of the host image.