Efficiency Evaluation Parameters of Digital Image Watermarking Techniques

There are a good number of photo editing tools. Hence it is very easy to tamper a watermarked image. Image watermarking techniques are used in various applications like copy right protection, image authentication, image tamper correction etc. This paper narrates the various efficacy parameters of watermarking techniques used in images. The performance of a digital image watermarking technique is mainly measured by the parameters like hiding capacity (HC), imperceptibility, robustness, computational complexity, and security. The HC is the magnitude of bits that can be hidden in a image in terms of watermark bits. Peak signal-to-noise ratio (PSNR) estimates the distortion in the watermarked image. Structural similarity (SSIM) estimates the similarity between the original image and the watermarked image. The watermark should not be disturbed after some attacks are applied on the watermarked image. If the watermarked bits are altered by various attacks, then the purpose of watermarking will not be served. So, this article also describes the various attacks and counter measures on watermarked images.