This paper presents a review of hybrid image registration techniques (methodologies) that have been used in the medical field. This paper aims to present the survey of methods and methodologies available in context to image registration techniques according to a hybrid approach used to get images registered. Image registration is the first step in digital image processing which include the geometric alignment of sensed and reference images. Different areas of image processing like computer vision, remote sensing and medical image analysis have different methods for image registration along with different challenges associated with individuals. In this paper, work related to the hybrid image registration process is presented. In the hybrid approach, the individual superiority or advantage of different methods are combined in order to get the better results in comparison to individual approach.

In this paper, an efficiently DWT-based watermarking technique is proposed to embed gray-scale logos as watermark in images to attest the owner identification and discourage the unauthorized copying. The method transforms both the host image and watermark into the discrete wavelet domain where their coefficients are fused adaptively based on Human Visual System (HVS) model to hide a higher energy hidden watermark in salient image components. The method repeatedly merges the watermark coefficients at the various resolution levels of the host image which provides simultaneous spatial localization and frequency spread of the watermark to provide robustness against different attacks. From the simulation results it can be observed that proposed method is robust to wide variety of attacks, such as image compression, linear or non-linear filtering, noise addition, image resizing, cropping, and image enhancement, etc.

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This paper proposes a novel blind image adaptive watermarking scheme in Discrete Wavelet Transform (DWT) domain for copyright protection or robust tagging applications. Watermarking scheme effectively utilizes the contrast sensitivity model of Human Visual System (HVS) to embed the watermark adaptively without degradation of the original image. Watermark can be extracted without referring to the original image. Simulation results show the robustness of the proposed algorithm against various attacks.

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