This paper proposes a robust image hashing method which is robust against common image processing attacks and geometric distortion attacks. In order to resist against geometric attacks, the log-polar mapping (LPM) and contourlet transform are employed to obtain the low frequency sub-band image. Then the sub-band image is divided into some non-overlapping blocks, and low and middle frequency coe...

We present a novel methodology based on geometric approach to simulate magnification lens effects that can be utilized for Focus+Context (F+C) visualization. Our aim is to promote new applications of powerful geometric modeling techniques in visual computing. Conventional image processing/visualization methods are computed in two dimensional space (2D). we examine this conventional 2D manipulat...

Radial lens distortion prohibits use of simple pinhole camera models in computer vision applications, especially when using wide-angle lenses, which result in barreltype distortion. Usual approach to radial distortion is by the means of polynomial approximation, which introduces distortion-specific parameters into the camera model and requires iterative methods for their calculation. Based on t...

A commercially available open MRI unit is under routine use for radiation therapy simulation. The effects of a gradient distortion correction (GDC) program used to post process the images were assessed by comparison with the known geometry of a phantom. The GDC reduced the magnitude of the distortions at the periphery of the axial images from 12 mm to 2 mm horizontally along the central axis an...

This thesis describes a novel video mosaicing method which is capable of generating a geometric distortion-free mosaic image. Video mosaicing, which stitches partial images of a target into a larger image called a mosaic image, has been used to obtain high resolution images of documents. Generally, mosaic images are prone to two types of geometric distortions: perspective distortion which appea...

In today’s computer networks, the amount of digital images increases rapidly and enormously. However, images may be distorted through di.erent types of processing such as histogram equalization, quantization, smoothing, compression, noise corruption, geometric transformation, and changing of illumination. It is imperative to develop an e.ective method to retrieve the original images from very l...

Estimating the amount and center of distortion from lines in the scene has been addressed in the literature by the socalled “plumb-line” approach. In this paper we propose a new geometric method to estimate not only the distortion parameters but the entire camera calibration (up to an “angular” scale factor) using a minimum of 3 lines. We propose a new framework for the unsupervised simultaneou...