In this paper we report a novel method to estimate the scaling factor of a previously scaled watermarked image and the angle by which the image has been rotated. Scaling and rotation performed on a watermarked image, as part of the attacks the image may undergo, can very easily confuse the decoder unless it rescales and/or rotates the image back to its original size/orientation, i.e., recover t...

Many image processing systems have real-time performance constraints. Systems implemented on general purpose processors maximise performance by keeping busy the small fixed number of available functional units such as adders and multipliers. In this paper we investigate the use of programmable logic devices to accelerate the execution of an application. Field Programmable Gate Arrays (FPGAs) ca...

In this paper, we develop a novel method for camera calibration and correction. The novel method first employs a rigidity constraint from the rigid rotation matrix and the radial alignment constraint from the pin-hole camera model to estimate both camera intrinsic and extrinsic parameters with a closed-form solution without considering the camera distortion. Then the well-known Levernburg-Marqu...

Echo planar imaging (EPI) suffers from geometric distortions caused by magnetic field inhomogeneities, which can be time-varying as a result of small amounts of head motion that occur over seconds and minutes during fMRI experiments, also known as "dynamic geometric distortion". Phase Labeling for Additional Coordinate Encoding (PLACE) is a promising technique for geometric distortion correctio...

Introduction: Echo volumar imaging (EVI) is a 3D extension of echo-planar imaging (EPI) that allows data from an entire volume to be acquired following a single excitation. However, only a few studies to date have applied EVI to functional MRI (fMRI) due to its high sensitivity to field-inhomogeneity induced distortions. In this study, we extend two EPI distortion correction techniques to EVI: ...

Circuit topologies are introduced which should prove of use to the circuit designer of analog audio amplifiers. The objective is to produce circuits of' modest complexity that overcome the nonlinearities inherent in single-transistor and long-tail pair circuits. This allows amplifiers with excellent linearity to be designed without resorting to overall negative feedback with high loop gains. To...

We present a general proof of the distortion-correction theorem, that is, of the possibility of correcting wave distortion by the technique of optical phase conjugation. The proof is valid for fully vectorial nonparaxial propagation in the presence of a tensorial refractive-index perturbation and backscattering of the incident field.

In the paper the combination of additive iterative algorithm with averaging of dithered samples is designed for self-correction of ADC linearity error. Iterative method is known as the aid for automated error correction and dithering uses to be applied for quantiser performance enhancement. Dither theory for Gaussian noise has been used for exhibition of new method abilities in ADC characterist...

Many inexpensive camera lenses, especially zoom lenses, suffer from very clear distortion. We show that even with such a lens near perfect images can be obtained by using a correction algorithm based on a simple mathematical model and without any special measuring tools. See Figures 9–12 for reallife examples. The most typical cases of distortion, barrel and pincushion distortion, are illustrat...

We demonstrate the sensing and correction of an isoplanatic refractive distortion (not lens aberrations), using the complete measurement of the partially coherent field in an aperture that the previously described astigmatic coherence sensor provides. Isoplanatic distortions, and in general distortions that do not cause energy loss, maintain the orthogonality of the coherent modes. We use the f...