Introduction The signal loss by the susceptibility artifact makes it difficult analyze the fMRI data of the orbitofrontal region of the brain. In addition, an EPI sequence, which is used in many fMRI experiments, has the geometric distortion and Nyqust ghosts. For the fMRI experiment with correction of these artifact and distortion, we used a flat RF pulse which provides nearly constant signal ...

Fourier based feature extraction is a common and powerful technique used in texture classification. In case of endoscopic imaging, often significant barrel-type distortions affect the feature extraction. Although images can be rectified using distortion correction techniques, in previous work feature extraction proved to suffer not just from geometric distortions, but also from effects within d...

The off-axis location of the Advanced Camera for Surveys causes strong geometric distortion in all detectors – the Wide Field Camera (WFC), High Resolution Camera (HRC), and Solar Blind Camera (SBC). Dithered observations of rich star cluster fields are used to calibrate the dirtortion. We describe the observations obtained, the algorithms used to perform the calibrations and the accuracy achie...

During the past decade, several computational approaches have been proposed for the task of mapping highly convoluted surfaces of the human brain to simpler geometric objects such as a sphere or a topological disc. We report the results of a quantitative comparison of FreeSurfer, CirclePack, and LSCM with respect to measurements of geometric distortion and computational speed. Our results indic...

In this paper we show that radial distortion of images invalidates the geometric constraint on which self-calibration of a rotating camera is based — that 3D lines drawn between matched features all intersect at the rotation centre. We develop a geometric picture showing how radial distortion violates this constraint and discuss the implications for self-calibration of a rotating camera. In par...

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...