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Time-resolved, 3-dimensional phase-contrast magnetic resonance imaging (3D+t PCMRI) is employed to obtain complete spatial and temporal coverage of the vessels blood combined with spatially registered 3-directional pulsatile blood flow velocities[1][2]. Recent studies have reported that Wall Shear Stress (WSS) quantification from PCMRI are able to use the WSS as biomarkers for different aortas pathologies...
Classical Speckle Reducing Anisotropic Diffusion (SRAD) is a noise filtering method tailored to speckle reduction in digital images. It is well known that SRAD has a tendency to produce dislocated and un-sharp edges. This property of SRAD is highly attributed to its reliance on a homogeneous image region, selected initially, for a scaling factor calculation. Moreover, this scaling factor calculation...
The Non-Local Means (NLM) denoising algorithm uses a weighted average of pixels, within a defined search region in an image, to estimate the noise-free pixel value. The search region is usually a rectangular neighborhood, centered at the pixel of interest, which may include pixels whose original gray value do not match the value of the original central pixel. Consequently, their participation in the...
This paper proposes an efficient procedure for removal of salt and pepper noises from the noisy images on the basis of their local edge preserving filters. This algorithm consists of two major stages. In the first stage, the maximum and minimum pixel value in the the corrupted image is used to select noisy pixels or noise free pixels and then in second stage, local edge preserving filters are used...
Color cast is a crucial problem for color image processing. White balance has been widely used to eliminate color cast to improve the image's quality. Most of white balance implementations are based on color constancy hypothesis. A well-known color constancy hypothesis is given in [1], unifying White Patch [2], Grey World [3], Shades of Grey [4], and Grey Edge [1] assumptions in one expression. However,...
On a coarse level the lightness and chromatic adaptation of the human visual system (HVS) and signal processing in a video camera are comparable processes. Both adapt to changes in lighting environment and are time dependent. This study developed metrics for characterizing time-course of automatic exposure (AE) and white balance (AWB) controls in video cameras. To evaluate subjective preference for...
If a photograph is reproduced “faithfully”, i.e. preserving the relative colorimetric values of the original scene, the resulting image will often look less colorful and less contrasted than the original scene due to some mechanisms of the human visual system. Film and digital cameras must compensate these effects in order to obtain visually pleasing images, which reproduce the appearance of the original...
This paper compares several methods of thresholding applied to TerraSAR-X radar images in the presence of speckle noise and a method based on the use of the local extremas of the histogram. The methods used are Otsu's, Valley-emphasis, maximum entropy, fuzzy sets, Yagar's measure of fuzziness and histogram clustering. The local minimum of the histogram provides a good threshold candidate for global...
The segmentation and classification of image regions are very important tasks in the field of computer vision, and yet they remain one of its greatest challenges. These challenges arise from the fact that the same objects can come in different colors, shapes and sizes, and can appear in different contexts and under different illumination. In an attempt to overcome these obstacles, in this paper we...
This paper presents a novel approach to fully automatic satellite image registration to a local earth coordinate system based on the digital map of the road network. Automatic satellite image co-registration methods typically establish correspondences between points on the target and registered image using local image features such as SIFT, however they are not effective for multi-temporal and multi-sensor...
The segmentation problem can be viewed as a learning and merging problem based on superpixels (image segments), which can incorporate a group of cues to guide the segmentation. So the proposed multi-label segmentation algorithm mainly consists of two stages: the learning stage and the merging stage. In the learning stage, Gaussian Mixture Models (GMMs) firstly learn color models for different components...
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