Purpose: The most common metrics for resolution analysis in medical imaging are valid only for (approximately) linear systems. While analogues to these metrics have been used in attempts to describe resolution perform...
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Purpose: The most common metrics for resolution analysis in medical imaging are valid only for (approximately) linear systems. While analogues to these metrics have been used in attempts to describe resolution performance in nonlinear systems, the analysis is incomplete since distortion effects are often ignored. The authors have developed a methodology to analyze the amplitude modulation and waveform distortion properties of nonlinear systems with specific application to medical imageprocessingalgorithms. Methods: Using sinusoidal basis functions, two metrics were derived which distinguish amplitude modulation from nonlinear waveform distortion: principle frequency response and distortion power spectrum, respectively. Additionally, two figures of merit were developed to describe the relative impact of nonlinear distortion as a result of imageprocessing: distortion index (DI) and Sigma DI. Three nonlinear denoising algorithms, the median, bilateral, and wavelet denoising filters, were selected as example functions to demonstrate the utility of the metrics derived in this study. Results: Each filter showed very different resolution and waveform distortion properties. In particular, the amplitude and extent of nonlinear distortion depended strongly on image context and the type of nonlinear mechanism employed. Nonlinear waveform distortion constituted up to 30% of the median filter output signal power in high contrast-to-noise ratio (CNR) scenarios. Conversely, nonlinear distortion never exceeded 1% of the bilateral filter output signal power. The wavelet denoising response contained between 1% and 9% distortion which varied weakly as a function of CNR. Conclusions: The analytical metrics described in the paper demonstrate the importance of considering both resolution-and distortion-related effects in characterizing the performance of nonlinear imaging systems with specific application to imageprocessingalgorithms. Findings with three common nonlinear algorithms
This paper describes a uniform transform domain Video Codec where the motion estimation/compensation (ME) is performed in the transform domain. The estimation technique discussed here is a subpixel transform domain ME...
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ISBN:
(纸本)0780370414
This paper describes a uniform transform domain Video Codec where the motion estimation/compensation (ME) is performed in the transform domain. The estimation technique discussed here is a subpixel transform domain ME based on the Dual Tree Complex Wavelet Transform (DT CWT) and a maximum phase correlation technique. The DT CWT is a multiresolution fine-to-coarse bandpass, filtered decomposition of each still frame and has desirable properties of shiftablility, directional selectivity and perfect reconstruction (PR). Estimation is first performed at the finest resolution and successively proceeds to the coarse resolutions using a fine-to-coarse strategy. This gives multiresolution motion estimates enabling estimation of current frame transform coefficients from the corresponding ones in previous frame. The key difference of this approach is the transform domain error frames - a uniform transform domain Video Codec. This further simplifies the encoder and decoder resulting in computational savings with comparable performance to the standards.
Keypoint matching between pairs of images using popular descriptors like SIFT or a faster variant called SURF is at the heart of many computer vision algorithms including recognition, mosaicing, and structure from mot...
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ISBN:
(纸本)9781627480031
Keypoint matching between pairs of images using popular descriptors like SIFT or a faster variant called SURF is at the heart of many computer vision algorithms including recognition, mosaicing, and structure from motion. However, SIFT and SURF do not perform well for real-time or mobile applications. As an alternative very fast binary descriptors like BRIEF and related methods use pairwise comparisons of pixel intensities in an image patch. We present an analysis of BRIEF and related approaches revealing that they are hashing schemes on the ordinal correlation metric Kendall's tau. Here, we introduce Locally Uniform Comparison image Descriptor (LUCID), a simple description method based on linear time permutation distances between the ordering of RGB values of two image patches. LUCID is computable in linear time with respect to the number of pixels and does not require floating point computation.
Many of the physically injured use electric wheelchairs as an aid to locomotion. Usually, for commanding this type of wheelchair, it is required the use of one's hands and this poses a problem to those who, beside...
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ISBN:
(纸本)9789728865924
Many of the physically injured use electric wheelchairs as an aid to locomotion. Usually, for commanding this type of wheelchair, it is required the use of one's hands and this poses a problem to those who, besides being unable to use their legs, are also unable to properly use their hands. The aim of the work described here, is to create a prototype of a wheelchair command interface that do not require hand usage. Facial expressions were chosen instead, to provide the necessary visual information for the interface to recognize user commands. The facial expressions are captured by a digital camera and interpreted by an application running on a laptop computer on the wheelchair. The software includes digital imageprocessingalgorithms for feature detection, such as colour segmentation and edge detection, followed by the application of a neural network that uses these features to detect the desired facial expressions. A simple simulator, built on top of the known (Ciber-Mouse) was used to validate the approach by simulating the control of the intelligent wheelchair in a hospital environment. The results obtained from the platform provide strong evidence that it is possible to comfortably drive an intelligent wheelchair using facial expressions.
Efficient regional computation is a key for low power mid-level imageprocessing. In this paper, we show how to fit digital retinas with such capabilities. We propose a low power and fast hardware software solution to...
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Fingerprint image quality assessment is crucial for many fingerprint applications. It affects the performance and interoperability of fingerprint identification, authentication, and built on based crypto systems. In t...
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ISBN:
(纸本)9781424408818
Fingerprint image quality assessment is crucial for many fingerprint applications. It affects the performance and interoperability of fingerprint identification, authentication, and built on based crypto systems. In this paper we present a novel approach for objective fingerprint image quality measure derived from power-spectra of two dimensional Gabor features representation. We also classify existing assessment algorithms into two classes: structural and intelligent representation approaches. Approaches were implemented for accuracy and reliability tests using TIMA Database including good and faulty fingerprint images and compared with Gabor spectrum approach. The goal of our quality assessment approach is to automatically assess the quality of fingerprint image in agreement with correlation of human visual system judgment. The proposed approach shows improvement performance in the quality classification of finger print images than existing classified approaches. Experimental verification demonstrates very good correlation of Gabor Spectrum (GS) with subjective quality assessment. 3% improvement of power spectrum in false rejection rate, and 14% improvement of Gabor features in true acceptance rate were achieved.
Videokeratography is a common method used by clinicians and researchers to estimate the surface topography of the human cornea It is based on the object-to-image relationship of concentric rings reflected off the surf...
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ISBN:
(纸本)0819435279
Videokeratography is a common method used by clinicians and researchers to estimate the surface topography of the human cornea It is based on the object-to-image relationship of concentric rings reflected off the surface of the cornea, This technique works reliably in most cases for central cornea. However, the accuracy of corneal topography is reduced for peripheral cornea because of shadows caused by brews and nose and occlusions caused by eyelids. To achieve a broader coverage of the peripheral cornea, images of off-centered gaze in four directions (up, down, left and right) could be combined. One of the difficulties associated with this approach is that the shape of image rings in the peripheral cornea become very irregular, z-shaped, due to abrupt changes in surface topography near the limbus. These irregularities cause complications for current algorithms for estimating the location of edges along each image ring, Many current algorithms make assumptions about the shape and relative positions of image rings to distinguish between different rings. These assumptions no longer hold with off-centered images since the image rings can deviate dramatically from an ellipsoid, Our algorithm overcomes this problem by using fewer assumptions combined with a robust segmentation algorithm to distinguish between image rings.
Traditional raster images cannot be fitted to different display sizes dynamically. Although some vector conversion systems have provided with the ability to convert raster format data into vector format data, the size...
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ISBN:
(纸本)9783540897958
Traditional raster images cannot be fitted to different display sizes dynamically. Although some vector conversion systems have provided with the ability to convert raster format data into vector format data, the sizes of files they produced are large and consume most of time in image rendering. In this study, we adopt the SVG developed by W3C for the target vector format. We use the vector contour searching algorithms for removing extra spaces, combining the slope of clips, and merging similar color regions to compress the vector images. It converts comic images from raster format to SVG vector format. The factors affecting image quality and compression efficiency are studied. Compared with the existing methods, ours has a better performance in image quality, compressed ratio, and image rendering speed. It also makes the converted image able to display in different platforms.
We present in this article a new supervised evaluation criterion that enables the quantification of the quality of region segmentation algorithms. This criterion is compared with seven well-known criteria available in...
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ISBN:
(纸本)9783540746065
We present in this article a new supervised evaluation criterion that enables the quantification of the quality of region segmentation algorithms. This criterion is compared with seven well-known criteria available in this context. To that end, we test the different methods on natural images by using a subjective evaluation involving different experts from the French community in imageprocessing. Experimental results show the benefit of this new criterion.
Cost and time reduction in control operations, large-scale threedimensional measurement, high accuracy in hazardous environment, immediate results : these are today the industriel requirements. Within this context, th...
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ISBN:
(纸本)0819416851
Cost and time reduction in control operations, large-scale threedimensional measurement, high accuracy in hazardous environment, immediate results : these are today the industriel requirements. Within this context, the development of measurement systems by optical methods is gaining momentum. In addition to being efficient and competitive, these systems are progressively and effectively adapted to the new industrial requirements. Thanks to their adaptability and the potential developments, these systems are today the main assets for industrial sectors, always anxious to guarantee the quality oftheir products. The existing technics are numerous, varied and often complementary : CAT, interferometry, photogrammetry, videogrammetry, holography,. .. In this paper, we propose to discuss about one of these technics : videogrammetry also called digital photogrammetry. After some general remarks about this booming technic, we suggest to study the invoived methodology and to illustrate the industrial aspect with practical applications and examples of results.
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