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Single image shadow removal by optimization using non-shadow anchor values

Computational visual Media 2019年第3期5卷 311-324页

作者： Saritha Murali v.k.govindan Saidalavi kalady Department of Computer Science and Engineering National Institute of Technology Calicut

Shadow removal has evolved as a preprocessing step for various computer vision tasks.Several studies have been carried out over the past two decades to eliminate shadows from videos and images. Accurate shadow detection is an open problem because it is often considered difficult to interpret whether the darkness of a surface is contributed by a shadow incident on it or not. This paper introduces a color-model based technique to remove shadows from images. We formulate shadow removal as an optimization problem that minimizes the dissimilarities between a shadow area and its non-shadow counterpart.To achieve this, we map each shadow region to a set of non-shadow pixels, and compute an anchor value from the non-shadow pixels. The shadow region is then modified using a factor computed from the anchor value using particle swarm optimization. We demonstrate the efficiency of our technique on indoor shadows, outdoor shadows, soft shadows, and document shadows, both qualitatively and quantitatively.

关键词： mean-shift segmentation particle swarm optimization HSv YCbCr anchor values

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Nonlocal-Means Image Denoising Technique Using Robust M-Estimator

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Journal of Computer Science & Technology 2010年第3期25卷 623-631页

作者： Dinesh J. Peter v. k. govindan Abraham T. Mathew Department of Computer Science National Institute of Technology Calicut Department of Electrical Engineering National Institute of Technology Calicut

Edge preserved smoothing techniques have gained importance for the purpose of image processing applications A good edge preserving filter is given by nonlocal-means filter rather than any other linear model based approaches. This paper explores a different approach of nonlocal-means filter by using robust M-estimator function rather than the exponential function for its weight calculation. Here the filter output at each pixel is the weighted average of pixels with surrounding neighborhoods using the chosen robust M-estimator function. The main direction of this paper is to identify the best robust M-estimator function for nonlocal-means denoising algorithm. In order to speed up the computation, a new patch classification method is followed to eliminate the uncorrelated patches from the weighted averaging process. This patch classification approach compares favorably to existing techniques in respect of quality versus computational time. validations using standard test images and brain atlas images have been analyzed and the results were compared with the other known methods. It is seen that there is reason to believe that the proposed refined technique has some notable points.

关键词： image processing denoising technique nonlocal-means filter robust M-estimators

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维普期刊数据库

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Field and Laboratory Observations on Predation and Prey Selectivity of the Scyphomedusa Chrysaora cf.caliparea in Southeast Indian Waters

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Journal of Ocean University of China 2011年第1期10卷 47-54页

作者： govindan kanagaraj Pazhaniyappan Ezhilarasan Pitchai Sampathkumar André C.Morandini velayudhan pillai Sivakumar Southeastern Institute of Marine Biology Thomas Nagar Department of Zoology V.O.Chidambaram College Centre of Advanced Study in Marine Biology Departamento de Zoologia Instituto de BiociênciasUniversidade de So Paulo

Chrysaora cf.caliparea,one of the most abundant medusae species in India,seems to be an important predator in the coastal waters of Bay of Bengal.The ability of Chrysaora cf.caliparea to feed at maximum rate in high prey concentrations implies that this jellyfish can efficiently exploit dense prey patches,at least for a short period.This study presents preliminary information regarding digestion and feeding rate upon copepods in a warm water environment.The ingestion rate of the average-sized medusae Chrysaora cf.caliparea is well balanced in nature,which in turn implies that this jellyfish is tuned for optimal utilization of available prey resources.Comparison with earlier research indicates that prey escape speed is one important factor governing which prey will be captured.A full understanding of predation mechanics awaits further investigation of both predator and prey behavior.However,because of the scarcity of long-term quantitative population data most insights have to be made indirectly.Nevertheless,low abun-dance of Chrysaora cf.caliparea in the water column during summer (May 2007) and the overall annual abundance seem not to con-siderably affect the zooplankton population,especially copepods.The present work contributes to the knowledge of prey-predator relationship of the forgotten fauna in Indian waters,which is especially crucial for understanding the process of ecological recovery of coastal water environment.

关键词：被捕食印度河比照实验室东南亚动物种群沿岸海域环境生态

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