Browsing by Author "Gerek, O. N."
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Item Open Access Image coding(Wiley, 2006) Çetin, A. Enis; Gerek, O. N.; Akay, M.Item Open Access Lossless image compression by LMS adaptive filter banks(Elsevier, 2001) Öktem, R.; Çetin, A. Enis; Gerek, O. N.; Öktem, L.; Egiazarian, K.A lossless image compression algorithm based on adaptive subband decomposition is proposed. The subband decomposition is achieved by a two-channel LMS adaptive filter bank. The resulting coefficients are lossy coded first, and then the residual error between the lossy and error-free coefficients is compressed. The locations and the magnitudes of the nonzero coefficients are encoded separately by an hierarchical enumerative coding method. The locations of the nonzero coefficients in children bands are predicted from those in the parent band. The proposed compression algorithm, on the average, provides higher compression ratios than the state-of-the-art methods.Item Open Access Multiresolution block coding method for visualization of compressed images in multimedia applications(Society of Photo-Optical Instrumentation Engineers, 1994) Gerek, O. N.; Cetin, E. A.Multimedia and Picture Archiving and Communication System (PACS) applications require efficient ways of handling images for communication and visualization. In many Visual Information and Management Systems (VIMS), it may be required to get quick responses to queries. Usually, a VIMS database has a huge number of images and may provide lots of images for each query. For example, in a PACS, the VIMS provides 10 to 100 images for a typical query. Only a few of these images may actually be needed. In order to find the useful ones, the user has to preview each image by fully decompressing it. This is neither computationally efficient, nor user friendly. In this paper, we propose a scheme which provides a magnifying glass type previewing feature. With this method, a multiresolution previewing without decompressing the whole image is possible. Our scheme is based on block transform coding which is the most widely used technique in image and video coding. In the first step of our scheme, all of the queried images are displayed in the lowest possible resolution (constructed from the DC coefficients of the coded blocks). If the user requests more information for a region of a particular image by specifying its size and place, then that region is hierarchically decompressed and displayed. In this way, large amounts of computations and bandwidth usage are avoided and a good user interface is accomplished. This method changes the ordering strategy of transform coefficients, thus reduces the compression ratio, however this effect is small.Item Open Access Salient point region covariance descriptor for target tracking(SPIE, 2013-02-22) Cakir, S.; Aytac, T.; Yildirim, A.; Behesti, S.; Gerek, O. N.; Çetin, A. EnisFeatures extracted at salient points are used to construct a region covariance descriptor (RCD) for target tracking. In the classical approach, the RCD is computed by using the features at each pixel location, which increases the computational cost in many cases. This approach is redundant because image statistics do not change significantly between neighboring image pixels. Furthermore, this redundancy may decrease tracking accuracy while tracking large targets because statistics of flat regions dominate region covariance matrix. In the proposed approach, salient points are extracted via the Shi and Tomasi’s minimum eigenvalue method over a Hessian matrix, and the RCD features extracted only at these salient points are used in target tracking. Experimental results indicate that the salient point RCD scheme provides comparable and even better tracking results compared to a classical RCD-based approach, scale-invariant feature transform, and speeded-up robust features-based trackers while providing a computationally more efficient structure.Item Open Access The Topkapi Palace Museum(Wiley-Blackwell Publishing Ltd., 2000) Çetin, A. Enis; Gerek, O. N.; Tewfik, A. H.A city‐like ensemble overlooking the Marmara Sea and the Bosphorus, Istanbul’s legendary Topkapi Palace became a synonym for Ottoman history and the heart of a far‐flung empire for 400 years. Transformed into a museum, it houses a vast and disparate treasure. Presenting both the splendours of the palace and the richness of its collections on the Internet was the challenge described below. The authors, all with backgrounds in electrical engineering, are professionally involved in areas of advanced research in the new technologies. After having served as visiting associate professor at the University of Minnesota in the United States, A. Enis Cetin is a professor at Bilkent University in Ankara and chairman of the IEEE (Institute of Electrical and Electronics Engineers)‐EURASIP (European Association for Signal Processing) Nonlinear Signal and Image Processing Workshop, held in Ankara in June 1999. Omer N. Gerek is currently with the Signal Processing Laboratory of the Swiss Federal Institute of Technology‐EPFL in Lausanne (on leave from the Department of Electrical and Electronics Engineering, Anadolu University, Eskisehir, Turkey). Ahmed H. Tewfik is a professor of electronic communications at the University of Minnesota and was the first Editor‐in‐Chief of the IEEE Signal Processing Letters in 1993.