Showing papers by "Ioannis Pitas published in 1992"
01 Dec 1992
TL;DR: In this article, a family of nonlinear filters based on order statistics is presented, and the probabilistic and deterministic properties of the best known and most widely used filter, the median filter, are discussed.
Abstract: A family of nonlinear filters based on order statistics is presented. A mathematical tool derived through robust estimation theory, order statistics has allowed engineers to develop nonlinear filters with excellent robustness properties. These filters are well suited to digital image processing because they preserve the edges and the fine details of an image much better than conventional linear filters. The probabilistic and deterministic properties of the best known and most widely used filter in this family, the median filter, are discussed. In addition, the authors consider filters that, while not based on order statistics, are related to them through robust estimation theory. A table that ranks nonlinear filters under a variety of performance criteria is included. Most of the topics treated are very active research areas, and the applications are varied, including HDTV, multichannel signal processing of geophysical and ECG/EEG data, and a variety of telecommunications applications. >
511 citations
TL;DR: Experimental results verify the superiority of the proposed ML-estimator and the L-ESTimator over the straightforward choice of an arithmetic mean for speckle filtering in simulated tissue mimicking phantom ultrasound B-mode images.
49 citations
TL;DR: A new approach for shape representation is described, which provides a general scheme for object description and unifies some of the existing representation techniques, based on the use of simple geometric objects which are intuitively used by humans in their perception of shapes.
48 citations
TL;DR: Two novel adaptive nonlinear filter structures are proposed which are based on linear combinations of order statistics and have the ability to incorporate constraints imposed on coefficients in order to permit location-invariant and unbiased estimation of a constant signal in the presence of additive white noise.
44 citations
TL;DR: Two new methods are presented for using geometric proximity to reference points in region growing and image segmentation based on Voronoi tessellation and mathematical morphology.
35 citations
01 Jul 1992
TL;DR: The system proposed is capable of obtaining the rules that fit a set of examples and counterexamples based on the minimal entropy (ME) criterion and can also set various parameters of the rule in such a way that entropy is minimized.
Abstract: Learning from examples uses specific instances (examples and counterexamples) to produce general rules. It is a convenient learning scheme in cases where the process of interviewing human experts and analyzing and formalizing their decision is very difficult or time consuming. The system proposed is capable of obtaining the rules that fit a set of examples and counterexamples based on the minimal entropy (ME) criterion. The system proposed can also set various parameters of the rule (e.g., thresholds) in such a way that entropy is minimized. The system can also handle incremental learning from examples. Applications of the proposed system to seismic image analysis are included. >
25 citations
01 Oct 1992
TL;DR: A signal-adaptive Maximum Likelihood estimation algorithm is proposed, with local image adaptation based on a moving window, for the processing of Ultrasound (US) B-mode images.
Abstract: New techniques are presented for the processing of Ultrasound (US) B-mode images. A signal-adaptive Maximum Likelihood estimation algorithm is proposed, with local image adaptation based on a moving window. The algorithms are tested on US B-mode images obtained from simulated (phantom) and real liver scans1.
7 citations
01 Jan 1992
TL;DR: This paper presents a novel method for multichannel and color image equalization, which can be performed on the three channels RGB simultaneously, by using the joint pdf.
Abstract: This paper presents a novel method for multichannel and color image equalization. The equalization can be performed on the three channels RGB simultaneously, by using the joint pdf. Alternatively, equalization at the HSI domain can be performed, in order to avoid changes in digital image hue. A parallel algorithm is proposed for color image histogram calculation and equalization.
4 citations