Centroid

About: Centroid is a research topic. Over the lifetime, 4110 publications have been published within this topic receiving 53637 citations. The topic is also known as: barycenter (geometry) & geometric center of a plane figure.

Boundary based corner detection and localization using new 'cornerity' index: a robust approach

Abstract: In this paper, a novel boundary based corner detection algorithm is proposed. The proposed algorithm is computationally fast and efficient. The proposed method computes an expected point for every point on a boundary curve. An expected point corresponding to a point on the boundary curve is defined to be the geometrical centroid of the symmetrical boundary segment of size 2k+1, for some integer k>0, within the neighborhood of the point in consideration. A new 'cornerity' index for a point on the boundary curve is defined to be the distance between the point and its corresponding expected point. The larger the cornerity index, the stronger is the evidence that the boundary point is a corner point. A set of rules is worked out to guide the process of locating true corner points. The conducted experiments establish that the proposed approach is invariant to image transformations viz., rotation, translation and scaling.

A decentralized controller-observer scheme for multi-robot weighted centroid tracking

Abstract: A decentralized controller-observer scheme for centroid tracking with a multi-robot system is presented. The key idea is to develop, for each robot, an observer of the collective system's state; each local observer is updated by only using information of the state of the robot and of its neighbors. The local observers' estimations are then used by the individual robots to cooperatively track an assigned time-varying reference for the weighted centroid. Convergence of the scheme is proven for both fixed and switching communication topologies, as well as for directed and undirected communication graphs. Numerical simulations relative to different case studies are illustrated to validate the approach.

Tracking moving objects

Abstract: A method of tracking an object in a sequence of picture frames comprises inputting motion vectors (100) and segmenting the picture into areas of uniform motion (101). For the initial frame (1027) the object is located (103) either automatically or manually and its centroid and motion vector are calculated (104). For each subsequent frame (105) motion vectors (100) are input and the frame is segmented into areas of uniform motion (101). The forward motion vector of the object is calculated (120) and used to project the centroid of the object from the previous frame onto the present frame (106). The object is then grown round the projected centroid (107) by allocating areas similar to areas of the object in the previous frame and which together produce a centroid close to the projected centroid to a set of areas which define the object. A rectangle may then be drawn around the object (109) which may be used in a coding arrangement to define areas of different resolution. Backward motion vectors of the areas within the set are then calculated (110) and used to determine the similarity of areas in the next frame. Apparatus for performing the method is disclosed particularly in relation to tracking a head for videophone communications.

Centroid-based semi-fragile audio watermarking in hybrid domain

Abstract: Many previous (semi-) fragile audio watermarking schemes adopt binary images as watermarks, which reduce the security of watermarking systems. On the other hand, the content-based or feature-based second generation digital watermarking has limited applicability, and its partial feature points may be damaged by watermarking operations and various common signal processing. To overcome these problems, in this paper, a novel centroid-based semi-fragile audio watermarking scheme in hybrid domain is proposed. The theoretical lower limit of signal to noise ratio (SNR) for objective evaluation of the imperceptibility of watermarked audio signal is deduced, and the watermark embedding capacity and the tamper detection ability are theoretically analyzed. In the proposed scheme, first, the centroid of each audio frame is computed, then Hash function is performed on the obtained centroid to get the watermark, after that, the audio sub-band which carries centroid of audio frame is performed with discrete wavelet transform (DWT) and discrete cosine transform (DCT), and finally the encrypted watermark bits are embedded into the hybrid domain. Theoretical analysis and experimental results show that the proposed scheme is inaudible and applicable to different types of audio signals. Furthermore, its ability of tamper detection and tolerance against common signal processing operations are excellent. Comparing with the existing schemes, the proposed scheme can effectively authenticate the veracity and integrity of audio content, and greatly expand the applicability of the content-based audio watermarking scheme.