Showing papers on "Line segment published in 2008"

System and method for three-dimensional alignment of objects using machine vision

Abstract: This invention provides a system and method for determining the three-dimensional alignment of a modeled object or scene. After calibration, a 3D (stereo) sensor system views the object to derive a runtime 3D representation of the scene containing the object. Rectified images from each stereo head are preprocessed to enhance their edge features. A stereo matching process is then performed on at least two (a pair) of the rectified preprocessed images at a time by locating a predetermined feature on a first image and then locating the same feature in the other image. 3D points are computed for each pair of cameras to derive a 3D point cloud. The 3D point cloud is generated by transforming the 3D points of each camera pair into the world 3D space from the world calibration. The amount of 3D data from the point cloud is reduced by extracting higher-level geometric shapes (HLGS), such as line segments. Found HLGS from runtime are corresponded to HLGS on the model to produce candidate 3D poses. A coarse scoring process prunes the number of poses. The remaining candidate poses are then subjected to a further more-refined scoring process. These surviving candidate poses are then verified by, for example, fitting found 3D or 2D points of the candidate poses to a larger set of corresponding three-dimensional or two-dimensional model points, whereby the closest match is the best refined three-dimensional pose.

Detection and matching of rectilinear structures

Abstract: Indoor and outdoor urban environments posses many regularities which can be efficiently exploited and used for general image parsing tasks. We present a novel approach for detecting rectilinear structures and demonstrate their use for wide baseline stereo matching, planar 3D reconstruction, and computation of geometric context. Assuming a presence of dominant orthogonal vanishing directions, we proceed by formulating the detection of the rectilinear structures as a labeling problem on detected line segments. The line segment labels, respecting the proposed grammar rules, are established as the MAP assignment of the corresponding MRF. The proposed framework allows to detect both full as well as partial rectangles, rectangle-in-rectangle structures, and rectangles sharing edges. The use of detected rectangles is demonstrated in the context of difficult wide baseline matching tasks in the presence of repetitive structures and large appearance changes.

Discretization of a Continuous Curve

Abstract: We consider the problem of approximating a finite-length continuous curve by a piecewise linear one whose segments are assumed to be connected by 2 DOF joints. We solve the problem under the assumption that the endpoints of the line segments lie on the continuous curve. Analytical expressions for the relative orientations of each pair of line segments as a function of a single rotational DOF are found. This angle can be chosen arbitrarily or used to optimize a secondary task. The motivating application for this paper is the control of a snake-like robot using gaits designed from shape primitives.

Edge descriptors for robust wide-baseline correspondence

Abstract: This paper describes a method for finding wide-baseline correspondences between images at locations along gradient edges. We find edges in scale space using established methods and develop invariant descriptors for these edges based on orientation and scale histograms. Because edges are often found on occluding boundaries, we calculate and store two descriptors per edge, one on each side, for robustness to occlusions. We demonstrate the effectiveness of edge matching in the applications of wide-baseline correspondence, structure from motion from line segments, and object category recognition on the Caltech 101 dataset.

An improvement of the Standard Hough Transform to detect line segments

Abstract: The detection of lines in an image is an important task. The well-known Standard Hough Transform (SHT) and Progressive Probabilistic Hough Transform (PPHT) are two of the most efficient algorithms for line detection. SHT can detect almost straight lines in the image; moreover, it is highly resistant to noise. Line segments are found effectually by PPHT, but there are a few problems, resulting in this algorithm having lower accuracy than SHT. This paper proposes an extension of this robust algorithm to detect line segments accurately. The proposal contains three extensions: the technique of accumulation, the application of a local maxima rule in the SHT pace, and detection of line segments. The PPHT algorithm is used to compare the experimental results to the results of the proposed method.

Method And Tool For Recognizing A Hand-Drawn Table

Abstract: A computerized method of recognizing an input hand-drawn table formed by freeform line objects comprises transforming each freeform line object of the table into one of a vertical line segment and a horizontal line segment, generating a grid system based on the vertical and horizontal line segments and converting the generated grid system into a table object.

Using 3D Line Segments for Robust and Efficient Change Detection from Multiple Noisy Images

Abstract: In this paper, we propose a new approach to change detection that is based on the appearance or disappearance of 3D lines, which may be short, as seen in a new image. These 3D lines are estimated automatically and quickly from a set of previously-taken learning-images from arbitrary view points and under arbitrary lighting conditions. 3D change detection traditionally involves unsupervised estimation of scene geometry and the associated BRDF at each observable voxel in the scene, and the comparison of a new image with its prediction. If a significant number of pixels differ in the two aligned images, a change in the 3D scene is assumed to have occurred. The importance of our approach is that by comparing images of lines rather than of gray levels, we avoid the computationally intensive, and some-times impossible, tasks of estimating 3D surfaces and their associated BRDFs in the model-building stage. We estimate 3D lines instead where the lines are due to 3D ridges or BRDF ridges which are computationally much less costly and are more reliably detected. Our method is widely applicable as man-made structures consisting of 3D line segments are the main focus of most applications. The contributions of this paper are: change detection based on appropriate interpretation of line appearance and disappearance in a new image; unsupervised estimation of "short" 3D lines from multiple images such that the required computation is manageable and the estimation accuracy is high.

Automatic building detection in aerial and satellite images

Abstract: Automatic creation of 3D urban city maps could be an innovative way for providing geometric data for varieties of applications such as civilian emergency situations, natural disaster management, military situations, and urban planning. Reliable and consistent extraction of quantitative information from remotely sensed imagery is crucial to the success of any of the above applications. This paper describes the development of an automated roof detection system from single monocular electro-optic satellite imagery. The system employs a fresh approach in which each input image is segmented at several levels. The border line definition of such segments combined with line segments detected on the original image are used to generate a set of quadrilateral rooftop hypotheses. For each hypothesis a probability score is computed that represents the evidence of true building according to the image gradient field and line segment definitions. The presented results demonstrate that the system is capable of detecting small gabled residential rooftops with variant light reflection properties with high positional accuracies.

Tunnel‐Free Supercover 3D Polygons and Polyhedra

Abstract: A new discrete 3D line and 3D polygon, called Supercover 3D line and Supercover 3D polygon, are introduced. Analytical definitions are provided. The Supercover 3D polygon is a tunnel free plane segment defined by vertices and edges. An edge is a Supercover 3D line segment. Two different polygons can share a common edge and if they do, the union of both polygons is tunnel free. This definition of discrete polygons has the “most” properties in common with the continuous polygons. It is particularly interesting for modeling of discrete scenes, especially using tunnel-free discrete polyhedra. Algorithms for computing Supercover 3D Lines and Polygons are given and illustrated.

Efficient multi-resolution curve rendering

Abstract: A method, system, and computer-readable storage medium are disclosed for generating a triangulation of a path comprising one or more path segments. In one embodiment, one or more interior triangles in the triangulation may be automatically generated. Each interior triangle may comprise a line segment between a starting point and an ending point of a path segment, leaving a remainder of a first plurality of exterior regions of the path. A first set of one or more exterior triangles in the triangulation may be automatically generated by inscribing a triangle in each exterior regions of the path whose corresponding portion of the one or more path segments does not meet a flatness threshold. Successive sets of exterior triangles may be generated within remaining exterior regions while the flatness threshold is unmet.

Method and device for fault location of series-compensated transmission line

Abstract: A transmission line system, a device for fault protection and computer programs, and a method for locating a fault in a series-compensated two-terminal power transmission line including a compensating bank for providing series-compensation to the transmission line. Different subroutines are utilized for locating faults on line segments from the first terminal to the compensating bank and line segments from the second terminal to the compensating bank. A selection is then made in order to determine a valid result. The subroutines utilize three phase currents synchronized measurements from both terminals and a three phase voltage measurements from one terminal for determining the respective per unit distance to a fault.

Path integral approach to eikonal and next-to-eikonal exponentiation

Abstract: We approach the issue of exponentiation of soft gauge boson corrections to scattering amplitudes from a path integral point of view. We show that if one represents the amplitude as a first quantized path integral in a mixed coordinate-momentum space representation, a charged particle interacting with a soft gauge field is represented as a Wilson line for a semi-infinite line segment, together with calculable fluctuations. Combining such line segments, we show that exponentiation in an abelian field theory follows immediately from standard path-integral combinatorics. In the non-abelian case, we consider color singlet hard interactions with two outgoing external lines, and obtain a new viewpoint for exponentiation in terms of ``webs'', with a closed form solution for their corresponding color factors. We investigate and clarify the structure of next-to-eikonal corrections.

Tracking objects with networked scattered directional sensors

Abstract: We study the problem of object tracking using highly directional sensors--sensors whose field of vision is a line or a line segment. A network of such sensors monitors a certain region of the plane. Sporadically, objects moving in straight lines and at a constant speed cross the region. A sensor detects an object when it crosses its line of sight, and records the time of the detection. No distance or angle measurements are available. The task of the sensors is to estimate the directions and speeds of the objects, and the sensor lines, which are unknown a priori. This estimation problem involves the minimization of a highly nonconvex cost function. To overcome this difficulty, we introduce an algorithm, which we call "adaptive basis algorithm." This algorithm is divided into three phases: in the first phase, the algorithm is initialized using data from six sensors and four objects; in the second phase, the estimates are updated as data from more sensors and objects are incorporated. The third phase is an optional coordinated transformation. The estimation is done in an "ad-hoc" coordinate system, which we call "adaptive coordinate system." When more information is available, for example, the location of six sensors, the estimates can be transformed to the "real-world" coordinate system. This constitutes the third phase.

Line removal and object detection in an image

Abstract: In one aspect, lines in image data of an event are automatically found and repaired. For example, the event may be a sporting event which is played on a field, and the line segment is a field line on the field which may be obscured by a player, game ball or other object. The line segment is automatically detected in a mask image, and a portion of the line segment which is occluded by the object is automatically determined, and the object is automatically removed. The line segment can also be repaired. Optionally, a virtual viewpoint of the event is provided from the image, with the line repaired and the object removed. In another aspect, an object in an image of an event is automatically located by detecting blobs in the image which meet at least one specified criterion, such as size, aspect ratio, density or color profile.

Image encoding method, image decoding method, image encoder, image decoder, image encoding program, image decoding program, and recording medium recording programs and readable by computer

Abstract: PROBLEM TO BE SOLVED: To provide a new technology for achieving in-screen prediction encoding with higher compression efficiency when an image is encoded by using in-screen prediction. SOLUTION: A prediction straight line used for generating a prediction signal of a prediction pixel is generated based on coordinates of the prediction pixel and a prediction angle set at any angle. Intersection coordinates between the generated prediction straight line and a line segment generated by a reference pixel are calculated. A distance between the calculated intersection coordinate and a center coordinate of the reference pixel positioned at the intersection coordinate is calculated. A ratio value of the calculated distance and a distance between the reference pixels is calculated. The prediction signal of the prediction pixel is generated based on the calculated ratio value and values of the plurality of reference pixels including the reference pixel positioned at the intersection coordinate. In this configuration, the prediction angle can be set at any angle, and thus, the number of prediction modes can be increased. Accordingly, the in-screen prediction encoding with higher compression efficiency can be achieved. COPYRIGHT: (C)2010,JPO&INPIT

One-sided offset approximation of freeform curves for interference-free NURBS machining

Abstract: Generating valid tool path curves in NURBS form is important in realizing an efficient NURBS machining. In this paper, a method for computing one-sided offset approximations of freeform curves with NURBS format as tool paths is presented. The approach first uses line segments to approximate the progenitor curve with one-sided deviations. Based on the obtained line approximating curve and its offsets, a unilateral tolerance zone (UTZ) is constructed subsequently. Finally, a C^1-continuous and completely interference-free NURBS offset curve is generated within the UTZ to satisfy the required tolerance globally. Since all of the geometric computations involved are linear, the proposed method is efficient and robust. Interference-free tool path generation thus can be achieved in NURBS based NC machining.

Modelling Positional Uncertainty of Line Features by Accounting for Stochastic Deviations from Straight Line Segments

Abstract: The assessment of positional uncertainty in line and area features is often based on uncertainty in the coordinates of their elementary vertices which are assumed to be connected by straight lines. Such an approach disregards uncertainty caused by sampling and approximation of a curvilinear feature by a sequence of straight line segments. In this article, a method is proposed that also allows for the latter type of uncertainty by modelling random rectangular deviations from the conventional straight line segments. Using the model on a dense network of sub-vertices, the contribution of uncertainty due to approximation is emphasised; the sampling effect can be assessed by applying it on a small set of randomly inserted sub-vertices. A case study demonstrates a feasible way of parameterisation based on assumptions of joint normal distributions for positional errors of the vertices and the rectangular deviations and a uniform distribution of missed sub-vertices along line segments. Depending on the magnitudes of the different sources of uncertainty, not accounting for potential deviations from straight line segments may drastically underestimate the positional uncertainty of line features.

A fast visual line segment tracker

Abstract: We present a fast line segment tracker which does not require any knowledge about the motion of the camera nor the structure of the observed scene. It runs on 320 times 240 pixel images at 30 Hz. We adapted the RAPiD tracker with a new way of handling multiple line hypotheses to deal with the simple model of a single line segment. We discuss the difficulty of using a chi2-test as merging criterion and also present a new approach to overcome it. Furthermore, instead of making assumptions about the camera motion, a constant velocity motion model to predict the line segment position in the following frame is used. We explain how to deal with the instability of the endpoint extraction in this motion model to avoid unintentional motion along the line. Finally, we present results on real world indoor and urban outdoor image sequences.

Line segments and elliptic arcs on the boundary of a numerical range

Abstract: For an n-by-n complex matrix A, we consider the numbers of line segments and elliptic arcs on the boundary @WðAÞ of its numerical range. We show that (a) if n � 4 and A has an (n � 1)-by-(n � 1) submatrix B with W(B) an elliptic disc, then there can be at most 2n � 2 line segments on @WðAÞ, and (b) if n � 3, then @WðAÞ contains at most (n � 2) arcs of any ellipse. Moreover, both upper bounds are sharp. For nilpotent matrices, we also obtain analogous results with sharper bounds.

Efficient and compact indexing structure for processing of spatial queries in line-based databases

Abstract: Points, lines and regions are the three basic entities for constituting vector-based objects in spatial databases. Many indexing schemes have been widely discussed for handling point or region data. These traditional schemes can efficiently organize point or region objects in a space into a hashing or hierarchical directory, and they provide efficient access methods for accurate retrievals. However, two difficulties arise when applying such methods to line segments: (1) the spatial information of line segments may not be precisely expressed in terms of that of points and/or regions, and (2) traditional methods for handling line segments can generate a large amount of dead space and overlapping areas in internal and external nodes in the hierarchical directory. The first problem impedes high-quality spatial conservation of line segments in a line-based database, while the second degrades the system performance over time. This study develops a novel indexing structure of line segments based on compressed B^+ trees. The proposed method significantly improves the time and space efficiencies over that of the R-tree indexing scheme.

Analysis of methods for reducing line segments in maps: Towards a general approach

Abstract: Segment-based maps are emerging as an efficient way to represent the environments in which mobile robots operate. When compared to grid-based maps, maps composed of line segments usually need less space to be stored. However, very little effort has been devoted to methods that allow to reduce the size of segment-based maps by removing redundant line segments that represent the same object in the environment. This problem is usually addressed with rather ad hoc methods that are embedded in mapping systems. In this paper, we put forward the problem of reducing the size of segment-based maps by presenting a survey of the existing methods and by experimentally evaluating some of them. Our results can be used to set out some guidelines for the development of a general approach to reducing redundant line segments in maps.

An efficient dynamic point algorithm for line-based collision detection in real time virtual environments involving haptics

Abstract: In real time computer graphics, “interactivity” is limited to a display rate of 30 frames per second. However, in multimodal virtual environments involving haptic interactions, a much higher update rate of about 1 kHz is necessary to ensure continuous interactions and smooth transitions. The simplest and most efficient interaction paradigm in such environments is to represent the haptic cursor as a point. However, in many situations, such as those in the development of real time medical simulations involving the interactions of long slender surgical tools with soft deformable organs, such a paradigm is nonrealistic and at least a line-based interaction is desirable. While such paradigms exist, the main impediment to their widespread use is the associated computational complexity. In this paper, we introduce, for the first time, an efficient algorithm for computing the interaction of a line-shaped haptic cursor and polygonal surface models which has a near constant complexity. The algorithm relies on space-time coherence, topological information, and the properties of lines in 3D space to maintain proximity information between a line segment and triangle meshes. For interaction with convex objects, the line is represented by its end points and a dynamic point, which is the closest point on the line to any potentially colliding triangle. To deal with multiple contacts and non-convexities, the line is decomposed into segments and a dynamic point is used for each segment. The algorithm may be used to compute collision detection and response with rigid as well as deformable objects with no performance penalty. Realistic examples are presented to demonstrate the effectiveness of our approach. Copyright © 2008 John Wiley & Sons, Ltd.

Real-time license plate localization based on a new scale and rotation invariant texture descriptor

Abstract: In this paper, we present a real-time and robust license plate localization method for traffic control applications. According to our approach, edge content of gray-scale image is approximated using line segments features by means of a local connective Hough transform. Then a new, scale and rotation invariant, texture descriptor which describes the regularity, similarity, directionality and alignment is proposed for grouping lines segments into potential license plates. After a line-based slope estimation and correction, false candidates are eliminated by using geometrical and statistical constraints. Proposed method has been integrated in a optimal license plate localization system. Evaluation is conducted on two image databases which were taken from real scene under various configurations and variability. The result shows that our method is real-time, robust to illumination condition and viewpoint changes.

Smallest enclosing circle centered on a query line segment

Abstract: Given a set of n points P = {p1,p2,...,pn} in the plane, we show how to preprocess P such that for any query line segment L we can report in O(logn) time the smallest enclosing circle whose center is constrained to lie on L . The preprocessing time and space complexity are O(nlogn) and O(n) respectively. We then show how to use this data structure in order to compute the smallest enclosing circle of P whose center is restricted to lie in one of several polygons having a total of m edges, in O((m + n)logn) time, a significant improvement over previous known algorithms.

Multi-coordinate end milling process tool position optimization method using longitude line division tool bit

Abstract: The invention discloses an optimization method for a multi-coordinates end milling processing cutter spacing which adopts a meridian division cutter. Firstly, the working face of a cutter is dispersed into a set of enough dense meridians, and then the minimum distance among the meridians and a designed curved face so as to get a set of minimum-distance line segments; secondly, the points on the minimum-distance line segment at the cutter working face are connected together to form a curve in space, namely, a typical line; the typical line arranged in a programming tolerance range is regarded as an effective typical segment; with the distance between two endpoints of the effective typical segment, the surface projection vertical to the feed direction of the cutter is used as processing line width; the maximum of the processing line width is regarded as the object function of cutter spacing optimization; the non-negative distance between all meridians and the designed curved face is regarded as one of constraint conditions; a mathematic model of the cutter spacing optimization is constructed and is combined with a cutter rail for fair and smooth processing, getting the optimization cutter spacing through a solution procedure. The optimization method can be used for effectively avoiding interference and control the mismachining tolerance and improving the working efficiency.

Embroidery data generating apparatus and computer readable medium storing embroidery data generating program

Abstract: An embroidery data generating apparatus includes a thread color acquisition device that acquires available thread colors for an embroidery pattern, a line segment data generating device that generates line segment data, a dividing device that divides a whole area of an image into divided areas, a determining device that determines a representative color for each of the divided areas, an area thread color allocating device that allocates to the divided area at least one area thread color satisfying a predetermined condition, an associating device that associates the line segment data and the divided area, an embroidery thread color allocating device that allocates, from among the at least one area thread color, an embroidery thread color to each piece of the line segment data, a connecting line segment data generating device that generates connecting line segment data, and an embroidery data generating device that generates embroidery data.

Vision based navigation for power transmission line inspection robot

Abstract: Inspection robot must plan its behavior to loose or grasp the power transmission line, or recognize the obstacles from the complex background when it is crawling along the line in order to negotiate reliably. This paper describes a vision-based navigation system for a power line inspection robot. The main emphasis of this paper is on the ability of object recognition. A recognition method based on straight line extraction is proposed, which is used to recognize the typical obstacles in the power transmission line. Random sample consensus (RANSAC) paradigm is used to group the line segments. The proposed method scales well with respect to the size of the input image and the number and size of the shapes within the data. Moreover the algorithm is conceptually simple and easy to implement. Experimental results show that good recognition can be achieved using the proposed vision system.