OpenRaiser/Intern-Atlas huggingface dataset:
Morphological Feature Detection
Authors: J. Alison Noble
Venue: ICCV
Year: 1988

We describe investigations applying grey-scale mathematical morphology to the problem of feature detection. We show how a combination of morphological operators can be interpreted in terms of the differential geometrical characteristics of the intensity surface. This is significant in that it provides in-sight into how morphological operators manipulate image data in a manner that has no parallel in traditional convolution-based image processing. Results using a simple morphologi-cal boundary detector compare favourably with the output of a normal edge detector 3uch as the Canny operator. How-ever, boundary detection differs in two important respects; the performance is generally better in regions of high image curvature and image junction information remains explicit. We provide experimental evidence to support these claims. An image description is only of use if it is an aid to im-age understanding. We conclude with a brief discussion of a morphologically derived scheme based on boundary surface features and indicate how such a description provides po-tentially powerful constraints for correspondence algorithms.
An Adaptive Clustering Algorithm For Image Segmentation
Authors: Thrasyvoulos N. Pappas, Nikil S. Jayant
Venue: ICCV
Year: 1988

A generalization of the K-means clustering algorithm to include spatial constraints and to account for local intensity variations in the image is proposed. Spatial constraints are included by the use of a Gibbs random field model. Local intensity variations are accounted for in an iterative procedure involving averaging over a sliding window whose size decreases as the algorithm progresses. Results with an eight-neighbor Gibbs random field model applied to pictures of industrial objects and a variety of other images show that the algorithm performs better than the K-means algorithm and its nonadaptive extensions. >
Shape Information From Shading: A Theory About Human Perception
Authors: Alex Pentland
Venue: ICCV
Year: 1988

I show that people assume a simple, linear reflectance function when interpreting shading information. Using this reflectance function I derive a closed-form solution to the problem extracting shape information from image shading. The solution does not employ a assumptions about surface smoothness and so is directly applicable to complex natural surfaces such as hair or cloth. A simple biological mechanism is proposed to implement this recovery of shape. It is shown that this simple mechanism can also extract significant shape information from line drawings.
Optimal Corner Detector
Authors: Krishnan Rangarajan, Mubarak Shah, David Van Brackle
Venue: ICCV
Year: 1988

A corner is defined as the junction point of two or more stright line edges. Corners are special features in a image. They are of great use in computing the optical flow and structure from motion. In this paper, we report an optimal corner detector which uses a mathematical model for a corner. An optimal gray tone corner detector is derived for a restricted case of corners, i.e., corners made by lines which are symmetric about a horizontal axis. The resultant corner detector is described by the product of the sine in x and an exponential in the y direction in a portion of the mask and by the product of two sines in x and y directions in the remaining portion. It is then generalized to include any corner of an arbitrary angle and orientation. This results in an approximation of all corners by a total of twelve major types. It is observed that all the twelve masks can actually be configured with four smaller sub-masks, and this results in a significant reduction in the computations. The computations are further reduced by using the separability of masks. Results for synthetic and real scenes are reported.
Singularities Of Principal Direction Fields From 3-D Images
Authors: Peter T. Sander, Steven W. Zucker
Venue: ICCV
Year: 1988

Generic singularities can provide position-independent information about the qualitative shape of surfaces. The authors determine the singularities of the principal direction fields of a surface (its umbilic points) from a computation of the index of the fields. The authors present examples both for 3-D synthetic images to which noise has been added and for clinical magnetic resonance images. >
Robust Depth Estimation From Optical Flow
Authors: Behzad Shahraray, Michael K. Brown
Venue: ICCV
Year: 1988

A robust method for obtaining dense depth-maps from a sequence of noisy intensity images (obtained by a moving camera is presented. Controlled camera motion is exploited to reduce the complexity of the optical flow solution to closed-form. It is well known that optical flow computations suffer from high noise sensitivity. Tensor-product smoothing splines are employed to construct a 3-D continuous approximation to the time-varying intensity data which serves to reduce the effects of noise and restore the properties of continuous optical flow. Spatial and temporal derivative estimates obtained from the 3-D spline approximation are used to compute the depth. Unreliable depth estimates are discarded based on the temporal rate of change of intensity. The effectiveness of the smoothing spline approximation coupled with the efficiency of tensor products and the closed form solution for depth leads to a robust method for obtaining dense depth maps with low computational cost. Experimental results are presented which demonstrate the robustness of the method applied to real image data. These experiments indicate an average relative error of 3.7 percent in the depth measurement is obtainable using a sequence of seven 8-bit quantized images. Suggestions for further improvements in the quality of the depth maps by adjusting the parameters of the smoothing spline are discussed.
Shape From Angles Under Perspective Projection
Authors: Takeshi Shakunaga, Hiroshi Kaneko
Venue: ICCV
Year: 1988

This paper provides a mathematical framework for shape-from-angle problems, and discusses four primitive problems based on it. For three of them, algebraic equations are provided from a geometric analysis. A generic lD search algorithm is proposed for designing a 1-D search algorithm, usable for any shape-from-angle problems. By designing the problem-dependent parts of the generic algorithm, specific l-D search algorithms are constructed for each problem. The generic algorithm finds all the feasible configurations by detecting the zero-crossing points of a problem-dependent test function on a constraint curve. Experimental results show the effectiveness of each specific algorithm and the applicability of the generic algorithm to several types of shape-from-angle problems.
Aligning A Model To An Image Using Minimal Information
Authors: Doron Shoham, Shimon Ullman
Venue: ICCV
Year: 1988

The ability to determine the geometrical transformation which aligns a 3D object with its 2D image plays an important role in recognition and other visual tasks. We suggest that since usually the possible. transformations are constrained, they can be determined by using a small number of features. We prove that combinations of three co-planar points and lines can determine the alignment transformation uniquely or almost uniquely.
Learnable And Non-learnable Visual Concepts
Authors: Haim Shvaytser
Venue: ICCV
Year: 1988

Valiant’s theory of the learnable is applied to visual concepts in digital pictures. Several visual concepts that are easily perceived by humans are shown to be learnable from examples by a simple algorithm. These include inaccurate copies of a picture, multiple objects, and lines in a fixed slope. However, there are simple characterizations of visual concepts which are apparently non-learnable from examples. It is shown that templates for template matching cannot be learned from a feasible number of positive examples.
Optimal Computing Of Structure From Motion Using Point Correspondences In Two Frames
Authors: Minas E. Spetsakis, John Aloimonos
Venue: ICCV
Year: 1988

One of the problems associated with any approach to the structure from motion problem using point correspondence, i.e. recovering the structure of a moving object from its successive images, is the use of least squares on dependent variables. We formulate the problem as a quadratic minimization problem with a non-linear constraint. Then we derive the condition for i,he solution to be optimal under the assumption of Gaussian noise in the input, in the Maximum Likelihood Principle sense. This constraint minimization reduces to the solution of a nonlinear system which in the presence of modest noise is easy to approximate. We present two efficient ways to approximate it and we discuss some inherent limitations of the structure from motion problem when two frames are used that should be taken into account in robotics applications that involve dynamic imagery. In addition, our formulation introduces a framework in which previous works on the subject become special cases.
Aspect Graphs And Nonlinear Optimization In 3-D Object Recognition
Authors: Louise Stark, David W. Eggert, Kevin W. Bowyer
Venue: ICCV
Year: 1988

Several researchers have previously described approaches to 3-D object recognition which use nonlinear optimization to control the matching of features of a 3-D object niodel to features found in an image. Recognition, in this context, includes estimating the parameters of translation and orientation of the object. A major problem acknowledged by previous researchers is how to efficiently choose a set of starting paranleter estimates which will avoid recognition errors due to local minima. The unique contribution of this paper is that it outlines an approach for using the perspective projection aspect gruph representation to alleviate the problems encountered by previous researchers, describes a particular implementation of this general approach, and presents data to illustrate the effectiveness (of the approac!].
Creating The Perspective Projection Aspect Graph Of Polyhedral Objects
Authors: John H. Stewman, Kevin W. Bowyer
Venue: ICCV
Year: 1988

An algorithm is presented for constructing the perspective projection aspect graph of polyhedra. The first phase determines the set of surfaces involved in the parcellation of viewing space around the object. Three types of surfaces are involved: object planes, in which the faces of the object lie, auxiliary planes, defined by the visual interaction of edge-vertex pairs, and auxiliary quadric surfaces, defined by the visual interaction of edge triplets. Auxiliary planes and surfaces in a sense enumerate the potential self-occlusions of the object. A list is constructed for each type of surface. Next the algorithm constructs the geometric incidence lattice representing the arrangement of object planes, and distinguishes each 3-face (node) as representing either object or viewing space. The auxiliary planes and surfaces are then added to the lattice. Each 3-face (node) in the lattice has visibility attributes which identify the potentially visible object features from viewpoints within it. These attributes are updated throughout the process of building the lattice. Finally, the lattice is traversed to make a final update of the visibility attributes and merge neighboring 3-faces which have the same visible features. The resulting structure represents the perspective projection aspect graph.
Self-calibration Of Stereo Cameras
Authors: Hironobu Takahashi, Fumiaki Tomita
Venue: ICCV
Year: 1988

All stereo systems assume that the correct camera parameters are obtained. In fact, those parameters can be calibrated in advance using known test patterns. However, not only there is calibration errors but also some parameters are easy to change after the calibration. Even if the errors may be small, the effects on identifying corresponding points and computing distances are very large. It is infeasible to compute camera parameters every time befort? observation especially for stereo cameras which change its focus of attention by convergence or those on mobile robots which observe their environment and acquire depth information. The self-calibration of stereo cameras, which autonomously computes its current camera parameters from unknown observed data, is really necessary for real stereo systlxns. In this paper, we propose a self-calibration method based on boundary representations of a pair of stereo images.
Using Symmetries For Analysis Of Shape From Contour
Authors: Fatih Ulupinar, Ramakant Nevatia
Venue: ICCV
Year: 1988

Inference of 3-D shape from 2-D contours in a single image is an important problem in machine vision. We survey classes of techniques proposed in the past and provide a critical analysis. We propose two kinds of symmetries in figures, which we call parallel and mirror symmetries, give significant information about surface shape for a variety of objects. We show the constraints imposed by these symmetries and how to use them to infer 3-D shape. Our method is applicable to any zero-gaussian curvature surface, and also to a variety of doubly curved surfaces. One of our mathematical results is that for a cone, the surface shape can be constructed uniquely under very simple assumptions. We also show some preliminary results on extraction of symmetries from real images.
Application Of Qualitative Depth And Shape From Stereo
Authors: Daphna Weinshall
Venue: ICCV
Year: 1988

Obtaining exact depth from binocular dis- parities is hard if camera calibration is needed. We will show that qualitative depth and shape information can be obtained from stereo disparities with almost no computations, and with no prior knowledge (or computation) of camera's parameters. First, we derive two expressions that order matched points in the images in two distinct depth-consistent ways from image coor- dinates only. Their use demonstrates some anomalies that have been observed in psychophysical experiments, most notably the induced size effect. Second, we apply the same approach to estimate some qualitative behavior of the normal to the surface of any object in the field of view. In a similar way we develop an algorithm to compute axes of zero-curvature from disparities alone. The algorithm is shown to be quite robust against viola- tions of the basic assumptions of the computation on synthetic images, with relatively large controlled deviations. It performs almost as well on real images, as demonstrated on an image of four cans at different orientations. In this example, the true zero- curvature axes have been found for three cans, and an estimate with some small error has been found for the fourth.
Two-view Matching
Authors: Juyang Weng, Narendra Ahuja, Thomas S. Huang
Venue: ICCV
Year: 1988

Establishing correspondences between images of the same scene is one of the most challenging and critical stcps in motion and scene analysis. Part of the difficulty is due to a wide variety of three-dimension structural discontinuities and occlusions that occur in real world scenes. This paper describes a computational approach to image matching that uses multiple attributes associated with a pixel to yield a generally overdetermined system of constraints, taking into account possible structural discontinuities and occlusions. In the algorithm implemented, intensity, edgeness, and comemess attributes are used in conjunction with the constraints arising from intraregional smoothness, field continuity and discontinuity, and occlusions to compute dense displacement fields and occlusion maps at pixel grids. A multiresolution multigrid structure is employed to deal with large disparities. Coarser level attributes are obtained by blurring the finer level attributes. The algorithms are tested on real world scenes containing depth discontinuities and occlusions. A special case of two-view matching is stereo matching where the motion between two images is known. The general algorithm given here can be easily spccialized to perfonn stereo matching using epipolar line constraint.
Translating Optical Flow Into Token Matches And Depth From Looming
Authors: Lance R. Williams, Allen R. Hanson
Venue: ICCV
Year: 1988

MOTION IN THE ENVIRONMENT MANIFESTS ITSELF IN CHANGES OF MANY KINDS, NOT JUST IMAGE PLANE VELOCITIES, YET THESE ARE ALL THAT AN OPTICAL FLOW FIELD MAKES EXPLICIT. WE VIEW OPTICAL FLOW AS A USEFUL LOW-LEVEL REPRESENTATION FROM WHICH A SYMBOLIC DESCRIPTION OF CHANGE, IN THE FORM OF TOKEN MATCHES, CAN BE COMPUTED. THE TOKENS OF INTEREST TO US ARE THOSE PRODUCED BY PERCEPTUAL ORGANIZATION PROCESSES, AND ARE MORE ABSTRACT THAN EDGES OR INTEREST POINTS. WE DEMONSTRATE A WORKING SYSTEM FOR MATCHING LINE TOKENS WHICH USES THE OPTICAL FLOW FIELD IN A HEURISTIC MANNER TO LIMIT THE SEARCH FOR THE `MINIMAL BIPARTITE COVER'' OF THE SET OF TOKENS FROM EACH FRAME. AS AN EXAMPLE APPLICATION, WE DEMONSTRATE A TECHNIQUE FOR COMPUTING DISTANCE TO ENVIRONMENTAL SURFACES SUITABLE FOR OBSTACLE RECOGNITION BY A MOBILE ROBOT. ACCURATE KNOWLEDGE OF THE CAMERA MOTION PARAMETERS IS NOT REQUIRED. WE DESCRIBE HOW MOTION IN DEPTH MANIFESTS ITSELF IN THE PROJECTED LENGTHS AND AREAS OF ENVIRONMENTAL SURFACES WHOSE EXTENT IN DEPTH IS SMALL RELATIVE TO THEIR DISTANCE FROM THE CAMERA. RESULTS ON TWO SEQUENCES TAKEN BY A MOBILE ROBOT ARE PRESENTED TO DEMONSTRATE THE ACCURACY OF THE METHOD.
Analysis Of A Sequence Of Stereo Scenes Containing Multiple Moving Objects Using Rigidity Constraints
Authors: Zhengyou Zhang, Olivier D. Faugeras, Nicholas Ayache
Venue: ICCV
Year: 1988

Iri this paper, we describe a method for comput.ing the rriovc~rrient. of objects as well as that of a mobile robot from ii scqiicrice of stereo frames. Stereo frames are obtained at ~iifl’(~reiit, instants by a stereo rig, when the mobile robot rIilvigat(>s in an unknown environment possibly containing ~)iiit: rrioving rigid objects. An approach based on rigidity ( oiihlraiiit,s is presented for registering two stereo frames. Wcs dernoristrate how the uncertainty of measurements can IN^ integrated with the formalism of the rigidity constraints. A iiew technique is described to match very noisy segments. ‘1‘11~ iiifluence of egomotion on observed movement:; of ob,j(~ 1,s is discussed in detail. Egomotion is fir:jt determined itiid then eliminated before determination of the motion of o1)jt:cl.s. The proposed algorithm is completely automatic. I~:xperirnerital results are provided. Some remarks conclude ths paper.
The Organization Of Curve Detection: Coarse Tangent Fields And Fine Spline Coverings
Authors: Steven W. Zucker, Chantal David, Allan Dobbins, Lee Iverson
Venue: ICCV
Year: 1988

We propose a new paradigm for curve detection in which an autonomous and atomic description is computed between measurements on the image and global curves. The description takes the form of a discrete tangent field, i.e.. an estimated representation of quantized tangents and curvatures at each possible trace point. We then present a new algorithm for inferring global curves through this tangent field. by inferring a covering of the global curve. The elements of the covering are short splines, each of which moves according to a potential distribution computed from the tangent field. Both stages of the algorithm are parallel and both bear some analogy to biological mechanisms for curve detection
Active surface reconstruction by integrating focus, vergence, stereo, and camera calibration
Authors: A. Lynn Abbott, Narendra Ahuja
Venue: ICCV
Year: 1990

A method is described for estimating surfaces from stereo images. A single pair of stereo images can yield surface reconstruction for only a small volume of space. Since the scene may be large, images are obtained dynamically using different camera configurations through the control of focus and camera vergence. For smooth objects, this results in the reconstruction of surface patches that are contiguous and overlapping. These sequentially acquired surface maps are merged into a central. composite representation. During camera reconfiguration, unpredictable calibration errors may arise. Therefore, this method permits small changes in calibration parameter values to achieve agreement between adjacent reconstructed patches in the areas of overlap. To integrate the different sources of depth information, and to balance the effects they have on the resulting surface estimate, the surface reconstruction problem is formulated as one of optimization.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Dynamic integration of height maps into a 3-D world representation from range image sequences
Authors: Minoru Asada, Masahiro Kimura, Yoshiaki Shirai
Venue: ICCV
Year: 1990

An approach is presented for building a 3-D world model from range image sequences derived from road scenes including moving objects. First, a range image is transformed into a height map representing the height information from the assumed ground plane, and then it is segmented into the ground plane and objects on it. In order to capture the resolution and accuracy of the range information and to represent the consistency of the height information between different height maps, the authors define a reliability of the height information for each point on the height map. Using the reliability, the system finds the correspondences of both static and moving objects between different observations, and successively refines the height information and its reliability with newly acquired data, dealing with inconsistent data. The authors show the results obtained using landscape models and a range finder based on the structured light. >
Active 3D object models
Authors: Ruud M. Bolle, Andrea Califano, Rick Kjeldsen, Rakesh Mohan
Venue: ICCV
Year: 1990

A novel approach is presented for pruning the amount of search needed to match image features to object models. The technique relies on active networks which capture various visibility and geometric constraints between features of a model to prune these features from search space during matching. The networks, which can be efficiently implemented in Boolean logic, integrate harmoniously with the previous work in feature recognition and object matching. A method is proposed for clustering model features (vsets) and four types of constraints which assist in building the networks. The authors show, both analytically and empirically, the dramatic reduction in search provided by activation nets.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Dynamic edge warping: experiments in disparity estimation under weak constraints
Authors: Kim L. Boyer, Daniel M. Wuescher, Sudeep Sarkar
Venue: ICCV
Year: 1990

A technique, dynamic edge warping, for recovering reasonable disparity maps from uncalibrated stereo image pairs is presented. No precise knowledge of the epipolar camera geometry is assumed. The technique is part of a system including structural stereopsis and digital photogrammetry for self-calibrating stereo image pairs with application in autonomous extraction of terrain maps from stereo aerial photographs and autonomous calibration maintenance in robotic vision. The system substitutes high-level information and constraints for precise geometric knowledge, in constraining the matching process.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>