OpenRaiser/Intern-Atlas huggingface dataset:
Accuracy assessment on camera calibration method not considering lens distortion
Authors: Sheng-Wen Shih, Yi-Ping Hung, Wei-Song Lin
Venue: CVPR
Year: 1992

The authors investigate the effect of neglecting lens distortion, and present a theoretical analysis of the calibration accuracy. The error bound derived is a function of a few factors, including the number of calibration points, the observation error of 2-D image points, the radial lens distortion coefficient, and the image size and resolution. This error bound provides a guideline for selecting both a proper camera calibration configuration and an appropriate camera model while providing the desired accuracy. Experimental results from both computer simulations and real experiments are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Vector field analysis for oriented patterns
Authors: Chiao-Fe Shu, Ramesh C. Jain
Venue: CVPR
Year: 1992

Presents a method, based on the properties of vector fields, for the estimation of a set of symbolic descriptors (node, saddle, star-node, improper-node, center, and spiral) from linear orientation fields. Planar first-order phase portraits are used to model the linear orientation fields. A weighted linear estimator is developed to estimate linear phase portraits, using only the flow orientation. A classification scheme for planar first-order phase portraits, based on their local properties: curl, divergence, and deformation is developed. The authors present results of experiments on noise-added synthetic flow patterns and real oriented textures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Neural network models for illusory contour perception
Authors: Josef Skrzypek, Brian Ringer
Venue: CVPR
Year: 1992

A physiologically motivated model of illusory contour perception is examined by simulating a neural network architecture that was tested with gray-level images. The results indicate that a model that combines a bottom-up feature aggregation strategy with recurrent processing is best suited for describing this type of perceptual completion.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Extracting the shape and roughness of specular lobe objects using four light photometric stereo
Authors: Fredric Solomon, Katsushi Ikeuchi
Venue: CVPR
Year: 1992

We propose a noncontact method for the measurement of surface shape and surface roughness. The method, which we call "four light photometric stereo", uses four lights, which sequentially illuminate the object under inspection, and a video camera for taking images of the object. The method has successfully been applied to a number of real objects.
Multi-resolution surface modeling from multiple range views
Authors: Marc Soucy, Denis Laurendeau
Venue: CVPR
Year: 1992

A multiresolution surface modeling technique is presented. Several registered range views obtained from different viewpoints are first integrated into a nonredundant surface triangulation. The integration technique is based on the reparameterization of the canonic subsets of the Venn diagram of the set of views. The resulting triangulation is then input to a sequential optimization process that computes different levels of resolution of the surfaces of interest.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Indexing function-based categories for generic recognition
Authors: Louise Stark, Kevin W. Bowyer
Venue: CVPR
Year: 1992

The authors report the implementation and evaluation of a function-based recognition system that takes an uninterrupted 3-D object shape as its input and reasons to determine if the object belongs to the superordinate category furniture, and if so, into which (sub)category it falls. The system has analyzed over 250 input objects, and the results largely agree with intuitive human interpretation of the objects. The study confirms that a relatively small number of knowledge primitives may be used as the basis for defining a relatively broad range of object categories. The greatest derivation from intuitive human interpretation occurs with objects that humans would not typically label as one of the known categories defined, but which have some novel orientation in which they could serve the function of one of these categories. This is because the system uses a purely function-based definition of the object category.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Robust statistics in shape fitting
Authors: Andrew Stein, Michael Werman
Venue: CVPR
Year: 1992

The concept of robustness in statistics is examined. Starting from the concepts of the breakdown point and equivariance properties of an estimator, the desired equivariance properties for shape fitting are defined, and high breakdown point methods with these properties are found.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
On the derivation of geometric constraints in stereo
Authors: Charles V. Stewart
Venue: CVPR
Year: 1992

Probability density functions (PDFs) are derived for many of the geometric measurements upon which stereo matching techniques are based, including orientation differences between matching line segments or curves, the gradient of disparity, the directional derivative of disparity, and disparity differences between matches. The PDFs resulting from the transformations are used to critically examine many existing stereo techniques. Several techniques based on these PDFs are proposed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Depth from defocus and rapid autofocusing: a practical approach
Authors: Murali Subbarao, Tse-Chung Wei
Venue: CVPR
Year: 1992

A method for determining depth (range) from image defocus and rapid autofocusing of a camera named DFD1F, is presented. It requires only two images in theory, but three images in the present implementation. DFD1F is based on computing only one-dimensional Fourier coefficients as opposed to two-dimensional Fourier coefficients for a related prior method, thus providing not only computational advantage but also robustness in practical applications. DFD1F is independent of the form of the modulation transfer function of the camera. DFD1F has been successfully implemented and tested on an actual camera system named SPARCS. SPARCS can determine the distance of an object placed in front of it at any distance in the range of 0.5 m to infinity, and can successfully focus the object by moving the lens with a root-mean-square error of less than 6% in terms of lens position.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Shape-from-texture by wavelet-based measurement of local spectral moments
Authors: Boaz J. Super, Alan C. Bovik
Venue: CVPR
Year: 1992

A closed-form solution to the problem of computing 3D curved-surface shape from texture cues is presented. An expression showing the dependence of localized image spectral moments on localized surface spectral moments and on local surface orientation is derived. The local image spectra are measured with wavelets, and the expression is solved for the surface orientation at each point. Because the method uses localized spectral information, it operates at a very low level in the visual hierarchy. No extraction of texture or edge elements is required. The wavelet-based computation used is biologically plausible, easily parallelized for rapid computation, and has been shown to be the basis for effective solutions to a variety of other vision tasks. The method is demonstrated on a number of real-world examples.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Computing occlusion-free viewpoints
Authors: Konstantinos A. Tarabanis, Roger Y. Tsai
Venue: CVPR
Year: 1992

This paper presents methods to compute the locus of all viewpoints from which features on known polyhedral objects can be viewed in their entirety without being occluded by anything in the environment. Convex and concave polyhedra with or without holes and the viewing model of perspective projection are employed in this work. Initially, properties of the occlusion-free and occluded loci of viewpoints are determined. Based on these properties, two methods to construct these loci together with their complexity analysis are presented. In the first method, a boundary representation of the occlusion-free locus is obtained. In the second method, the locus of occluded viewpoints is expressed in terms of a constructive solid geometry representation that consists of a union of component solids. Implementation results and comparison of the two methods are given.
Parametrizing and fitting bounded algebraic curves and surfaces
Authors: Gabriel Taubin, Fernando Cukierman, Steve Sullivan, Jean Ponce, David J. Kriegman
Venue: CVPR
Year: 1992

An approach to fitting of implicit algebraic curves and surfaces to point data is introduced. Two families of polynomials with bounded zero sets are presented. Members of these families have the same number of degrees of freedom as general polynomials of the same degree. Methods for fitting members of these families of polynomials to measured data points are described. Experimental results for sets of points in R/sup 2/ and R/sup 3/ for curves and surfaces, respectively, are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
A fast linear shape from shading
Authors: Ping-Sing Tsai, Mubarak Shah
Venue: CVPR
Year: 1992

A method for computing depth from a single shaded image is presented. Discrete approximations for p and q using finite differences are used, and the reflectance in Z/sub ij/ is linearized. The method is faster, since each operation is purely local. In addition, it gives good results for spherical surfaces, in contrast to other linear methods.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Recovery of 3-D objects with multiple curved surfaces from 2-D contours
Authors: Fatih Ulupinar, Ramakant Nevatia
Venue: CVPR
Year: 1992

The authors describe a technique for inference of 3-D shape from 2-D contours that utilizes not only the shapes of individual surfaces but also the interactions between them. The analysis applies to objects made of zero-Gaussian curvature surfaces viewed under orthographic projection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Adaptive meshes and shells: irregular triangulation, discontinuities, and hierarchical subdivision
Authors: M. Alex O. Vasilescu, Demetri Terzopoulos
Venue: CVPR
Year: 1992

The adaptive mesh model is extended in several ways. Open adaptive meshes and closed adaptive shells based on triangular and rectangular elements are developed. A discontinuity detection and preservation algorithm suitable for the model is proposed. Techniques for adaptive hierarchical subdivision of adaptive meshes and shells are also developed. The extended model is applied to image and 3D surface data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Multifractals, texture, and image analysis
Authors: Jacques Lévy Véhel, Pascal Mignot, Jean-Paul Berroir
Venue: CVPR
Year: 1992

Image analysis using texture and multifractal paradigms is addressed. Multifractal theory and its application to image description are discussed, and it is shown that this approach allows the discrete signal to be worked on directly. A system for texture classification that is based on a learning scheme and does not make use of any a priori model is introduced. Image segmentation is then considered, and the notion of mixed classes, which allows accurate detection of texture boundaries on complex images, is introduced.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Morphological grayscale reconstruction: definition, efficient algorithm and applications in image analysis
Authors: Luc Vincent
Venue: CVPR
Year: 1992

Gray-scale reconstruction is formally defined for discrete images. A brief summary of the existing techniques to compute it is provided, and a hybrid algorithm that is an order of magnitude faster than any other algorithm is introduced. Some of its application to image filtering and segmentation are listed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
A MRF approach to optical flow estimation
Authors: John A. Vlontzos, Davi Geiger
Venue: CVPR
Year: 1992

A Markov random field (MRF) formulation for the problem of optical flow computation is studied. An adaptive window matching scheme is used to obtain a good measure of the correlation between the two images. A confidence measure for each match is also used. Thus, the input to the system is the adaptive correlation and the corresponding confidence. The MRF model is then used to estimate the velocity field and the velocity discontinuities. The problem of occlusions is addressed, and a relationship between occlusions and motion discontinuities is established.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Controlling illumination color to enhance object discriminability
Authors: Mark Vriesenga, Glenn Healey, Kalman Peleg, Jack Sklansky
Venue: CVPR
Year: 1992

The authors describe how to design color illumination to improve the discriminability of objects in color images. This procedure is useful in applications where the illumination can be controlled, such as inspection tasks. From the physics of color image formation, the optimal color illumination for discriminating materials is derived using a parametrically defined set of illuminants. The authors suggest how such an approach might be extended to sets of materials and more general classes of light sources. Experiments with painted color patches and live potato plantlets are used to illustrate the usefulness of actively controlling illumination color in machine vision.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
A geometric approach to machine-printed character recognition
Authors: Li Wang 0003, Theo Pavlidis
Venue: CVPR
Year: 1992

An approach to feature extraction that eliminates binarization by extracting features directly from gray scale images is presented. It not only allows the processing of poor quality input (e.g., low contrast, dirty images), but also offers the possibility of significantly lower resolution for digitization.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Local shape approximation from shading
Authors: Daphna Weinshall
Venue: CVPR
Year: 1992

Exact shape cannot be inferred from a local analysis of shading, but for shape interpolation, a crude local approximation may be sufficient. The author explores the limits of such local approximations that are easy to compute. In particular, the shape of shading is used to approximate the surface in areas of monotonic change of intensity. This analysis is complemented by a method to compute the direction of a single point light source from the shading on occluding contours.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Noise resistant projective and affine invariants
Authors: Isaac Weiss
Venue: CVPR
Year: 1992

A method of obtaining local projective and affine invariants that is more robust than existing methods is presented. These shape descriptors are useful for object recognition because they eliminate the search for the unknown viewpoint. Being local, these invariants are much less sensitive to occlusion than the global ones used elsewhere. The basic ideas are (i) using an implicit curve representation without a curve parameter, thus increasing robustness; and (ii) using a canonical coordinate system which is defined by the intrinsic properties of the shape, regardless of any given coordinate system, and is thus invariant. Several configurations are treated: a general curve without any correspondence, and curves with known correspondence of feature points or lines.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Uncertain views
Authors: Peter Whaite, Frank P. Ferrie
Venue: CVPR
Year: 1992

The possibility that what we do not know about the world can be used to guide the way in which they explore it is raised. The authors previously hypothesized that the spatial structure of uncertainty can be used to guide the acquisition of additional data in a way that significantly improves knowledge of a scene. An exploration strategy based on the hypothesis is constructed, and experimental results which verified that it works are presented. Conditions which cause it to break down are studied. The results indicate that there are inherent degeneracies in certain data configurations, but that the authors' strategy can navigate these areas successfully.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Active object recognition
Authors: David Wilkes, John K. Tsotsos
Venue: CVPR
Year: 1992

The concept of active object recognition is introduced, and a proposal for its solution is described. The camera is mounted on the end of a robot arm on a mobile base. The system exploits the mobility of the camera by using low-level image data to drive the camera to a standard viewpoint with respect to an unknown object. From such a viewpoint, the object recognition task is reduced to a two-dimensional pattern recognition problem. The system uses an efficient tree-based, probabilistic indexing scheme to find the model object that is likely to have generated the observed data, and for line tracking uses a modification of the token-based tracking scheme of J.L. Crowley et al. (1988). The system has been successfully tested on a set of origami objects. Given sufficiently accurate low-level data, recognition time is expected to grow only logarithmically with the number of objects stored.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Diffuse reflection [intensity reflectance model]
Authors: Lawrence B. Wolff
Venue: CVPR
Year: 1992

An intensity reflectance model is proposed for diffuse reflection originating from subsurface multiple scattering within inhomogeneous dielectric materials. One of the most common assumptions in computer vision from inhomogeneous dielectrics is Lambertian. The proposed model utilizes the subsurface intensity distribution predicted by modeling subsurface multiple scattering based upon radiative transfer theory. For an optically smooth surface boundary this subsurface intensity distribution becomes altered by Fresnel attenuation upon refraction into air, making it become significantly non-Lambertian. This resulting intensity distribution serves as a reflection law for individual optically smooth microfacets that compose an opaque rough surface, producing a physical unification of diffuse reflection with the Torrance-Sparrow specular reflection model. Experimental results that verify the accuracy of the model are presented. A relatively simple formula that approximates closely the true behaviour of diffuse reflection and can be used in place of a Lambertian term is presented. The non-Lambertian nature of the diffuse component becomes most significant near occluding contours and sometimes produces a previously unnoticed intensity effect that can aid in their detection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Image segmentation via edge contour finding: a graph theoretic approach
Authors: Zhenyu Wu, Richard M. Leahy
Venue: CVPR
Year: 1992

A graph-theoretic approach for image segmentation is presented. The pixels of the image are represented by the vertices of an undirected adjacency graph G. All neighboring pairs of pixels are linked by arcs with capacities assigned to reflect the strength of an edge element between the linked vertices. Segmentation is achieved by removing arcs corresponding to selected minimum cuts of G to form mutually exclusive subgraphs such that the largest intersubgraph maximum flow is minimized. This is equivalent to partitioning the image using closed contours of edge elements, which consist mostly of strong edges. The method accurately locates region boundaries and at the same time rejects contours containing isolated strong edges. The minimum cuts in G can be computed from a partially cut-equivalent tree of G. A fast algorithm for constructing partially equivalent trees that can handle graphs with several hundred thousand vertices is developed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Frontmatter
Venue: CVPR
Year: 1992

This article reviews the current state-of-theart for algae use in aquaculture, plus recent developments in algal biomass as a micro- or bulk ingredient in formulated animal feeds (terrestrial livestock and aquaculture species). Microalgae provide an important direct or indirect feed source for early developmental stages of many farmed finfish, shellfish and invertebrate species. Hatcheries typically cultivate microalgae in-house, with commercial concentrates now also being used widely. Different strains of micro- and macroalgae vary in their efficacy within formulated animal feeds, although there is sufficient evidence of good nutritional properties to promote algal biomass as a source of micronutrients or as a bulk feedstuff. High costs of algal biomass compared to commodity feedstuffs currently confine their commercial use to niche animal feed applications; greater availability/lower price, via biofuels and biorefinery would en able more widespread use in future.
Right straight homogeneous generalized cylinders with symmetrical cross-sections: recovery of pose and shape from image contours
Authors: Gang Xu, Hiromi T. Tanaka, Saburo Tsuji
Venue: CVPR
Year: 1992

The straight homogeneous generalized cylinder (SHGC) comprises a class of objects for which recovery of pose and shape from image is generally an underconstrained problem. It is shown that for a major subclass of SHGCs, namely, the right straight homogeneous generalized cylinders, the 3-D pose (tilt and slant) and shape (cross section and scaling function) can be completely determined if the cross sections are symmetrical. From the mutual orthogonality of the cylinder axis, the symmetry axis and transverse axis of the cross section, their slants can be determined from their tilts, the 2-D orientations of their projections onto the image. The 2-D cylinder axis and skewed symmetry axis of the cross sections are extracted by using the property that tangents to the image curves at corresponding points meet on the axes. Once the pose is recovered, the cross section and scaling function of the object can also be determined from the cross section contour and extremal contours, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Computational ground and airborne localization over rough terrain
Authors: Yaser Yacoob, Larry S. Davis
Venue: CVPR
Year: 1992

An approach for autonomous localization of ground vehicles on natural terrain is proposed. The localization problem is solved using measurements including attitude, heading, and distances to specific environmental points. The algorithm utilizes random acquisition of distance measurements to prune the possible location(s) of the viewer. The approach is also applicable to airborne localization.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>