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Proceedings ArticleDOI

Object recognition from local scale-invariant features

20 Sep 1999-Vol. 2, pp 1150-1157
TL;DR: Experimental results show that robust object recognition can be achieved in cluttered partially occluded images with a computation time of under 2 seconds.
Abstract: An object recognition system has been developed that uses a new class of local image features. The features are invariant to image scaling, translation, and rotation, and partially invariant to illumination changes and affine or 3D projection. These features share similar properties with neurons in inferior temporal cortex that are used for object recognition in primate vision. Features are efficiently detected through a staged filtering approach that identifies stable points in scale space. Image keys are created that allow for local geometric deformations by representing blurred image gradients in multiple orientation planes and at multiple scales. The keys are used as input to a nearest neighbor indexing method that identifies candidate object matches. Final verification of each match is achieved by finding a low residual least squares solution for the unknown model parameters. Experimental results show that robust object recognition can be achieved in cluttered partially occluded images with a computation time of under 2 seconds.

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Citations
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Journal ArticleDOI
TL;DR: It is found that on a database of more than 100 categories, the Bayesian approach produces informative models when the number of training examples is too small for other methods to operate successfully.
Abstract: Learning visual models of object categories notoriously requires hundreds or thousands of training examples. We show that it is possible to learn much information about a category from just one, or a handful, of images. The key insight is that, rather than learning from scratch, one can take advantage of knowledge coming from previously learned categories, no matter how different these categories might be. We explore a Bayesian implementation of this idea. Object categories are represented by probabilistic models. Prior knowledge is represented as a probability density function on the parameters of these models. The posterior model for an object category is obtained by updating the prior in the light of one or more observations. We test a simple implementation of our algorithm on a database of 101 diverse object categories. We compare category models learned by an implementation of our Bayesian approach to models learned from by maximum likelihood (ML) and maximum a posteriori (MAP) methods. We find that on a database of more than 100 categories, the Bayesian approach produces informative models when the number of training examples is too small for other methods to operate successfully.

2,976 citations


Cites background from "Object recognition from local scale..."

  • ...Unfortunately, it is often difficult and expensive to acquire large sets of training examples....

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  • ...It is common knowledge in statistics that estimating a given number of parameters requires a many-fold larger number of training examples—as a consequence, learning one object category requires a batch process involving thousands or tens of thousands of training examples [13], [34], [39], [36]....

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Proceedings ArticleDOI
27 Jun 2004
TL;DR: The incremental algorithm is compared experimentally to an earlier batch Bayesian algorithm, as well as to one based on maximum-likelihood, which have comparable classification performance on small training sets, but incremental learning is significantly faster, making real-time learning feasible.
Abstract: Current computational approaches to learning visual object categories require thousands of training images, are slow, cannot learn in an incremental manner and cannot incorporate prior information into the learning process. In addition, no algorithm presented in the literature has been tested on more than a handful of object categories. We present an method for learning object categories from just a few training images. It is quick and it uses prior information in a principled way. We test it on a dataset composed of images of objects belonging to 101 widely varied categories. Our proposed method is based on making use of prior information, assembled from (unrelated) object categories which were previously learnt. A generative probabilistic model is used, which represents the shape and appearance of a constellation of features belonging to the object. The parameters of the model are learnt incrementally in a Bayesian manner. Our incremental algorithm is compared experimentally to an earlier batch Bayesian algorithm, as well as to one based on maximum-likelihood. The incremental and batch versions have comparable classification performance on small training sets, but incremental learning is significantly faster, making real-time learning feasible. Both Bayesian methods outperform maximum likelihood on small training sets.

2,924 citations


Cites background from "Object recognition from local scale..."

  • ...Significant progress has been made on the issues of representation of objects [17,18] and object categories [2,3,5–8] with a broad agreement for models that are composed of ‘parts’ (textured patches, features) and ‘geometry’ (or mutual position of the parts)....

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Journal ArticleDOI
TL;DR: The Structure-from-Motion (SfM) method as mentioned in this paper solves the camera pose and scene geometry simultaneously and automatically, using a highly redundant bundle adjustment based on matching features in multiple overlapping, offset images.

2,901 citations


Cites methods from "Object recognition from local scale..."

  • ...This package contains a number of open-source applications including, in order of execution, SiftGPU (Lowe, 1999, 2004), Bundler (Snavely et al., 2008), CMVS and PMVS2 (Furukawa and Ponce, 2007; Furukawa et al., 2010), all of which may be run independently if desired....

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  • ...This is implemented in 197 SFMToolkit3, through the incorporation of the SiftGPU algorithm (Lowe, 1999; 2004)....

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Journal ArticleDOI
01 Sep 2005
TL;DR: This paper builds on the idea of the Harris and Förstner interest point operators and detects local structures in space-time where the image values have significant local variations in both space and time and illustrates how a video representation in terms of local space- time features allows for detection of walking people in scenes with occlusions and dynamic cluttered backgrounds.
Abstract: Local image features or interest points provide compact and abstract representations of patterns in an image. In this paper, we extend the notion of spatial interest points into the spatio-temporal domain and show how the resulting features often reflect interesting events that can be used for a compact representation of video data as well as for interpretation of spatio-temporal events. To detect spatio-temporal events, we build on the idea of the Harris and Forstner interest point operators and detect local structures in space-time where the image values have significant local variations in both space and time. We estimate the spatio-temporal extents of the detected events by maximizing a normalized spatio-temporal Laplacian operator over spatial and temporal scales. To represent the detected events, we then compute local, spatio-temporal, scale-invariant N-jets and classify each event with respect to its jet descriptor. For the problem of human motion analysis, we illustrate how a video representation in terms of local space-time features allows for detection of walking people in scenes with occlusions and dynamic cluttered backgrounds.

2,684 citations


Cites background from "Object recognition from local scale..."

  • ...Highly successful applications of interest points have been presented for image indexing (Schmid and Mohr, 1997), stereo matching (Tuytelaars and Van Gool, 2000; Mikolajczyk and Schmid, 2002; Tell and Carlsson, 2002), optic flow estimation and tracking (Smith and Brady, 1995; Bretzner and Lindeberg, 1998), and object recognition (Lowe, 1999; Hall et al., 2000; Fergus et al., 2003; Wallraven et al., 2003)....

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  • ...…2000; Mikolajczyk and Schmid, 2002; Tell and Carlsson, 2002), optic flow estimation and tracking (Smith and Brady, 1995; Bretzner and Lindeberg, 1998), and object recognition (Lowe, 1999; Hall, de Verdiere and Crowley, 2000; Fergus, Perona and Zisserman, 2003; Wallraven, Caputo and Graf, 2003)....

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Journal ArticleDOI
TL;DR: This review covers computer-assisted analysis of images in the field of medical imaging and introduces the fundamentals of deep learning methods and their successes in image registration, detection of anatomical and cellular structures, tissue segmentation, computer-aided disease diagnosis and prognosis, and so on.
Abstract: This review covers computer-assisted analysis of images in the field of medical imaging. Recent advances in machine learning, especially with regard to deep learning, are helping to identify, classify, and quantify patterns in medical images. At the core of these advances is the ability to exploit hierarchical feature representations learned solely from data, instead of features designed by hand according to domain-specific knowledge. Deep learning is rapidly becoming the state of the art, leading to enhanced performance in various medical applications. We introduce the fundamentals of deep learning methods and review their successes in image registration, detection of anatomical and cellular structures, tissue segmentation, computer-aided disease diagnosis and prognosis, and so on. We conclude by discussing research issues and suggesting future directions for further improvement.

2,653 citations


Cites methods from "Object recognition from local scale..."

  • ...Moreover, the features [e.g., local patches and scale-invariant feature transform (SIFT) (86)] either detect too many noncorresponding points when using the entire intensity patch as the feature vector (Figure 5d ) or have too-low responses and thus miss the correspondence when using SIFT (Figure 5e)....

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  • ...F or p er so na l u se o nl y. a Template b Subject c Registered subject image d Local patches e SIFT f SAE Figure 5 Similarity maps identifying the correspondence for the point indicated by the red cross in the template (a) with regard to the subject (b) by hand-designed features (d,e) and by stacked auto-encoder (SAE) features learned through unsupervised deep learning ( f )....

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  • ..., local patches and scale-invariant feature transform (SIFT) (86)] either detect too many noncorresponding points when using the entire intensity patch as the feature vector (Figure 5d ) or have too-low responses and thus miss the correspondence when using SIFT (Figure 5e)....

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  • ...Abbreviation: SIFT, scale-invariant feature transform. the subject point under consideration, making it easy to locate the correspondence of the template point in the subject image domain....

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References
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Journal ArticleDOI
TL;DR: In this paper, color histograms of multicolored objects provide a robust, efficient cue for indexing into a large database of models, and they can differentiate among a large number of objects.
Abstract: Computer vision is moving into a new era in which the aim is to develop visual skills for robots that allow them to interact with a dynamic, unconstrained environment. To achieve this aim, new kinds of vision algorithms need to be developed which run in real time and subserve the robot's goals. Two fundamental goals are determining the identity of an object with a known location, and determining the location of a known object. Color can be successfully used for both tasks. This dissertation demonstrates that color histograms of multicolored objects provide a robust, efficient cue for indexing into a large database of models. It shows that color histograms are stable object representations in the presence of occlusion and over change in view, and that they can differentiate among a large number of objects. For solving the identification problem, it introduces a technique called Histogram Intersection, which matches model and image histograms and a fast incremental version of Histogram Intersection which allows real-time indexing into a large database of stored models. It demonstrates techniques for dealing with crowded scenes and with models with similar color signatures. For solving the location problem it introduces an algorithm called Histogram Backprojection which performs this task efficiently in crowded scenes.

5,672 citations

Journal ArticleDOI
TL;DR: It is shown how the boundaries of an arbitrary non-analytic shape can be used to construct a mapping between image space and Hough transform space, which makes the generalized Houghtransform a kind of universal transform which can beused to find arbitrarily complex shapes.

4,310 citations

Journal ArticleDOI
TL;DR: A near real-time recognition system with 20 complex objects in the database has been developed and a compact representation of object appearance is proposed that is parametrized by pose and illumination.
Abstract: The problem of automatically learning object models for recognition and pose estimation is addressed. In contrast to the traditional approach, the recognition problem is formulated as one of matching appearance rather than shape. The appearance of an object in a two-dimensional image depends on its shape, reflectance properties, pose in the scene, and the illumination conditions. While shape and reflectance are intrinsic properties and constant for a rigid object, pose and illumination vary from scene to scene. A compact representation of object appearance is proposed that is parametrized by pose and illumination. For each object of interest, a large set of images is obtained by automatically varying pose and illumination. This image set is compressed to obtain a low-dimensional subspace, called the eigenspace, in which the object is represented as a manifold. Given an unknown input image, the recognition system projects the image to eigenspace. The object is recognized based on the manifold it lies on. The exact position of the projection on the manifold determines the object's pose in the image. A variety of experiments are conducted using objects with complex appearance characteristics. The performance of the recognition and pose estimation algorithms is studied using over a thousand input images of sample objects. Sensitivity of recognition to the number of eigenspace dimensions and the number of learning samples is analyzed. For the objects used, appearance representation in eigenspaces with less than 20 dimensions produces accurate recognition results with an average pose estimation error of about 1.0 degree. A near real-time recognition system with 20 complex objects in the database has been developed. The paper is concluded with a discussion on various issues related to the proposed learning and recognition methodology.

2,037 citations

Journal ArticleDOI
TL;DR: This paper addresses the problem of retrieving images from large image databases with a method based on local grayvalue invariants which are computed at automatically detected interest points and allows for efficient retrieval from a database of more than 1,000 images.
Abstract: This paper addresses the problem of retrieving images from large image databases. The method is based on local grayvalue invariants which are computed at automatically detected interest points. A voting algorithm and semilocal constraints make retrieval possible. Indexing allows for efficient retrieval from a database of more than 1,000 images. Experimental results show correct retrieval in the case of partial visibility, similarity transformations, extraneous features, and small perspective deformations.

1,756 citations


"Object recognition from local scale..." refers background or methods in this paper

  • ...This allows for the use of more distinctive image descriptors than the rotation-invariant ones used by Schmid and Mohr, and the descriptor is further modified to improve its stability to changes in affine projection and illumination....

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  • ...For the object recognition problem, Schmid & Mohr [19] also used the Harris corner detector to identify interest points, and then created a local image descriptor at each interest point from an orientation-invariant vector of derivative-of-Gaussian image measurements....

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  • ..., Schmid & Mohr [19]) has shown that efficient recognition can often be achieved by using local image descriptors sampled at a large number of repeatable locations....

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  • ...However, recent research on the use of dense local features (e.g., Schmid & Mohr [19]) has shown that efficient recognition can often be achieved by using local image descriptors sampled at a large number of repeatable locations....

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Journal ArticleDOI
TL;DR: A robust approach to image matching by exploiting the only available geometric constraint, namely, the epipolar constraint, is proposed and a new strategy for updating matches is developed, which only selects those matches having both high matching support and low matching ambiguity.

1,574 citations


"Object recognition from local scale..." refers methods in this paper

  • ...[23] used the Harris corner detector to identify feature locations for epipolar alignment of images taken from differing viewpoints....

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