Visual Feature Spaces for Image Representation and Processing: The Multiscale Local Jet

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1 Visual Feature Spaces for Image Representation and Processing: The Multiscale Local Jet Antoine Manzanera ENSTA-ParisTech Workshop AMINA Oct, 19, 2010 Antoine Manzanera Visual Feature Spaces et caetera 1 / 53

2 Objectives and problem statement Objectives and problem statement Related works Our global objective is to propose a unied framework for representing and processing the visual data, trying to reach the maximal: Universality: from the lowest (denoising, registration,...) to the highest level (recognition, understanding,...) of vision. Computational eciency: tractable complexity for embedded video systems. Antoine Manzanera Visual Feature Spaces et caetera 2 / 53

3 Objectives and problem statement Objectives and problem statement Related works The principle of our framework is to adjoin to the video data an alternate (feature space) data structure whose metrics is related to visual similarity, and made up of dierent components: Feature space (local jet) projection. Quantisation (Codebook) of the feature space. Nearest Neighbour Search in the feature space. Indexing of the feature space for back-projection. Antoine Manzanera Visual Feature Spaces et caetera 3 / 53

4 Outline Introduction Objectives and problem statement Related works 1 Introduction Objectives and problem statement Related works 2 Local jet based similarity LJ feature space Metrics and invariance Computation and data structures 3 NL-means ltering Optical ow Background subtraction 4 Codebook histograms Singularities and Modes in the feature space 5 Conclusion and ongoing Antoine Manzanera work Visual Feature Spaces et caetera 4 / 53

5 Related works Introduction Objectives and problem statement Related works Manifold Image Processing The projected data form a manifold in some feature space [Peyré 09]. is made by transformation of the manifold, followed by a back-projection onto the image space. Filter Banks and Codebook Many visual representation frameworks, for texture (e.g. textons) or objects (e.g. visual bag of features) are based on lter banks and clustering [Freeman 91], [Rubner 99]. Nearest Neighbour Search We use Binary Search Trees to represent highly sparse sets from the feature space with a minimal amount of memory, and eciently perform Nearest Neighbour Search [Arya and Mount 07]. Antoine Manzanera Visual Feature Spaces et caetera 5 / 53

6 Outline Introduction Local jet based similarity LJ feature space Metrics and invariance Computation and data structures 1 Introduction Objectives and problem statement Related works 2 Local jet based similarity LJ feature space Metrics and invariance Computation and data structures 3 NL-means ltering Optical ow Background subtraction 4 Codebook histograms Singularities and Modes in the feature space 5 Conclusion and ongoing Antoine Manzanera work Visual Feature Spaces et caetera 6 / 53

7 Local derivatives and visual similarity Local jet based similarity LJ feature space Metrics and invariance Computation and data structures SSD based similarity d f (x, y) = k( i )(f (x + i) f (y + i)) 2 i W(O) Taylor expansion f (x + c) = r k=0 i=0 k ( ) k i c k i 1 c i 2 k f x k i 1 x i 2 (x) + o( c r ) Local jet based similarity d f (x, y) α (i,j) (f ij (x) f ij (y)) 2, with f ij = i+j f x1 i x j 2 i+j r Antoine Manzanera Visual Feature Spaces et caetera 7 / 53

8 Local jet based representation Local jet based similarity LJ feature space Metrics and invariance Computation and data structures The Local jet seen as a summary of the patch information (Reconstruction of the patch using Taylor expansion)... 1 Original patches 2 Order 0 (1d feature) 3 Order 1 (3d feature) 4 Order 2 (6d feature) (1) (2) (3) (4) Antoine Manzanera Visual Feature Spaces et caetera 8 / 53

9 Gaussian multiscale local jet Local jet based similarity LJ feature space Metrics and invariance Computation and data structures We do not use patches, but Gaussian Local Jet at a certain scale: Projection in the Local Jet space x ˆx = (a σ ij f σ ij (x)) i+j r Gaussian multiscale local jet f σ ij = f i+j G σ x i 1 x j 2 Normalised local jet a σ ij = σi+j i+j+1 Gσ is the 2d Gaussian function with variance σ 2. σ i+j is the scale space normalisation [Lindeberg 98]. i + j + 1 is the number of (i + j) th order derivatives. Antoine Manzanera Visual Feature Spaces et caetera 9 / 53

10 Multiscale Cartesian Local jet Local jet based similarity LJ feature space Metrics and invariance Computation and data structures f f f f f f f f f f f f Antoine Manzanera Visual Feature Spaces et caetera 10 / 53

11 Rotation invariance Introduction Local jet based similarity LJ feature space Metrics and invariance Computation and data structures f = f 00 f g = (f 2 + f 2 10 f t = 0 f gg = (f 20 f 2 f tt = (f 20 f 2 01) 1/ f 11 f 10 f 01 + f 02 f f 11 f 10 f 01 + f 02 f 2 f gt = (f 10 f 01 (f 20 f 02 ) + f 11 (f 2 g 01)f 2 g 10)f 2 01 f 2 10))f 2 g Antoine Manzanera Visual Feature Spaces et caetera 11 / 53

12 Multiscale Rotation Invariant Local jet Local jet based similarity LJ feature space Metrics and invariance Computation and data structures f 1.0 fg 1.0 fgg 1.0 fgt 1.0 ftt 1.0 f 4.0 fg 4.0 fgg 4.0 fgt 4.0 ftt 4.0 Antoine Manzanera Visual Feature Spaces et caetera 12 / 53

13 Local jet based similarity LJ feature space Metrics and invariance Computation and data structures Contrast change (and inversion!) Invariant Local jet Gradient direction Main absolute curvature direction Antoine Manzanera Visual Feature Spaces et caetera 13 / 53

14 Local jet based similarity LJ feature space Metrics and invariance Computation and data structures Local jet pixel categories and similarity metrics A reduced description useful for pixel comparison can be obtained by categorizing the local jet. See also [Crozier 10]. Antoine Manzanera Visual Feature Spaces et caetera 14 / 53

15 Some metrics Introduction Local jet based similarity LJ feature space Metrics and invariance Computation and data structures Single scale distance d σ f (x, y) = i+j r (f σ ij (x) f σ ij (y)) 2 Pan-scalic distance D S f (x, y) = i+j r,σ S (f σ ij (x) f σ ij (y)) 2 Trans-scalic distance d S f (x, y) = min (f σ 1 (σ 1,σ 2 ) S 2 ij (x) f σ 2 ij (y)) 2 i+j r Antoine Manzanera Visual Feature Spaces et caetera 15 / 53

16 Local jet similarity map: one example Local jet based similarity LJ feature space Metrics and invariance Computation and data structures (1) (2) (3) Antoine Manzanera Visual Feature Spaces et caetera 16 / 53

17 Parallel computation of the Local Jet Local jet based similarity LJ feature space Metrics and invariance Computation and data structures The local jet features lend themselves to a high level of parallel / cascaded computation. As an example, the recursive computation [Van Vliet 98] of the local jet at order 2 requires 9 couples of image scans, with only 2 levels of dependance. Antoine Manzanera Visual Feature Spaces et caetera 17 / 53

18 Data projection and representation Local jet based similarity LJ feature space Metrics and invariance Computation and data structures The pixel data are projected in the feature space. The feature vectors are collected within a binary search tree. Every feature vector is attached to a pixel index. Antoine Manzanera Visual Feature Spaces et caetera 18 / 53

19 Quantisation of the feature space Local jet based similarity LJ feature space Metrics and invariance Computation and data structures The feature space can be quantised through vector quantisation. Every codebook word keeps record of a set of pixel indices. Antoine Manzanera Visual Feature Spaces et caetera 19 / 53

20 Outline Introduction NL-means ltering Optical ow Background subtraction 1 Introduction Objectives and problem statement Related works 2 Local jet based similarity LJ feature space Metrics and invariance Computation and data structures 3 NL-means ltering Optical ow Background subtraction 4 Codebook histograms Singularities and Modes in the feature space 5 Conclusion and ongoing Antoine Manzanera work Visual Feature Spaces et caetera 20 / 53

21 NL-means in the feature space NL-means ltering Optical ow Background subtraction The NL-means lter calculates a weighted average of every pixel, with the weights dened as a function of local similarity. Here we simply use the distance in the feature space... ω(u, v) = e u v 2 2 h with:. a norm in the feature space. h a decay parameter....and perform the average on a neighbourhood of x in the image space (Limited Range), or on a neighbourhood of ˆx in the feature space (Unlimited range). Antoine Manzanera Visual Feature Spaces et caetera 21 / 53

22 Limited Range LJ-NL-Means NL-means ltering Optical ow Background subtraction The weights (in the LJ space) are calculated in a limited neighbourhood of x in the image space: Limited range NL-means flr NL(x) = 1 f (y)ω(ˆx, ŷ) ζ(x) y N (x) Antoine Manzanera Visual Feature Spaces et caetera 22 / 53

23 Unlimited Range LJ-NL-Means NL-means ltering Optical ow Background subtraction The weights (in the LJ space) are calculated in a limited neighbourhood of ˆx in the LJ space: Unlimited range NL-means fur NL(x) = 1 f (ǔ)ω(ˆx, u) ξ(x) u W(ˆx) Antoine Manzanera Visual Feature Spaces et caetera 23 / 53

24 NL-means ltering Optical ow Background subtraction LJ-NL-means: Relative computation time Patch based LR Local Jet LR LJ ( N (x) = 17 17), order 2. 1 scale 2 scales 3 scales 4 scales UR LJ ( W(ˆx f ) = 30), order 2, exact search ε = 0.0 ε = 1.0 ε = 3.0 ε = Same (4 scales), approximate search No quantisation 1622 words 795 words (40.9) 23.0 (19.7) Same (ε = 3.0), with quantisation (In parentheses: quantisation time). Antoine Manzanera Visual Feature Spaces et caetera 24 / 53

25 LJ-NL-means: results NL-means ltering Optical ow Background subtraction 1 Classical Patch based ( N (x) = 17 17) 2 Limited range ( N (x) = 17 17) 3 Unlimited range, exact search ( W(ˆx f ) = 30, single scale). 4 Same, 4 scales. 5 Same, approximate search (ε = 3.0). 6 Same, with quantisation ( 800 word codebook). (1) (2) (3) Antoine Manzanera (4) Visual Feature (5) Spaces et caetera (6) 25 / 53

26 NL-means ltering Optical ow Background subtraction Apparent motion in the feature space The optical ow estimation can be expressed by a simple nearest neighbour search in the feature space: u(f t 1, f t, x) = arg min d F (ˆx ft, v) v F ft 1 followed (in the case of a quantised feature space) by an optimization in the image space: y(f t 1, f t, x) = arg min d I (x, z) z F 1 (u(f t 1,f f t 1 t,x)) Antoine Manzanera Visual Feature Spaces et caetera 26 / 53

27 NL-means ltering Optical ow Background subtraction Apparent motion in the feature space Antoine Manzanera Visual Feature Spaces et caetera 27 / 53

28 NL-means ltering Optical ow Background subtraction Feature space optical ow: NL-Mean formulation A more general formulation can be obtained following the NL-Mean framework: y(f t 1, f t, x) = 1 ξ F (x) m ω F (ˆx ft, ν F f t 1 k (ˆx ft )) ξ I (x) k=1 z F 1 f t 1 (νf f t 1 k (ˆx ft )) Every nearest neighbour in the quantised feature space is weighted according to the feature space distance. Every image point from the reciprocal image of the quantised feature is weighted according to the distance between pixels. ω I (x, z)z Antoine Manzanera Visual Feature Spaces et caetera 28 / 53

29 Optical ow: results Introduction NL-means ltering Optical ow Background subtraction Antoine Manzanera Visual Feature Spaces et caetera 29 / 53

30 Optical ow: results Introduction NL-means ltering Optical ow Background subtraction Antoine Manzanera Visual Feature Spaces et caetera 30 / 53

31 NL-means ltering Optical ow Background subtraction Application: Characterization of Cardiac Motion Patterns [PhD F. Rodríguez, UNAL Bogotá] Antoine Manzanera Visual Feature Spaces et caetera 31 / 53

32 NL-means ltering Optical ow Background subtraction Background modelling by the feature space codebook The codebook of the quantised feature space can be used to model the visual apparence of the background in the methods based on sample and consensus. The principle is to keep record, for every pixel x, of a collection of M prototypes {m j (f, x)} j {1,M}, such that every prototype is a word from the quantised feature space (sampling phase). Antoine Manzanera Visual Feature Spaces et caetera 32 / 53

33 NL-means ltering Optical ow Background subtraction Background subtraction in the feature space The foreground classication is then performed by counting, for every x at time t, the number of prototypes that are close enough to ˆx ft (consensus phase). e(f, t, x) = 1 if {j {1, M}; d F (ˆx ft, m j (f, x)) > ρ} > τ = 0 otherwise Nota: The same codebook is used for the whole sequence. Antoine Manzanera Visual Feature Spaces et caetera 33 / 53

34 NL-means ltering Optical ow Background subtraction The ViBe algorithm in the feature space Antoine Manzanera Visual Feature Spaces et caetera 34 / 53

35 Motion detection: results NL-means ltering Optical ow Background subtraction Antoine Manzanera Visual Feature Spaces et caetera 35 / 53

36 Outline Introduction Codebook histograms Singularities and Modes in the feature space 1 Introduction Objectives and problem statement Related works 2 Local jet based similarity LJ feature space Metrics and invariance Computation and data structures 3 NL-means ltering Optical ow Background subtraction 4 Codebook histograms Singularities and Modes in the feature space 5 Conclusion and ongoing Antoine Manzanera work Visual Feature Spaces et caetera 36 / 53

37 Codebook histograms Codebook histograms Singularities and Modes in the feature space The distribution of the words (histogram) of the codebook provides a possible representation for an image or any visual category. See for example [Rubner 99] Second order statistics of the codebook, i.e. co-occurrence in the image domain of the back-projected words should also be a useful descriptor. Antoine Manzanera Visual Feature Spaces et caetera 37 / 53

38 Quantisation of the feature space Codebook histograms Singularities and Modes in the feature space Antoine Manzanera Visual Feature Spaces et caetera 38 / 53

39 Singularities of the feature space Codebook histograms Singularities and Modes in the feature space The isolated points in the feature space (i.e. the feature vectors whose average distance to their K nearest neighbours is the greatest), can be consider as a relevant way to fuse the detection of salient point and the calculation of attached descriptors. See also [Kervrann 08]. Antoine Manzanera Visual Feature Spaces et caetera 39 / 53

40 Singularities of the feature space Codebook histograms Singularities and Modes in the feature space Antoine Manzanera Visual Feature Spaces et caetera 40 / 53

41 Modes of the feature space Codebook histograms Singularities and Modes in the feature space The clusters in the feature space (whose center are the feature vectors whose average distance to their K nearest neighbours is the smallest), are also an interesting way to reduce the visual information to the most relevant features. The clusters (or modes) are calculated - see [Burman 09] - by (dynamically) dening a topology in the cloud of feature vectors, then labelling the connected component containing the current center point (feature point with smallest distance to its neighbours). The back-projection of the clusters in the image space correspond to the detection of large homogeneous coulours, long straight edges or regular texture elements. Antoine Manzanera Visual Feature Spaces et caetera 41 / 53

42 Modes of the feature space Codebook histograms Singularities and Modes in the feature space Antoine Manzanera Visual Feature Spaces et caetera 42 / 53

43 Outline Introduction 1 Introduction Objectives and problem statement Related works 2 Local jet based similarity LJ feature space Metrics and invariance Computation and data structures 3 NL-means ltering Optical ow Background subtraction 4 Codebook histograms Singularities and Modes in the feature space 5 Conclusion and ongoing Antoine Manzanera work Visual Feature Spaces et caetera 43 / 53

44 Overview of the framework Antoine Manzanera Visual Feature Spaces et caetera 44 / 53

45 Parallel NN search [Matthieu Garrigues 2010] Ecient parallel NN search is developped on GP-GPU: It is based on a volumic representation of the image NN spaces, and a recursive search of the NN that allow exponential search in the image space Antoine Manzanera Visual Feature Spaces et caetera 45 / 53

46 Parallel NN search [Matthieu Garrigues 2010] Antoine Manzanera Visual Feature Spaces et caetera 46 / 53

47 Parallel NN search [Matthieu Garrigues 2010] Antoine Manzanera Visual Feature Spaces et caetera 47 / 53

48 Bibliography Introduction [Peyré 09] G. PEYRE Manifold Models for Signals and Images Computer Vision and Image Understanding 113(2), (2009) [Lindeberg 98] T. LINDEBERG Feature detection with automatic scale selection International Journal of Computer Vision 30(2), (1998) [Koenderink 87] J.J. KOENDERINK and A.J. VAN DOORN Representation of Local Geometry in the Visual System Biological Cybernetics 55, (1987) Antoine Manzanera Visual Feature Spaces et caetera 48 / 53

49 Bibliography Introduction [Freeman 91] W.T. FREEMAN and E.H. ADELSON The design and use of Steerable Filters IEEE Trans. on Pattern Analysis and Machine Intelligence 13(9), (1991) [Crosier 10] M. CROSIER and L.D. GRIFFIN Using Basic Image Features for Texture Classication International Journal of Computer Vision 88(3), (2010) [Rubner 99] Y. RUBNER and C. TOMASI Texture-Based Image Retrieval Without Segmentation IEEE International Conference on Computer Vision, Kerkyra, Greece (1999) Antoine Manzanera Visual Feature Spaces et caetera 49 / 53

50 Bibliography Introduction [Mount 97] D.M. MOUNT and S. ARYA ANN: A Library for Approximate Nearest Neighbor Searching CGC Workshop on Computational Geometry (1997) [Burman 09] P. BURMAN and W. POLONIK Multivariate mode hunting: Data analytic tools with measures of signicance Journal of Multivariate Analysis 100(6), (2009) [Van Vliet 98] L.J. VAN VLIET, I.T. YOUNG and P.W. VERBEEK Recursive Gaussian derivative lters Proc. Int. Conf. on Pattern Recognition vol. 1, (1998) Antoine Manzanera Visual Feature Spaces et caetera 50 / 53

51 Bibliography Introduction [Buades 05] A. BUADES, B. COLL and J.M. MOREL A non-local algorithm for image denoising Proc. IEEE Conf. on Computer Vision and Pattern Recognition vol. 2, (2005) [Orchard 08] J. ORCHARD, M. EBRAHIMI and A. WONG Ecient Non-Local Means Denoising using the SVD Proc. Int. Conf. on Image Processing (2008) [Kervrann 08] C. KERVRANN and J. BOULANGER Local adaptivity to variable smoothness for exemplar-based image denoising and representation International Journal of Computer Vision 79(1), (2008) Antoine Manzanera Visual Feature Spaces et caetera 51 / 53

52 Bibliography Introduction [Barnich 09] O. BARNICH and M. VAN DROGENBROECK ViBe: a powerful random technique to estimate the background in video sequences International Conference on Acoustics, Speech, and Signal Processing (2009) [Wang 07] H. WANG and D. SUTER A consensus-based method for tracking: Modelling background scenario and foreground appearance Pattern Recognition 40(3), (2007) [Kim 04] K. KIM, T.H. CHALIDABHONGSE, D. HARDWOOD and L. DAVIS Background modeling and subtraction by codebook construction Proc. Int. Conf. on Image Processing (2004) Antoine Manzanera Visual Feature Spaces et caetera 52 / 53

53 Bibliography Introduction [Manzanera 10a] A. MANZANERA and processing through multiscale local jet features ENSTA-ParisTech Research Report (2010) [Manzanera 10b] A. MANZANERA Local Jet Based Similarity for NL-Means Filtering Proc. Int. Conf. on Pattern Recognition, Istambul, Turkey (2010) Antoine Manzanera Visual Feature Spaces et caetera 53 / 53

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