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Karlsson, Stefan
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Ranftl, A., Alonso-Fernandez, F., Karlsson, S. & Bigun, J. (2017). A Real-Time AdaBoost Cascade Face Tracker Based on Likelihood Map and Optical Flow. IET Biometrics, 6(6), 468-477
Öppna denna publikation i ny flik eller fönster >>A Real-Time AdaBoost Cascade Face Tracker Based on Likelihood Map and Optical Flow
2017 (Engelska)Ingår i: IET Biometrics, ISSN 2047-4938, E-ISSN 2047-4946, Vol. 6, nr 6, s. 468-477Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We present a novel face tracking approach where optical flow information is incorporated into a modified version of the Viola-Jones detection algorithm. In the original algorithm, detection is static, as information from previous frames is not considered; in addition, candidate windows have to pass all stages of the classification cascade, otherwise they are discarded as containing no face. In contrast, the proposed tracker preserves information about the number of classification stages passed by each window. Such information is used to build a likelihood map, which represents the probability of having a face located at that position. Tracking capabilities are provided by extrapolating the position of the likelihood map to the next frame by optical flow computation. The proposed algorithm works in real time on a standard laptop. The system is verified on the Boston Head Tracking Database, showing that the proposed algorithm outperforms the standard Viola-Jones detector in terms of detection rate and stability of the output bounding box, as well as including the capability to deal with occlusions. We also evaluate two recently published face detectors based on Convolutional Networks and Deformable Part Models, with our algorithm showing a comparable accuracy at a fraction of the computation time.

Ort, förlag, år, upplaga, sidor
Stevenage: The Institution of Engineering and Technology, 2017
Nationell ämneskategori
Signalbehandling
Identifikatorer
urn:nbn:se:hh:diva-33836 (URN)10.1049/iet-bmt.2016.0202 (DOI)000415218200012 ()
Projekt
SIDUS-AIR
Forskningsfinansiär
Vetenskapsrådet, 2012-4313KK-stiftelsen, CAISRKK-stiftelsen, SIDUS-AIR
Tillgänglig från: 2017-05-11 Skapad: 2017-05-11 Senast uppdaterad: 2017-11-29Bibliografiskt granskad
Ranftl, A., Alonso-Fernandez, F. & Karlsson, S. (2015). Face Tracking Using Optical Flow: Development of a Real-Time AdaBoost Cascade Face Tracker. In: : . Paper presented at 14th International Conference of the Biometrics Special Interest Group, BIOSIG, Darmstadt, Germany, 9-11 September, 2015.
Öppna denna publikation i ny flik eller fönster >>Face Tracking Using Optical Flow: Development of a Real-Time AdaBoost Cascade Face Tracker
2015 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

In this paper a novel face tracking approach is presented where optical flow information is incorporated into the Viola-Jones face detection algorithm. In the original algorithm from Viola and Jones face detection is static as information from previous frames is not considered. In contrast to the Viola-Jones face detector and also to other known dynamic enhancements, the proposed facetracker preserves information about near-positives. The algorithm builds a likelihood map from the intermediate results of the Viola-Jones algorithm which is extrapolated using optical flow. The objects get extracted from the likelihood map using image segmentation techniques. All steps can be computed very efficiently in real-time. The tracker is verified on the Boston Head Tracking Database showing that the proposed algorithm outperforms the standard Viola-Jones face detector.

Nyckelord
Face Tracking, Likelihood Map, Optical Flow, AdaBoost Cascade Classifier
Nationell ämneskategori
Signalbehandling
Identifikatorer
urn:nbn:se:hh:diva-29090 (URN)10.1109/BIOSIG.2015.7314604 (DOI)000380513800012 ()2-s2.0-84959557956 (Scopus ID)
Konferens
14th International Conference of the Biometrics Special Interest Group, BIOSIG, Darmstadt, Germany, 9-11 September, 2015
Forskningsfinansiär
Vetenskapsrådet
Anmärkning

This paper follows a master thesis which was written within the double degree master program in Embedded and Intelligent Systems of Salzburg University of Applied Sciences, Austria and Halmstad University, Sweden.

Tillgänglig från: 2015-08-06 Skapad: 2015-08-06 Senast uppdaterad: 2018-03-22Bibliografiskt granskad
Cooney, M. & Karlsson, S. M. (2015). Impressions of Size-Changing in a Companion Robot. In: Hugo Plácido da Silva, Pierre Chauvet, Andreas Holzinger, Stephen Fairclough & Dennis Majoe (Ed.), PhyCS 2015 – 2nd International Conference on Physiological Computing Systems, Proceedings: . Paper presented at 2nd International Conference on Physiological Computing Systems, PhyCS 2015, ESEO, Angers, Loire Valley, France, 11-13 February, 2015 (pp. 118-123). SciTePress
Öppna denna publikation i ny flik eller fönster >>Impressions of Size-Changing in a Companion Robot
2015 (Engelska)Ingår i: PhyCS 2015 – 2nd International Conference on Physiological Computing Systems, Proceedings / [ed] Hugo Plácido da Silva, Pierre Chauvet, Andreas Holzinger, Stephen Fairclough & Dennis Majoe, SciTePress, 2015, s. 118-123Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

Physiological data such as head movements can be used to intuitively control a companion robot to perform useful tasks. We believe that some tasks such as reaching for high objects or getting out of a person’s way could be accomplished via size changes, but such motions should not seem threatening or bothersome. To gain insight into how size changes are perceived, the Think Aloud Method was used to gather typical impressions of a new robotic prototype which can expand in height or width based on a user’s head movements. The results indicate promise for such systems, also highlighting some potential pitfalls.

Ort, förlag, år, upplaga, sidor
SciTePress, 2015
Nyckelord
Adaptive Interfaces, Physiology-driven Robotics, Human-Robot Interaction, Size-Changing
Nationell ämneskategori
Datorseende och robotik (autonoma system)
Identifikatorer
urn:nbn:se:hh:diva-29320 (URN)10.5220/0005328801180123 (DOI)2-s2.0-84938811552 (Scopus ID)978-989-758-085-7 (ISBN)
Konferens
2nd International Conference on Physiological Computing Systems, PhyCS 2015, ESEO, Angers, Loire Valley, France, 11-13 February, 2015
Forskningsfinansiär
KK-stiftelsen
Tillgänglig från: 2015-08-31 Skapad: 2015-08-31 Senast uppdaterad: 2018-03-22Bibliografiskt granskad
Karlsson, S. (2013). Real-Time optical flow.
Öppna denna publikation i ny flik eller fönster >>Real-Time optical flow
2013 (Engelska)Övrigt (Övrigt vetenskapligt)
Nationell ämneskategori
Datorseende och robotik (autonoma system)
Identifikatorer
urn:nbn:se:hh:diva-26580 (URN)
Forskningsfinansiär
Vetenskapsrådet
Tillgänglig från: 2014-09-24 Skapad: 2014-09-24 Senast uppdaterad: 2018-03-22Bibliografiskt granskad
Karlsson, S. M. & Bigun, J. (2012). Lip-motion events analysis and lip segmentation using optical flow. In: : . Paper presented at 2012 IEEE Computer Society Conference on Computer Vision and Pattern Recognition Workshops, CVPRW 2012, 16-21 June, 2012, Rhode Island, USA (pp. 138-145). Piscataway, N.J.: IEEE Press, Article ID 6239228.
Öppna denna publikation i ny flik eller fönster >>Lip-motion events analysis and lip segmentation using optical flow
2012 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

We propose an algorithm for detecting the mouth events of opening and closing. Our method is translation and ro- tation invariant, works at very fast speeds, and does not re- quire segmented lips. The approach is based on a recently developed optical flow algorithm that handles the motion of linear structure in a stable and consistent way.Furthermore, we provide a semi-automatic tool for gen- erating groundtruth segmentation of video data, also based on the optical flow algorithm used for tracking keypoints at faster than 200 frames/second. We provide groundtruth for 50 sessions of speech of the XM2VTS database [16] avail- able for download, and the means to segment further ses- sions at a relatively small amount of user interaction.We use the generated groundtruth to test the proposed al- gorithm for detecting events, and show it to yield promising result. The semi-automatic tool will be a useful resource for researchers in need of groundtruth segmentation from video for the XM2VTS database and others.

Ort, förlag, år, upplaga, sidor
Piscataway, N.J.: IEEE Press, 2012
Serie
IEEE Computer Society Conference on Computer Vision and Pattern Recognition workshops. Proceedings, ISSN 2160-7508
Nyckelord
Keypoints, Linear structures, Lip segmentation, Optical flow algorithm, Rotation invariant, Semi-automatic tools, User interaction, Video data
Nationell ämneskategori
Signalbehandling
Identifikatorer
urn:nbn:se:hh:diva-19645 (URN)10.1109/CVPRW.2012.6239228 (DOI)2-s2.0-84864974582 (Scopus ID)978-1-4673-1612-5 (ISBN)
Konferens
2012 IEEE Computer Society Conference on Computer Vision and Pattern Recognition Workshops, CVPRW 2012, 16-21 June, 2012, Rhode Island, USA
Forskningsfinansiär
Vetenskapsrådet
Anmärkning

©2012 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Tillgänglig från: 2012-10-04 Skapad: 2012-09-17 Senast uppdaterad: 2018-03-22Bibliografiskt granskad
Bigun, J. & Karlsson, S. M. (2011). Histogram of directions by the structure tensor. In: Proceedings of the 4th International Symposium on Applied Sciences in Biomedical and Communication Technologies. Paper presented at The 4th International Symposium on Applied Sciences in Biomedical and Communication Technologies, ISABEL’11, October 26-29, Barcelona. New York, NY: Association for Computing Machinery (ACM)
Öppna denna publikation i ny flik eller fönster >>Histogram of directions by the structure tensor
2011 (Engelska)Ingår i: Proceedings of the 4th International Symposium on Applied Sciences in Biomedical and Communication Technologies, New York, NY: Association for Computing Machinery (ACM), 2011Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

Many low-level features, as well as varying methods of extraction and interpretation rely on directionality analysis (for example the Hough transform, Gabor filters, SIFT descriptors and the structure tensor). The theory of the gradient based structure tensor (a.k.a. the second moment matrix) is a very well suited theoretical platform in which to analyze and explain the similarities and connections (indeed often equivalence) of supposedly different methods and features that deal with image directionality. Of special interest to this study is the SIFT descriptors (histogram of oriented gradients, HOGs). Our analysis of interrelationships of prominent directionality analysis tools offers the possibility of computation of HOGs without binning, in an algorithm of comparative time complexity.

Ort, förlag, år, upplaga, sidor
New York, NY: Association for Computing Machinery (ACM), 2011
Nyckelord
complex weighting, histogram of oriented gradients, structure tensor
Nationell ämneskategori
Signalbehandling
Identifikatorer
urn:nbn:se:hh:diva-19888 (URN)10.1145/2093698.2093794 (DOI)2-s2.0-84856697701 (Scopus ID)978-1-4503-0913-4 (ISBN)
Konferens
The 4th International Symposium on Applied Sciences in Biomedical and Communication Technologies, ISABEL’11, October 26-29, Barcelona
Tillgänglig från: 2012-12-19 Skapad: 2012-10-29 Senast uppdaterad: 2018-03-22Bibliografiskt granskad
Karlsson, S. & Bigun, J. (2011). Synthesis and detection of log-spiral codes. Paper presented at SSBA Symposium i bildanalys, 17-18 mars 2011, Linköping.
Öppna denna publikation i ny flik eller fönster >>Synthesis and detection of log-spiral codes
2011 (Engelska)Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
Abstract [en]

Simultaneous positioning and identifying objects accurately and reliably is a fundamental problem in computer vision. General solutions to this problem is still challenging. For certain applications to achieve high accuracy and reliability in both tasks can be achieved if the objects can be labeled, e.g. multiple simultaneous robot tracking and navigation. We suggest a labeling technique using spiral patterns for optimal position estimation and identity recognition using the generalized structure tensor and tresholds. The technique adapts the synthesis of the labels to the frequency characteristics of the detection method. The approach has been implemented and tested by an over-head camera to track and control 8 robots in real-time.

Nyckelord
computer vision, robots, real-time
Nationell ämneskategori
Datorseende och robotik (autonoma system)
Identifikatorer
urn:nbn:se:hh:diva-16123 (URN)
Konferens
SSBA Symposium i bildanalys, 17-18 mars 2011, Linköping
Tillgänglig från: 2011-09-06 Skapad: 2011-09-05 Senast uppdaterad: 2018-03-22Bibliografiskt granskad
Karlsson, S. M., Pont, S. C., Koenderink, J. J. & Zisserman, A. (2010). Illuminance Flow Estimation by Regression. International Journal of Computer Vision, 90(3), 304-312
Öppna denna publikation i ny flik eller fönster >>Illuminance Flow Estimation by Regression
2010 (Engelska)Ingår i: International Journal of Computer Vision, ISSN 0920-5691, E-ISSN 1573-1405, Vol. 90, nr 3, s. 304-312Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We investigate the estimation of illuminance flow using Histograms of Oriented Gradient features (HOGs). In a regression setting, we found for both ridge regression and support vector machines, that the optimal solution shows close resemblance to the gradient based structure tensor (also known as the second moment matrix). Theoretical results are presented showing in detail how the structure tensor and the HOGs are connected. This relation will benefit computer vision tasks such as affine invariant texture/object matching using HOGs. Several properties of HOGs are presented, among others, how many bins are required for a directionality measure, and how to estimate HOGs through spatial averaging that requires no binning.

Ort, förlag, år, upplaga, sidor
Amsterdam: Elsevier, 2010
Nyckelord
Illuminance flow, Surface 3D texture, Histogram of oriented gradients, Illuminant estimation
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:hh:diva-18894 (URN)10.1007/s11263-010-0353-7 (DOI)000282782700003 ()2-s2.0-78149283686 (Scopus ID)
Tillgänglig från: 2012-06-27 Skapad: 2012-06-25 Senast uppdaterad: 2018-03-22Bibliografiskt granskad
Karlsson, S. & Bigun, J. (2007). Multiscale complex moments of the local power spectrum. Journal of the Optical Society of America A, 24(3), 618-625
Öppna denna publikation i ny flik eller fönster >>Multiscale complex moments of the local power spectrum
2007 (Engelska)Ingår i: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 24, nr 3, s. 618-625Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Complex moments of the local power spectrum (CMP) are investigated in a multiscale context. The multiscale CMPs are shown to approximate well the 1D angular Fourier transform of the band in question. This observation is used to derive further properties of the power spectrum in terms of texture orientations or n-folded symmetry patterns. A method is presented to approximate the power spectrum using only separable filtering in the spatial domain. Interesting implications to the Gabor decomposition are shown. The number of orientations in the filter bank is related to the order of n-folded symmetry detectable. Furthermore, the multiscale CMPs can be estimated incrementally in the spatial domain, which is both fast and reliable. Experiments on power spectrum estimation, orientation estimation, and texture segmentation are presented.

Ort, förlag, år, upplaga, sidor
Washington: Optical Society of America, 2007
Nyckelord
Image analysis, Pattern recognition, Rotation-invariant pattern recognition
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:hh:diva-2069 (URN)10.1364/JOSAA.24.000618 (DOI)000244407300006 ()17301851 (PubMedID)2-s2.0-34047124800 (Scopus ID)2082/2464 (Lokalt ID)2082/2464 (Arkivnummer)2082/2464 (OAI)
Tillgänglig från: 2008-10-20 Skapad: 2008-10-20 Senast uppdaterad: 2018-03-23Bibliografiskt granskad
Hoang, H., Buttazzo, G., Jonsson, M. & Karlsson, S. (2006). Computing the minimum EDF feasible deadline in periodic systems. In: 12th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, 2006. Proceedings. Paper presented at 12th IEEE Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA 2006), 16-18 August 2006, Sydney, Australia (pp. 125-134). Los Alamitos, Calif.: IEEE Press
Öppna denna publikation i ny flik eller fönster >>Computing the minimum EDF feasible deadline in periodic systems
2006 (Engelska)Ingår i: 12th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, 2006. Proceedings, Los Alamitos, Calif.: IEEE Press, 2006, s. 125-134Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

In most real-time applications, deadlines are artifices that need to be enforced to meet different performance requirements. For example, in periodic task sets, jitter requirements can be met by assigning suitable relative deadlines and guaranteeing the feasibility of the schedule. This paper presents a method (called minD) for calculating the minimum EDF-feasible deadline of a real-time task. More precisely, given a set of periodic tasks with hard real-time requirements, which is feasible under EDF, the proposed algorithm allows computing the shortest deadline that can be assigned to an arbitrary task in the set, or to a new incoming task (periodic or aperiodic), still preserving the EDF feasibility of the new task set. The algorithm has a pseudo polynomial complexity and handles arbitrary relative deadlines, which can be less than, equal to, or greater than periods.

Ort, förlag, år, upplaga, sidor
Los Alamitos, Calif.: IEEE Press, 2006
Serie
IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, ISSN 1533-2306 ; 2006
Nyckelord
Real-time, Scheduling
Nationell ämneskategori
Data- och informationsvetenskap
Identifikatorer
urn:nbn:se:hh:diva-372 (URN)10.1109/RTCSA.2006.22 (DOI)000240851900019 ()2-s2.0-34547275304 (Scopus ID)2082/696 (Lokalt ID)0-7695-2676-4 (ISBN)2082/696 (Arkivnummer)2082/696 (OAI)
Konferens
12th IEEE Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA 2006), 16-18 August 2006, Sydney, Australia
Anmärkning

©2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Tillgänglig från: 2007-01-05 Skapad: 2007-01-05 Senast uppdaterad: 2018-03-23Bibliografiskt granskad
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