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Professor Maria Petrou’s Professional Career
Pattern Recognition Letters 48 (2014) 100–102
Contents lists available at ScienceDirect
Pattern Recognition Letters journal homepage: www.elsevier.com/locate/patrec
Professor Maria Petrou’s Professional Career Professor Maria Petrou at Surrey University
Maria Petrou was born in Greece and educated at the University of Thessaloniki, where she graduated in Physics in 1975. For her outstanding performance she was awarded a studentship, giving her an opportunity to study abroad. The award brought her to the United Kingdom to study Mathematics Part III at Churchill College, Cambridge, which was followed by PhD studies in Astronomy. She gained a PhD degree from the University of Cambridge in 1981. After her PhD she returned to Greece to take up a post of Lecturer at the Department of Astronomy, University of Athens, but her longing for a fulfilling research career brought her back to the United Kingdom to take up Research Fellowship at St Hildas College, Department of Theoretical Physics, Oxford in 1983. She married a fellow PhD researcher with whom she had one son. With two astronomers in the family, Maria decided, in 1986, to switch her field of research from science to engineering and accepted a postdoctoral research position in image processing, first at Reading University, and subsequently at the Rutherford Appleton Laboratory. She joined the University of Surrey as Lecturer in Image Analysis in 1988. She played a key role in the development of the Centre for Vision, Speech and Signal Processing, and deserves all the credit for its growth in the areas of Remote Sensing and Medical Imaging. In recognition of her outstanding research achievements, she was rapidly promoted to increasingly senior academic positions, http://dx.doi.org/10.1016/j.patrec.2014.06.007
culminating in Professor of Image Analysis in 1998. She enjoyed teaching as much as research. Her Wiley book on Image Processing: The fundamentals, published in 1999, was very popular, and was reprinted several times. In the scientific community, Maria is famous for her outstanding contributions to image analysis and its application, especially to remote sensing. She proposed a novel image representation for image matching known as trace transform. She developed advanced techniques for edge and line detection, for texture analysis and for image segmentation. She was a specialist in colour image processing and developed an award winning stereo-based 3D mensuration system for the stone industry. The number of citations to her work runs into thousands. For her outstanding contributions to Engineering, she obtained her ScD degree from Cambridge University in 2009. During her illustrious academic career she worked on challenging projects, such as the EPSRC Basic Research project Reverse engineering the human vision system. Being a working mother, she had a bee in her bonnet about domestic chores, and eventually succeeded in getting funding from the Cognitive Systems and Robotics Programme of the European Commission to develop an ironing robot. Ironing is a particularly challenging task from the Computer Vision point of view because cloths have complex shapes and difficult nonrigid surfaces for vision systems to understand. She also contributed enthusiastically and tirelessly to the activities of professional societies in various capacities. She served as Chairman of the British Machine Vision Association during 1999–2002. She was on the editorial board of several scientific journals, including IEEE Transactions on Image Processing (1994–98). She was heavily involved in the organisation of many scientific conferences. In the IET, she served as an Honorary Editor of IET Electronics Letters, as an elected member of the Council of IET (2004–2007), as a Trustee of IET (2007–2009), and as a member of the Publications Board of IET (2006–2008). In the International Association for Pattern Recognition (IAPR) she held the post of Chairman of IAPR Technical Committee TC7: Remote Sensing (1998–2002), and that of IAPR Treasurer during 2002–2006. In the period 1994–1998 she served as IAPR Newsletter Editor. She loved that job which gave her an opportunity to share her sense of humour with the IAPR community. She also enjoyed drawing cartoons, which lightened many issues of the IAPR Newsletter. The external recognition of her academic achievements, and contributions to professional activities includes many accolades. She was elected Fellow of IEE in 1998, and Fellow of IAPR in 2000. In 2004 she was elected Fellow of the Royal Academy of Engineering and in 2006 she was awarded the title of Distinguished Fellow of BMVA. Professor Petrou left the University of Surrey in 2005 to lead the Communications and Signal Processing Group at the Department of
Personal Report / Pattern Recognition Letters 48 (2014) 100–102
Electrical Engineering, Imperial College London. In 2009 she became the Director of the Informatics and Telematics Institute in the Centre for Research and Development, Hellas, in Thessaloniki, Greece. Marias outstanding achievements were the product of her scientific excellence and hard work, as well as her enormous courage and determination. Marias energy, devotion, professionalism, empathy and friendship marked the lives of many of us, and of her students, in an unforgettable way. It was a pleasure to work with her and to benefit from her wisdom and generosity. It was privilege to know her. She will be sadly missed by her friends and colleagues in the international pattern recognition and image analysis community. Josef Kittler University of Surrey, United Kingdom
Professor Maria Petrou as Director of CERTH-ITI Professor Petrou joined the Information Technologies Institute, Centre for Research and Technology Hellas (CERTH-ITI), ThermiThessaloniki, Greece, http://www.iti.gr, as Director in October 2008, after a competitive international open call and evaluation. As the Director, she had a major responsibility for the management and operations at CERTH-ITI. She was highly interested in integrating educational and research activities and she followed an open and extrovert approach believing that research results should be widely disseminated and directly help our society. Having led a distinguished career highlighted by her assignment to prestigious positions in many universities in England, when she arrived in Greece as director of CERTH-ITI, Maria attempted to establish a direct scientific channel between two of England’s top ranked universities (i.e. Imperial College London and Surrey University) and Greek postgraduate students through the so-called ‘‘split’’ PhD programs. In the 3 years of serving in the director’s position, Prof Maria Petrou managed to initiate nine such programs, two of which were officially under her direct supervision, covering a wide variety of her fields of expertise such as signal/image processing, computer vision, pattern recognition also expanding to new areas: visual analytics, event and social media analysis. In this concept, one of the most interesting published works, that has been completed by researchers of the CERTH-ITI under the supervision of Prof Maria Petrou, presented a novel probabilistic framework that succeeded to enhance the accuracy of existing biometric systems by modelling the systematic error induced in the measurement of soft biometric traits of the user [1]. One of her main objectives once she joined CERTH-ITI was to expand the research activities of the Institute to new, promising research directions increasing its potential, impact and sustainability. Maria recognized the latest trends in global monitoring for environment and security and the advancing importance that spaceborne active and passive sensing and analysis techniques are gaining in the decision making and policy implementation at all levels and sectors of the public administration and private innovation initiatives. Remote Sensing coupled with geospatial data analysis upgrades the quality of services and products to the citizen, and promotes the entrepreneurship capabilities and competitiveness of those joining and specializing in the domain. Maria decided to enhance the capacity of her team towards specialization in Remote Sensing applications and downstreaming related services (from space to place), joining networks of high prestige in Europe, attracting topic-related funds from the European Commission, hiring a new senior researcher, and supervising PhD theses in remote sensing and
101
environment related applications. With these results as a concrete basis, currently the target for the Institute is the development of a core team of excellence and the respective infrastructure in Remote Sensing, aiming to become a respectable member and equally valued partner of the remote sensing science society in Europe and the globe, while at the same time remaining close and supportive to private sector initiatives. Another priority set by Prof Petrou was the further strengthening of the interaction between the Institute and the local industry and community. In support of this goal, Prof Petrou conceived the idea of setting up a dedicated demo room at the ITI premises. All related pieces of equipment (e.g. a camera for supporting user interaction during relevant demonstrations) were arranged in the room in such a way that several demonstrations could be held in parallel. In the first two years following the establishment of the demo room, several hundred members of the local community, including many high-school students from various cities of Northern Greece and students of the local Universities, as well as individuals from different local businesses, visited this demonstration facility and were introduced to the work carried out in the Institute and its benefits and further opportunities for the community. Additionally, she established and managed a series of regular seminars by CERTH-ITI researchers and invited distinguished speakers open to the general public, which highly contributed to the educational activities of the Institute. Maria has been involved in many activities and undertook several roles in her career but above all she has always been a researcher. There was no exception when she joined CERTH-ITI as a Director. She was active in ongoing and new research areas, establishing a team in CERTH-ITI and attracting funding through National and EU funded projects. For more than 15 years, Maria Petrou envisioned the ‘‘ironing robot’’ not only wishing to relief people, and women in particular, from this boring everyday chore but also as a grand challenge for robotic perception and manipulation skills. Recently, funding for this research was secured through a collaborative European research project [2]. In this project, Maria’s team works on two of her favorite research topics: photometric stereo sensing and high level perception and reasoning. A new miniature photometric stereo sensor is being designed for very close range imaging of garment surfaces, with the ultimate goal of inferring the material and its properties. Although the task builds on her past research on photometric stereo [3], the small distance between the sensor and the surface introduces new challenges in modelling the light sources and surface reflection properties. First results of this effort are quite encouraging [4]. Maria and her team recently proposed a hierarchical bottom-up and top-down learning and inference framework called the ‘‘Tower of knowledge’’ [5]. This was applied for parsing man-made scenes such as building facades [6]. In the current project her students continue this work by applying it to garment understanding, dealing with challenges such as occluded parts, deformations and articulations. The incorporation of action in this framework is also one of the novel directions in this work. Based on her strong background in high level perception and reasoning, Maria was very much interested in brain cognitive processes research. She wished to extend her state of the art work on 2D Vector Field Tomography (VFT) [7], to 3D as a tool to understand the cognitive processes in the brain, and in particular cognitive vision. For these highly innovative and multidisciplinary ideas, she was awarded the project entitled ‘‘CPB: Cognitive Signal Processing Lab’’ after a very competitive ‘‘Research Excellence’’ national call. CERTH-ITI benefits with the establishment of the new Lab (the CBP), which will be reinforced with a state of the art computer-based equipment for EEG supporting up to 256-channel measurements. As a result, a new activity starts in CERTH-ITI on brain cognitive processes research, creating an interdisciplinary team of researchers
102
Personal Report / Pattern Recognition Letters 48 (2014) 100–102
with complementary skills that will utilize this equipment, in conjunction with VFT, but also with other state of the art techniques that will be explored, like connectivity analysis. This enhances the links of the Institute with the Electrical Engineering and Medical Schools of the Aristotle University of Thessaloniki, by exploiting the options of using the methodologies developed by the team for direct communication with patients unable to verbalise their state of mind. The project will also contribute to brain-computer interaction research, with the ultimate aim of being used for communicating with patients unable to communicate otherwise. Continuing her long research on remote sensing related issues, in 2010 Maria Petrou participated in the EU funded research project in biodiversity monitoring BIO_SOS. The main objective of the project is the development of a knowledge-based pre-operational ecological modelling system suitable for effective and timely multiannual monitoring of NATURA 2000 sites and their surrounding areas, particularly exposed to different and combined type of pressures. Once land cover classes and habitats are described through a semantic language, any site can theoretically be mapped and subsequently monitored over time. Maria’s engagement concerned, among others, state of the art texture analysis of the remote sensing images for the determination of surrogates of biophysical parameters [8], the conceptual design of a framework to handle missing information cases and uncertainty in data acquisition and expert rules. She was also responsible for the scientific co-guidance of the consortium and the quality assurance of the deliverables of the project. In conclusion, Professor Maria Petrou contributed to active and emerging research areas and was a dedicated and extrovert Director promoting team spirit, openness and technology transfer. Her vision resides as her legacy in the on going work of our colleagues, in the examples she set, and the remaining infrastructure. She will always
be remembered and appreciated by us and the numerous researchers and minds she influenced with her work and collaboration. I. Kompatsiaris S. Malasiotis P. Daras N. Grammalidis V. Mezaris I. Manakos D. Tzovaras CERTH-ITI, Thessaloniki, Greece
References [1] A. Drosou, K. Moustakas, D. Tzovaras, M. Petrou, Systematic error analysis for the enhancement of biometric systems using soft biometrics, IEEE Signal Process. Lett. 19 (12) (2012) 833–836. [2] CloPeMa: Cloth Perception and Manipulation, European Union 7th Framework Programme, 2012–2015. [3] S. Barsky, M. Petrou, The 4-source photometric stereo technique for threedimensional surfaces in the presence of highlights and shadows, IEEE Trans. Pattern Anal. Machine Intell. 25 (10) (2003) 1239–1252. [4] D. Gorpas, C. Kampouris, S. Malassiotis, Miniature photometric stereo system for textile surface structure reconstruction, in: Proc. SPIE 8791, Videometrics, Range Imaging, and Applications XII; and Automated Visual Inspection, 2013. [5] M. Petrou, Learning in computer vision: some thoughts, in: L. Rueda, D. Mery, J. Kittler (Eds.), Proceedings of the 12th Iberoamerican Congress on Pattern Recognition, CIAPR, LNCS, vol. 4756, Springer Verlag, Berlin, 2007, pp. 1–12. [6] M. Xu, M. Petrou, Learning logic rules for the Tower of Knowledge using Markov logic networks, Int. J. Pattern Recognit. Artif. Intell. 25 (2011) 889–908. [7] M. Petrou, A. Giannakidis, Full tomographic reconstruction of 2-d vector fields using discrete integral data, Comput. J. 54 (2011) 1491–1504. [8] Z. Petrou, C. Tarantino, M. Adamo, P. Blonda, M. Petrou, Estimation of vegetation height through satellite image texture analysis, in: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol. XXXIX-B8, XXII ISPRS Congress, Melbourne, 2012, pp. 321–326.
Contents lists available at ScienceDirect
Pattern Recognition Letters journal homepage: www.elsevier.com/locate/patrec
Professor Maria Petrou’s Professional Career Professor Maria Petrou at Surrey University
Maria Petrou was born in Greece and educated at the University of Thessaloniki, where she graduated in Physics in 1975. For her outstanding performance she was awarded a studentship, giving her an opportunity to study abroad. The award brought her to the United Kingdom to study Mathematics Part III at Churchill College, Cambridge, which was followed by PhD studies in Astronomy. She gained a PhD degree from the University of Cambridge in 1981. After her PhD she returned to Greece to take up a post of Lecturer at the Department of Astronomy, University of Athens, but her longing for a fulfilling research career brought her back to the United Kingdom to take up Research Fellowship at St Hildas College, Department of Theoretical Physics, Oxford in 1983. She married a fellow PhD researcher with whom she had one son. With two astronomers in the family, Maria decided, in 1986, to switch her field of research from science to engineering and accepted a postdoctoral research position in image processing, first at Reading University, and subsequently at the Rutherford Appleton Laboratory. She joined the University of Surrey as Lecturer in Image Analysis in 1988. She played a key role in the development of the Centre for Vision, Speech and Signal Processing, and deserves all the credit for its growth in the areas of Remote Sensing and Medical Imaging. In recognition of her outstanding research achievements, she was rapidly promoted to increasingly senior academic positions, http://dx.doi.org/10.1016/j.patrec.2014.06.007
culminating in Professor of Image Analysis in 1998. She enjoyed teaching as much as research. Her Wiley book on Image Processing: The fundamentals, published in 1999, was very popular, and was reprinted several times. In the scientific community, Maria is famous for her outstanding contributions to image analysis and its application, especially to remote sensing. She proposed a novel image representation for image matching known as trace transform. She developed advanced techniques for edge and line detection, for texture analysis and for image segmentation. She was a specialist in colour image processing and developed an award winning stereo-based 3D mensuration system for the stone industry. The number of citations to her work runs into thousands. For her outstanding contributions to Engineering, she obtained her ScD degree from Cambridge University in 2009. During her illustrious academic career she worked on challenging projects, such as the EPSRC Basic Research project Reverse engineering the human vision system. Being a working mother, she had a bee in her bonnet about domestic chores, and eventually succeeded in getting funding from the Cognitive Systems and Robotics Programme of the European Commission to develop an ironing robot. Ironing is a particularly challenging task from the Computer Vision point of view because cloths have complex shapes and difficult nonrigid surfaces for vision systems to understand. She also contributed enthusiastically and tirelessly to the activities of professional societies in various capacities. She served as Chairman of the British Machine Vision Association during 1999–2002. She was on the editorial board of several scientific journals, including IEEE Transactions on Image Processing (1994–98). She was heavily involved in the organisation of many scientific conferences. In the IET, she served as an Honorary Editor of IET Electronics Letters, as an elected member of the Council of IET (2004–2007), as a Trustee of IET (2007–2009), and as a member of the Publications Board of IET (2006–2008). In the International Association for Pattern Recognition (IAPR) she held the post of Chairman of IAPR Technical Committee TC7: Remote Sensing (1998–2002), and that of IAPR Treasurer during 2002–2006. In the period 1994–1998 she served as IAPR Newsletter Editor. She loved that job which gave her an opportunity to share her sense of humour with the IAPR community. She also enjoyed drawing cartoons, which lightened many issues of the IAPR Newsletter. The external recognition of her academic achievements, and contributions to professional activities includes many accolades. She was elected Fellow of IEE in 1998, and Fellow of IAPR in 2000. In 2004 she was elected Fellow of the Royal Academy of Engineering and in 2006 she was awarded the title of Distinguished Fellow of BMVA. Professor Petrou left the University of Surrey in 2005 to lead the Communications and Signal Processing Group at the Department of
Personal Report / Pattern Recognition Letters 48 (2014) 100–102
Electrical Engineering, Imperial College London. In 2009 she became the Director of the Informatics and Telematics Institute in the Centre for Research and Development, Hellas, in Thessaloniki, Greece. Marias outstanding achievements were the product of her scientific excellence and hard work, as well as her enormous courage and determination. Marias energy, devotion, professionalism, empathy and friendship marked the lives of many of us, and of her students, in an unforgettable way. It was a pleasure to work with her and to benefit from her wisdom and generosity. It was privilege to know her. She will be sadly missed by her friends and colleagues in the international pattern recognition and image analysis community. Josef Kittler University of Surrey, United Kingdom
Professor Maria Petrou as Director of CERTH-ITI Professor Petrou joined the Information Technologies Institute, Centre for Research and Technology Hellas (CERTH-ITI), ThermiThessaloniki, Greece, http://www.iti.gr, as Director in October 2008, after a competitive international open call and evaluation. As the Director, she had a major responsibility for the management and operations at CERTH-ITI. She was highly interested in integrating educational and research activities and she followed an open and extrovert approach believing that research results should be widely disseminated and directly help our society. Having led a distinguished career highlighted by her assignment to prestigious positions in many universities in England, when she arrived in Greece as director of CERTH-ITI, Maria attempted to establish a direct scientific channel between two of England’s top ranked universities (i.e. Imperial College London and Surrey University) and Greek postgraduate students through the so-called ‘‘split’’ PhD programs. In the 3 years of serving in the director’s position, Prof Maria Petrou managed to initiate nine such programs, two of which were officially under her direct supervision, covering a wide variety of her fields of expertise such as signal/image processing, computer vision, pattern recognition also expanding to new areas: visual analytics, event and social media analysis. In this concept, one of the most interesting published works, that has been completed by researchers of the CERTH-ITI under the supervision of Prof Maria Petrou, presented a novel probabilistic framework that succeeded to enhance the accuracy of existing biometric systems by modelling the systematic error induced in the measurement of soft biometric traits of the user [1]. One of her main objectives once she joined CERTH-ITI was to expand the research activities of the Institute to new, promising research directions increasing its potential, impact and sustainability. Maria recognized the latest trends in global monitoring for environment and security and the advancing importance that spaceborne active and passive sensing and analysis techniques are gaining in the decision making and policy implementation at all levels and sectors of the public administration and private innovation initiatives. Remote Sensing coupled with geospatial data analysis upgrades the quality of services and products to the citizen, and promotes the entrepreneurship capabilities and competitiveness of those joining and specializing in the domain. Maria decided to enhance the capacity of her team towards specialization in Remote Sensing applications and downstreaming related services (from space to place), joining networks of high prestige in Europe, attracting topic-related funds from the European Commission, hiring a new senior researcher, and supervising PhD theses in remote sensing and
101
environment related applications. With these results as a concrete basis, currently the target for the Institute is the development of a core team of excellence and the respective infrastructure in Remote Sensing, aiming to become a respectable member and equally valued partner of the remote sensing science society in Europe and the globe, while at the same time remaining close and supportive to private sector initiatives. Another priority set by Prof Petrou was the further strengthening of the interaction between the Institute and the local industry and community. In support of this goal, Prof Petrou conceived the idea of setting up a dedicated demo room at the ITI premises. All related pieces of equipment (e.g. a camera for supporting user interaction during relevant demonstrations) were arranged in the room in such a way that several demonstrations could be held in parallel. In the first two years following the establishment of the demo room, several hundred members of the local community, including many high-school students from various cities of Northern Greece and students of the local Universities, as well as individuals from different local businesses, visited this demonstration facility and were introduced to the work carried out in the Institute and its benefits and further opportunities for the community. Additionally, she established and managed a series of regular seminars by CERTH-ITI researchers and invited distinguished speakers open to the general public, which highly contributed to the educational activities of the Institute. Maria has been involved in many activities and undertook several roles in her career but above all she has always been a researcher. There was no exception when she joined CERTH-ITI as a Director. She was active in ongoing and new research areas, establishing a team in CERTH-ITI and attracting funding through National and EU funded projects. For more than 15 years, Maria Petrou envisioned the ‘‘ironing robot’’ not only wishing to relief people, and women in particular, from this boring everyday chore but also as a grand challenge for robotic perception and manipulation skills. Recently, funding for this research was secured through a collaborative European research project [2]. In this project, Maria’s team works on two of her favorite research topics: photometric stereo sensing and high level perception and reasoning. A new miniature photometric stereo sensor is being designed for very close range imaging of garment surfaces, with the ultimate goal of inferring the material and its properties. Although the task builds on her past research on photometric stereo [3], the small distance between the sensor and the surface introduces new challenges in modelling the light sources and surface reflection properties. First results of this effort are quite encouraging [4]. Maria and her team recently proposed a hierarchical bottom-up and top-down learning and inference framework called the ‘‘Tower of knowledge’’ [5]. This was applied for parsing man-made scenes such as building facades [6]. In the current project her students continue this work by applying it to garment understanding, dealing with challenges such as occluded parts, deformations and articulations. The incorporation of action in this framework is also one of the novel directions in this work. Based on her strong background in high level perception and reasoning, Maria was very much interested in brain cognitive processes research. She wished to extend her state of the art work on 2D Vector Field Tomography (VFT) [7], to 3D as a tool to understand the cognitive processes in the brain, and in particular cognitive vision. For these highly innovative and multidisciplinary ideas, she was awarded the project entitled ‘‘CPB: Cognitive Signal Processing Lab’’ after a very competitive ‘‘Research Excellence’’ national call. CERTH-ITI benefits with the establishment of the new Lab (the CBP), which will be reinforced with a state of the art computer-based equipment for EEG supporting up to 256-channel measurements. As a result, a new activity starts in CERTH-ITI on brain cognitive processes research, creating an interdisciplinary team of researchers
102
Personal Report / Pattern Recognition Letters 48 (2014) 100–102
with complementary skills that will utilize this equipment, in conjunction with VFT, but also with other state of the art techniques that will be explored, like connectivity analysis. This enhances the links of the Institute with the Electrical Engineering and Medical Schools of the Aristotle University of Thessaloniki, by exploiting the options of using the methodologies developed by the team for direct communication with patients unable to verbalise their state of mind. The project will also contribute to brain-computer interaction research, with the ultimate aim of being used for communicating with patients unable to communicate otherwise. Continuing her long research on remote sensing related issues, in 2010 Maria Petrou participated in the EU funded research project in biodiversity monitoring BIO_SOS. The main objective of the project is the development of a knowledge-based pre-operational ecological modelling system suitable for effective and timely multiannual monitoring of NATURA 2000 sites and their surrounding areas, particularly exposed to different and combined type of pressures. Once land cover classes and habitats are described through a semantic language, any site can theoretically be mapped and subsequently monitored over time. Maria’s engagement concerned, among others, state of the art texture analysis of the remote sensing images for the determination of surrogates of biophysical parameters [8], the conceptual design of a framework to handle missing information cases and uncertainty in data acquisition and expert rules. She was also responsible for the scientific co-guidance of the consortium and the quality assurance of the deliverables of the project. In conclusion, Professor Maria Petrou contributed to active and emerging research areas and was a dedicated and extrovert Director promoting team spirit, openness and technology transfer. Her vision resides as her legacy in the on going work of our colleagues, in the examples she set, and the remaining infrastructure. She will always
be remembered and appreciated by us and the numerous researchers and minds she influenced with her work and collaboration. I. Kompatsiaris S. Malasiotis P. Daras N. Grammalidis V. Mezaris I. Manakos D. Tzovaras CERTH-ITI, Thessaloniki, Greece
References [1] A. Drosou, K. Moustakas, D. Tzovaras, M. Petrou, Systematic error analysis for the enhancement of biometric systems using soft biometrics, IEEE Signal Process. Lett. 19 (12) (2012) 833–836. [2] CloPeMa: Cloth Perception and Manipulation, European Union 7th Framework Programme, 2012–2015. [3] S. Barsky, M. Petrou, The 4-source photometric stereo technique for threedimensional surfaces in the presence of highlights and shadows, IEEE Trans. Pattern Anal. Machine Intell. 25 (10) (2003) 1239–1252. [4] D. Gorpas, C. Kampouris, S. Malassiotis, Miniature photometric stereo system for textile surface structure reconstruction, in: Proc. SPIE 8791, Videometrics, Range Imaging, and Applications XII; and Automated Visual Inspection, 2013. [5] M. Petrou, Learning in computer vision: some thoughts, in: L. Rueda, D. Mery, J. Kittler (Eds.), Proceedings of the 12th Iberoamerican Congress on Pattern Recognition, CIAPR, LNCS, vol. 4756, Springer Verlag, Berlin, 2007, pp. 1–12. [6] M. Xu, M. Petrou, Learning logic rules for the Tower of Knowledge using Markov logic networks, Int. J. Pattern Recognit. Artif. Intell. 25 (2011) 889–908. [7] M. Petrou, A. Giannakidis, Full tomographic reconstruction of 2-d vector fields using discrete integral data, Comput. J. 54 (2011) 1491–1504. [8] Z. Petrou, C. Tarantino, M. Adamo, P. Blonda, M. Petrou, Estimation of vegetation height through satellite image texture analysis, in: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol. XXXIX-B8, XXII ISPRS Congress, Melbourne, 2012, pp. 321–326.