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A robust similarity measure for volumetric image registration with outliers (2016)
Journal Article
Snape, P., Pszczolkowski, S., Zafeiriou, S., Tzimiropoulos, G., Ledig, C., & Rueckert, D. (2016). A robust similarity measure for volumetric image registration with outliers. Image and Vision Computing, 52, https://doi.org/10.1016/j.imavis.2016.05.006

Image registration under challenging realistic conditions is a very important area of research. In this paper, we focus on algorithms that seek to densely align two volumetric images according to a global similarity measure. Despite intensive researc... Read More about A robust similarity measure for volumetric image registration with outliers.

Deep Machine Learning provides state-of-the-art performance in image-based plant phenotyping (2016)
Working Paper
Pound, M. P., Burgess, A. J., Wilson, M. H., Atkinson, J. A., Griffiths, M., Jackson, A. S., …French, A. P. Deep Machine Learning provides state-of-the-art performance in image-based plant phenotyping

Deep learning is an emerging field that promises unparalleled results on many data analysis problems. We show the success offered by such techniques when applied to the challenging problem of image-based plant phenotyping, and demonstrate state-of-th... Read More about Deep Machine Learning provides state-of-the-art performance in image-based plant phenotyping.

300 faces in-the-wild challenge: database and results (2016)
Journal Article
Sagonas, C., Antonakos, E., Tzimiropoulos, G., Zafeiriou, S., & Pantic, M. (2016). 300 faces in-the-wild challenge: database and results. Image and Vision Computing,

Computer Vision has recently witnessed great research advance towards automatic facial points detection. Numerous methodologies have been proposed during the last few years that achieve accurate and efficient performance. However, fair comparison bet... Read More about 300 faces in-the-wild challenge: database and results.

The first Facial Landmark Tracking in-the-Wild Challenge: benchmark and results (2015)
Conference Proceeding
Shen, J., Zafeiriou, S., Chrysos, G. G., Kossaifi, J., Tzimiropoulos, G., & Pantic, M. (2015). The first Facial Landmark Tracking in-the-Wild Challenge: benchmark and results.

Detection and tracking of faces in image sequences is among the most well studied problems in the intersection of statistical machine learning and computer vision. Often, tracking and detection methodologies use a rigid representation to describe the... Read More about The first Facial Landmark Tracking in-the-Wild Challenge: benchmark and results.

Fast and exact bi-directional fitting of active appearance models (2015)
Conference Proceeding
Kossaifi, J., Tzimiropoulos, G., & Pantic, M. (2015). Fast and exact bi-directional fitting of active appearance models.

Finding landmarks on objects like faces is a challenging computer vision problem, especially in real life conditions (or in-the-wild) and Active Appearance Models have been widely used to solve it. State-of-the-art algorithms for fitting an AAM to a... Read More about Fast and exact bi-directional fitting of active appearance models.

Feature-based Lucas-Kanade and Active Appearance Models (2015)
Journal Article
Antonakos, E., Alabort-i-Medina, J., Tzimiropoulos, G., & Zafeiriou, S. P. (2015). Feature-based Lucas-Kanade and Active Appearance Models. IEEE Transactions on Image Processing, 24(9), https://doi.org/10.1109/TIP.2015.2431445

Lucas-Kanade and Active Appearance Models are among the most commonly used methods for image alignment and facial fitting, respectively. They both utilize non-linear gradient descent, which is usually applied on intensity values. In this paper, we pr... Read More about Feature-based Lucas-Kanade and Active Appearance Models.

Project-out cascaded regression with an application to face alignment (2015)
Conference Proceeding
Tzimiropoulos, G. (2015). Project-out cascaded regression with an application to face alignment.

Cascaded regression approaches have been recently shown to achieve state-of-the-art performance for many computer vision tasks. Beyond its connection to boosting, cascaded regression has been interpreted as a learning-based approach to iterative opti... Read More about Project-out cascaded regression with an application to face alignment.

A 3D scene analysis framework and descriptors for risk evaluation (2015)
Conference Proceeding
Dupre, R., Argyriou, V., Greenhill, D., & Tzimiropoulos, G. (2015). A 3D scene analysis framework and descriptors for risk evaluation.

In this paper we evaluate the notion of scene analysis with regard to risk. We consider the problem of evaluating risk and potential hazards in an environment and providing a quantified risk score. A definition of risk is given incorporating two elem... Read More about A 3D scene analysis framework and descriptors for risk evaluation.

Active orientation models for face alignment in-the-wild (2014)
Journal Article
Tzimiropoulos, G., Medina, J. A., Zafeiriou, S., & Pantic, M. (2014). Active orientation models for face alignment in-the-wild. IEEE Transactions on Information Forensics and Security, 9(12), https://doi.org/10.1109/TIFS.2014.2361018

We present Active Orientation Models (AOMs), generative models of facial shape and appearance, which extend the well-known paradigm of Active Appearance Models (AAMs) for the case of generic face alignment under unconstrained conditions. Robustness s... Read More about Active orientation models for face alignment in-the-wild.

HOG active appearance models (2014)
Conference Proceeding
Antonakos, E., Alabort-i-Medina, J., Tzimiropoulos, G., & Zafeiriou, S. (2014). HOG active appearance models. . https://doi.org/10.1109/ICIP.2014.7025044

We propose the combination of dense Histogram of Oriented Gradients (HOG) features with Active Appearance Models (AAMs). We employ the efficient Inverse Compositional optimization technique and show results for the task of face fitting. By taking adv... Read More about HOG active appearance models.

From pixels to response maps: discriminative image filtering for face alignment in the wild (2014)
Journal Article
Asthana, A., Zafeiriou, S., Tzimiropoulos, G., Cheng, S., & Pantic, M. (2014). From pixels to response maps: discriminative image filtering for face alignment in the wild. IEEE Transactions on Pattern Analysis and Machine Intelligence, 37(6), https://doi.org/10.1109/TPAMI.2014.2362142

We propose a face alignment framework that relies on the texture model generated by the responses of discriminatively trained part-based filters. Unlike standard texture models built from pixel intensities or responses generated by generic filters (e... Read More about From pixels to response maps: discriminative image filtering for face alignment in the wild.

Online learning and fusion of orientation appearance models for robust rigid object tracking (2014)
Journal Article
Marras, I., Tzimiropoulos, G., Zafeiriou, S., & Pantic, M. (2014). Online learning and fusion of orientation appearance models for robust rigid object tracking. Image and Vision Computing, 32(10), 707-727. https://doi.org/10.1016/j.imavis.2014.04.017

We introduce a robust framework for learning and fusing of orientation appearance models based on both texture and depth information for rigid object tracking. Our framework fuses data obtained from a standard visual camera and dense depth maps obtai... Read More about Online learning and fusion of orientation appearance models for robust rigid object tracking.

Online learning and fusion of orientation appearance models for robust rigid object tracking (2013)
Conference Proceeding
Marras, I., Medina, J. A., Tzimiropoulos, G., Zafeiriou, S., & Pantic, M. (2013). Online learning and fusion of orientation appearance models for robust rigid object tracking. In 2013 10th IEEE International Conference and Workshops on Automatic Face and Gesture Recognition (FG). https://doi.org/10.1109/FG.2013.6553798

We present a robust framework for learning and fusing different modalities for rigid object tracking. Our method fuses data obtained from a standard visual camera and dense depth maps obtained by low-cost consumer depths cameras such as the Kinect. T... Read More about Online learning and fusion of orientation appearance models for robust rigid object tracking.

A semi-automatic methodology for facial landmark annotation (2013)
Conference Proceeding
Sagonas, C., Tzimiropoulos, G., Zafeiriou, S., & Pantic, M. (2013). A semi-automatic methodology for facial landmark annotation.

Developing powerful deformable face models requires massive, annotated face databases on which techniques can be trained, validated and tested. Manual annotation of each facial image in terms of landmarks requires a trained expert and the workload is... Read More about A semi-automatic methodology for facial landmark annotation.

Subspace learning from image gradient orientations (2012)
Journal Article
Tzimiropoulos, G., Zafeiriou, S., & Pantic, M. (2012). Subspace learning from image gradient orientations. IEEE Transactions on Pattern Analysis and Machine Intelligence, 34(12), 2454-2466. https://doi.org/10.1109/TPAMI.2012.40

We introduce the notion of subspace learning from image gradient orientations for appearance-based object recognition. As image data is typically noisy and noise is substantially different from Gaussian, traditional subspace learning from pixel inten... Read More about Subspace learning from image gradient orientations.