Javier Lorenzo

A comparison of face and facial feature detectors based on the Viola–Jones general object detection framework

The human face provides useful information during interaction; therefore, any system integrating Vision-Based Human Computer Interaction requires fast and reliable face and facial feature detection. Different approaches have focused on this ability but only open source implementations have been extensively used by researchers. A good example is the Viola–Jones object detection framework that particularly in the context of facial processing has been frequently used. The OpenCV community shares a collection of public domain classifiers for the face detection scenario. However, these classifiers have been trained in different conditions and with different data but rarely tested on the same datasets. In this paper, we try to fill that gap by analyzing the individual performance of all those public classifiers presenting their pros and cons with the aim of defining a baseline for other approaches. Solid comparisons will also help researchers to choose a specific classifier for their particular scenario. The experimental setup also describes some heuristics to increase the facial feature detection rate while reducing the face false detection rate.

Smile Detection for User Interfaces

Perceptual User Interfaces (PUIs) aim at facilitating humancomputer interaction with the aid of human-like capacities (computer vision, speech recognition, etc.). In PUIs, the human face is a central element, since it conveys not only identity but also other important information, particularly with respect to the user’s mood or emotional state. This paper describes both a face detector and a smile detector for PUIs. Both are suitable for real-time interaction. The face detector provides eye, mouth and nose locations in frontal or nearly-frontal poses, whereas the smile detector is able to give a smile intensity measure. Experiments confirm that they are competitive with respect to extant detectors. These two detectors are used in an unobtrusive application that allows to interact with an Instant Messaging (IM) client.Perceptual User Interfaces (PUIs) aim at facilitating human-computer interaction with the aid of human-like capacities (computer vision, speech recognition, etc.). In PUIs, the human face is a central element, since it conveys not only identity but also other important information, particularly with respect to the users mood or emotional state. This paper describes both a face detector and a smile detector for PUIs. Both are suitable for real-time interaction. The face detector provides eye, mouth and nose locations in frontal or nearly-frontal poses, whereas the smile detector is able to give a smile intensity measure. Experiments confirm that they are competitive with respect to extant detectors. These two detectors are used in an unobtrusive application that allows to interact with an Instant Messaging (IM) client.

On the use of a low-cost thermal sensor to improve Kinect people detection in a mobile robot.

Detecting people is a key capability for robots that operate in populated environments. In this paper, we have adopted a hierarchical approach that combines classifiers created using supervised learning in order to identify whether a person is in the view-scope of the robot or not. Our approach makes use of vision, depth and thermal sensors mounted on top of a mobile platform. The set of sensors is set up combining the rich data source offered by a Kinect sensor, which provides vision and depth at low cost, and a thermopile array sensor. Experimental results carried out with a mobile platform in a manufacturing shop floor and in a science museum have shown that the false positive rate achieved using any single cue is drastically reduced. The performance of our algorithm improves other well-known approaches, such as C4 and histogram of oriented gradients (HOG).

CASIMIRO: a robot head for human-computer interaction

The physical appearance and behavior of a robot is an important asset in terms of human-computer interaction. Multimodality is also fundamental, as we humans usually expect to interact in a natural way with voice, gestures, etc. people approach complex interaction devices with stances similar to those used in their interaction with other people. In this paper we describe a robot head, currently under development, that aims to be a multimodal (vision, voice, gestures, ...) perceptual user interface. Modules are described for face detection, tracking, facial movement, action selection and sound localization. Preliminary results indicate that the robot head can potentially achieve the goals we are interested in, namely human interaction and assistance.

An Incremental Learning Algorithm for Face Recognition

In face recognition, where high-dimensional representation spaces are generally used, it is very important to take advantage of all the available information. In particular, many labelled facial images will be accumulated while the recognition system is functioning, and due to practical reasons some of them are often discarded. In this paper, we propose an algorithm for using this information. The algorithm has the fundamental characteristic of being incremental. On the other hand, the algorithm makes use of a combination of classification results for the images in the input sequence. Experiments with sequences obtained with a real person detection and tracking system allow us to analyze the performance of the algorithm, as well as its potential improvements.

Short-term wind power forecast based on cluster analysis and artificial neural networks

In this paper an architecture for an estimator of short-term wind farm power is proposed. The estimator is made up of a Linear Machine classifier and a set of k Multilayer Perceptrons, training each one for a specific subspace of the input space. The splitting of the input dataset into the k clusters is done using a k-means technique, obtaining the equivalent Linear Machine classifier from the cluster centroids. In order to assess the accuracy of the proposed estimator, some experiments will be carried out with actual data of wind speed and power of an experimental wind farm. We also compute the output of an ideal wind turbine to enrich the dataset and estimate the performance of the estimator on one isolated turbine.

An engineering approach to sociable robots

Robotics researchers and cognitive scientists are becoming more and more interested in so-called sociable robots. These machines normally have expressive power (facial features, voice, …) as well as abilities for locating, paying attention to, and addressing people. The design objective is to make robots which are able to sustain natural interactions with people. This capacity falls within the range classed as social intelligence in humans. This position paper argues that the reproduction of social intelligence, as opposed to other types of human ability, may lead to fragile performance, in the sense that tested cases may produce rather different performances to future (untested) cases and situations. This limitation stems from the fact that our social abilities, which appear early in life, are mainly unconscious in origin. This is in contrast with other human abilities that we carry out using conscious effort, and for which we can easily conceive algorithms and representations. This novel perspective is deemed useful for defining the obstacles and limitations of a field that is generating increasing interest. Taking into account the mentioned issues, a development approach suited to the problem is proposed. The use of this approach is demonstrated in the development of CASIMIRO, a robotic head with basic interaction abilities.

A Procedure for Biological Sensitive Pattern Matching in Protein Sequences

A Procedure for fast pattern matching in protein sequences is presented. It uses a biological metric, based on the substitution matrices as PAM or BLOSUM, to compute the matching. Biological sensitive pattern matching does pattern detection according to the available empirical data about similarity and affinity relations between amino acids in protein sequences. Sequence alignments is a string matching procedure used in Genomic; it includes insert/delete operators and dynamic programming techniques; it provides more sophisticate results that other pattern matching procedures but with higher computational cost. Heuristic procedures for local alignments as FASTA or BLAST are used to reduce this cost. They are based on some successive tasks; the first one uses a pattern matching procedure with very short sequences, also named k-tuples. This paper shows how using the L1 metric this matching task can be efficiently computed by using SIMD instructions. To design this procedure, a table that maps the substitution matrices is needed. This table defines a representation of each amino acid residue in a n-dimensional space of lower dimensionality as possible; this is accomplished by using techniques of Multidimensional Scaling used in Pattern Recognition and Machine Learning for dimensionality reduction. Based on the experimental tests, the proposed procedure provides a favorable ration of cost vs matching quality.

Computer vision based eyewear selector

The widespread availability of portable computing power and inexpensive digital cameras are opening up new possibilities for retailers in some markets. One example is in optical shops, where a number of systems exist that facilitate eyeglasses selection. These systems are now more necessary as the market is saturated with an increasingly complex array of lenses, frames, coatings, tints, photochromic and polarizing treatments, etc. Research challenges encompass Computer Vision, Multimedia and Human-Computer Interaction. Cost factors are also of importance for widespread product acceptance. This paper describes a low-cost system that allows the user to visualize different glasses models in live video. The user can also move the glasses to adjust its position on the face. The system, which runs at 9.5 frames/s on general-purpose hardware, has a homeostatic module that keeps image parameters controlled. This is achieved by using a camera with motorized zoom, iris, white balance, etc. This feature can be specially useful in environments with changing illumination and shadows, like in an optical shop. The system also includes a face and eye detection module and a glasses management module.

Exploring the Use of Local Binary Patterns as Focus Measure

In this work local binary patterns based focus measures are presented. Local binary patterns (LBP) have been introduced in computer vision tasks like texture classification or face recognition. In applications where recognition is based on LBP, a computational saving can be achieved with the use of LBP in the focus measures. The behavior of the proposed measures is studied to test if they fulfill the properties of the focus measures and then a comparison with some well know focus measures is carried out in different scenarios.