Douglas Gray

Viewpoint Invariant Pedestrian Recognition with an Ensemble of Localized Features

Viewpoint invariant pedestrian recognition is an important yet under-addressed problem in computer vision. This is likely due to the difficulty in matching two objects with unknown viewpoint and pose. This paper presents a method of performing viewpoint invariant pedestrian recognition using an efficiently and intelligently designed object representation, the ensemble of localized features (ELF). Instead of designing a specific feature by hand to solve the problem, we define a feature space using our intuition about the problem and let a machine learning algorithm find the best representation. We show how both an object class specific representation and a discriminative recognition model can be learned using the AdaBoost algorithm. This approach allows many different kinds of simple features to be combined into a single similarity function. The method is evaluated using a viewpoint invariant pedestrian recognition dataset and the results are shown to be superior to all previous benchmarks for both recognition and reacquisition of pedestrians.

A Viewpoint Invariant Approach for Crowd Counting

This paper describes a viewpoint invariant learning-based method for counting people in crowds from a single camera. Our method takes into account feature normalization to deal with perspective projection and different camera orientation. The training features include edge orientation and blob size histograms resulted from edge detection and background subtraction. A density map that measures the relative size of individuals and a global scale measuring camera orientation are estimated and used for feature normalization. The relationship between the feature histograms and the number of pedestrians in the crowds is learned from labeled training data. Experimental results from different sites with different camera orientation demonstrate the performance and the potential of our method

Counting Pedestrians in Crowds Using Viewpoint Invariant Training.

This paper describes a learning-based method for counting people in crowds from a single camera. Our method takes into account feature normalization to deal with perspective projection and different camera orientation. Thus, our system is trained to be viewpoint invariant and can be deployed with minimal setup for a new site. This is achieved by applying background subtraction and edge detection to each frame and extracting edge orientation and blob size histograms as features. A homography is computed between the ground plane and the image plane coordinates for the region of interest (ROI). A density map that measures the relative size of individuals and a global scale measuring camera orientation are also estimated and used for feature normalization. The relationship between the feature histograms and the number of pedestrians in the crowds is learned from labeled training data. The two training methods used in the current system are linear fitting and neural networks. Experimental results from different sites with different camera orientation demonstrate the performance and the potential of our method.

Predicting facial beauty without landmarks

A fundamental task in artificial intelligence and computer vision is to build machines that can behave like a human in recognizing a broad range of visual concepts. This paper aims to investigate and develop intelligent systems for learning the concept of female facial beauty and producing human-like predictors. Artists and social scientists have long been fascinated by the notion of facial beauty, but study by computer scientists has only begun in the last few years. Our work is notably different from and goes beyond previous works in several aspects: 1) we focus on fully-automatic learning approaches that do not require costly manual annotation of landmark facial features but simply take the raw pixels as inputs; 2) our study is based on a collection of data that is an order of magnitude larger than that of any previous study; 3) we imposed no restrictions in terms of pose, lighting, background, expression, age, and ethnicity on the face images used for training and testing. These factors significantly increased the difficulty of the learning task. We show that a biologically-inspired model with multiple layers of trainable feature extractors can produce results that are much more human-like than the previously used eigenface approach. Finally, we develop a novel visualization method to interpret the learned model and revealed the existence of several beautiful features that go beyond the current averageness and symmetry hypotheses.

Wikireality: Augmenting reality with community driven websites

We present a system for making community driven websites easily accessible from the latest mobile devices. Many of these new devices contain an ensemble of sensors such as cameras, GPS and inertial sensors. We demonstrate how these new sensors can be used to bring the information contained in sites like Wikipedia to users in a much more immersive manner than text or maps. We have collected a large database of images and articles from Wikipedia and show how a user can query this database by simply snapping a photo. Our system uses the location sensors to assist with image matching and the inertial sensors to provide a unique and intuitive user interface for browsing results.

Efficient Exploration of Text Regions in Natural Scene Images Using Adaptive Image Sampling

An adaptive image sampling framework is proposed for identifying text regions in natural scene images. A small fraction of the pixels actually correspond to text regions. It is desirable to eliminate non-text regions at the early stages of text detection. First, the image is sampled row-by-row at a specific rate and each row is tested for containing text using an 1D adaptation of the Maximally Stable Extremal Regions (MSER) algorithm. The surrounding rows of the image are recursively sampled at finer rates to fully contain the text. The adaptive sampling process is performed on the vertical dimension as well for the identified regions. The final output is a binary mask which can be used for text detection and/or recognition purposes. The experiments on the ICDAR’03 dataset show that the proposed approach is up to 7x faster than the MSER baseline on a single CPU core with comparable text localization scores. The approach is inherently parallelizable for further speed improvements.