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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Computer Science

Year Degree Awarded

Spring 2014

First Advisor

Erik Learned-Miller

Subject Categories

Applied Statistics | Artificial Intelligence and Robotics | Computer Sciences | Statistical Models | Statistics and Probability

Abstract

Semantic labeling is the task of assigning category labels to regions in an image. For example, a scene may consist of regions corresponding to categories such as sky, water, and ground, or parts of a face such as eyes, nose, and mouth. Semantic labeling is an important mid-level vision task for grouping and organizing image regions into coherent parts. Labeling these regions allows us to better understand the scene itself as well as properties of the objects in the scene, such as their parts, location, and interaction within the scene. Typical approaches for this task include the conditional random field (CRF), which is well-suited to modeling local interactions among adjacent image regions. However the CRF is limited in dealing with complex, global (long-range) interactions between regions in an image, and between frames in a video. This thesis presents approaches to modeling long-range interactions within images and videos, for use in semantic labeling.

In order to model these long-range interactions, we incorporate priors based on the restricted Boltzmann machine (RBM). The RBM is a generative model which has demonstrated the ability to learn the shape of an object and the CRBM is a temporal extension which can learn the motion of an object. Although the CRF is a good baseline labeler, we show how the RBM and CRBM can be added to the architecture to model both the global object shape within an image and the temporal dependencies of the object from previous frames in a video. We demonstrate the labeling performance of our models for the parts of complex face images from the Labeled Faces in the Wild database (for images) and the YouTube Faces Database (for videos). Our hybrid models produce results that are both quantitatively and qualitatively better than the baseline CRF alone for both images and videos.

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