Human face super-resolution

Pao Yue-kong Library Electronic Theses Database

Human face super-resolution

 

Author: Liu, Ying
Title: Human face super-resolution
Degree: M.Sc.
Year: 2012
Subject: High resolution imaging.
Image processing -- Digital techniques.
Image processing -- Mathematical models.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Electronic and Information Engineering
Pages: 98 p. : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2507549
URI: http://theses.lib.polyu.edu.hk/handle/200/6523
Abstract: In this thesis, we have investigated different algorithms for human face super-resolution (SR), which are important for applications such as face recognition, video surveillance and application of many digital devices etc. With these face SR algorithms, face-image resolution can be increased while the facial-image quality is maintained. We have studied two types of SR algorithms: reconstruction-based and learning-based methods. For reconstruction-based methods, we have investigated and implemented the "bilinear" method and the "bicubic" method. These methods are simple, but can achieve only a limited performance, since limitation of information provided. In order to achieve a better performance, learning-based methods are usually employed; these learn the relations between low-resolution (LR) and high-resolution (HR) images from a dataset containing pairs of LR-HR pairs. We have investigated and implemented the "eigentransformation" method, which use principal component analysis (PCA) to represent a face image as a linear combination of training samples. We have proposed two improvements to this method. The first improvement is that, instead of considering the linear relations between a LR face image and the LR training samples, LR images are first super-resolved using a reconstruction-based method, and then the linear relations are computed. The other improvement is to use a face-recognition method to search similar faces to an input LR face before eigentransformation is applied. We also compare the eigentransformation methods to a patch-based method, namely position patch. We evaluate the respective performances of the different algorithms in terms of visual quality and some other objective measurements.

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