SPIE’s
46th Annual Meeting, Proc. SPIE, Application of Digital
Image Proce. XXIV, July-Aug. 2001
Foveated Wavelet Image
Quality Index
Zhou
Wang1, Alan C. Bovik1,
Ligang Lu2 and Jack Kouloheris2
1 Laboratory for Image and Video Engineering
(LIVE), Department of Electrical and Computer Engineering, The University of
Texas at Austin, Austin, TX 78712-1084
2 IBM T. J. Watson Research Center, Yorktown
Heights, NY 10598
Abstract: The human visual system (HVS) is highly
non-uniform in sampling, coding, processing and understanding. The spatial resolution
of the HVS is highest around the point of fixation (foveation point) and
decreases rapidly with increasing eccentricity. Currently, most image quality
measurement methods are designed for uniform resolution images. These methods
do not correlate well with the perceived foveated image quality. Wavelet
analysis delivers a convenient way to simultaneously examine localized spatial
as well as frequency information. We developed a new image quality metric
called foveated wavelet image quality index (FWQI) in the wavelet transform
domain. FWQI considers multiple factors of the HVS, including the space
variance of the contrast sensitivity function, the spatial variance of the
local visual cut-off frequency, the variance of human visual sensitivity in different
wavelet subbands, and the influence of the viewing distance on the display
resolution and the HVS features. FWQI can be employed for foveated region of
interest (ROI) image coding and quality enhancement. We show its effectiveness
by using it as a guide for optimal bit assignment of an embedded foveated image
coding system. The coding system demonstrates very good coding performance and
scalability in terms of foveated objective as well as subjective quality
measurement.
Keywords: image quality
assessment, human visual system (HVS), foveation, wavelet, image coding