Retinal image quality assessment through a visual similarity index

Retinal image quality is commonly analyzed through parameters inherited from instrumental optics. These parameters are defined for ‘good optics’ so they are hard to translate into visual quality metrics. Instead of using point or artificial functions, we propose a quality index that takes into account properties of natural images. These images usually show strong local correlations that help to interpret the image. Our aim is to derive an objective index that quantifies the quality of vision by taking into account the local structure of the scene, instead of focusing on a particular aberration. As we show, this index highly correlates with visual acuity and allows inter-comparison of natural images around the retina. The usefulness of the index is proven through the analysis of real eyes before and after undergoing corneal surgery, which usually are hard to analyze with standard metrics.

Water-quality assessment of the Lower Susquehanna River Basin, Pennsylvania and Maryland : sources, characteristics, anaylsis, and limitations of nutrient and suspended-seditment data, 1975-90 /

"National Water-Quality Assessment Program"

Advisory Committee on Federal Workforce Quality Assessment.

Mode of access: Internet.

Water-quality assessment of Francis E. Walter reservoir, Luzerne and Carbon Counties, Pennsylvania /

"June 1983."

Water-quality assessment of the Indiana Dunes National Lakeshore, 1973-74 /

Mode of access: Internet.

Water-quality assessment of White River between Lake Sequoyah and Beaver Reservoir, Washington County, Arkansas /

Mode of access: Internet.

Water-quality assessment of the Cypress Creek watershed, Warrick County, Indiana /

Mode of access: Internet.

Lake water quality assessment program : northeastern Illinois lakes /

"The Northeastern Illinois Planning Commission's Natural Resources Dept. conducted the lake assessment data collection effort for the six county northeastern Illinois region." -- P. iii.

Lake water quality assessment program, 1993 : northeastern Illinois lakes /

"January 1995."

Water quality assessment of Governor Bond (Greenville New) Lake Bond County, Illinois : 1977-1982.

"IEPA/WPC/84-011." -- Cover.

Methods for comparing water-quality conditions among National Water-Quality Assessment Study Units, 1992-1995 /

Mode of access: Internet.

Rainfall-runoff relationships and water-quality assessment of Coon Creek watershed, Anoka County, Minnesota /

Bibliography: p. 71-73.

No-reference image quality assessment in contourlet domain

The target of no-reference (NR) image quality assessment (IQA) is to establish a computational model to predict the visual quality of an image. The existing prominent method is based on natural scene statistics (NSS). It uses the joint and marginal distributions of wavelet coefficients for IQA. However, this method is only applicable to JPEG2000 compressed images. Since the wavelet transform fails to capture the directional information of images, an improved NSS model is established by contourlets. In this paper, the contourlet transform is utilized to NSS of images, and then the relationship of contourlet coefficients is represented by the joint distribution. The statistics of contourlet coefficients are applicable to indicate variation of image quality. In addition, an image-dependent threshold is adopted to reduce the effect of content to the statistical model. Finally, image quality can be evaluated by combining the extracted features in each subband nonlinearly. Our algorithm is trained and tested on the LIVE database II. Experimental results demonstrate that the proposed algorithm is superior to the conventional NSS model and can be applied to different distortions. © 2009 Elsevier B.V. All rights reserved.

Exploring the effect of buffer behaviour on perceived video quality

In this work we deal with video streams over TCP networks and propose an alternative measurement to the widely used and accepted peak signal to noise ratio (PSNR) due to the limitations of this metric in the presence of temporal errors. A test-bed was created to simulate buffer under-run in scalable video streams and the pauses produced as a result of the buffer under-run were inserted into the video before being employed as the subject of subjective testing. The pause intensity metric proposed in [1] was compared with the subjective results and it was shown that in spite of reductions in frame rate and resolution, a correlation with pause intensity still exists. Due to these conclusions, the metric may be employed in layer selection in scalable video streams. © 2011 IEEE.