Objective Estimation Methods for the Quality of HDR Images and Their Evaluation with Subjective Assessment

Hirofumi TAKANO  Naoyuki AWANO  Kenji SUGIYAMA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E98-A   No.8   pp.1689-1695
Publication Date: 2015/08/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E98.A.1689
Type of Manuscript: Special Section PAPER (Special Section on Image Media Quality)
high dynamic range image,  objective estimation,  subjective assessment,  weighted SNR,  

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High dynamic range (HDR) images that include large differences in brightness levels are studied to address the lack of knowledge on the quality estimation method for real HDR images. For this, we earlier proposed a new metric, the independent signal-to-noise ratio (ISNR), using the independent pixel value as the signal instead of the peak value (PSNR). Next, we proposed the local peak signal-to-noise ratio (LPSNR), using the maximum value of neighboring pixels, as an improved version. However, these methods did not sufficiently consider human perception. To address this issue, here we proposed an objective estimation method that considers spatial frequency characteristics based on the actual brightness. In this method, the approximated function for human characteristics is calculated and used as a 2D filter on an FFT for spatial frequency weighting. In order to confirm the usefulness of this objective estimation method, we compared the results of the objective estimation with a subjective assessment. We used the organic EL display which has a perfect contrast ratio for the subjective assessment. The results of experiments showed that perceptual weighting improves the correlation between the SNR and MOS of the subjective assessment. It is recognized that the weighted LPSNR gives the best correlation.