Sharpness metric for no-reference image visual quality assessment

N.N. Ponomarenko, O.I. Eremeev, O.Yu. Rogoza, V.V. Lukin

A new sharpness metric for color images can be used for no-reference assessment of image visual quality. The metric basically relies on local power of wavelet transform high-frequency coefficients. It also takes into account a possibility of the presence of macrophotography and portrait photography effects in an image where the image part (usually central one) in sharp whilst the remained part (background) is smeared. Besides, we propose a simple mechanism for blocking artifact accounting (if an image is compressed by JPEG) and compensation of this factor contribution. Optimization of weights for all stages of sharpness metric calculation is carried out for specialized database NRTID that contains 500 test images with previously determined MOS (Mean Opinion Score). Spearman rank order correlation coefficient (SROCC) determined for the designed sharpness metric and MOS is used as an optimization criterion. After optimization, it reaches 0.71. This is larger than for other known available no-reference metrics considered at a verification stage.

Keywords: blind quality assessment, visual quality, human vision system, no-reference metric, image analysis.