  An average observer perceives the world in color instead of black and white.
Moreover, the visual system focuses on structures and segments instead of
individual pixels. Based on these observations, we propose a full reference
objective image quality metric modeling visual system characteristics and
chroma similarity in the perceptually uniform color domain (Lab). Laplacian of
Gaussian features are obtained in the L channel to model the retinal ganglion
cells in human visual system and color similarity is calculated over the a and
b channels. In the proposed perceptual similarity index (PerSIM), a
multi-resolution approach is followed to mimic the hierarchical nature of human
visual system. LIVE and TID2013 databases are used in the validation and PerSIM
outperforms all the compared metrics in the overall databases in terms of
ranking, monotonic behavior and linearity.
