  The human visual system pays attention to salient regions while perceiving an
image. When viewing a stereoscopic 3D (S3D) image, we hypothesize that while
most of the contribution to saliency is provided by the 2D image, a small but
significant contribution is provided by the depth component. Further, we claim
that only a subset of image edges contribute to depth perception while viewing
an S3D image. In this paper, we propose a systematic approach for depth
saliency estimation, called Salient Edges with respect to Depth perception
(SED) which localizes the depth-salient edges in an S3D image. We demonstrate
the utility of SED in full reference stereoscopic image quality assessment
(FRSIQA). We consider gradient magnitude and inter-gradient maps for predicting
structural similarity. A coarse quality estimate is derived first by comparing
the 2D saliency and gradient maps of reference and test stereo pairs. We refine
this quality using SED maps for evaluating depth quality. Finally, we combine
this luminance and depth quality to obtain an overall stereo image quality. We
perform a comprehensive evaluation of our metric on seven publicly available
S3D IQA databases. The proposed metric shows competitive performance on all
seven databases with state-of-the-art performance on three of them.
