Structural Approaches to Image Quality Assessment

This chapter introduces the basic ideas and algorithms of structural approaches for image quality assessment. It describes the concepts, the structural similarity (SSIM) index algorithm, and the image synthesis-based performance evaluation algorithm in the image space. It demonstrates the fact that image distortions along different directions in the image space have different perceptual meanings. The structural approaches attempt to separate the directions associated with structural distortions from those with nonstructural distortions. This separation gives a new coordinate system in the image space. The new coordinate system is not fixed as in traditional image decomposition frameworks but has adapted to the underlying image structures.