Empirical study on subjective quality evaluation of compressed images
Timo Kaukoranta, Pasi Fränti, Olli Nevalainen · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1996
In the present work we study image quality evaluation from an empirical point of view and want to find out (1) what kind of distortion existing compression algorithms generate; (2) how annoying a human observer finds certain types of distortion; (3) what are the possibilities of mathematically analyzing the distortion. A set of test images was compressed by several different compression algorithms and the visual quality of compressed images was evaluated by a group of humans. The distortion caused by compression can be classified to blockiness, blurring, jaggedness, ghost figures, and quantization errors. Blockiness is the most annoying type of distortion. For the other types the amount is more important than the type of the distortion. Blurring and quantization errors can be detected by local analysis of the image. Blockiness, jaggedness and ghost figures are harder to detect since they are composed of structural changes in the image.