The idea is from "The Blur Effect: Perception and Estimation with a New No-Reference Perceptual Blur Metric"

Crété-Roffet F., Dolmiere T., Ladret P., Nicolas M. - GRENOBLE - 2007

In SPIE proceedings - SPIE Electronic Imaging Symposium Conf Human Vision and Electronic Imaging, É tats-Unis d Amérique (2007)-Measure the blur level of still image.