A new metric for image quality assessment is presented in terms of image sharpness while the sharpness is considered as characteristics of blurring.The blur parameter is estimated using edge information.To improve the system efficiency,a criterion for edge sharpness is employed and only the sharpest edge is selected for the extraction of line spread function(LSF).The effect of nearby edges on edge feature and LSF is analyzed and a space constrain is put forward to select appropriate LSFs.A new method for pi...