Method and apparatus for determining a sharpness metric of an image

In order to objectively and efficiently measure, visualize and evaluate the quality of images in terms of sharpness, a method for determining a sharpness metric (S) of an image is described. The method includes performing edge detection that results in gradients for the pixels of the image, determining a value representing a contrast metric C of the image, calculating at least three different thresholds (t1,t2,t3) from the image content, and classifying the pixels according to their gradient into at least four groups defined by the thresholds. The sharpness metric (S) is calculated from relationships between the amounts of pixels in the different groups and a multiplicative factor (m) between the at least three thresholds.