Is there some robust metric of image sharpness or bluriness? I have various set of images with different parameters of saturation and captured from different optical systems, and i heed to show user something like "quality" of focusing. For getting most focused image i use metric getted with Sobel-Tenengrad operator(summ of high-contrast pixels), but the problem is that for different objects are quite different range of metric(depends on unknown parameters of image intensity, optical system ) - needed some metric where possible to say that image has bad focus whithout comparing with reference image, like this is "bad" or "good" focused image.
Answer
You can calculate the accutance of the image by calculating the mean of the Gradient Filter.
Reference this StackOverflow answer to a similar question.