1. A method for enhancing quality of an image, comprising: a) deriving, from an initial low-resolution image, an initial high-resolution image by upsampling; b) providing, based on the initial high-resolution image at least one downsampled filtered image as an auxiliary image having a resolution less than that of the initial low resolution image; c) providing, based on the initial low-resolution image, an unfiltered image having the same resolution as said at least one downsampled filtered image; d) selecting a patch from said initial high-resolution image; e) finding two or more filial patches similar to said selected patch in said at least one downsampled filtered image; f) finding, in said unfiltered image, parent patches locally associated to said filial patches; g) linearly combining the parent patches in order to form an enhanced quality patch; and h) combining enhanced quality patches obtained by repeatedly carrying out d) to f) to form an enhanced quality high-resolution image.