Abstract: A method for estimating noise in a reconstructed image through post-processing includes the steps: dividing the reconstructed image to generate image segments; applying a multi-resolution transformation or directional filter bank on at least part of the image segments to generate transformed image segments; and for each transformed image segment estimating a direction dependent noise power S0(?); calculating a first noise covariance matrix from an isotropic power spectral density |??G(?)|2; and calculating a second noise covariance matrix in the transformed image segment through the product of the direction dependent noise power S0(?) and the first noise covariance matrix.