A method of processing a digital image, the method comprising receiving a digital image, modifying each row of pixel colour values and then each column of modified pixel colour values or vice versa, represented as an array X of pixel or modified pixel colour values x(i), by calculating each value y(i) of an array Y as a function at least of an exponentially weighted moving average a(i) of the array X, calculated in ascending order of the array X value indices, and an exponentially weighted moving average b(i) of the array X, calculated in descending order of the array X value indices, or an exponentially weighted moving average b′(j) of an array X′ containing the values of the array X in reverse order, calculated in ascending order of the array X′ value indices, where i, j are the array value indices, wherein 0≤i