1. A method comprising: for each of a set of pixel values representing a signal, updating a first memory location based on the pixel value and an exponential decay function that is based on a Gaussian filter kernel; updating a second memory location based on the current updated value in the first memory location as well as a decay factor of the exponential decay function and a current value stored in the second memory location computing a filtered pixel value as a combination of the updated values in the first and second memory locations, the filtered pixel value approximating a filtering of the signal by the Gaussian filter kernel.