1. A method for estimating additive noise in an image, said method comprising: computing a statistical feature value for each image patch in a plurality of image patches associated with an image-channel image; forming a histogram of said computed statistical feature values; searching said histogram for a first significant peak; and when said first significant peak is found: computing a peak-width measure; and when said peak-width measure does not indicate a broad peak, computing an additive-noise estimate using a histogram-bin location of said first significant peak and said peak-width measure.