1. A method comprising: partitioning an image into a plurality of image segments, each image segment of the plurality of image segments includes a first plurality of image pixels; partitioning the plurality of image segments into a plurality of subsegments, each image subsegment of the plurality of subsegments includes a second plurality of image pixels; estimating a grey value for a corresponding image pixel of the first and second plurality of image pixels; estimating mean and standard deviation of the grey value for the corresponding image pixel of the first and second plurality of image pixels; and in response to the corresponding image pixel of the first and second plurality of image pixels having the standard deviation below a pre-determined threshold, assigning a first grey membership parameter to the corresponding image pixel; in response to the corresponding image pixel of the first and second plurality of image pixels having the standard deviation above the pre-determined threshold, assigning a second grey membership parameter to the corresponding image pixel; and combining the first and second grey membership parameter to estimate a net grey membership parameter for the corresponding image pixel of the first and second plurality of image segments.