1. A method for identifying a robust average intensity of a portion of an embedding site comprising a plurality of pixels of a common class to extract a data value represented as a difference between a first robust average intensity value of a first portion of the plurality of pixels in the embedding site and a second robust average intensity value of a second portion of the plurality of pixels in the embedding site, the method comprising: selecting reliable intensity value pixels from a first portion of the plurality of pixels to form a first set of reliable pixels; iteratively pruning, from the first set of reliable pixels, reliable intensity value pixels that reside in an outer region of a histogram of the first set of reliable pixels until a difference between successive average intensity values of the first set of reliable pixels is less than a difference threshold; and setting a first robust average intensity value of the first set of reliable pixels based upon at least one of the successive average intensity values that had less than a difference threshold.