1. A method comprising: determining a transfer function relating integral projection curves of a face region in a first frame that has a predefined position and a predetermined size and a co-located window in a second frame; determining a scaling factor based upon the transfer function; determining integral gradient projections for the window in the second frame with the window having a size that is based upon the scaling factor and utilized for verification of the scaling factor; determining a distance between the integral gradient projections of the face region in the first frame and the window in the second frame that has a size that is based upon the scaling factor; and determining whether the scaling factor is verified based on a relationship between the distance and a predefined threshold.