1. A method to discriminate input sources to a touch-surface device, comprising: obtaining a proximity image; compensating the proximity image for background noise; filtering the proximity image to reduce spurious peaks; segmenting the proximity image to identify a plurality of patches; reducing or down-scaling peripheral patch pixel values for one or more of the plurality of patches based on the compensated proximity image and the filtered proximity image; determining a major axis radius value for at least one patch having a reducing or down-scaling peripheral patch pixel value; identifying the at least one patch as being associated with a large object when the determined major axis radius value of the at least one patch is above a first specified threshold; and using the identified patch to control an operation of the touch-surface device.