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, the filtering being distinct from the compensating; segmenting the proximity image to identify a plurality of patches having patch pixel values; 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, the reducing or down-scaling being distinct from the compensating and filtering; determining an eccentricity value for one or more of the reduced or down-scaled peripheral patch pixel values of the plurality of patches; identifying a first patch having an eccentricity value greater than a first threshold; and using the identified patch to control an operation of a touch-surface device.