1. A computer-implemented image processing method, comprising: receiving, using at least one processing circuit, a plurality of image frames of a video; constructing, using at least one processing circuit, a plurality of statistical models of the plurality of image frames at a plurality of pixel granularity levels; constructing, using at least one processing circuit, a plurality of probabilistic models of an input image frame at a plurality of channel granularity levels based on the plurality of statistical models; merging at least some of the plurality of probabilistic models based on a weighted average to form a single probability image; and determining background pixels, based on a probability threshold value, from the single probability image, wherein the plurality of statistical models comprise spatio-temporal (S-T) histogram for each of the pixels from the plurality of image frames, wherein a horizontal axis of the S-T histogram represents channel value bins, and wherein a vertical axis of the S-T histogram represents counts of image frames per bin.