A method is provided, suitable for use in extraction of foreground objects from image stream. The method comprises: providing input image data of a region of interest, providing background model of said region of interest, and utilizing said background model for processing each image of the input image data. The processing comprises: determining a background gradient map for pixels in said background model and an image gradient map for pixels in the image; defining a predetermined number of one or more segments in said image and corresponding one or more segments in the background model; determining, for each image segment, an edge density factor is a first relation between the image and background gradient maps for said segment; and calculating foreground detection threshold based on said certain relation, thereby enabling use of said foreground detection threshold for classifying each pixel in the segment as being a foreground or background pixel.