1. A method for detecting a constant region of an image frame, comprising: at a previous position of an image analysis window, determining whether the image analysis window contains a constant region; should the determining whether the image analysis window contains a constant region result in a determination that the image analysis window contains a constant region, then the following process is performed: shifting the image analysis window to a current position so that the image analysis window includes a new line of pixels from the image frame in comparison to the previous position of the image analysis window, wherein an entire area of the image analysis window at the previous position is a first constant region of pixels and wherein a constant region is defined as a region wherein all pixels contained therein are substantially similar in value; determining whether the entire area of the image analysis window at the current position is a second constant region by analyzing a first pixel at a predetermined location in the image analysis window at the current position, the predetermined location being defined relative to a boundary of the image analysis window, wherein the analyzing comprises: determining if the first pixel has a value equal to a value of a second pixel at the predetermined location relative to the boundary of the image analysis window when the image analysis window was at the previous position, if the value of the first pixel has a value equal to the value of the second pixel, then analyzing only the new line of pixels to determine if the second constant region is present.