A method is described that includes defining a window of one or more consecutive pixel values in a linear array of pixel values of an image. The defining includes adding a pixel value in the linear array to the window so long as the pixel value does not deviate from the pixel values that exist within the window to a degree that causes a threshold value to be exceeded, and, wherein the threshold value decreases as the size of the window increases. The method also includes encoding the window of pixel values with a value determined from pixel values within the window and the number of pixel values within the window.