in the image 2 automatic adjustment of reference color estimates by calculation based on the original color observed in the image and 3 shadow extraction removal of the background from the image is achieved by subtracting from the image the background reference frame modulated by the matte alpha channel since the matte and its generation is a frequent reference its equation is shown here vs the rgb value of the estimated subject color contributing to the observed pixel color and vc the rgb value of the estimated background color contributing to the observed pixel color and 34 distance 34 is a function yielding the distance in color space between two colors an image is considered to consist of a composition of a user selected subject and its background specifically the user can designate a region of the image as opaque subject free of any elements of the background this uncontaminated subject color can be referred to as the true subject color and is also referred to as the subject reference color this color when extrapolated into the transition area generates the estimated subject color another region may be designated as background free of any elements of the subject this uncontaminated background color may be referred to as the true background color or background reference color this color when extrapolated interpolated into the transition area generates the estimated background color these regions can be designated by any region selection method such as a computer mouse graphics tablet or equivalent device to draw a contour enclosing the region or by clicking a.