Comprehensive method for removing from an image the background surrounding a selected subject

In most cases, the estimated subject color and/or the estimated background color for a given pixel will have a certain amount of error, which could result in either not enough background removal, or removal of all of the background and some of the foreground. By manually or automatically altering the estimated subject color and/or background color, the errors in matte calculation and subsequent removal of the background can be minimized or eliminated. Manual alteration of a subject or background color is achieved by using a cursor to select a true color from the background for example, and inserting it in one or more areas in the background area being partially obscured by the subject. Automatic alteration of one of the estimated subject or background colors involves its computation as a projection in color space of the observed transition pixel color, onto a plane defined by the subject and background reference colors or other defined planes. By treating the shadow as a semitransparent subject, a matte (alpha channel) may be generated to represent the shadow's transition densities, thus permitting the shadow to be regenerated over the new background.