METHOD OF AND ARRANGEMENT FOR DERIVING A CONTROL SIGNAL FOR INSERTING A BACKGROUND SIGNAL INTO PARTS OF A FOREGROUND SIGNAL

In a method, in which a control signal assumes a first value when the foreground signal represents a color in the region of the key color and a second value when the foreground signal represents a different color, and in which the control signal has a transition range between the two values, the distances between the color locations of the pixels of the foreground signal and the color location of the key color are computed for distinguishing color locations associated with foreground objects or with the key color from color locations to be associated with the transition range. Those color locations whose distance is distinguished from color locations of one or a plurality of adjacent pixels by more than a predetermined distance (not complying with a homogeneity criterion) are considered to be associated with the transition range. Intermediate values of the control signal are computed for the color locations in the transition range.