Image Number 4 for United States Patent #4496966.
The invention concerns a method and apparatus for mixing a foreground signal and a background signal under the control of a switching signal which is derived as a function of the color of the foreground signal. In response to the switching signal selected parts of the foreground signal are desaturated while maintaining their luminance component substantially unchanged; non-corresponding parts of the background signal are suppressed. Both signals so treated are additively superimposed. This leads to a better representation of fine details in the contours of a foreground object of interest.