A decorative painting kit including multiple-color paint applicators and a method of decoratively painting a surface though in situ surface blending of two or more paints of different colors by using a multiple-color paint applicator which is stroked over the same surface a sufficient number of time to at least partially blend the different paint colors. A border processing unit extracts and adds a range-of-influence part of the power source network that can electrically influence a border between the partitioned area partitioned by the area partitioning processing unit and an adjacent power source network area. When a light signal travels through the first lens in the 4-fiber collimator to a filter, the film on the filter causes distortion to the light signal resulting in a large insertion loss. The sliding filtering is performed using a sliding low pass filter in certain embodiments of the invention.