JPS6436285A - Picture synthesizer - Google Patents

Abstract

PURPOSE:To make the boundary line of an image into a natural feeling and to prevent from being conspicuous by applying gain control to a key signal, adding the result to three primary colors of a first image signal to obtain the key signal, making the level of the three primary color signal the same, and erasing a color at the background color part of the first image signal. CONSTITUTION:Three primary color signals R1, G1 and B1 are supplied to a key signal generating circuit 15, and a key signal K, which goes to a low level at a blue part which is the background color in the output of a video camera 1 and goes to a high level at other part, is obtained from the generating circuit 15. The key signal K from the key signal generating circuit 15 is supplied through gain control circuits 18R, 18G and 18B to adder circuits 13R, 13G and 13B. The output signal of the adder circuit is respectively supplied to one side input edge of comparing circuits 19R, 19G and 19B. The signal level of the blue background part of a picture A of the primary color signals R1, G1 and B1 through input terminals 11R, 11G and 11B are controlled so as to go to the same luminance signal level by adding the key signal K these. The effect that the level of the three primary color signals is equal means the white color, the white level is equal to the luminance level of the screen A, and therefore, the boundary line of two images is made more natural.