| 摘要 |
PURPOSE:To generate a key signal of soft chromakey by finding a color signal being separated digitally in color as a function of a reference phase phi by using a demodulation function based upon a cot function. CONSTITUTION:When the timing of a sampling phase is limited to axes I and Q, a color signal theta out of phase with the axis Q is represented as I=Csintheta and Q=Ccostheta on the axes I and Q. Then when the color phase of a part where another image is fitted is theta and a digital demodulation function is approximated by a cot function, we have F(theta-phi)=a¦cot(theta-phi)¦-b. In a PROM11, values of costheta and sintheta are stored and then multiplied by an I and a Q signal through multipliers 12-15; and the results are applied to an adder 16 and a subtracter 17 to calculate the numerator and denominator of cot(theta-phi). A PROM18 is a circuit for finding a reciprocal and a multiplier 19 calculates cot(theta-phi). |
