| 摘要 |
<p>A chroma keying signal generator has an input (1) to which digitally encoded colour difference signals (R-Y and BY) are applied and output (27) at which a keying signal is produced. The arrangement calculates a value tan -1 R-YB-Y which represents the hue and a value (R-Y)2 + (B-Y)2 which represents the (saturation)2. Preselected values of hue and (saturation)2 are stored in latches (20,22) and compared with the calculated values derived from the incoming colour difference signals in comparators (24,25). When the calculated hue is substantially equal to the value stored in latch (20) and the calculated (saturation)2 is greater than the value stored in latch (21) both comparators (24,25) produce an output which causes the AND gate (26) to produce a keying signal which is applied to output 27.</p> |
