| 摘要 |
A luminance selection apparatus for correcting the hue, saturation and luminance of an input color video signal as a function of the luminance of the signal. The system allows setting and storing luminance threshold levels which are used in conjunction with other color selection circuitry to select a region of interest in a video image being displayed. An operator selects a particular hue of interest with color selection circuitry, and then sets a luminance threshold level which discriminates between the same or similar hues in a video image which differ in luminance. In one embodiment, pre-stored digital correction values are retrieved from memory and converted into analog correction signals which modify the phase, amplitude and DC level of the composite video signal only when the input luminance exceeds the threshold level. In another embodiment, independent color derivative signals are employed in conjunction with the luminance of the input video signal to route signals from operator controls to a channel carrying video signals of the selected hue, so that only a selected hue which does not exceed the luminance threshold level receives color correction.
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