| 摘要 |
An apparatus and method effecting a linear color transformation between foreground video and insert video, in a chroma key video image. A determination is made whether a particular pel, or pixel in the foreground video image is either a full foreground pel, a full blue screen pel, or a transition pel. Predetermined "look up" tables store color values in vectorscope domain which correspond to endpoint UV foreground and endpoint full background UV blue values, for each foreground to background transition pel. A key signal related to the percent distance of each such transition pel from these two endpoints in the UV plane is created. The composite output pel is formed from the current YUV transition pel value, by subtracting the selected full blue YUV from it, and adding insert video to it in proportion to the key signal. Three methods are disclosed to determine whether the UV value of a current pel, or alternatively the UV values of pels within a spatial neighborhood of the current pel, identify the current pel as a transition pel. If so, the methods select and store full foreground and full blue transition color value endpoints, so an appropriate key signal for the composite output pel can be generated.
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