直方图在vImageHistogramCalculation_Planar8中的不同通道是如何工作的

I am attempting to calculate a histogram for the Y channel in a kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange image buffer. When I use vImageHistogramCalculation_Planar8 I pass in a reference to only a single histogram. I am attempting to calculate a histogram for th