Convert from BGR to YCbCr with 4:2:0 sampling


FwStatus   fwiBGRToYCbCr420_8u_C3P3R ( const Fw8u * pSrcint srcStepFw8u * const pDst[3]int dstStep[3]FwiSize roiSize );
FwStatus   fwiBGRToYCbCr420_8u_AC4P3R ( const Fw8u * pSrcint srcStepFw8u * const pDst[3]int dstStep[3]FwiSize roiSize );


dstStep[3]   Destination three-channel planar buffer step size (array values define width of each plane in bytes).
pDst[3]   Pointer to a location in a three-channel planar destination buffer (array values point to a location in each plane).
pSrc   Pointer to a location in a source buffer.
roiSize   Specifies the height and width of an ROI.
srcStep   Source buffer step size (width of the buffer in bytes).


These functions step through an ROI in a source buffer, convert the source data from the BGR color model to the YCbCr color space with 4:2:0 chroma subsampling, and writes the converted data to a destination buffer.

A gamma-corrected BGR image (pSrc) is converted to a YCbCr image with 4:2:0 chroma subsampling.

 Y = 0.257*R + 0.504*G + 0.098*B + 16
 Cb = -0.148*R - 0.291*G + 0.439*B + 128
 Cr = 0.439*R - 0.368*G - 0.071*B + 128

The input RGB contains the range [0 to 255].

The output Y nominally contains the range [16 to 235].

The output Cb and Cr contains the range [16 to 240], with 128 corresponding to zero.