opencv rgb转YUV公式
https://docs.opencv.org/master/de/d25/imgproc_color_conversions.html#color_convert_rgb_ycrcb
RGB ? YCrCb JPEG (or YCC)
Y←0.299?R+0.587?G+0.114?B
Cr←(R?Y)?0.713+delta
Cb←(B?Y)?0.564+delta
R←Y+1.403?(Cr?delta)
G←Y?0.714?(Cr?delta)?0.344?(Cb?delta)
B←Y+1.773?(Cb?delta)
where
delta=?????128327680.5for 8-bit imagesfor 16-bit imagesfor floating-point images
Y, Cr, and Cb cover the whole value range.