🚀 go-pugleaf

If the user has an RGB space "u" and he wants to apply
the YCrCb conversion with NTSC "n" primaries then has to
transform twice:

XYZ = Cxu * RGBu
RGBn = Cnx * XYZ
YCbCr= Cyr * RGBn

All these published transformations are indeed based on
predefined RGB spaces.

We don�t know what the OP really wants, and YCrCb is just
an assumption, because I don�t know any YCC.

I had also mentioned the JPEG application. Here the RGB
values are decoded as they were encoded (with minor errors,
because of the quantization). In this case the sender has to take
care, that he uses sRGB as source space, unless he tells
the receiver the working space (embedded or explicit profile).
What I want to say: NTSC has no meaning in this context, it�s
just an intermediate mathematical coordinate system.
There is not even a gamma correction - simply raw image data
are used.

My calculation examples show clearly, how the specific RGB
spaces are defined (sorry, it�s in the code, but this prevents any
typing error).

Best regards --Gernot Hoffmann