Convert RGB color values to NTSC color space
In the NTSC color space, the luminance is the grayscale signal used to display
pictures on monochrome (black and white) televisions. The other components carry the hue
and saturation information. The value 0
corresponds to the absence of
the component, while the value 1
corresponds to full saturation of
the component.
rgb2ntsc
defines the NTSC components using