Q:

What are the normalization numbers for YCbCr image?

I don't seem to find how I can normalize YCbCr color format. For example, it is common to divide by 255 every number of an RGB image. So, what's is that for YCbCr? Or, it doesn't make any sense?

A:

It is your assumption that values of RGB are between 0 to 255 (per channel). HTML standardized it, but there are many other possibility. 0 to 1 (and I think this will be the future) or 0 to 100 are standard choices. Video format have often a range or R, G, B from 16 to 235 (but allowing some extra values for super white or blacker black, just 0 and 255 are reserved), and just for 8 bits per channel.  If you have 10 or 12 bits per channel, you have other maximum values (video format defines such limits). My screen is 10bit per channel, so my RGB is not 0 to 255.
Cb and Cr have usually values between 16 and 240. Y from 16 to 235, if 8 bit per channel. For more bits per channel, there are other limits.
Note: some video format allow also full range, so Y, Cb and Cr from 0 to 255.
You should keep in mind that RGB, YcbCr, etc. are just color models. The implementation defines exactly the range, the chromaticies, the gamma, and other details. Picture and video formats usually allow many kind of colour space (usually defined in the headers), so you should check which kind of RGB or YCbCr you are encoding/decoding.
ADDENDUM (from comments).
Just a division is not good, because some values are reserved (0 and 255 for 8 bits; a larger range for encoding with more bits per channel), and as I wrote above, other values should be displayed in an equivalent manner (as pure white or as pure black).
So you for X you should do (Y-16)/(235-16) and clip values to that result will be in the range 0 to (235-16).  In an analog manner for C channel (but using maximum value of 240 (instead of 235).

