how to convert rgb values to numbers in compositor?
simply as is 
Basically converting it will automatically put it in a math state. If you mean you’d like to see the values, then click your mouse in the render area, the values will appear in 2 color numerical formats.
If you mean to use for a comp.
Add: Converter>Separate RGB
Connect: Converter>Math
Connect image/ render to Separate RGB
Connect R, G, or B to Math node (or add more math nodes) Set open node to “0”
However this is the same thing if you don’t use the math node at all, but the math node will allow some additional configurations if the other node is a G or B for example- and other math functions are used.
If you mean is there a numerical display node- I don’t think so (it would be nice), but see the first suggestion.
If this didn’t answer it, it might help to explain what you are trying to do…
Hope that helps!
thanks R3sili3nt for your answer 
the thing i’m trying to do is that i have a velocity map i rendered it in max, and as you know wont go in blender vector blur node, so i’m trying to separate the velocity map i have into RGB then convert each channel to a value i could input in vector blur since it inputs a X, Y, and Z as speed.
i think it will work, it could save me a big render time on blurry things
so i welcome any help you could offer.
Hm,
I did try it and I don’t think think its possible as the data from the vector channels don’t seem to translate to or from image mapping data. However, that doesn’t mean it not possible. But it doesn’t seem to work for me…