Convert RGB color to CMYK?

Question

I\'m looking for an algorithm to convert an RGB color to CMYK. Photoshop is performing the conversion below:

R = 220 G = 233 B = 174

C = 15 M = 0 Y = 40 K =

Answer 1

I agree with the previous answers, but I want to say that:

if ( K == 1 ) 
{ 
   C = 0
   M = 0
   Y = 0
} 

It can be if r = g = b = 0.