# File lib/color/rgb.rb, line 138
138:   def to_cmyk
139:     c = 1.0 - @r.to_f
140:     m = 1.0 - @g.to_f
141:     y = 1.0 - @b.to_f
142: 
143:     k = [c, m, y].min
144:     k = k - (k * brightness)
145: 
146:     c = [1.0, [0.0, c - k].max].min
147:     m = [1.0, [0.0, m - k].max].min
148:     y = [1.0, [0.0, y - k].max].min
149:     k = [1.0, [0.0, k].max].min
150: 
151:     Color::CMYK.from_fraction(c, m, y, k)
152:   end