# 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