module Sass::Script::Functions
def mix(color1, color2, weight = Number.new(50))
-
(ArgumentError)
- if `color1` or `color2` aren't colors,
Returns:
-
(Color)
-
Parameters:
-
weight
(Number
) -- between 0% and 100% -
color2
(Color
) -- -
color1
(Color
) --
Overloads:
-
mix(color1, color2, weight = 50%)
def mix(color1, color2, weight = Number.new(50)) assert_type color1, :Color assert_type color2, :Color assert_type weight, :Number unless (0..100).include?(weight.value) raise ArgumentError.new("Weight #{weight} must be between 0% and 100%") end # This algorithm factors in both the user-provided weight # and the difference between the alpha values of the two colors # to decide how to perform the weighted average of the two RGB values. # # It works by first normalizing both parameters to be within [-1, 1], # where 1 indicates "only use color1", -1 indicates "only use color 0", # and all values in between indicated a proportionately weighted average. # # Once we have the normalized variables w and a, # we apply the formula (w + a)/(1 + w*a) # to get the combined weight (in [-1, 1]) of color1. # This formula has two especially nice properties: # # * When either w or a are -1 or 1, the combined weight is also that number # (cases where w * a == -1 are undefined, and handled as a special case). # # * When a is 0, the combined weight is w, and vice versa # # Finally, the weight of color1 is renormalized to be within [0, 1] # and the weight of color2 is given by 1 minus the weight of color1. p = weight.value/100.0 w = p*2 - 1 a = color1.alpha - color2.alpha w1 = (((w * a == -1) ? w : (w + a)/(1 + w*a)) + 1)/2.0 w2 = 1 - w1 rgb = color1.rgb.zip(color2.rgb).map {|v1, v2| v1*w1 + v2*w2} alpha = color1.alpha*p + color2.alpha*(1-p) Color.new(rgb + [alpha]) end