def adjust_color(color, kwargs)
assert_type color, :Color
with = Sass::Util.map_hash({
"red" => [-255..255, ""],
"green" => [-255..255, ""],
"blue" => [-255..255, ""],
"hue" => nil,
"saturation" => [-100..100, "%"],
"lightness" => [-100..100, "%"],
"alpha" => [-1..1, ""]
}) do |name, (range, units)|
next unless val = kwargs.delete(name)
assert_type val, :Number, name
Sass::Util.check_range("$#{name}: Amount", range, val, units) if range
adjusted = color.send(name) + val.value
adjusted = [0, Sass::Util.restrict(adjusted, range)].max if range
[name.to_sym, adjusted]
end
unless kwargs.empty?
name, val = kwargs.to_a.first
raise ArgumentError.new("Unknown argument $#{name} (#{val})")
end
color.with(with)
end