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Contents
# -*- ruby encoding: utf-8 -*-
class Color::RGB
# Outputs how much contrast this color has with another RGB color.
# Computes the same regardless of which one is considered foreground. If
# the other color does not have a #to_rgb method, this will throw an
# exception. Anything over about 0.22 should have a high likelihood of
# being legible, but the larger the difference, the more contrast.
# Otherwise, to be safe go with something > 0.3
def contrast(other)
other = coerce(other)
# The following numbers have been set with some care.
((diff_brightness(other) * 0.65) +
(diff_hue(other) * 0.20) +
(diff_luminosity(other) * 0.15))
end
private
# Provides the luminosity difference between two rbg vals
def diff_luminosity(other)
other = coerce(other)
l1 = (0.2126 * (other.r) ** 2.2) +
(0.7152 * (other.b) ** 2.2) +
(0.0722 * (other.g) ** 2.2);
l2 = (0.2126 * (self.r) ** 2.2) +
(0.7152 * (self.b) ** 2.2) +
(0.0722 * (self.g) ** 2.2);
((([l1, l2].max) + 0.05) / ( ([l1, l2].min) + 0.05 ) - 1) / 20.0
end
# Provides the brightness difference.
def diff_brightness(other)
other = other.to_rgb
br1 = (299 * other.r + 587 * other.g + 114 * other.b)
br2 = (299 * self.r + 587 * self.g + 114 * self.b)
(br1 - br2).abs / 1000.0;
end
# Provides the euclidean distance between the two color values
def diff_euclidean(other)
other = other.to_rgb
((((other.r - self.r) ** 2) +
((other.g - self.g) ** 2) +
((other.b - self.b) ** 2)) ** 0.5) / 1.7320508075688772
end
# Difference in the two colors' hue
def diff_hue(other)
other = other.to_rgb
((self.r - other.r).abs +
(self.g - other.g).abs +
(self.b - other.b).abs) / 3
end
end
Version data entries
109 entries across 109 versions & 2 rubygems