Module: Colorscore::Metrics

Defined in:
lib/colorscore/metrics.rb

Class Method Summary collapse

Class Method Details

.degrees(radians) ⇒ Object 



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# File 'lib/colorscore/metrics.rb', line 139

def self.degrees(radians); radians * 180 / Math::PI; end

.delta_e_cie_2000(l1, a1, b1, l2, a2, b2) ⇒ Object

Ported from colormath for Python.



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# File 'lib/colorscore/metrics.rb', line 16

def self.delta_e_cie_2000(l1, a1, b1, l2, a2, b2)
  kl = kc = kh = 1
  
  avg_lp = (l1 + l2) / 2.0
  c1 = Math.sqrt((a1 ** 2) + (b1 ** 2))
  c2 = Math.sqrt((a2 ** 2) + (b2 ** 2))
  avg_c1_c2 = (c1 + c2) / 2.0

  g = 0.5 * (1 - Math.sqrt((avg_c1_c2 ** 7.0) / ((avg_c1_c2 ** 7.0) + (25.0 ** 7.0))))

  a1p = (1.0 + g) * a1
  a2p = (1.0 + g) * a2
  c1p = Math.sqrt((a1p ** 2) + (b1 ** 2))
  c2p = Math.sqrt((a2p ** 2) + (b2 ** 2))
  avg_c1p_c2p = (c1p + c2p) / 2.0

  if degrees(Math.atan2(b1,a1p)) >= 0
    h1p = degrees(Math.atan2(b1,a1p))
  else
    h1p = degrees(Math.atan2(b1,a1p)) + 360
  end

  if degrees(Math.atan2(b2,a2p)) >= 0
    h2p = degrees(Math.atan2(b2,a2p))
  else
    h2p = degrees(Math.atan2(b2,a2p)) + 360
  end

  if (h1p - h2p).abs > 180
    avg_hp = (h1p + h2p + 360) / 2.0
  else
    avg_hp = (h1p + h2p) / 2.0
  end

  t = 1 - 0.17 * Math.cos(radians(avg_hp - 30)) + 0.24 * Math.cos(radians(2 * avg_hp)) + 0.32 * Math.cos(radians(3 * avg_hp + 6)) - 0.2 * Math.cos(radians(4 * avg_hp - 63))

  diff_h2p_h1p = h2p - h1p
  if diff_h2p_h1p.abs <= 180
    delta_hp = diff_h2p_h1p
  elsif diff_h2p_h1p.abs > 180 && h2p <= h1p
    delta_hp = diff_h2p_h1p + 360
  else
    delta_hp = diff_h2p_h1p - 360
  end

  delta_lp = l2 - l1
  delta_cp = c2p - c1p
  delta_hp = 2 * Math.sqrt(c2p * c1p) * Math.sin(radians(delta_hp) / 2.0)

  s_l = 1 + ((0.015 * ((avg_lp - 50) ** 2)) / Math.sqrt(20 + ((avg_lp - 50) ** 2.0)))
  s_c = 1 + 0.045 * avg_c1p_c2p
  s_h = 1 + 0.015 * avg_c1p_c2p * t

  delta_ro = 30 * Math.exp(-((((avg_hp - 275) / 25) ** 2.0)))
  r_c = Math.sqrt(((avg_c1p_c2p ** 7.0)) / ((avg_c1p_c2p ** 7.0) + (25.0 ** 7.0)));
  r_t = -2 * r_c * Math.sin(2 * radians(delta_ro))

  delta_e = Math.sqrt(((delta_lp / (s_l * kl)) ** 2) + ((delta_cp / (s_c * kc)) ** 2) + ((delta_hp / (s_h * kh)) ** 2) + r_t * (delta_cp / (s_c * kc)) * (delta_hp / (s_h * kh)))
end

.distance(color_1, color_2) ⇒ Object 



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# File 'lib/colorscore/metrics.rb', line 7

def self.distance(color_1, color_2)
  l1, a1, b1 = xyz_to_lab(*rgb_to_xyz(color_1))
  l2, a2, b2 = xyz_to_lab(*rgb_to_xyz(color_2))
  
  distance = delta_e_cie_2000(l1, a1, b1, l2, a2, b2)
  scale(distance, 0..100)
end

.radians(degrees) ⇒ Object 



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# File 'lib/colorscore/metrics.rb', line 138

def self.radians(degrees); degrees * Math::PI / 180; end

.rgb_to_xyz(color) ⇒ Object 



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# File 'lib/colorscore/metrics.rb', line 76

def self.rgb_to_xyz(color)
  color = color.to_rgb
  r, g, b = color.r, color.g, color.b
  
  # assuming sRGB (D65)
  r = (r <= 0.04045) ? r/12.92 : ((r+0.055)/1.055) ** 2.4
  g = (g <= 0.04045) ? g/12.92 : ((g+0.055)/1.055) ** 2.4
  b = (b <= 0.04045) ? b/12.92 : ((b+0.055)/1.055) ** 2.4
  
  r *= 100
  g *= 100
  b *= 100
  
  x = 0.412453*r + 0.357580*g + 0.180423*b
  y = 0.212671*r + 0.715160*g + 0.072169*b
  z = 0.019334*r + 0.119193*g + 0.950227*b
  
  [x, y, z]
end

.scale(number, from_range, to_range = 0..1, clamp = true) ⇒ Object 



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# File 'lib/colorscore/metrics.rb', line 126

def self.scale(number, from_range, to_range=0..1, clamp=true)
  if clamp && number <= from_range.begin
    position = 0
  elsif clamp && number >= from_range.end
    position = 1
  else
    position = (number - from_range.begin).to_f / (from_range.end - from_range.begin)
  end
  
  position * (to_range.end - to_range.begin) + to_range.begin
end

.similarity(a, b) ⇒ Object 



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# File 'lib/colorscore/metrics.rb', line 3

def self.similarity(a, b)
  1 - distance(a, b)
end

.xyz_to_lab(x, y, z) ⇒ Object 



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# File 'lib/colorscore/metrics.rb', line 96

def self.xyz_to_lab(x, y, z)
  x /= 95.047
  y /= 100.000
  z /= 108.883

  if x > 0.008856
    x = x ** (1.0/3)
  else
    x = (7.787 * x) + (16.0 / 116)
  end
  
  if y > 0.008856
    y = y ** (1.0/3)
  else
    y = (7.787 * y) + (16.0 / 116)
  end
  
  if z > 0.008856
    z = z ** (1.0/3)
  else
    z = (7.787 * z) + (16.0 / 116)
  end

  l = (116.0 * y) - 16.0
  a = 500.0 * (x - y)
  b = 200.0 * (y - z)

  [l, a, b]
end