Class: ColorConverters::OklabConverter

Inherits:
BaseConverter show all
Defined in:
lib/color_converters/converters/oklab_converter.rb

Constant Summary

Constants inherited from BaseConverter

BaseConverter::IMPORT_DP, BaseConverter::OUTPUT_DP

Instance Attribute Summary

Attributes inherited from BaseConverter

#original_value, #rgba

Class Method Summary collapse

Methods inherited from BaseConverter

#alpha, #cielab, #cielch, #cmyk, factory, #hex, #hsb, #hsl, #hsv, inherited, #initialize, #name, #oklab, #oklch, #rgb, #xyz

Constructor Details

This class inherits a constructor from ColorConverters::BaseConverter

Class Method Details

.bounds ⇒ Object 



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# File 'lib/color_converters/converters/oklab_converter.rb', line 11

def self.bounds
  { l: [0.0, 100.0], a: [-0.5, 0.5], b: [-0.5, 0.5] }
end

.matches?(colour_input) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/color_converters/converters/oklab_converter.rb', line 5

def self.matches?(colour_input)
  return false unless colour_input.is_a?(Hash)

  colour_input.keys - [:l, :a, :b, :space] == [] && colour_input[:space].to_s == 'ok'
end

.oklab_to_xyz(colour_input) ⇒ Object 



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# File 'lib/color_converters/converters/oklab_converter.rb', line 34

def self.oklab_to_xyz(colour_input)
  l = colour_input[:l].to_d
  a = colour_input[:a].to_d
  b = colour_input[:b].to_d

  # Now, scale l to a decimal
  l /= 100.0.to_d

  # Convert Oklab (L*a*b*) to LMS'
  lab_to_lms_matrix = ::Matrix[
    [1.0000000000000000.to_d, 0.3963377773761749.to_d,  0.2158037573099136.to_d],
    [1.0000000000000000.to_d, -0.1055613458156586.to_d, -0.0638541728258133.to_d],
    [1.0000000000000000.to_d, -0.0894841775298119.to_d, -1.2914855480194092.to_d]
  ]

  l_lms, m_lms, s_lms = (lab_to_lms_matrix * ::Matrix.column_vector([l, a, b])).to_a.flatten

  l_lms **= 3.0.to_d
  m_lms **= 3.0.to_d
  s_lms **= 3.0.to_d

  lms_to_xyz_matrix = ::Matrix[
    [1.2268798758459243.to_d, -0.5578149944602171.to_d, 0.2813910456659647.to_d],
    [-0.0405757452148008.to_d, 1.1122868032803170.to_d, -0.0717110580655164.to_d],
    [-0.0763729366746601.to_d, -0.4214933324022432.to_d, 1.5869240198367816.to_d]
  ]

  x, y, z = (lms_to_xyz_matrix * ::Matrix.column_vector([l_lms, m_lms, s_lms])).to_a.flatten

  x *= 100.0.to_d
  y *= 100.0.to_d
  z *= 100.0.to_d

  [x, y, z]
end

.xyz_to_oklab(xyz_array) ⇒ Object 



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# File 'lib/color_converters/converters/oklab_converter.rb', line 70

def self.xyz_to_oklab(xyz_array)
  x, y, z = xyz_array.map(&:to_d)

  # The transformation matrix expects normalised X, Y, Z values.
  x /= 100.0.to_d
  y /= 100.0.to_d
  z /= 100.0.to_d

  # Given XYZ relative to D65, convert to OKLab
  xyz_to_lms_matrix = ::Matrix[
    [0.8190224379967030.to_d, 0.3619062600528904.to_d, -0.1288737815209879.to_d],
    [0.0329836539323885.to_d, 0.9292868615863434.to_d, 0.0361446663506424.to_d],
    [0.0481771893596242.to_d, 0.2642395317527308.to_d, 0.6335478284694309.to_d]
  ]

  l_lms, m_lms, s_lms = (xyz_to_lms_matrix * ::Matrix.column_vector([x, y, z])).to_a.flatten

  cube_root = (1.0.to_d / 3.0.to_d)
  l_lms **= cube_root
  m_lms **= cube_root
  s_lms **= cube_root

  lms_to_lab_matrix = ::Matrix[
    [0.2104542683093140.to_d, 0.7936177747023054.to_d, -0.0040720430116193.to_d],
    [1.9779985324311684.to_d, -2.4285922420485799.to_d, 0.4505937096174110.to_d],
    [0.0259040424655478.to_d, 0.7827717124575296.to_d, -0.8086757549230774.to_d]
  ]

  l_lab, a_lab, b_lab = (lms_to_lab_matrix * ::Matrix.column_vector([l_lms, m_lms, s_lms])).to_a.flatten

  # Now, scale l to a percentage
  l_lab *= 100.0.to_d

  [l_lab, a_lab, b_lab]
end