Class: Abachrome::Converters::XyzToOklab

Inherits:
Base
  • Object
show all
Defined in:
lib/abachrome/converters/xyz_to_oklab.rb

Instance Attribute Summary

Attributes inherited from Base

#from_space, #to_space

Class Method Summary collapse

Methods inherited from Base

#can_convert?, #convert, find_converter, #initialize, raise_unless, register

Constructor Details

This class inherits a constructor from Abachrome::Converters::Base

Class Method Details

.convert(xyz_color) ⇒ Abachrome::Color

Converts a color from XYZ color space to OKLAB color space.

This method implements the XYZ to OKLAB transformation by first converting XYZ coordinates to the intermediate LMS (Long, Medium, Short) color space, then applying the LMS to OKLAB transformation matrix.

the same alpha as the input color

Parameters:

Returns:

Raises:

  • (ArgumentError) —

    If the input color is not in XYZ color space



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# File 'lib/abachrome/converters/xyz_to_oklab.rb', line 14

def self.convert(xyz_color)
  raise_unless xyz_color, :xyz

  x, y, z = xyz_color.coordinates.map { |_| AbcDecimal(_) }

  # XYZ to LMS transformation matrix
  l = (x * AD("0.8189330101")) + (y * AD("0.3618667424")) - (z * AD("0.1288597137"))
  m = (x * AD("0.0329845436")) + (y * AD("0.9293118715")) + (z * AD("0.0361456387"))
  s = (x * AD("0.0482003018")) + (y * AD("0.2643662691")) + (z * AD("0.6338517070"))

  # Apply cube root transformation
  l_ = AbcDecimal(l)**Rational(1, 3)
  m_ = AbcDecimal(m)**Rational(1, 3)
  s_ = AbcDecimal(s)**Rational(1, 3)

  # LMS to OKLAB transformation matrix
  lightness = (AD("0.2104542553") * l_) + (AD("0.793617785") * m_) - (AD("0.0040720468") * s_)
  a         = (AD("1.9779984951") * l_) - (AD("2.4285922050") * m_) + (AD("0.4505937099") * s_)
  b         = (AD("0.0259040371") * l_) + (AD("0.7827717662") * m_) - (AD("0.8086757660") * s_)

  Color.new(ColorSpace.find(:oklab), [lightness, a, b], xyz_color.alpha)
end