Module: Okmain::Oklab

Defined in:
lib/okmain/oklab.rb

Class Method Summary collapse

Class Method Details

.linear_rgb_to_oklab(r, g, b) ⇒ Object

Linear RGB (0..1) → Oklab [L, a, b]



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# File 'lib/okmain/oklab.rb', line 8

def linear_rgb_to_oklab(r, g, b)
  l_ = 0.4122214708 * r + 0.5363325363 * g + 0.0514459929 * b
  m_ = 0.2119034982 * r + 0.6806995451 * g + 0.1073969566 * b
  s_ = 0.0883024619 * r + 0.2817188376 * g + 0.6299787005 * b

  l_cbrt = Math.cbrt(l_)
  m_cbrt = Math.cbrt(m_)
  s_cbrt = Math.cbrt(s_)

  l = 0.2104542553 * l_cbrt + 0.7936177850 * m_cbrt - 0.0040720468 * s_cbrt
  a = 1.9779984951 * l_cbrt - 2.4285922050 * m_cbrt + 0.4505937099 * s_cbrt
  b_ = 0.0259040371 * l_cbrt + 0.7827717662 * m_cbrt - 0.8086757660 * s_cbrt

  [l, a, b_]
end

.linear_to_srgb(c) ⇒ Object

Linear (0..1) → sRGB component (0..255), clamped



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# File 'lib/okmain/oklab.rb', line 52

def linear_to_srgb(c)
  c = c.clamp(0.0, 1.0)
  c = if c <= 0.0031308
        12.92 * c
      else
        1.055 * (c**(1.0 / 2.4)) - 0.055
      end
  (c * 255.0).round.clamp(0, 255)
end

.oklab_to_linear_rgb(l, a, b) ⇒ Object

Oklab [L, a, b] → linear RGB (0..1)



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# File 'lib/okmain/oklab.rb', line 25

def oklab_to_linear_rgb(l, a, b)
  l_ = l + 0.3963377774 * a + 0.2158037573 * b
  m_ = l - 0.1055613458 * a - 0.0638541728 * b
  s_ = l - 0.0894841775 * a - 1.2914855480 * b

  l_cubed = l_ * l_ * l_
  m_cubed = m_ * m_ * m_
  s_cubed = s_ * s_ * s_

  r =  4.0767416621 * l_cubed - 3.3077115913 * m_cubed + 0.2309699292 * s_cubed
  g = -1.2684380046 * l_cubed + 2.6097574011 * m_cubed - 0.3413193965 * s_cubed
  b_ = -0.0041960863 * l_cubed - 0.7034186147 * m_cubed + 1.7076147010 * s_cubed

  [r, g, b_]
end

.oklab_to_srgb8(l, a, b) ⇒ Object

Oklab → sRGB [r, g, b] (0..255)



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# File 'lib/okmain/oklab.rb', line 63

def oklab_to_srgb8(l, a, b)
  r, g, b_ = oklab_to_linear_rgb(l, a, b)
  [linear_to_srgb(r), linear_to_srgb(g), linear_to_srgb(b_)]
end

.srgb_to_linear(c) ⇒ Object

sRGB component (0..255) → linear (0..1)



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# File 'lib/okmain/oklab.rb', line 42

def srgb_to_linear(c)
  c = c / 255.0
  if c <= 0.04045
    c / 12.92
  else
    ((c + 0.055) / 1.055)**2.4
  end
end