Class: Abachrome::Converters::SrgbToYiq

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

Class Method Summary collapse

Class Method Details

.convert(srgb_color) ⇒ Abachrome::Color

Converts a color from sRGB color space to YIQ color space. This method applies the NTSC standard transformation matrix.

with the same alpha value as the input color

Parameters:

Returns:



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# File 'lib/abachrome/converters/srgb_to_yiq.rb', line 30

def self.convert(srgb_color)
  r, g, b = srgb_color.coordinates.map { |c| AbcDecimal(c) }

  # NTSC RGB to YIQ transformation matrix
  # Y = 0.299R + 0.587G + 0.114B  (Rec. 601 luma)
  # I = 0.596R - 0.275G - 0.321B  (In-phase: orange-blue)
  # Q = 0.212R - 0.523G + 0.311B  (Quadrature: purple-green)
  y = (AD("0.299") * r) + (AD("0.587") * g) + (AD("0.114") * b)
  i = (AD("0.5959") * r) - (AD("0.2746") * g) - (AD("0.3213") * b)
  q = (AD("0.2115") * r) - (AD("0.5227") * g) + (AD("0.3112") * b)

  Color.new(
    ColorSpace.find(:yiq),
    [y, i, q],
    srgb_color.alpha
  )
end