Method: PSD::Compose#overlay

Defined in:
lib/psd/renderer/compose.rb

#overlay(fg, bg, opacity) ⇒ Object

Contrasting blend modes



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# File 'lib/psd/renderer/compose.rb', line 155

def overlay(fg, bg, opacity)
  return apply_opacity(fg, opacity) if fully_transparent?(bg)
  return bg if fully_transparent?(fg)

  mix_alpha, dst_alpha = calculate_alphas(fg, bg, opacity)

  calculate_foreground = Proc.new do |b, f|
    if b < 128
      b * f >> 7
    else
      255 - ((255 - b) * (255 - f) >> 7)
    end
  end

  new_r = blend_channel(r(bg), calculate_foreground.call(r(bg), r(fg)), mix_alpha)
  new_g = blend_channel(g(bg), calculate_foreground.call(g(bg), g(fg)), mix_alpha)
  new_b = blend_channel(b(bg), calculate_foreground.call(b(bg), b(fg)), mix_alpha)

  rgba(new_r, new_g, new_b, dst_alpha)
end