Method: PSD::Compose#difference

Defined in:
lib/psd/compose.rb

#difference(fg, bg, opts = {}) ⇒ Object

Inversion blend modes



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# File 'lib/psd/compose.rb', line 300

def difference(fg, bg, opts={})
  return fg if fully_transparent?(bg)
  return bg if fully_transparent?(fg)

  mix_alpha, dst_alpha = calculate_alphas(fg, bg, DEFAULT_OPTS.merge(opts))

  new_r = blend_channel(r(bg), (r(bg) - r(fg)).abs, mix_alpha)
  new_g = blend_channel(g(bg), (g(bg) - g(fg)).abs, mix_alpha)
  new_b = blend_channel(b(bg), (b(bg) - b(fg)).abs, mix_alpha)

  rgba(new_r, new_g, new_b, dst_alpha)
end