Module: PSD::Compose

Extended by:
Compose
Included in:
Compose
Defined in:
lib/psd/renderer/compose.rb

Overview

Collection of methods that composes two RGBA pixels together in various ways based on Photoshop blend modes.

Mostly based on similar code from libpsd.

Instance Method Summary collapse

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method, *args, &block) ⇒ Object

If the blend mode is missing, we fall back to normal composition.



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# File 'lib/psd/renderer/compose.rb', line 326

def method_missing(method, *args, &block)
  normal(*args)
end

Instance Method Details

#color_burn(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 54

def color_burn(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 f > 0
      f = ((255 - b) << 8) / f
      f > 255 ? 0 : (255 - f)
    else
      b
    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

#color_dodge(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 119

def color_dodge(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|
    f < 255 ? [(b << 8) / (255 - f), 255].min : b
  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

#darken(fg, bg, opacity) ⇒ Object

Subtractive blend modes



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# File 'lib/psd/renderer/compose.rb', line 30

def darken(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)
  new_r = r(fg) <= r(bg) ? blend_channel(r(bg), r(fg), mix_alpha) : r(bg)
  new_g = g(fg) <= g(bg) ? blend_channel(g(bg), g(fg), mix_alpha) : g(bg)
  new_b = b(fg) <= b(bg) ? blend_channel(b(bg), b(fg), mix_alpha) : b(bg)

  rgba(new_r, new_g, new_b, dst_alpha)
end

#difference(fg, bg, opacity) ⇒ Object

Inversion blend modes



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# File 'lib/psd/renderer/compose.rb', line 295

def difference(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)

  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

#exclusion(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 308

def exclusion(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)

  new_r = blend_channel(r(bg), r(bg) + r(fg) - (r(bg) * r(fg) >> 7), mix_alpha)
  new_g = blend_channel(g(bg), g(bg) + g(fg) - (g(bg) * g(fg) >> 7), mix_alpha)
  new_b = blend_channel(b(bg), b(bg) + b(fg) - (b(bg) * b(fg) >> 7), mix_alpha)

  rgba(new_r, new_g, new_b, dst_alpha)
end

#hard_light(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 194

def hard_light(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 f < 128
      b * f >> 7
    else
      255 - ((255 - f) * (255 - b) >> 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

#hard_mix(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 278

def hard_mix(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)

  new_r = blend_channel(r(bg), (r(bg) + r(fg) <= 255) ? 0 : 255, mix_alpha)
  new_g = blend_channel(g(bg), (g(bg) + g(fg) <= 255) ? 0 : 255, mix_alpha)
  new_b = blend_channel(b(bg), (b(bg) + b(fg) <= 255) ? 0 : 255, mix_alpha)

  rgba(new_r, new_g, new_b, dst_alpha)
end

#lighten(fg, bg, opacity) ⇒ Object

Additive blend modes



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# File 'lib/psd/renderer/compose.rb', line 93

def lighten(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)

  new_r = r(fg) >= r(bg) ? blend_channel(r(bg), r(fg), mix_alpha) : r(bg)
  new_g = g(fg) >= g(bg) ? blend_channel(g(bg), g(fg), mix_alpha) : g(bg)
  new_b = b(fg) >= b(bg) ? blend_channel(b(bg), b(fg), mix_alpha) : b(bg)
  
  rgba(new_r, new_g, new_b, dst_alpha)
end

#linear_burn(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 76

def linear_burn(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)

  new_r = blend_channel(r(bg), (r(fg) < (255 - r(bg))) ? 0 : r(fg) - (255 - r(bg)), mix_alpha)
  new_g = blend_channel(g(bg), (g(fg) < (255 - g(bg))) ? 0 : g(fg) - (255 - g(bg)), mix_alpha)
  new_b = blend_channel(b(bg), (b(fg) < (255 - b(bg))) ? 0 : b(fg) - (255 - b(bg)), mix_alpha)

  rgba(new_r, new_g, new_b, dst_alpha)
end

#linear_dodge(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 136

def linear_dodge(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)

  new_r = blend_channel(r(bg), (r(bg) + r(fg)) > 255 ? 255 : r(bg) + r(fg), mix_alpha)
  new_g = blend_channel(g(bg), (g(bg) + g(fg)) > 255 ? 255 : g(bg) + g(fg), mix_alpha)
  new_b = blend_channel(b(bg), (b(bg) + b(fg)) > 255 ? 255 : b(bg) + b(fg), mix_alpha)

  rgba(new_r, new_g, new_b, dst_alpha)
end

#linear_light(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 236

def linear_light(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 < 255
      [f * f / (255 - b), 255].min
    else
      255
    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

#multiply(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 42

def multiply(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)
  new_r = blend_channel(r(bg), r(fg) * r(bg) >> 8, mix_alpha)
  new_g = blend_channel(g(bg), g(fg) * g(bg) >> 8, mix_alpha)
  new_b = blend_channel(b(bg), b(fg) * b(bg) >> 8, mix_alpha)

  rgba(new_r, new_g, new_b, dst_alpha)
end

#normal(fg, bg, opacity) ⇒ Object Also known as: passthru

Normal blend modes



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# File 'lib/psd/renderer/compose.rb', line 13

def normal(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)
  new_r = blend_channel(r(bg), r(fg), mix_alpha)
  new_g = blend_channel(g(bg), g(fg), mix_alpha)
  new_b = blend_channel(b(bg), b(fg), mix_alpha)

  rgba(new_r, new_g, new_b, dst_alpha)
end

#overlay(fg, bg, opacity) ⇒ Object

Contrasting blend modes



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# File 'lib/psd/renderer/compose.rb', line 154

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

#pin_light(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 257

def pin_light(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 f >= 128
      [b, (f - 128) * 2].max
    else
      [b, f * 2].min
    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

#screen(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 106

def screen(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)

  new_r = blend_channel(r(bg), 255 - ((255 - r(bg)) * (255 - r(fg)) >> 8), mix_alpha)
  new_g = blend_channel(g(bg), 255 - ((255 - g(bg)) * (255 - g(fg)) >> 8), mix_alpha)
  new_b = blend_channel(b(bg), 255 - ((255 - b(bg)) * (255 - b(fg)) >> 8), mix_alpha)

  rgba(new_r, new_g, new_b, dst_alpha)
end

#soft_light(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 175

def soft_light(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|
    c1 = b * f >> 8
    c2 = 255 - ((255 - b) * (255 - f) >> 8)
    ((255 - b) * c1 >> 8) + (b * c2 >> 8)
  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

#vivid_light(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 215

def vivid_light(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 f < 255
      [(b * b / (255 - f) + f * f / (255 - b)) >> 1, 255].min
    else
      b
    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