Module: PSD::Compose

Extended by:
ChunkyPNG::Color, 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 323

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 55

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 120

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 31

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 296

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 309

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 195

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 279

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 94

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 77

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 137

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 237

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 43

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 14

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 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

#pin_light(fg, bg, opacity) ⇒ Object 



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# File 'lib/psd/renderer/compose.rb', line 258

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 107

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 176

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 216

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