Class: RImageAnalysisTools::Skeletonizer

Inherits:
Object
  • Object
show all
Defined in:
lib/rimageanalysistools/skeletonizer.rb

Instance Method Summary collapse

Constructor Details

#initialize(im) ⇒ Skeletonizer

implementation of skeletonization algorithm presented in Gonzalez & Woods, p 651-652



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# File 'lib/rimageanalysistools/skeletonizer.rb', line 38

def initialize(im)

  @im = im

end

Instance Method Details

#compute_n(ic) ⇒ Object 



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# File 'lib/rimageanalysistools/skeletonizer.rb', line 44

def compute_n(ic)

  temp_ic = ImageCoordinate.cloneCoord(ic)

  n = -1  # compensate for 0,0 case

  x_off = [-1,0,1]
  y_off = [-1,0,1]

  x_off.each do |x|
    y_off.each do |y|

      temp_ic[:x] = ic[:x] + x
      temp_ic[:y] = ic[:y] + y

      if @im.inBounds(temp_ic) and @im[temp_ic] == @im[ic] then
        n += 1
      end

    end

  end

  temp_ic.recycle

  n

end

#compute_pixel_product(ic, pixel_offsets) ⇒ Object 



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# File 'lib/rimageanalysistools/skeletonizer.rb', line 110

def compute_pixel_product(ic, pixel_offsets)

  temp_ic = ImageCoordinate.cloneCoord(ic)

  pixel_offsets.each do |po|

    temp_ic[:x]= ic[:x] + po[0]
    temp_ic[:y]= ic[:y] + po[1]
    
    unless @im.inBounds(temp_ic) and @im[temp_ic] == @im[ic] then
      temp_ic.recycle
      return 0
    end

  end

  temp_ic.recycle

  1

end

#compute_t(ic) ⇒ Object 



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# File 'lib/rimageanalysistools/skeletonizer.rb', line 73

def compute_t(ic)

  temp_ic1 = ImageCoordinate.cloneCoord(ic)
  temp_ic2 = ImageCoordinate.cloneCoord(ic)

  pixel_offsets = [[0, -1], [1, -1], [1, 0], [1, 1], [0, 1], [-1, 1], [-1, 0], [-1, -1], [0, -1]]

  t = 0

  0.upto(pixel_offsets.length - 2) do |i|
    
    p1 = pixel_offsets[i]
    p2 = pixel_offsets[i+1]

    temp_ic1[:x] = ic[:x] + p1[0]
    temp_ic2[:x] = ic[:x] + p2[0]

    temp_ic1[:y] = ic[:y] + p1[1]
    temp_ic2[:y] = ic[:y] + p2[1]

    v1 = 0
    v2 = 0

    v1 = 1 if @im.inBounds(temp_ic1) and @im[ic] == @im[temp_ic1]
    v2 = 1 if @im.inBounds(temp_ic2) and @im[ic] == @im[temp_ic2]

    t += 1 if v2 - v1 == 1

  end

  temp_ic1.recycle
  temp_ic2.recycle

  t

end

#do_iteration ⇒ Object 



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# File 'lib/rimageanalysistools/skeletonizer.rb', line 184

def do_iteration

  flagged1 = []

  @im.each do |ic|

    next if @im[ic] == 0

    should_flag = pass1(ic)

    if should_flag then
      flagged1 << ImageCoordinate.cloneCoord(ic)
    end

  end

  flagged1.each do |ic|

    @im[ic]= 0

    ic.recycle

  end

  flagged2 = []

  @im.each do |ic|
    
    next if @im[ic] == 0

    should_flag = pass2(ic)

    if should_flag then

      flagged2 << ImageCoordinate.cloneCoord(ic)

    end

  end

  flagged2.each do |ic|
    
    @im[ic]= 0

    ic.recycle

  end

  changed = (not (flagged1.empty? and flagged2.empty?))

  changed

end

#pass1(ic) ⇒ Object 



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# File 'lib/rimageanalysistools/skeletonizer.rb', line 132

def pass1(ic)

  n = compute_n(ic)
  
  return false if n < 2 or n > 6

  t = compute_t(ic)

  return false unless t == 1

  pixels246 = [[0, -1], [1, 0], [0, 1]]

  p246 = compute_pixel_product(ic, pixels246)

  return false unless p246 == 0

  pixels468 = [[1, 0], [0, 1], [-1, 0]]

  p468 = compute_pixel_product(ic, pixels468)

  return false unless p468 == 0

  true

end

#pass2(ic) ⇒ Object 



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# File 'lib/rimageanalysistools/skeletonizer.rb', line 158

def pass2(ic)

  n = compute_n(ic)
  
  return false if n < 2 or n > 6

  t = compute_t(ic)

  return false unless t == 1

  pixels248 = [[0, -1], [1, 0], [-1, 0]]

  p248 = compute_pixel_product(ic, pixels248)

  return false unless p248 == 0

  pixels268 = [[0, -1], [0, 1], [-1, 0]]

  p268 = compute_pixel_product(ic, pixels268)

  return false unless p268 == 0

  true

end

#skeletonize ⇒ Object 



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# File 'lib/rimageanalysistools/skeletonizer.rb', line 238

def skeletonize

  while do_iteration do
    
  end

end