Class: Geospatial::Polygon

Inherits:
Object
  • Object
show all
Defined in:
lib/geospatial/polygon.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(points, bounding_box = nil) ⇒ Polygon

Returns a new instance of Polygon.



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# File 'lib/geospatial/polygon.rb', line 41

def initialize(points, bounding_box = nil)
  @points = points
  @bounding_box = bounding_box
end

Instance Attribute Details

#points ⇒ Object (readonly)

Returns the value of attribute points.



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# File 'lib/geospatial/polygon.rb', line 46

def points
  @points
end

Class Method Details

.[](*points) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 25

def self.[] *points
  self.new(points)
end

.dump(polygon) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 35

def self.dump(polygon)
  if polygon
    JSON.dump(polygon.points.map(&:to_a))
  end
end

.is_left(p0, p1, p2) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 142

def self.is_left(p0, p1, p2)
  a = p1 - p0
  b = p2 - p0
  
  return (a[0] * b[1]) - (b[0] * a[1])
end

.load(data) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 29

def self.load(data)
  if data
    self.new(JSON.parse(data).map{|point| Vector.elements(point)})
  end
end

Instance Method Details

#[](index) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 48

def [] index
  a = @points[index.floor]
  b = @points[index.ceil % @points.size]
  
  return a + (b - a) * (index % 1.0)
end

#area(radius = 1.0) ⇒ Object

Parameters:

  • (defaults to: 1.0)

    The radius of the sphere on which to compute the area.



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# File 'lib/geospatial/polygon.rb', line 81

def area(radius = 1.0)
  if @points.size > 2
    area = 0.0
    
    self.edges.each do |p1, p2|
      r1 = (p2[0] - p1[0]) * D2R
      r2 = 2 + Math::sin(p1[1] * D2R) + Math::sin(p2[1] * D2R)
      
      area += r1 * r2
    end
    
    return (area * radius * radius / 2.0).abs
  else
    return 0.0
  end
end

#bounding_box ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 59

def bounding_box
  @bounding_box ||= Box.enclosing_points(@points).freeze
end

#edge_intersection(a, b) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 185

def edge_intersection(a, b)
  line = Line.new(a, b)
  
  edges.each_with_index do |(pa, pb), i|
    edge = Line.new(pa, pb)
    
    if line.intersect?(edge)
      return i
    end
  end
  
  return nil
end

#edges ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 70

def edges
  return to_enum(:edges) unless block_given?
  
  size = @points.size
  
  @points.each_with_index do |point, index|
    yield point, @points[(index+1)%size]
  end
end

#freeze ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 63

def freeze
  @points.freeze
  bounding_box.freeze
  
  super
end

#include?(other) ⇒ Boolean

Returns:



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# File 'lib/geospatial/polygon.rb', line 208

def include?(other)
  other.corners.all?{|corner| self.include_point?(corner)}
end

#include_point?(point) ⇒ Boolean

Returns:



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# File 'lib/geospatial/polygon.rb', line 171

def include_point?(point)
  return false unless bounding_box.include_point?(point)
  
  self.winding_number(point).odd?
end

#intersect?(other) ⇒ Boolean

Returns:



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# File 'lib/geospatial/polygon.rb', line 199

def intersect?(other)
  case other
  when Box
    intersect_with_box?(other)
  when Circle
    intersect_with_circle?(other)
  end
end

#intersect_with_box?(other) ⇒ Boolean

Returns:



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# File 'lib/geospatial/polygon.rb', line 177

def intersect_with_box?(other)
  return true if @points.any?{|point| other.include_point?(point)}
  
  return true if other.corners.any?{|corner| self.include_point?(corner)}
  
  return false
end

#simplify ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 98

def simplify
  simplified_points = @points.first(1)
  
  (1...@points.size).each do |index|
    point = @points[index]
    
    next_point = @points[(index+1) % @points.size]
    
    if yield(simplified_points.last, point, next_point)
      simplified_points << point
    end
  end
  
  self.class.new(simplified_points, bounding_box)
end

#subdivide ⇒ Object

polygon.subdivide do |a, b| a = Geospatial::Location.new(*a) b = Geospatial::Location.new(*b) if a.distance_from(b) > maximum_distance a.midpoints(b, 2) end end



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# File 'lib/geospatial/polygon.rb', line 122

def subdivide
  simplified_points = @points.first(1)
  
  (1..@points.size).each do |index|
    point = @points[index % @points.size]
    next_point = @points[(index+1) % @points.size]
    
    if points = yield(simplified_points.last, point, next_point)
      simplified_points.concat(points)
    end
    
    # Polygons are represented by a closed sequence of points, but we need to subdivide by the last point at the first point too. However, we don't add the first point a 2nd time.
    if index < @points.size
      simplified_points << point
    end
  end
  
  self.class.new(simplified_points, bounding_box)
end

#to_s ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 55

def to_s
  "#{self.class}#{@points.inspect}"
end

#winding_number(p) ⇒ Number

Test a 2D point for inclusion in the polygon.

Parameters:

  • The point to test.

Returns:

  • The number of times the polygon winds around the point (0 if outside).



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# File 'lib/geospatial/polygon.rb', line 152

def winding_number(p)
  count = 0
  
  edges.each do |pa, pb|
    if pa[1] <= p[1]
      if pb[1] >= p[1] and Polygon.is_left(pa, pb, p) > 0
        count += 1
      end
    else
      if pb[1] <= p[1] and Polygon.is_left(pa, pb, p) < 0
        count -= 1
      end
    end
    
  end
  
  return count
end