Class: PerfectShape::Polygon

Inherits:
Shape
  • Object
show all
Includes:
MultiPoint
Defined in:
lib/perfect_shape/polygon.rb

Overview

Mostly ported from java.awt.geom: docs.oracle.com/javase/8/docs/api/java/awt/Polygon.html

Instance Attribute Summary

Attributes included from MultiPoint

#points

Instance Method Summary collapse

Methods included from MultiPoint

#initialize, #max_x, #max_y, #min_x, #min_y

Methods inherited from Shape

#==, #bounding_box, #center_point, #center_x, #center_y, #height, #max_x, #max_y, #min_x, #min_y, #normalize_point, #width

Instance Method Details

#contain?(x_or_point, y = nil, outline: false, distance_tolerance: 0) ⇒ @code true

Checks if polygon contains point (two-number Array or x, y args) using the Ray Casting Algorithm (aka Even-Odd Rule): en.wikipedia.org/wiki/Point_in_polygon

the polygon, false if the point lies outside of the polygon’s bounds.

Parameters:

  • x —

    The X coordinate of the point to test.

  • y (defaults to: nil) —

    The Y coordinate of the point to test.

Returns:

  • (@code true) —

    if the point lies within the bound of



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# File 'lib/perfect_shape/polygon.rb', line 40

def contain?(x_or_point, y = nil, outline: false, distance_tolerance: 0)
  x, y = normalize_point(x_or_point, y)
  return unless x && y
  if outline
    edges.any? { |edge| edge.contain?(x, y, distance_tolerance: distance_tolerance) }
  else
    npoints = points.count
    xpoints = points.map(&:first)
    ypoints = points.map(&:last)
    return false if npoints <= 2 || !bounding_box.contain?(x, y)
    hits = 0
  
    lastx = xpoints[npoints - 1]
    lasty = ypoints[npoints - 1]
  
    # Walk the edges of the polygon
    npoints.times do |i|
      curx = xpoints[i]
      cury = ypoints[i]
  
      if cury == lasty
        lastx = curx
        lasty = cury
        next
      end
  
      if curx < lastx
        if x >= lastx
          lastx = curx
          lasty = cury
          next
        end
        leftx = curx
      else
        if x >= curx
          lastx = curx
          lasty = cury
          next
        end
        leftx = lastx
      end
  
      if cury < lasty
        if y < cury || y >= lasty
          lastx = curx
          lasty = cury
          next
        end
        if x < leftx
          hits += 1
          lastx = curx
          lasty = cury
          next
        end
        test1 = x - curx
        test2 = y - cury
      else
        if y < lasty || y >= cury
          lastx = curx
          lasty = cury
          next
        end
        if x < leftx
          hits += 1
          lastx = curx
          lasty = cury
          next
        end
        test1 = x - lastx
        test2 = y - lasty
      end
  
      hits += 1 if (test1 < (test2 / (lasty - cury) * (lastx - curx)))
    end
  
    (hits & 1) != 0
  end
end

#edges ⇒ Object 



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# File 'lib/perfect_shape/polygon.rb', line 119

def edges
  points.zip(points.rotate(1)).map do |point1, point2|
    Line.new(points: [[point1.first, point1.last], [point2.first, point2.last]])
  end
end