Class: NSWTopo::GeoJSON::MultiPolygon

Inherits:
Object
  • Object
show all
Includes:
StraightSkeleton
Defined in:
lib/nswtopo/gis/geojson/multi_polygon.rb

Constant Summary

Constants included from StraightSkeleton

StraightSkeleton::DEFAULT_ROUNDING_ANGLE

Instance Method Summary collapse

Instance Method Details

#area ⇒ Object 



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# File 'lib/nswtopo/gis/geojson/multi_polygon.rb', line 6

def area
  @coordinates.flatten(1).sum(&:signed_area)
end

#buffer(*margins, **options) ⇒ Object 



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# File 'lib/nswtopo/gis/geojson/multi_polygon.rb', line 89

def buffer(*margins, **options)
  nodes = Nodes.new @coordinates.flatten(1)
  margins.each do |margin|
    nodes.progress limit: -margin, **options.slice(:rounding_angle, :cutoff_angle)
  end
  interior_rings, exterior_rings = nodes.readout.partition(&:hole?)
  polygons, foo = exterior_rings.sort_by(&:signed_area).inject [[], interior_rings] do |(polygons, interior_rings), exterior_ring|
    claimed, unclaimed = interior_rings.partition do |interior_ring|
      interior_ring.first.within? exterior_ring
    end
    [polygons << [exterior_ring, *claimed], unclaimed]
  end
  MultiPolygon.new polygons.entries, @properties
end

#centrelines(**options) ⇒ Object 



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# File 'lib/nswtopo/gis/geojson/multi_polygon.rb', line 85

def centrelines(**options)
  centres(**options, interval: nil, lines: true)
end

#centrepoints(interval:, **options) ⇒ Object 



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# File 'lib/nswtopo/gis/geojson/multi_polygon.rb', line 81

def centrepoints(interval:, **options)
  centres(**options, interval: interval, lines: false)
end

#centres(fraction: 0.5, min_width: nil, interval:, lines: true) ⇒ Object 



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# File 'lib/nswtopo/gis/geojson/multi_polygon.rb', line 18

def centres(fraction: 0.5, min_width: nil, interval:, lines: true)
  neighbours = Hash.new { |neighbours, node| neighbours[node] = [] }
  samples, tails, node1 = {}, {}, nil

  Nodes.new(@coordinates.flatten(1)).progress(interval: interval) do |event, *args|
    case event
    when :nodes
      node0, node1 = *args
      neighbours[node0] << node1
      neighbours[node1] << node0
    when :interval
      travel, rings = *args
      samples[travel] = rings.flat_map do |ring|
        ring.sample_at interval
      end
    end
  end

  samples[node1.travel] = [node1.point.to_f]
  max_travel = neighbours.keys.map(&:travel).max
  min_travel = [fraction * max_travel, min_width && 0.5 * min_width].compact.max

  features = samples.select do |travel, points|
    travel > min_travel
  end.map do |travel, points|
    MultiPoint.new points, @properties
  end.reverse
  return features unless lines

  loop do
    break unless neighbours.reject do |node, (neighbour, *others)|
      others.any? || neighbours[neighbour].one?
    end.each do |node, (neighbour, *)|
      next if neighbours[neighbour].one?
      neighbours.delete node
      neighbours[neighbour].delete node
      nodes, length = tails.delete(node) || [[node], 0]
      candidate = [nodes << neighbour, length + [node.point, neighbour.point].distance]
      tails[neighbour] = [tails[neighbour], candidate].compact.max_by(&:last)
    end.any?
  end

  lengths, lines, candidates = Hash.new(0), Hash.new, tails.values
  while candidates.any?
    (*nodes, node), length = candidates.pop
    next if (neighbours[node] - nodes).each do |neighbour|
      candidates << [[*nodes, node, neighbour], length + [node.point, neighbour.point].distance]
    end.any?
    index = nodes.find(&:index).index
    tail_nodes, tail_length = tails[node] || [[node], 0]
    lengths[index], lines[index] = length + tail_length, nodes + tail_nodes.reverse if length + tail_length > lengths[index]
  end

  linestrings = lines.values.flat_map do |nodes|
    nodes.chunk do |node|
      node.travel >= min_travel
    end.select(&:first).map(&:last).reject(&:one?).map do |nodes|
      nodes.map(&:point).to_f
    end
  end
  features.prepend MultiLineString.new(linestrings, @properties)
end

#centroids ⇒ Object 



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# File 'lib/nswtopo/gis/geojson/multi_polygon.rb', line 104

def centroids
  MultiPoint.new @coordinates.map(&:first).map(&:centroid), @properties
end

#samples(interval) ⇒ Object 



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# File 'lib/nswtopo/gis/geojson/multi_polygon.rb', line 108

def samples(interval)
  points = @coordinates.flatten(1).flat_map do |ring|
    ring.sample_at interval
  end
  MultiPoint.new points, @properties
end

#skeleton ⇒ Object 



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# File 'lib/nswtopo/gis/geojson/multi_polygon.rb', line 10

def skeleton
  segments = []
  Nodes.new(@coordinates.flatten(1)).progress do |event, node0, node1|
    segments << [node0.point, node1.point].to_f
  end
  MultiLineString.new segments, @properties
end