Class: Prawn::SVG::Calculators::PathLength

Inherits:
Object
  • Object
show all
Defined in:
lib/prawn/svg/calculators/path_length.rb

Defined Under Namespace

Classes: Segment

Constant Summary collapse

SUBDIVISION_TOLERANCE = 
0.01
LOOKUP_TABLE_STEPS = 
64

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(commands) ⇒ PathLength 



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# File 'lib/prawn/svg/calculators/path_length.rb', line 10

def initialize(commands)
  @segments = []
  @total_length = 0.0

  current_point = nil
  subpath_start = nil

  commands.each do |command|
    case command
    when Prawn::SVG::Pathable::Move
      current_point = command.destination
      subpath_start = current_point

    when Prawn::SVG::Pathable::Close
      if current_point && subpath_start && current_point != subpath_start
        add_line_segment(current_point, subpath_start)
        current_point = subpath_start
      end

    when Prawn::SVG::Pathable::Line
      if current_point
        add_line_segment(current_point, command.destination)
        current_point = command.destination
      end

    when Prawn::SVG::Pathable::Curve
      if current_point
        add_curve_segment(current_point, command.point1, command.point2, command.destination)
        current_point = command.destination
      end
    end
  end
end

Instance Attribute Details

#total_length ⇒ Object (readonly)

Returns the value of attribute total_length.



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# File 'lib/prawn/svg/calculators/path_length.rb', line 8

def total_length
  @total_length
end

Instance Method Details

#point_at(distance) ⇒ Object 



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# File 'lib/prawn/svg/calculators/path_length.rb', line 44

def point_at(distance)
  return nil if distance.negative? || distance > @total_length || @segments.empty?

  @segments.each do |segment|
    start_distance = segment.cumulative_length - segment.segment_length

    next unless distance <= segment.cumulative_length

    local_distance = distance - start_distance

    case segment.type
    when :line
      t = segment.segment_length.positive? ? local_distance / segment.segment_length : 0.0
      x = segment.start_point[0] + (t * (segment.end_point[0] - segment.start_point[0]))
      y = segment.start_point[1] + (t * (segment.end_point[1] - segment.start_point[1]))
      dx = segment.end_point[0] - segment.start_point[0]
      dy = segment.end_point[1] - segment.start_point[1]
      angle = Math.atan2(dy, dx) * 180.0 / Math::PI
      return [x, y, angle]

    when :curve
      t = find_t_for_distance(segment, local_distance)
      p0, p1, p2, p3 = segment.start_point, *segment.control_points, segment.end_point
      x, y = evaluate_cubic(p0, p1, p2, p3, t)
      dx, dy = evaluate_cubic_derivative(p0, p1, p2, p3, t)
      angle = Math.atan2(dy, dx) * 180.0 / Math::PI
      return [x, y, angle]
    end
  end

  # Exactly at the end
  segment = @segments.last
  [segment.end_point[0], segment.end_point[1], end_angle(segment)]
end