Module: Cairo::Context::Path

Included in:
Cairo::Context
Defined in:
lib/cairo/context/path.rb

Instance Method Summary collapse

Instance Method Details

#map_path_onto(path) ⇒ Object 



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# File 'lib/cairo/context/path.rb', line 21

def map_path_onto(path)
  parameterized_path = parameterize_path(path)
  transformed_path = transform_path(copy_path) do |x, y|
    current_point = nil
    d = x
    i = -1
    type = points = nil
    path.each do |_type, _points|
      type, points = _type, _points
      i += 1
      break if d < parameterized_path[i]
      d -= parameterized_path[i]
      case type
      when PATH_MOVE_TO
        current_point = points[0]
      when PATH_LINE_TO
        current_point = points[0]
      when PATH_CURVE_TO
        current_point = points[2]
      when PATH_CLOSE_PATH
      end
    end

    case type
    when PATH_MOVE_TO
      [x, y]
    when PATH_LINE_TO
      ratio = d / parameterized_path[i]
      current_x, current_y = current_point
      lx, ly = points[0]
      new_x = current_x * (1 - ratio) + lx * ratio
      new_y = current_y * (1 - ratio) + ly * ratio
      dx = -(current_x - lx)
      dy = -(current_y - ly)

      ratio = y / parameterized_path[i]
      [new_x + -dy * ratio, new_y + dx * ratio]
    when PATH_CURVE_TO
      ratio = d / parameterized_path[i]
      current_x, current_y = current_point
      cx0, cy0 = points[0]
      cx1, cy1 = points[1]
      cx2, cy2 = points[2]

      new_x = current_x * (1 - ratio) * (1 - ratio) * (1 - ratio) +
              3 * cx0   * (1 - ratio) * (1 - ratio) * ratio +
              3 * cx1   * (1 - ratio) *      ratio  * ratio +
                  cx2   *      ratio  *      ratio  * ratio
      new_y = current_y * (1 - ratio) * (1 - ratio) * (1 - ratio) +
              3 * cy0   * (1 - ratio) * (1 - ratio) * ratio +
              3 * cy1   * (1 - ratio) *      ratio  * ratio +
                  cy2   *      ratio  *      ratio  * ratio

      dx = -3 * current_x * (1 - ratio) * (1 - ratio) +
            3 * cx0       * (1 - 4 * ratio + 3 * ratio * ratio) +
            3 * cx1       * (    2 * ratio - 3 * ratio * ratio) +
            3 * cx2       *      ratio  * ratio
      dy = -3 * current_y * (1 - ratio) * (1 - ratio) +
            3 * cy0       * (1 - 4 * ratio + 3 * ratio * ratio) +
            3 * cy1       * (    2 * ratio - 3 * ratio * ratio) +
            3 * cy2       *      ratio  * ratio

      ratio = y / Math.sqrt(dx ** 2 + dy ** 2)

      [new_x + -dy * ratio, new_y + dx * ratio]
    when PATH_CLOSE_PATH
      [x, y]
    end
  end
  new_path
  append_path(transformed_path)
end

#transform_path(path, &block) ⇒ Object 



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# File 'lib/cairo/context/path.rb', line 4

def transform_path(path, &block)
  transformed_path = Cairo::Path.new
  path.each do |type, points|
    case type
    when PATH_MOVE_TO
      transformed_path.move_to(*points.collect(&block).flatten)
    when PATH_LINE_TO
      transformed_path.line_to(*points.collect(&block).flatten)
    when PATH_CURVE_TO
      transformed_path.curve_to(*points.collect(&block).flatten)
    when PATH_CLOSE_PATH
      transformed_path.close
    end
  end
  transformed_path
end