module Cairo::Context::Path - cairo-1.12.9 Documentation

# module Cairo::Context::Path

### Public Instance Methods

map_path_onto(path) click to toggle source

    # 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) click to toggle source

    # 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

### Private Instance Methods

parameterize_path(path) click to toggle source

    # File lib/cairo/context/path.rb, line 95
    def parameterize_path(path)
      current_point = nil
      path.collect do |type, points|
        result = 0
        case type
        when PATH_MOVE_TO
          current_point = points[0]
        when PATH_LINE_TO
          result = current_point.distance(points[0])
          current_point = points[0]
        when PATH_CURVE_TO
          result = current_point.distance(points[0])
          result += points[0].distance(points[1])
          result += points[1].distance(points[2])
          current_point = points[2]
        when PATH_CLOSE_PATH
        end
        result
      end
    end