如果你想使用opencv区分边界的话，可以使用findContours，但是在确认边界后，

你又想知道边界里面或者外面是什么，你可以使用pointPolygonTest方法来判断。

如下例子：

cv::Point2f findPointInContour(cv::Rect& rect, std::vector< cv::Point > contour)
{
  cv::Point2f onTheEdge1;
  int where = 0;

  for (int i = rect.x; i < rect.x + rect.width; i++) {
    for (int j = rect.y; j < rect.y + rect.height; j++) {
      where = (int) (cv::pointPolygonTest(contour, cv::Point2f(i, j), false));

      //cout << "x = " << i << " y = " << j << "distance " << where << endl;
      if (where > 0) { //inside
        return cv::Point2f(i, j);
      } else if (where == 0) { //on the edge
        onTheEdge1 = cv::Point2f(i, j);
      }
    }
  }

  return onTheEdge1;
}