Method NthPoint

annotation/psimpl.h:491–519

! \brief Performs the nth point routine (NP). NP is an O(n) algorithm for polyline simplification. It keeps only the first, last and each nth point. As an example, consider any random line of 8 points. Using n = 3 will always yield a simplification consisting of points: 1, 4, 7, 8 \image html psimpl_np.png NP is ap

            \return             one beyond the last coordinate of the simplified polyline
        */
        OutputIterator NthPoint (
            InputIterator first,
            InputIterator last,
            unsigned n,
            OutputIterator result)
        {
            diff_type coordCount = std::distance (first, last);
            diff_type pointCount = DIM              // protect against zero DIM
                                   ? coordCount / DIM
                                   : 0;

            // validate input and check if simplification required
            if (coordCount % DIM || pointCount < 3 || n < 2) {
                return std::copy (first, last, result);
            }

            unsigned remaining = pointCount - 1;    // the number of points remaining after key
            InputIterator key = first;              // indicates the current key

            // the first point is always part of the simplification
            CopyKey (key, result);

            // copy each nth point
            while (Forward (key, n, remaining)) {
                CopyKey (key, result);
            }

            return result;
        }

        /*!
            \brief Performs the (radial) distance between points routine (RD).