renaming file

Algorithms/DouglasPeucker.cpp

@@ -0,0 +1,166 @@
+/*
+
+Copyright (c) 2013, Project OSRM, Dennis Luxen, others
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+Redistributions of source code must retain the above copyright notice, this list
+of conditions and the following disclaimer.
+Redistributions in binary form must reproduce the above copyright notice, this
+list of conditions and the following disclaimer in the documentation and/or
+other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+*/
+
+#include "DouglasPeucker.h"
+
+//These thresholds are more or less heuristically chosen.
+static double DouglasPeuckerThresholds[19] = {
+    32000000., //z0
+    16240000., //z1
+     8240000., //z2
+     4240000., //z3
+     2000000., //z4
+     1000000., //z5
+      500000., //z6
+      240000., //z7
+      120000., //z8
+       60000., //z9
+       30000., //z10
+       19000., //z11
+        5000., //z12
+        2000., //z13
+         200., //z14
+          16., //z15
+           6., //z16
+           3., //z17
+           3.  //z18
+};
+
+/**
+ * This distance computation does integer arithmetic only and is about twice as
+ * fast as the other distance function. It is an approximation only, but works
+ * more or less ok.
+ */
+int DouglasPeucker::fastDistance(
+    const FixedPointCoordinate& point,
+    const FixedPointCoordinate& segA,
+    const FixedPointCoordinate& segB
+) const {
+    const int p2x = (segB.lon - segA.lon);
+    const int p2y = (segB.lat - segA.lat);
+    const int something = p2x*p2x + p2y*p2y;
+    double u = ( 0 == something  ? 0 : ((point.lon - segA.lon) * p2x + (point.lat - segA.lat) * p2y) / something);
+
+    if (u > 1) {
+        u = 1;
+    } else if (u < 0) {
+        u = 0;
+    }
+
+    const int x = segA.lon + u * p2x;
+    const int y = segA.lat + u * p2y;
+
+    const int dx = x - point.lon;
+    const int dy = y - point.lat;
+
+    const int dist = (dx*dx + dy*dy);
+
+    return dist;
+}
+
+void DouglasPeucker::Run(
+    std::vector<SegmentInformation> & input_geometry,
+    const unsigned zoom_level
+) {
+    {
+        BOOST_ASSERT_MSG(zoom_level < 19, "unsupported zoom level");
+        BOOST_ASSERT_MSG(1 < input_geometry.size(), "geometry invalid");
+        std::size_t left_border = 0;
+        std::size_t right_border = 1;
+        //Sweep linerarily over array and identify those ranges that need to be checked
+        do {
+            BOOST_ASSERT_MSG(
+                input_geometry[left_border].necessary,
+                "left border must be necessary"
+            );
+            BOOST_ASSERT_MSG(
+                input_geometry.back().necessary,
+                "right border must be necessary"
+            );
+
+            if(input_geometry[right_border].necessary) {
+                recursion_stack.push(std::make_pair(left_border, right_border));
+                left_border = right_border;
+            }
+            ++right_border;
+        } while( right_border < input_geometry.size());
+    }
+    while(!recursion_stack.empty()) {
+        //pop next element
+        const PairOfPoints pair = recursion_stack.top();
+        recursion_stack.pop();
+        BOOST_ASSERT_MSG(
+            input_geometry[pair.first].necessary,
+            "left border mus be necessary"
+        );
+        BOOST_ASSERT_MSG(
+            input_geometry[pair.second].necessary,
+            "right border must be necessary"
+        );
+        BOOST_ASSERT_MSG(
+            pair.second < input_geometry.size(),
+            "right border outside of geometry"
+        );
+        BOOST_ASSERT_MSG(
+            pair.first < pair.second,
+            "left border on the wrong side"
+        );
+        int max_distance = INT_MIN;
+
+        std::size_t farthest_element_index = pair.second;
+        //find index idx of element with max_distance
+        for(std::size_t i = pair.first+1; i < pair.second; ++i){
+            const int temp_dist = fastDistance(
+                                    input_geometry[i].location,
+                                    input_geometry[pair.first].location,
+                                    input_geometry[pair.second].location
+                                );
+            const double distance = std::fabs(temp_dist);
+            if(
+                distance > DouglasPeuckerThresholds[zoom_level] &&
+                distance > max_distance
+            ) {
+                farthest_element_index = i;
+                max_distance = distance;
+            }
+        }
+        if (max_distance > DouglasPeuckerThresholds[zoom_level]) {
+            //  mark idx as necessary
+            input_geometry[farthest_element_index].necessary = true;
+            if (1 < (farthest_element_index - pair.first) ) {
+                recursion_stack.push(
+                    std::make_pair(pair.first, farthest_element_index)
+                );
+            }
+            if (1 < (pair.second - farthest_element_index) ) {
+                recursion_stack.push(
+                    std::make_pair(farthest_element_index, pair.second)
+                );
+            }
+        }
+    }
+}