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Apply strong heuristics to speed up line generalization

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This commit is contained in:
Dennis Luxen 2014-05-30 19:10:37 +02:00
parent f3ad14cb7f
commit a671f63a3e
1 changed files with 67 additions and 26 deletions
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87
Algorithms/DouglasPeucker.cpp
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@ -37,23 +37,61 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include <limits>
struct CoordinatePairCalculator
{
CoordinatePairCalculator() = delete;
CoordinatePairCalculator(const FixedPointCoordinate & coordinate_a, const FixedPointCoordinate &coordinate_b)
{
const float RAD = 0.017453292519943295769236907684886;
first_lat = (coordinate_a.lat / COORDINATE_PRECISION) * RAD;
first_lon = (coordinate_a.lon / COORDINATE_PRECISION) * RAD;
second_lat = (coordinate_b.lat / COORDINATE_PRECISION) * RAD;
second_lon = (coordinate_b.lon / COORDINATE_PRECISION) * RAD;
}
int operator()(FixedPointCoordinate & other) const
{
const float RAD = 0.017453292519943295769236907684886;
const float earth_radius = 6372797.560856;
const float float_lat1 = (other.lat / COORDINATE_PRECISION) * RAD;
const float float_lon1 = (other.lon / COORDINATE_PRECISION) * RAD;
const float x_value_1 = (first_lon - float_lon1) * cos((float_lat1 + first_lat) / 2.);
const float y_value_1 = first_lat - float_lat1;
const float dist1 = sqrt(std::pow(x_value_1, 2) + std::pow(y_value_1,2)) * earth_radius;
const float x_value_2 = (second_lon - float_lon1) * cos((float_lat1 + second_lat) / 2.);
const float y_value_2 = second_lat - float_lat1;
const float dist2 = sqrt(std::pow(x_value_2, 2) + std::pow(y_value_2,2)) * earth_radius;
const int other_dist = std::min(dist1, dist2);
return other_dist;
}
float first_lat;
float first_lon;
float second_lat;
float second_lon;
};
DouglasPeucker::DouglasPeucker()
: douglas_peucker_thresholds({2621440, // z0
1310720, // z1
655360, // z2
327680, // z3
163840, // z4
81920, // z5
40960, // z6
20480, // z7
9600, // z8
4800, // z9
2800, // z10
900, // z11
600, // z12
275, // z13
160, // z14
60, // z15
: douglas_peucker_thresholds({512440, // z0
256720, // z1
122560, // z2
56780, // z3
28800, // z4
14400, // z5
7200, // z6
3200, // z7
2400, // z8
1000, // z9
600, // z10
120, // z11
60, // z12
45, // z13
36, // z14
20, // z15
8, // z16
6, // z17
4 // z18
@ -63,9 +101,12 @@ DouglasPeucker::DouglasPeucker()
void DouglasPeucker::Run(std::vector<SegmentInformation> &input_geometry, const unsigned zoom_level)
{
input_geometry.front().necessary = true;
input_geometry.back().necessary = true;
unsigned point_count = 2;
BOOST_ASSERT_MSG(!input_geometry.empty(), "geometry invalid");
if (input_geometry.size() < 2)
{
@ -101,24 +142,23 @@ void DouglasPeucker::Run(std::vector<SegmentInformation> &input_geometry, const
int max_int_distance = 0;
unsigned farthest_element_index = pair.second;
// find index idx of element with max_distance
const CoordinatePairCalculator DistCalc(input_geometry[pair.first].location, input_geometry[pair.second].location);
for (unsigned i = pair.first + 1; i < pair.second; ++i)
{
const int int_dist = FixedPointCoordinate::OrderedPerpendicularDistanceApproximation(
input_geometry[i].location,
input_geometry[pair.first].location,
input_geometry[pair.second].location);
const int distance = DistCalc(input_geometry[i].location);
if (int_dist > max_int_distance && int_dist > douglas_peucker_thresholds[zoom_level])
if (distance > max_int_distance && distance > douglas_peucker_thresholds[zoom_level])
{
farthest_element_index = i;
max_int_distance = int_dist;
max_int_distance = distance;
}
}
if (max_int_distance > douglas_peucker_thresholds[zoom_level])
{
// mark idx as necessary
input_geometry[farthest_element_index].necessary = true;
++point_count;
if (1 < (farthest_element_index - pair.first))
{
recursion_stack.emplace(pair.first, farthest_element_index);
@ -129,4 +169,5 @@ void DouglasPeucker::Run(std::vector<SegmentInformation> &input_geometry, const
}
}
}
SimpleLogger().Write() << "size: " << input_geometry.size() << ", necessary: " << point_count;
}