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use integer approximation for polyline generalization

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This commit is contained in:
Dennis Luxen 2014-05-30 14:34:04 +02:00
parent 21eb5b661d
commit f3ad14cb7f
2 changed files with 28 additions and 34 deletions
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60
Algorithms/DouglasPeucker.cpp
View File

@ -38,25 +38,25 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include <limits>
DouglasPeucker::DouglasPeucker()
: douglas_peucker_thresholds({262144.f, // z0
131072.f, // z1
65536.f, // z2
32768.f, // z3
16384.f, // z4
8192.f, // z5
4096.f, // z6
2048.f, // z7
960.f, // z8
480.f, // z9
240.f, // z10
90.f, // z11
50.f, // z12
25.f, // z13
15.f, // z14
5.f, // z15
.65f, // z16
.5f, // z17
.35f // z18
: 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
8, // z16
6, // z17
4 // z18
})
{
}
@ -79,16 +79,10 @@ void DouglasPeucker::Run(std::vector<SegmentInformation> &input_geometry, const
// Sweep over array and identify those ranges that need to be checked
do
{
if (!input_geometry[left_border].necessary)
{
SimpleLogger().Write() << "broken interval [" << left_border << "," << right_border << "]";
}
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)
{
BOOST_ASSERT(input_geometry[left_border].necessary);
BOOST_ASSERT(input_geometry[right_border].necessary);
recursion_stack.emplace(left_border, right_border);
left_border = right_border;
}
@ -104,24 +98,24 @@ void DouglasPeucker::Run(std::vector<SegmentInformation> &input_geometry, const
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");
float max_distance = std::numeric_limits<float>::min();
int max_int_distance = 0;
unsigned farthest_element_index = pair.second;
// find index idx of element with max_distance
for (unsigned i = pair.first + 1; i < pair.second; ++i)
{
const float temp_dist = FixedPointCoordinate::ComputePerpendicularDistance(
const int int_dist = FixedPointCoordinate::OrderedPerpendicularDistanceApproximation(
input_geometry[i].location,
input_geometry[pair.first].location,
input_geometry[pair.second].location);
const float distance = std::abs(temp_dist);
if (distance > douglas_peucker_thresholds[zoom_level] && distance > max_distance)
if (int_dist > max_int_distance && int_dist > douglas_peucker_thresholds[zoom_level])
{
farthest_element_index = i;
max_distance = distance;
max_int_distance = int_dist;
}
}
if (max_distance > douglas_peucker_thresholds[zoom_level])
if (max_int_distance > douglas_peucker_thresholds[zoom_level])
{
// mark idx as necessary
input_geometry[farthest_element_index].necessary = true;

2
Algorithms/DouglasPeucker.h
View File

@ -44,7 +44,7 @@ struct SegmentInformation;
class DouglasPeucker
{
private:
std::vector<float> douglas_peucker_thresholds;
std::vector<int> douglas_peucker_thresholds;
typedef std::pair<unsigned, unsigned> GeometryRange;
// Stack to simulate the recursion