root/GPXSee
1
0
Fork 0
mirror of https://github.com/tumic0/GPXSee.git synced 2024-11-28 05:34:47 +01:00
Code Issues Projects Releases Activity

Fixed centroid computation

Browse Source
This commit is contained in:
Martin Tůma 2023-02-19 14:47:57 +01:00
parent 8a9b7dc7ec
commit 9538d15d79
1 changed files with 14 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
src/map/ENC/rastertile.cpp
View File

@ -59,10 +59,11 @@ static double area(const QVector<Coordinates> &polygon)
{
double area = 0;
for (int i = 0; i < polygon.size(); i++) {
int j = (i + 1) % polygon.size();
area += polygon.at(i).lon() * polygon.at(j).lat();
area -= polygon.at(i).lat() * polygon.at(j).lon();
for (int i = 0; i < polygon.size() - 1; i++) {
const Coordinates &pi = polygon.at(i);
const Coordinates &pj = polygon.at(i+1);
area += pi.lon() * pj.lat();
area -= pi.lat() * pj.lon();
}
area /= 2.0;
@ -71,15 +72,18 @@ static double area(const QVector<Coordinates> &polygon)
static Coordinates centroid(const QVector<Coordinates> &polygon)
{
Q_ASSERT(polygon.size() > 3);
Q_ASSERT(polygon.first() == polygon.last());
double cx = 0, cy = 0;
double factor = 1.0 / (6.0 * area(polygon));
for (int i = 0; i < polygon.size(); i++) {
int j = (i + 1) % polygon.size();
qreal f = (polygon.at(i).lon() * polygon.at(j).lat()
- polygon.at(j).lon() * polygon.at(i).lat());
cx += (polygon.at(i).lon() + polygon.at(j).lon()) * f;
cy += (polygon.at(i).lat() + polygon.at(j).lat()) * f;
for (int i = 0; i < polygon.size() - 1; i++) {
const Coordinates &pi = polygon.at(i);
const Coordinates &pj = polygon.at(i+1);
double f = (pi.lon() * pj.lat() - pj.lon() * pi.lat());
cx += (pi.lon() + pj.lon()) * f;
cy += (pi.lat() + pj.lat()) * f;
}
return Coordinates(cx * factor, cy * factor);