/* Test the method 'scaleSize'.*/
TEST_F(PositionVectorTest, test_method_scaleSize) {
PositionVector square;
square.push_back(Position(0,0));
square.push_back(Position(1,0));
square.push_back(Position(1,1));
square.push_back(Position(0,1));
square.push_back(Position(0,0));
EXPECT_DOUBLE_EQ(square.area(), 1);
square.scaleSize(3);
EXPECT_DOUBLE_EQ(square.area(), 9);
PositionVector expected;
expected.push_back(Position(-1,-1));
expected.push_back(Position(2,-1));
expected.push_back(Position(2,2));
expected.push_back(Position(-1,2));
expected.push_back(Position(-1,-1));
EXPECT_EQ(expected.getCentroid(), square.getCentroid());
for (size_t i = 0; i < square.size(); i++) {
EXPECT_DOUBLE_EQ(expected[i].x(), square[i].x());
EXPECT_DOUBLE_EQ(expected[i].y(), square[i].y());
}
}
Position
PositionVector::getCentroid() const {
PositionVector tmp = *this;
if (!isClosed()) { // make sure its closed
tmp.push_back(tmp[0]);
}
const int endIndex = (int)tmp.size() - 1;
SUMOReal div = 0; // 6 * area including sign
SUMOReal x = 0;
SUMOReal y = 0;
if (tmp.area() != 0) { // numerical instability ?
// http://en.wikipedia.org/wiki/Polygon
for (int i = 0; i < endIndex; i++) {
const SUMOReal z = tmp[i].x() * tmp[i + 1].y() - tmp[i + 1].x() * tmp[i].y();
div += z; // area formula
x += (tmp[i].x() + tmp[i + 1].x()) * z;
y += (tmp[i].y() + tmp[i + 1].y()) * z;
}
div *= 3; // 6 / 2, the 2 comes from the area formula
return Position(x / div, y / div);
} else {
// compute by decomposing into line segments
// http://en.wikipedia.org/wiki/Centroid#By_geometric_decomposition
SUMOReal lengthSum = 0;
for (int i = 0; i < endIndex; i++) {
SUMOReal length = tmp[i].distanceTo(tmp[i + 1]);
x += (tmp[i].x() + tmp[i + 1].x()) * length / 2;
y += (tmp[i].y() + tmp[i + 1].y()) * length / 2;
lengthSum += length;
}
if (lengthSum == 0) {
// it is probably only one point
return tmp[0];
}
return Position(x / lengthSum, y / lengthSum);
}
}