@Override
public void computeAcircularity(ConvexHull convexHull) {
double perimeter = convexHull.getPerimeter();
double area = convexHull.getArea();
double acircularity = Math.pow(perimeter, 2) / (4 * Math.PI * area);
convexHull.setAcircularity(acircularity);
}
/**
* @param convexHull
* @return
*/
private GeometricPoint[] getClosedPolygonFromHull(ConvexHull convexHull) {
Iterable<GeometricPoint> hull = convexHull.getHull();
// get the size of the hull: number of vertices of polygon
int n = convexHull.getHullSize();
// we take n + 1
GeometricPoint[] geometricPoints = new GeometricPoint[n + 1];
int j = 0;
for (GeometricPoint geometricPoint : hull) {
geometricPoints[j++] = geometricPoint;
}
// close the polygon: last point of polygon has to be equal to first point
geometricPoints[n] = geometricPoints[0];
return geometricPoints;
}
@Override
public void computePerimeter(ConvexHull convexHull) {
GeometricPoint[] closedPolygonFromHull = getClosedPolygonFromHull(convexHull);
// init perimeter to zer
double perimeter = 0;
// sum up the length of each edge of the polygon
for (int i = 0; i < closedPolygonFromHull.length - 1; i++) {
perimeter += closedPolygonFromHull[i].euclideanDistanceTo(closedPolygonFromHull[i + 1]);
}
convexHull.setPerimeter(perimeter);
}
@Override
public void computeArea(ConvexHull convexHull) {
GeometricPoint[] closedPolygonFromHull = getClosedPolygonFromHull(convexHull);
// init area to zero
double area = 0;
// sum up the cross products around each vertex of the hull
for (int i = 0; i < closedPolygonFromHull.length - 1; i++) {
double xUp = closedPolygonFromHull[i].getX();
double yDown = closedPolygonFromHull[i + 1].getY();
double yUp = closedPolygonFromHull[i].getY();
double xDown = closedPolygonFromHull[i + 1].getX();
area += (xUp * yDown) - (yUp * xDown);
}
convexHull.setArea(area / 2);
}
@Override
public void computeDirectionality(ConvexHull convexHull) {
double directionality =
convexHull.getMostDistantPointsPair().getMaxSpan() / convexHull.getArea();
convexHull.setDirectionality(directionality);
}