Skip to content

FIX: Work out the area of polygons with holes and of split intersections #152

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Automation51D merged 2 commits into from
Sep 18, 2026
+83 −8
Merged

FIX: Work out the area of polygons with holes and of split intersections #152

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
a866be2
FIX: Work out the area of polygons with holes and of split intersections
YaroslavVlasenko Sep 17, 2026
229b915
Update console/src/main/java/fiftyone/ipintelligence/examples/console…
YaroslavVlasenko Sep 17, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
45 changes: 37 additions & 8 deletions console/src/main/java/fiftyone/ipintelligence/examples/console/areas/Calculations.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,8 @@
import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.LinearRing;
import org.locationtech.jts.geom.Polygon;
import org.locationtech.jts.geom.TopologyException;
import org.locationtech.jts.io.WKTReader;
import org.locationtech.proj4j.CoordinateTransform;
Expand Down Expand Up @@ -163,10 +165,10 @@ private static double getArea(Geometry geo, Rectangle rectangle) {
}
else {
for (int i = 0; i < intersect.getNumGeometries(); i++) {
if (geo.getGeometryN(i).getArea() > 0) {
if (intersect.getGeometryN(i).getArea() > 0) {
area += getArea(
geo,
geo.getGeometryN(i),
intersect.getGeometryN(i),
rectangle.getTransformation());
}
}
Expand Down Expand Up @@ -197,22 +199,49 @@ private static double getArea(
private static Geometry transformGeometry(
Geometry geometry,
CoordinateTransform transform) {
GeometryFactory factory = geometry.getFactory();
Coordinate[] coordinates = new Coordinate[
geometry.getCoordinates().length];
// A multipolygon or collection can arrive holding a single piece,
// for example from the TopologyException fallback or the intersection
// of a collection. Each polygon in it is transformed on its own.
if (geometry instanceof Polygon == false) {
List<Geometry> parts = new ArrayList<>();
for (int i = 0; i < geometry.getNumGeometries(); i++) {
Geometry part = geometry.getGeometryN(i);
if (part.getDimension() == 2) {
parts.add(transformGeometry(part, transform));
}
}
return geometry.getFactory().buildGeometry(parts);
}
// The outer boundary and each hole are separate rings. Joining their
// points into one ring does not close, so they are handled apart.
Polygon polygon = (Polygon) geometry;
Comment thread
YaroslavVlasenko marked this conversation as resolved.
LinearRing[] holes = new LinearRing[polygon.getNumInteriorRing()];
for (int i = 0; i < holes.length; i++) {
holes[i] = transformRing(polygon.getInteriorRingN(i), transform);
}
return geometry.getFactory().createPolygon(
transformRing(polygon.getExteriorRing(), transform),
holes);
}

private static LinearRing transformRing(
LinearRing ring,
CoordinateTransform transform) {
Coordinate[] source = ring.getCoordinates();
Coordinate[] coordinates = new Coordinate[source.length];

for (int i = 0; i < coordinates.length; i++) {
ProjCoordinate transformed = transform.transform(
new ProjCoordinate(
geometry.getCoordinates()[i].getX(),
geometry.getCoordinates()[i].getY()),
source[i].getX(),
source[i].getY()),
new ProjCoordinate());
coordinates[i] = new Coordinate(
transformed.x,
transformed.y);
}

return factory.createPolygon(coordinates);
return ring.getFactory().createLinearRing(coordinates);
}

/**
Expand Down
46 changes: 46 additions & 0 deletions console/src/test/java/fiftyone/ipintelligence/examples/console/areas/CalculationsTest.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
import org.junit.Test;
import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.LinearRing;
import org.locationtech.jts.geom.Polygon;

import static org.junit.Assert.assertEquals;
Expand Down Expand Up @@ -98,6 +99,51 @@ public void testWktPolygon() throws Exception {
assertEquals(1, result.getGeometries());
}

@Test
public void testPolygonWithHole() throws Exception {
Polygon outer = createRectangle(0, 51, 1);
Polygon hole = createRectangle(0.25, 51.25, 0.5);
Polygon withHole = factory.createPolygon(
outer.getExteriorRing(),
new LinearRing[]{hole.getExteriorRing()});
assertAreaEquals(
Calculations.getAreas(outer, 0, 0).getSquareKms() -
Calculations.getAreas(hole, 0, 0).getSquareKms(),
Calculations.getAreas(withHole, 0, 0).getSquareKms());
}

@Test
public void testPolygonSplitByGridCell() throws Exception {
// A U shape whose arms cross into the next grid cell, where they
// are two separate pieces.
Polygon shape = factory.createPolygon(new Coordinate[]{
new Coordinate(0.2, 50.5),
new Coordinate(0.8, 50.5),
new Coordinate(0.8, 51.5),
new Coordinate(0.6, 51.5),
new Coordinate(0.6, 50.7),
new Coordinate(0.4, 50.7),
new Coordinate(0.4, 51.5),
new Coordinate(0.2, 51.5),
new Coordinate(0.2, 50.5)});
Polygon whole = factory.createPolygon(new Coordinate[]{
new Coordinate(0.2, 50.5),
new Coordinate(0.8, 50.5),
new Coordinate(0.8, 51.5),
new Coordinate(0.2, 51.5),
new Coordinate(0.2, 50.5)});
Polygon gap = factory.createPolygon(new Coordinate[]{
new Coordinate(0.4, 50.7),
new Coordinate(0.6, 50.7),
new Coordinate(0.6, 51.5),
new Coordinate(0.4, 51.5),
new Coordinate(0.4, 50.7)});
assertAreaEquals(
Calculations.getAreas(whole, 0, 0).getSquareKms() -
Calculations.getAreas(gap, 0, 0).getSquareKms(),
Calculations.getAreas(shape, 0, 0).getSquareKms());
}

@Test
public void testContains() throws Exception {
Result result = Calculations.getAreas(
Expand Down
Loading