[geos-commits] [SCM] GEOS branch main updated. 4b9a5ad063a7ea31662d6cd054a123b8b32099a6
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Tue May 6 09:48:28 PDT 2025
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- Log -----------------------------------------------------------------
commit 4b9a5ad063a7ea31662d6cd054a123b8b32099a6
Author: Roman Karavia <3082173+rkaravia at users.noreply.github.com>
Date: Tue May 6 18:47:59 2025 +0200
Allow GeoJSONWriter to force polygons to be counterclockwise (#1262)
Add a `setForceCCW` function to GeoJSONWriter, which enables conversion
of polygons to follow the RFC 7946 winding order.
When `isForceCCW` is true, linear rings in Polygons and MultiPolygons
follow the right-hand rule, meaning exterior rings are counterclockwise,
and holes are clockwise.
See https://datatracker.ietf.org/doc/html/rfc7946#section-3.1.6
This addition to GEOS is inspired by a corresponding change in JTS,
see https://github.com/locationtech/jts/pull/694
diff --git a/include/geos/io/GeoJSONWriter.h b/include/geos/io/GeoJSONWriter.h
index 002a6f501..d8011b872 100644
--- a/include/geos/io/GeoJSONWriter.h
+++ b/include/geos/io/GeoJSONWriter.h
@@ -95,13 +95,27 @@ public:
*/
void setOutputDimension(uint8_t newOutputDimension);
+ /*
+ * Sets whether the GeoJSON should be output following counter-clockwise orientation aka Right Hand Rule defined in
+ * RFC7946. See <a href="https://tools.ietf.org/html/rfc7946#section-3.1.6">RFC 7946 Specification</a>
+ * for more context.
+ *
+ * @param newIsForceCCW true if the GeoJSON should be output following the RFC7946
+ * counter-clockwise orientation aka Right Hand Rule
+ */
+ void setForceCCW(bool newIsForceCCW);
+
private:
uint8_t defaultOutputDimension = 3;
+ bool isForceCCW = false;
+
std::vector<double> convertCoordinate(const geom::Coordinate* c);
std::vector<std::vector<double>> convertCoordinateSequence(const geom::CoordinateSequence* c);
+ std::vector<std::vector<std::vector<double>>> convertLinearRings(const geom::Polygon *poly);
+
void encode(const geom::Geometry* g, GeoJSONType type, geos_nlohmann::ordered_json& j);
void encodeGeometry(const geom::Geometry* g, geos_nlohmann::ordered_json& j);
diff --git a/src/io/GeoJSONWriter.cpp b/src/io/GeoJSONWriter.cpp
index 8c9db9d7b..b6981600c 100644
--- a/src/io/GeoJSONWriter.cpp
+++ b/src/io/GeoJSONWriter.cpp
@@ -52,6 +52,10 @@ GeoJSONWriter::setOutputDimension(uint8_t dims)
defaultOutputDimension = dims;
}
+void GeoJSONWriter::setForceCCW(bool newIsForceCCW) {
+ isForceCCW = newIsForceCCW;
+}
+
std::string GeoJSONWriter::write(const geom::Geometry* geometry, GeoJSONType type)
{
json j;
@@ -223,7 +227,13 @@ void GeoJSONWriter::encodeGeometry(const geom::Geometry* geometry, geos_nlohmann
}
else if (type == GEOS_POLYGON) {
auto poly = static_cast<const geom::Polygon*>(geometry);
- encodePolygon(poly, j);
+ if (isForceCCW) {
+ auto ccwPoly = poly->clone();
+ ccwPoly->orientRings(false);
+ encodePolygon(ccwPoly.get(), j);
+ } else {
+ encodePolygon(poly, j);
+ }
}
else if (type == GEOS_MULTIPOINT) {
auto multiPoint = static_cast<const geom::MultiPoint*>(geometry);
@@ -264,14 +274,7 @@ void GeoJSONWriter::encodeLineString(const geom::LineString* line, geos_nlohmann
void GeoJSONWriter::encodePolygon(const geom::Polygon* poly, geos_nlohmann::ordered_json& j)
{
j["type"] = "Polygon";
- std::vector<std::vector<std::vector<double>>> rings;
- auto ring = poly->getExteriorRing();
- rings.reserve(poly->getNumInteriorRing()+1);
- rings.push_back(convertCoordinateSequence(ring->getCoordinates().get()));
- for (size_t i = 0; i < poly->getNumInteriorRing(); i++) {
- rings.push_back(convertCoordinateSequence(poly->getInteriorRingN(i)->getCoordinates().get()));
- }
- j["coordinates"] = rings;
+ j["coordinates"] = convertLinearRings(poly);
}
void GeoJSONWriter::encodeMultiPoint(const geom::MultiPoint* multiPoint, geos_nlohmann::ordered_json& j)
@@ -298,14 +301,13 @@ void GeoJSONWriter::encodeMultiPolygon(const geom::MultiPolygon* multiPolygon, g
polygons.reserve(multiPolygon->getNumGeometries());
for (size_t i = 0; i < multiPolygon->getNumGeometries(); i++) {
const Polygon* polygon = multiPolygon->getGeometryN(i);
- std::vector<std::vector<std::vector<double>>> rings;
- auto ring = polygon->getExteriorRing();
- rings.reserve(polygon->getNumInteriorRing() + 1);
- rings.push_back(convertCoordinateSequence(ring->getCoordinates().get()));
- for (size_t j = 0; j < polygon->getNumInteriorRing(); j++) {
- rings.push_back(convertCoordinateSequence(polygon->getInteriorRingN(j)->getCoordinates().get()));
+ if (isForceCCW) {
+ auto ccwPolygon = polygon->clone();
+ ccwPolygon->orientRings(false);
+ polygons.push_back(convertLinearRings(ccwPolygon.get()));
+ } else {
+ polygons.push_back(convertLinearRings(polygon));
}
- polygons.push_back(rings);
}
json["coordinates"] = polygons;
}
@@ -342,5 +344,17 @@ std::vector<std::vector<double>> GeoJSONWriter::convertCoordinateSequence(const
return coordinates;
}
+std::vector<std::vector<std::vector<double>>> GeoJSONWriter::convertLinearRings(const geom::Polygon* poly)
+{
+ std::vector<std::vector<std::vector<double>>> rings;
+ auto ring = poly->getExteriorRing();
+ rings.reserve(poly->getNumInteriorRing() + 1);
+ rings.push_back(convertCoordinateSequence(ring->getCoordinates().get()));
+ for (size_t i = 0; i < poly->getNumInteriorRing(); i++) {
+ rings.push_back(convertCoordinateSequence(poly->getInteriorRingN(i)->getCoordinates().get()));
+ }
+ return rings;
+}
+
} // namespace geos.io
} // namespace geos
diff --git a/tests/unit/io/GeoJSONWriterTest.cpp b/tests/unit/io/GeoJSONWriterTest.cpp
index e075e577f..4256e6bab 100644
--- a/tests/unit/io/GeoJSONWriterTest.cpp
+++ b/tests/unit/io/GeoJSONWriterTest.cpp
@@ -453,4 +453,40 @@ void object::test<30>
ensure_equals(result, "{\"type\":\"Feature\",\"geometry\":{\"type\":\"Point\",\"coordinates\":[0.0,0.0]},\"properties\":{\"array\":[{\"key\":\"value_1\"},{\"key\":\"value_2\"}]}}");
}
+// Test Polygon right-hand rule
+template<>
+template<>
+void object::test<31>
+()
+{
+ geojsonwriter.setForceCCW(true);
+ GeomPtr geom(wktreader.read("POLYGON ((0 0, 0 1, 1 1, 1 0, 0 0))"));
+ std::string result = geojsonwriter.write(geom.get());
+ ensure_equals(result, "{\"type\":\"Polygon\",\"coordinates\":[[[0.0,0.0],[1.0,0.0],[1.0,1.0],[0.0,1.0],[0.0,0.0]]]}");
+}
+
+// Test Polygon with hole right-hand rule
+template<>
+template<>
+void object::test<32>
+()
+{
+ geojsonwriter.setForceCCW(true);
+ GeomPtr geom(wktreader.read("POLYGON ((0 0, 0 20, 20 20, 20 0, 0 0), (1 1, 10 1, 10 10, 1 10, 1 1) )"));
+ std::string result = geojsonwriter.write(geom.get());
+ ensure_equals(result, "{\"type\":\"Polygon\",\"coordinates\":[[[0.0,0.0],[20.0,0.0],[20.0,20.0],[0.0,20.0],[0.0,0.0]],[[1.0,1.0],[1.0,10.0],[10.0,10.0],[10.0,1.0],[1.0,1.0]]]}");
+}
+
+// Test MultiPolygon right-hand rule
+template<>
+template<>
+void object::test<33>
+()
+{
+ geojsonwriter.setForceCCW(true);
+ GeomPtr geom(wktreader.read("MULTIPOLYGON (((0 0, 0 1, 1 1, 1 0, 0 0)), ((2 2, 2 3, 3 3, 3 2, 2 2)))"));
+ std::string result = geojsonwriter.write(geom.get());
+ ensure_equals(result, "{\"type\":\"MultiPolygon\",\"coordinates\":[[[[0.0,0.0],[1.0,0.0],[1.0,1.0],[0.0,1.0],[0.0,0.0]]],[[[2.0,2.0],[3.0,2.0],[3.0,3.0],[2.0,3.0],[2.0,2.0]]]]}");
+}
+
}
-----------------------------------------------------------------------
Summary of changes:
include/geos/io/GeoJSONWriter.h | 14 +++++++++++
src/io/GeoJSONWriter.cpp | 46 ++++++++++++++++++++++++-------------
tests/unit/io/GeoJSONWriterTest.cpp | 36 +++++++++++++++++++++++++++++
3 files changed, 80 insertions(+), 16 deletions(-)
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