Inverse Conversion Function from GEOSGeometry to OGRGeometry

write a inverse converting function for GEOSGeometry* OGRToGEOS(const OGRGeometry* ogrGeom) { if (!ogrGeom || ogrGeom->getGeometryType() != wkbPolygon) { return nullptr; // Handle error or unsupported geometry type }

	const OGRPolygon* ogrPolygon = static_cast<const OGRPolygon*>(ogrGeom);
	const OGRLinearRing* ogrRing = ogrPolygon->getExteriorRing();

	// Create GEOS coordinate sequence
	int numPoints = ogrRing->getNumPoints();
	GEOSCoordSequence* coordSeq = GEOSCoordSeq_create(numPoints, 2);

	// Fill the coordinate sequence
	for (int i = 0; i < numPoints; ++i) {
		double x, y;
		OGRPoint pt;
		ogrRing->getPoint(i, &pt);
		GEOSCoordSeq_setXY(coordSeq, i, pt.getX(), pt.getY());
	}

	// Create GEOS linear ring
	GEOSGeometry* geosRing = GEOSGeom_createLinearRing(coordSeq);

	// Create GEOS polygon
	GEOSGeometry* geosPolygon = GEOSGeom_createPolygon(geosRing, nullptr, 0);

	return geosPolygon;
}

To write an inverse converting function for the provided OGRToGEOS function, we need to convert a GEOSGeometry object back to an OGRGeometry object. The function will be named GEOSToOGR and will handle the conversion of a GEOSGeometry polygon to an OGRPolygon.

Here's the implementation of the GEOSToOGR function:

#include <geos_c.h>
#include <ogr_geometry.h>

OGRGeometry* GEOSToOGR(const GEOSGeometry* geosGeom) {
    if (!geosGeom || GEOSGeomTypeId(geosGeom) != GEOS_POLYGON) {
        return nullptr; // Handle error or unsupported geometry type
    }

    // Get the exterior ring from the GEOS polygon
    const GEOSGeometry* geosRing = GEOSGetExteriorRing(geosGeom);
    if (!geosRing) {
        return nullptr; // Handle error
    }

    // Get the coordinate sequence from the GEOS ring
    const GEOSCoordSequence* coordSeq = GEOSGeom_getCoordSeq(geosRing);
    if (!coordSeq) {
        return nullptr; // Handle error
    }

    // Get the number of points in the coordinate sequence
    unsigned int numPoints;
    GEOSCoordSeq_getSize(coordSeq, &numPoints);

    // Create an OGRLinearRing
    OGRLinearRing* ogrRing = new OGRLinearRing();
    ogrRing->setNumPoints(numPoints);

    // Fill the OGRLinearRing with points from the GEOS coordinate sequence
    for (unsigned int i = 0; i < numPoints; ++i) {
        double x, y;
        GEOSCoordSeq_getX(coordSeq, i, &x);
        GEOSCoordSeq_getY(coordSeq, i, &y);
        ogrRing->setPoint(i, x, y);
    }

    // Create an OGRPolygon and set the exterior ring
    OGRPolygon* ogrPolygon = new OGRPolygon();
    ogrPolygon->addRingDirectly(ogrRing);

    return ogrPolygon;
}

Explanation:

1. Check for Valid Input: The function first checks if the input GEOSGeometry is valid and of type GEOS_POLYGON.
2. Get Exterior Ring: It retrieves the exterior ring from the GEOS polygon using GEOSGetExteriorRing.
3. Get Coordinate Sequence: It obtains the coordinate sequence from the exterior ring using GEOSGeom_getCoordSeq.
4. Get Number of Points: It retrieves the number of points in the coordinate sequence using GEOSCoordSeq_getSize.
5. Create OGRLinearRing: It creates an OGRLinearRing and sets the number of points.
6. Fill OGRLinearRing: It fills the OGRLinearRing with points from the GEOS coordinate sequence.
7. Create OGRPolygon: It creates an OGRPolygon and sets the exterior ring using addRingDirectly.

This function should correctly convert a GEOSGeometry polygon back to an OGRPolygon. Make sure to link against the GEOS and GDAL libraries when compiling this code.