Intersecting OGRFeatureH and OGRGeometry in C with GDAL/OGR

Answer:

To get the intersection of an OGRFeatureH and an OGRGeometry in C using the GDAL/OGR library, you need to follow these steps:

Extract the geometry from the OGRFeatureH.
Compute the intersection of the extracted geometry with the given OGRGeometry.

Here is a step-by-step example:

Include the necessary headers:

#include "ogr_api.h"
#include "ogr_srs_api.h"

Initialize the GDAL/OGR library:
```
OGRRegisterAll();
```

Extract the geometry from the OGRFeatureH:

OGRFeatureH hFeature; // Assume this is already created and populated
OGRGeometryH hFeatureGeometry = OGR_F_GetGeometryRef(hFeature);

Compute the intersection:

OGRGeometryH hOtherGeometry; // Assume this is already created and populated
OGRGeometryH hIntersection = OGR_G_Intersection(hFeatureGeometry, hOtherGeometry);

Check the result and handle it:

if (hIntersection != NULL) {
    // Do something with the intersection geometry
    // For example, print it as WKT
    char* pszWKT = NULL;
    OGR_G_ExportToWkt(hIntersection, &pszWKT);
    printf("Intersection WKT: %s\n", pszWKT);
    CPLFree(pszWKT);

    // Destroy the intersection geometry when done
    OGR_G_DestroyGeometry(hIntersection);
} else {
    printf("No intersection found.\n");
}

Cleanup and close the GDAL/OGR library:
```
OGRCleanupAll();
```

Here is the complete example code:

#include "ogr_api.h"
#include "ogr_srs_api.h"
#include <stdio.h>

int main() {
    // Initialize GDAL/OGR
    OGRRegisterAll();

    // Assume hFeature and hOtherGeometry are already created and populated
    OGRFeatureH hFeature; // This should be initialized with a valid feature
    OGRGeometryH hOtherGeometry; // This should be initialized with a valid geometry

    // Extract the geometry from the feature
    OGRGeometryH hFeatureGeometry = OGR_F_GetGeometryRef(hFeature);

    // Compute the intersection
    OGRGeometryH hIntersection = OGR_G_Intersection(hFeatureGeometry, hOtherGeometry);

    // Check the result and handle it
    if (hIntersection != NULL) {
        // Print the intersection geometry as WKT
        char* pszWKT = NULL;
        OGR_G_ExportToWkt(hIntersection, &pszWKT);
        printf("Intersection WKT: %s\n", pszWKT);
        CPLFree(pszWKT);

        // Destroy the intersection geometry when done
        OGR_G_DestroyGeometry(hIntersection);
    } else {
        printf("No intersection found.\n");
    }

    // Cleanup GDAL/OGR
    OGRCleanupAll();

    return 0;
}

Note:

Ensure that hFeature and hOtherGeometry are properly initialized and populated with valid data before using them.
The OGR_G_Intersection function returns a new geometry that represents the intersection. You are responsible for destroying this geometry using OGR_G_DestroyGeometry when you are done with it.
The OGR_F_GetGeometryRef function returns a reference to the geometry of the feature. You should not destroy this geometry directly; it is managed by the feature itself.

Intersecting OGRFeatureH and OGRGeometry in C with GDAL/OGR

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