Retrieving Geometry Reference from OGRFeatureH in C++

In C++, get geometryRef from OGRFeatureH

In C++, when working with the GDAL/OGR library, you can retrieve the geometry reference from an OGRFeatureH handle using the OGR_F_GetGeometryRef function. This function returns a handle to the geometry associated with the feature.

Here's a step-by-step example of how you can achieve this:

1. Include the necessary headers: Make sure to include the GDAL/OGR headers in your source file.

   #include "ogrsf_frmts.h"
   

2. Initialize GDAL/OGR: Before using any GDAL/OGR functions, you need to initialize the GDAL/OGR library.

   OGRRegisterAll();
   

3. Open a data source and get a layer: Open your data source and get the layer from which you want to retrieve features.

   const char* pszDataSource = "path/to/your/datasource";
   GDALDatasetH hDS = GDALOpenEx(pszDataSource, GDAL_OF_VECTOR, NULL, NULL, NULL);
   if (hDS == NULL) {
       // Handle error
   }
   
   OGRLayerH hLayer = GDALDatasetGetLayer(hDS, 0);
   if (hLayer == NULL) {
       // Handle error
   }
   

4. Fetch a feature and get its geometry: Fetch a feature from the layer and retrieve its geometry.

   OGRFeatureH hFeature;
   OGR_L_ResetReading(hLayer);
   while ((hFeature = OGR_L_GetNextFeature(hLayer)) != NULL) {
       OGRGeometryH hGeometry = OGR_F_GetGeometryRef(hFeature);
       if (hGeometry != NULL) {
           // Do something with the geometry
       }
   
       // Destroy the feature to avoid memory leaks
       OGR_F_Destroy(hFeature);
   }
   

5. Clean up: After you are done, close the data source and clean up.

   GDALClose(hDS);
   

Here is the complete example:

#include "ogrsf_frmts.h"

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

    // Open the data source
    const char* pszDataSource = "path/to/your/datasource";
    GDALDatasetH hDS = GDALOpenEx(pszDataSource, GDAL_OF_VECTOR, NULL, NULL, NULL);
    if (hDS == NULL) {
        // Handle error
        return 1;
    }

    // Get the first layer
    OGRLayerH hLayer = GDALDatasetGetLayer(hDS, 0);
    if (hLayer == NULL) {
        // Handle error
        GDALClose(hDS);
        return 1;
    }

    // Fetch features and get their geometries
    OGRFeatureH hFeature;
    OGR_L_ResetReading(hLayer);
    while ((hFeature = OGR_L_GetNextFeature(hLayer)) != NULL) {
        OGRGeometryH hGeometry = OGR_F_GetGeometryRef(hFeature);
        if (hGeometry != NULL) {
            // Do something with the geometry
        }

        // Destroy the feature to avoid memory leaks
        OGR_F_Destroy(hFeature);
    }

    // Clean up
    GDALClose(hDS);

    return 0;
}

This example demonstrates how to open a data source, retrieve features from a layer, get the geometry reference from each feature, and clean up resources properly. Make sure to replace "path/to/your/datasource" with the actual path