Would you mind reading the "OGR C++ API Read/Write Tutorial" available on
http://gdal.org/ogr/ogr_apitut.html ? The answer is in the first code
snippet ;-)
Le Wednesday 03 March 2010 21:43:49 deadpickle, vous avez écrit :
> I have finally compiled my C program and tried running it for the
> first time. When I ran the file I got the error:
> [t...@updraft ~/Programs]$ ./gdal_test_convert
> ERROR 10: Pointer 'hDriver' is NULL in 'OGR_Dr_CreateDataSource'.
> I'm trying to load the ESRI Shapefile driver. When I compiled it I
> linked it to the libgdal.a library. Is there something I'm missing?
>
> #include "ogr_api.h"
> #include "ogr_srs_api.h"
> #include "stdio.h"
>
> int main()
> {
> //~ variable declaration
> const char *name = "testc.shp", *dir = "C:\\Users\\deadpickle\\Desktop
> \\case study\\verify\\";
> char *source, *target;
> const char *sprj = "+proj=lcc +lat_1=33.000000 +lat_2=45.000000
> +lat_0=39.000000 +lon_0=-96.000000 +x_0=0.0 +y_0=0.0 +datum=NAD83";
> const char *tprj = "WGS84";
> char c[100];
> OGRSFDriverH driver;
> OGRDataSourceH ds;
> OGRCoordinateTransformationH ctrans;
> OGRLayerH layer;
> OGRFieldDefnH fieldDefn;
> OGRGeometryH line;
> OGRFeatureDefnH featureDefn;
> OGRFeatureH feature;
> FILE *file;
>
> //~ working directory
> chdir(dir);
>
> //~ get driver and create ds
> driver = OGRGetDriverByName("ESRI Shapefile");
> ds = OGR_Dr_CreateDataSource(driver, "testc.shp", NULL);
>
> //~ create spatrefs and trans
> OSRNewSpatialReference(source);
> OSRNewSpatialReference(target);
> OSRSetFromUserInput(source, sprj);
> OSRSetFromUserInput(target, tprj);
> ctrans = OCTNewCoordinateTransformation(target, source);
>
> //~ create the layer
> layer = OGR_DS_CreateLayer(ds, "test", source, wkbMultiLineString,
> NULL);
>
> //~ add an id field
> fieldDefn = OGR_Fld_Create("id", OFTInteger);
> OGR_L_CreateField(layer, fieldDefn, FALSE);
>
> //~ create geometry
> line = OGR_G_CreateGeometry(wkbMultiLineString);
>
> //~ layer def and create feature
> featureDefn = OGR_L_GetLayerDefn(layer);
> feature = OGR_F_Create(featureDefn);
>
> //~ open file
> file = fopen("2006track.csv","r");
>
> if(file==NULL) {
> printf("Error: can't open file.\n");
> /* fclose(file); DON'T PASS A NULL POINTER TO fclose !! */
> return 1;
> }
> else {
> printf("File opened successfully. Contents:\n\n");
>
> while(fgets(c, 100, file)!=NULL) {
> /* keep looping until NULL pointer... */
> printf("String: %s", c);
> /* print the file one line at a time */
> }
>
> printf("\n\nNow closing file...\n");
> }
>
> //~ close file
> fclose(file);
> }
> _______________________________________________
> gdal-dev mailing list
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