Ming,
A OGRLayer is a *vector* layer, not a raster one. So you should rather
look at the raster API: https://gdal.org/tutorials/raster_api_tut.html
Depending on the kind of URL you provide to GDAL, you may get directly a
workable dataset, or just a placeholder that links to real datasets with
the subdataset (which can be seen as a king of raster layer) mechanism,
using GDALDataset::GetMetadata("SUBDATASETS") to get the list of
subdatasets, and then pass to GDALOpen() the value of one of the
SUBDATASET_xx_NAME item
Even
Le 17/06/2021 à 17:41, Ming Chin a écrit :
Hello GDAL devs,
I am a GDAL rookie, and I am trying to add WMS support to an
existing GDAL (2.2.4) implementation.
I saw in this example:
https://gis.stackexchange.com/questions/67416/using-gdal-to-connect-to-a-wfs
<https://gis.stackexchange.com/questions/67416/using-gdal-to-connect-to-a-wfs>
that its possible to provide OGRSFDriverRegistrar::Open(sURL, FALSE );
with a url and use it to open an OGRDataSource.
And in other examples I see that OGRSFDriverRegistrar::Open() has been
deprecated and that GDALOpen() should be used instead.
So I did that, adding cURL to our GDAL build, and then in my
implementation, I provided GDALOpen() with a URL like this:
GDALDataset *pDataset = (GDALDataset*)::GDALOpen(sURL, GA_ReadOnly);
if( pDataset )
{
int nLayers = pDataset->GetLayerCount();
OGRLayer *pLayer = pDataset->GetLayerByName(sLayerName);
}
This seems to partially work, in the sense that the GDALOpen function
returns a non-NULL pointer to a GDALDataset, but when I try to call
the member functions of the resulting GDALDataset, everything seems to
return zeros or nulls;
The above call returns nLayers = 0, and pLayer=NULL
but if I feed the same sURL into my web browser (Chrome), the browser
receives a properly formatted xml file that clearly has <Layer>(s)
defined in it.
What am I missing? Why am I unable to retrieve useful data from the
dataset?
Ming
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