Hello List,
Im having some trouble with the C api, that I assume is do my failure to
understand some part of it.
What I'm trying to do: Load a BSB raster file, apply a cutline to the file, and
warp it into a north-up projection. Im doing additional transformations to it
after that, but right now I'm stuck trying to get areas outside of the cutline
to be transparent instead of black.
An abbreviated version of what I'm doing now:
sourceDataset = GDALOpen(imageFilePath.UTF8String, GA_ReadOnly );
GDALWarpOptions *warpOptions = GDALCreateWarpOptions();
OGRGeometryH clipGeometry;
OGRErr polyStatus = OGR_G_CreateFromWkt(&pszWkt, spatialRef, &clipGeometry);
if(polyStatus == CE_None) {
warpOptions->hCutline = clipGeometry;
}
warpedDataset = GDALAutoCreateWarpedVRT(sourceDataset,
NULL,
NULL,
GRA_NearestNeighbour,
0.0,
warpOptions);
The source data does not have a no data value, i've tried setting one and
adding an entry to the color palette before calling GDALAutoCreateWarpedVRT,
and settings the same value in the VRT but that had no effect.
Any suggestions for the right way to do this? Am I just setting the no_data
value incorrectly, or is this a situation that requires a mask band? And if it
does require a mask band is there an easy way to create that from a cutline?
Thanks,
Jesse
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