[gdal-dev] GDALWarp fails to initialize

[user gdal]

Dear All,

I want to programmatically clip a raster ("inimg") with a polygon vector of
the format shp ("myshp"); both have the same geog. reference, which I
tested using std. SW, say, QGIS. I proceeded as per the code below. I am
getting an error "Unhandled exception... Access Violation", when no
pointers are NULL! What could have been the error in my understanding?


GDALDataset *inimg, *outimg;



outimg->(GDALDataset *) GDALOpen(filename, GA_Update);

outimg=driver->Create(filename, NewCol, NewRow, Band, DataType, NULL); /*
NewCol and NewRow, each have values of the range 30 */



GDALWarpOptions *WO=GDALCreateWarpOptions( );

if(WO)
{
  WO->hSrcDS=(GDALDatasetH)(inimg); WO->nBandCount=Band;



  // In a sample image I wish to use, Band =3, checked

  WO->hDstDS=(GDALDatasetH)(outimg); WO->hCutline=myshp; // OGRLayer *myshp;

  WO->panSrcBands=(int *) CPLMalloc(sizeof(int)*Band);
WO->panSrcBands[0]=Band;
  WO->panDstBands=(int *) CPLMalloc(sizeof(int)*Band);
WO->panDstBands[0]=Band;

  WO->pfnProgress=GDALTermProgress;

  GDALWarpOperation *operation=new GDALWarpOperation;

  if(operation)
  {
    operation->Initialize(WO);  // the speed breaker
    operation->ChunkAndWarpImage(0, 0, NewCol, NewRow);

    GDALDestroyWarpOptions(WO); WO=NULL; delete operation; operation=NULL;

   }

   GDALClose((GDALDatasetH) outimg); outimg=NULL;

  }



Referring to the above,


What is inimg?

Ans. The bigger input image from which I want to draw subset (i.e., clip)
with the help of a vector layer myshp. It' (inimg) is of type GDALDataset
*. In the declaration of variables, it would appear as GDALDataset *inimg
Also, in WO->hCutline (pl. see below), I am passing myshp (which has
strictly polygon topology), of the type OGRLayer * (i.e., OGRLayer *myshp).
Of course the shape file and inimg have the same projection.


What (exactly) are you passing as filename?

Ans. char *filename (such as e:\sub\subimage.img. There are no other
characters in the 'filename')

Can you try posting an actual, compilable example?

Ans. There is a GUI from which I extract parameters which can give us a lot
of inconvenience. The program compiles without 'abusing' me. What I am
getting is a run time (or debug time) error.



With thanks,




          Yours sincerely,



                               B.
Ramesh
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