[gdal-dev] writing a subregion with GDALRasterIO

[Joaquim Luis]

Hi,

I am having some troubles in writing a sub-region on an array with 
GDALRasterIO.

The story is this. GMT internal grid arrays have a padding of 2 rows and 
2 columns around the 'true data region' that is used for boundary 
conditions but that need to be striped off upon saving on file.

The following works well when I previously moved all real data in the 
'data' array to the beginning of the array. That is, when I sort of 
removed the the padding zone.

   hDstDS = GDALCreate( hDriver, "mem", nx, ny, n_bands, typeCLASS, NULL );
....
    GDALRasterIO( hBand, GF_Write, 0, 0, nx, ny, data, nx, ny, 
typeCLASS, 0, 0 );

However, I would like to avoid that step and read directly the zone of 
interest from 'data', which because of the padding has actually 
(nx+4)x(ny+4) elements. So I tried

     GDALRasterIO( hBand, GF_Write, 2, 2, nx, ny, data, nx+4, ny+4, 
typeCLASS, 0, 0 );

but get this error:

ERROR 5: mem, band 1: Access window out of range in RasterIO().  Requested
(2,2) of size 37x19 on raster of 37x19.

This happens because of the test on gdalrasterband.cpp

    if( nXOff < 0 || nXOff > INT_MAX - nXSize || nXOff + nXSize > 
nRasterXSize

but this means I'm stuck here because the nRasterXSize ('nx' in this 
case) comes from the GDALCreate() and that I cannot change and so
    nXOff + nXSize > nRasterXSize is always true.

Any way out of this gotcha?

Thanks

Joaquim