On 13-05-2012 20:28, Even Rouault wrote:
Le mardi 08 mai 2012 15:52:11, Joaquim Luis a écrit :
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 );
--> This call is indeed not valid according to the semantics of GDALRasterIO()
and the error message you get is expected.
Untested, but you could rather try something like (assuming your datatype is
Byte)
GDALRasterIO( hBand, GF_Write, 0, 0, nx, ny, data + 2 * nx + 2, nx, ny,
typeCLASS, 0, nx + 4 );
to offset the data buffer to the (2,2) pixel and providing a line stride of nx +
4.
Thanks Even,
The data was actually a float and we can't do the "data + 2 * nx + 2"
shift trick inside the GDALRasterIO call because it's (void *) there but
I applied the idea where due and it works fine.
Joaquim
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