Hi Even,
I'm playing with the C API for the GDAL programs inside GMT. More specifically
with the gdal_grid C API. All in all I managed to make it work but there are
some issues.
The main problem is that apparently the API was not thought to keep the result
in memory.
What ended up doing was this
hDstDS = GDALGrid("NUL", hSrcDS, psOptions, &bUsageError);
...
if ((tmp = calloc((size_t)nYSize * (size_t)nXSize, nPixelSize))
== NULL) {
GMT_Report (GMT->parent, GMT_MSG_NORMAL,
"gdalread: failure to allocate enough memory\n");
GDALDestroyDriverManager();
return -1;
}
if ((gdal_code = GDALRasterIO(hBand, GF_Read, 0, 0, nXSize,
nYSize, tmp,
nXSize, nYSize, GDALGetRasterDataType(hBand), 0,
0)) != CE_None) {
GMT_Report (GMT->parent, GMT_MSG_NORMAL,
"GDALRasterIO failed to open band [err = %d]\n", gdal_code);
}
-Note that I'm using "NUL" for the output file name because that was the only
way I found to prevent saving the file in disk (remember, I want to have it
memory).
-The second thing not shown above is that I had to use "-ot GTiff" in the
psOptions. Using "-ot Memory" lead to errors.
-Although using "NUL" works, GDAL prints these error messages when at the end I
close the DS (GDALClose(hSrcDS);)
ERROR 1: TIFFScanlineSize64:Computed scanline size is zero
ERROR 1: TIFFWriteEncodedStrip:Must set "ImageWidth" before
writing data
ERROR 1: FillEmptyTiles() failed because panByteCounts == NULL
-Last thing. I was forced to make a copy of the array in order to extract the
grid from the hDstDS handle via GDALRasterIO().
Ok, so my questions are. Is there a better way to do this? Could we, by some
mean, send in a pre-allocated array and owned by the external program to the
API so the duplication step could be avoided?
Thanks
Joaquim
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