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<p class="MsoNormal"><span lang="EN-US">Hi Even,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The main problem is that apparently the API was not thought to keep the result in memory.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">What ended up doing was this<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> hDstDS = GDALGrid("NUL", hSrcDS, psOptions, &bUsageError);
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">…<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> if ((tmp = calloc((size_t)nYSize * (size_t)nXSize, nPixelSize)) == NULL) {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> GMT_Report (GMT->parent, GMT_MSG_NORMAL, "gdalread: failure to allocate enough memory\n");<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> GDALDestroyDriverManager();<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> return -1;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> if ((gdal_code = GDALRasterIO(hBand, GF_Read, 0, 0, nXSize, nYSize, tmp,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> nXSize, nYSize, GDALGetRasterDataType(hBand), 0, 0)) != CE_None) {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> GMT_Report (GMT->parent, GMT_MSG_NORMAL, "GDALRasterIO failed to open band [err = %d]\n", gdal_code);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">-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).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">-The second thing not shown above is that I had to use “-ot GTiff” in the psOptions. Using “-ot Memory” lead to errors.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">-Although using “NUL” works, GDAL prints these error messages when at the end I close the DS (GDALClose(hSrcDS);)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ERROR 1: TIFFScanlineSize64:Computed scanline size is zero<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ERROR 1: TIFFWriteEncodedStrip:Must set "ImageWidth" before writing data<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ERROR 1: FillEmptyTiles() failed because panByteCounts == NULL<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">-Last thing. I was forced to make a copy of the array in order to extract the grid from the hDstDS handle via GDALRasterIO().<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Joaquim<o:p></o:p></span></p>
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