Why not build an OGC gpkg GEOPACKAGE it supports 4326 tiles you can extract the tile_data blob if you need to
On Thu, Oct 10, 2019, 5:51 PM <mlade...@distributel.net> wrote: > > Hello, > > I've been using GDAL for a while, but I am still a newbie to the API. > I see there are some experts on this group, so apologies if I'm asking > something simple (my searches did not reveal the answers I was looking > for). > > Here is my problem: > > I need to take an input raster, split into areas of various sizes, > resample each area into a 256x256 tile, reproject to EPSG:4326 and > send the resulting pixels to a DB. > > GDAL is perfect for this, but I am using the C# bindings and I'm not > sure what is the most performant way to do it. > > I used the following two references to create something that works, > but I am wondering if it can be improved: > > https://gis.stackexchange.com/questions/297831/using-gdalwarp-with-c-bindings > https://lists.osgeo.org/pipermail/gdal-dev/2017-February/046046.html > > How I do it right now: > > 1) Copy the input grid to RAM disk for fast access > 2) Invoke Gdal.wrapper_GDALWarpDestName() for reprojection, > resampling, and output to a /vsimem/ memory-mapped file > 3) Read the memory-mapped file into a Dataset (returned by > wrapper_GDALWarpDestName()) > 4) Write the Dataset values to DB > > What I would like to know: > > 1) To skip the /vsimem file creation, how can I use > Gdal.wrapper_GDALWarpDestDs() instead of -DestName? It requires a > dataset as a parameter, but I am not sure how to initialize it > correctly. I've tried Gdal.GetDriverByName("VRT").Create(...) and > .GetDriverByName("MEM").Create(...), but all the values end up being 0 > when I pass the dataset to wrapper_GDALWarpDestDs()? > > 2) Is there a more direct, efficient way to do what I'm doing? Here > is the relevant code > > <snip> > using (Dataset rasterInput = Gdal.Open(inputRasterPath, > Access.GA_ReadOnly)) > { > IntPtr[] ptr = {Dataset.getCPtr(inputRasterPath).Handle}; > GCHandle gcHandle = GCHandle.Alloc(ptr, GCHandleType.Pinned); > ... > var dss = new > SWIGTYPE_p_p_GDALDatasetShadow(gcHandle.AddrOfPinnedObject(), false, > null); > .. > foreach (var tileExtent in overlappingTileExtents) // tileExtent > just contains minX/minY/maxX/maxY > { > ... > > string vsiMemFilePath = > $"/vsimem/{destinationTableName}#{extentName}#tile{indexNumber}.vrt"; > string[] options = { > "-of", "VRT", > "-srcnodata", "99999.9", > "-dstnodata", "99999.9", > "-ot", "Float32", > "-t_srs", "EPSG:4326", > "-r", "average"), > "-te", tileExtent.xmin.ToString(), > tileExtent.ymin.ToString(), tileExtent.xmax.ToString(), > tileExtent.ymax.ToString(), > "-ts", "256", "256" > }; > > using (Dataset ds = > Gdal.wrapper_GDALWarpDestName(vsiMemFilePath, 1, dss, new > GDALWarpAppOptions(options), null, null)) > { > ... > //read the geotransform + first band and write each pixel > lat/long + value to the DB > ... > } > > Gdal.Unlink(vsiMemFilePath) > > .... > > Regards, > Mladen > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/gdal-dev
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