Hi list, first time poster here.
I'm using the GDAL C# bindings in .net core via the Gdal.Core Nuget package (https://www.nuget.org/packages/Gdal.Core/) Everyting seems to work fine, apart from the fact that I have to touch the file system in order to get my created GeoTiff as a memory stream Sample code: var outputRasterFileName = $"{Path.GetTempPath()}{Guid.NewGuid()}.tiff"; var driver = Gdal.GetDriverByName("GTiff"); var ds = driver.Create(outputRasterFileName, resolution.X, resolution.Y, 1, DataType.GDT_Byte, null); SetSrsFromLayer(ds, layer); var arg = new[] { envelope.MinX, pixelSize, 0, envelope.MinY, 0, pixelSize }; ds.SetGeoTransform(arg); var band = ds.GetRasterBand(1); band.SetNoDataValue(noDataValue); band.FlushCache(); var rasterizeOptions = new[] { "ALL_TOUCHED=TRUE" }; Gdal.RasterizeLayer(ds, 1, new[] { 1 }, layer, IntPtr.Zero, IntPtr.Zero, 1, new[] { 10.0 }, rasterizeOptions, null, null); ds.FlushCache(); var destination = new MemoryStream(); using (var source = File.Open(outputRasterFileName, FileMode.Open)) { source.CopyTo(destination); destination.Position = 0; return destination; } This works, but I do not like the idea of writing to disk when I don't have to. I then found these threads: http://osgeo-org.1560.x6.nabble.com/gdal-dev-NET-and-OGR-writing-to-stream-td3744067.html#a3744070 https://lists.osgeo.org/pipermail/gdal-dev/2016-August/045030.html Which says I can use the memory file system handler, and the python sample code provided by Even seems easy enough to translate: # Read /vsimem/output.png f = gdal.VSIFOpenL('/vsimem/output.png', 'rb') gdal.VSIFSeekL(f, 0, 2) # seek to end size = gdal.VSIFTellL(f) gdal.VSIFSeekL(f, 0, 0) # seek to beginning data = gdal.VSIFReadL(1, size, f) gdal.VSIFCloseL(f) # Cleanup gdal.Unlink('/vsimem/output.png') However, the C# bindings does not seem to include VSIFReadL, although Maksim Sestic seems to indicate that they are. Is this an issue with the Nuget-package? I then tried using C# Marshal.Copy, but this fails: var bufPtr = Gdal.VSIFOpenL(outputRasterFileName, "rb"); //outputRasterFileName is now "/vsimem/file.tiff" Gdal.VSIFSeekL(bufPtr, 0, 2); // seek to end var size = Gdal.VSIFTellL(bufPtr); Gdal.VSIFSeekL(bufPtr, 0, 0); // seek to beginning Gdal.VSIFCloseL(bufPtr); var data = new byte[size]; Marshal.Copy(bufPtr, data, 0, size); Gdal.Unlink(outputRasterFileName); I am by no means a C# expert, but I cannot see any reason this should fail? Given a memory pointer and size, read bytes, right? As a last alternative I've tried to use the examples provided here: https://trac.osgeo.org/gdal/browser/trunk/gdal/swig/csharp/apps/GDALReadDirect.cs This lets me read the bitmap of my raster, but all geotiff-metadata is lost. This also seems a bit overkill, as the actual GeoTiff is created and exists in memory! So, to sum up a large mail: 1. Should Gdal.VSIFReadL be available in the C# bindings? If so, how do I get them? 2. If not 1, Should I be able to use Marshal.Copy in the manner described above? Or are there any other ways of getting these bytes? 3. If not 2, is using the sample code in https://trac.osgeo.org/gdal/browser/trunk/gdal/swig/csharp/apps/GDALReadDirect.cs a feasible way to create a stream of a geotiff-file`? Thanks in advance for your replies, and thanks for a great library! -a -- Atle Frenvik Sveen a...@frenviksveen.net 45278689 atlefren.net _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
