<div dir="ltr">I do not know that code. But having a look I have the impression that you have to set the nodata also to papszCreateOptions, so the created dataset has it.<br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, 3 Nov 2023 at 21:36, Fitch, Simeon via gdal-dev <<a href="mailto:gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hi, <div><br></div><div>I'm one of the maintainers at the `georust/gdal` bindings project. 👋 </div><div><br></div><div>I'm currently working on exposing some of the GDAL Warp functionality in Rust, starting with a simple wrapper around `GDALCreateAndReprojectImage`. I'm having trouble getting the output file to include a no-data value in the band's metadata, despite the Warp operation properly respecting no-data values specified in `GDALWarpOptions`. </div><div><br></div><div>My C++ skills are very "rusty", so I'm hoping I can get away with explaining my problem with some Rust code that is pretty close to being 1:1 with the C API. My suspicion is I'm missing a step in the `GDALWarpOptions` setup.</div><div><br></div><div>This is the CLI operation I'm trying to replicate:<br><br> gdalwarp -t_srs EPSG:4269 -dstnodata 255 -r near input.tif output.tif</div><div><br></div><div><div>Here's the bare-bones Rust bindgen version:<br></div><div><br></div><div> <<a href="https://gist.github.com/metasim/d2a288d5b6126438aaa84b9e95707aff" target="_blank">https://gist.github.com/metasim/d2a288d5b6126438aaa84b9e95707aff</a>><br></div><div><br></div></div><div>The single band in `input.tif` is described by `gdalinfo` like this:<br></div><div><br></div><div> Band 1 Block=186x44 Type=Byte, ColorInterp=Gray<br></div><div> NoData Value=255<br> Metadata:<br> CLASSES=3<br></div><div><br></div><div><div>After running the Rust code, the results are correct (including Warp numerically respecting source and destination no-data values) _except_ `output.tif` does not have a no-data value in the band metadata. Here's what `gdalinfo` on `output.tif` shows:</div></div><div><br></div><div> Band 1 Block=210x39 Type=Byte, ColorInterp=Gray<br></div><div><br></div><div>The only way I've been able to get the behavior I need is to open the written dataset from the filesystem and set the no-data value explicitly in the band, which is inefficient and awkward. Given the CLI version does the right thing, it's obviously possible. I've spent several hours visually inspecting the C++ source code, but the CLI version doesn't call `GDALCreateAndReprojectImage` directly; rather it constructs the Warp pipeline itself.</div><div><br></div><div>Anyone have tips that might help me run this down? Am I missing a no-data handling step required when working with Warp routines? Could `GDALCreateAndReprojectImage` have a bug? </div><div><br></div><div>Thanks,</div><div><br></div><div>Simeon</div><div><div><br></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div>Simeon Fitch</div><div>Co-founder & CTO</div><div><span style="font-size:small">Astraea, Inc.</span><br style="font-size:small"></div><div><span style="font-size:small"><br></span></div></div></div></div></div>
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