On Fri, Jun 1, 2018 at 7:14 PM, Even Rouault <even.roua...@spatialys.com> wrote:
> On vendredi 1 juin 2018 18:25:27 CEST Sean Gillies wrote: > > Hi Even, > > > > I got waylaid in following up, but am finally doing so now. Yes, I can > also > > confirm that the .msk file is being read over the internet. I'm grateful > > for the CURL logging in GDAL, it's very handy. > > > > However, I'm perplexed by not being able to get the mask I expect from > the > > warped VRT I'm creating using GDALAutoCreateWarpedVRT. The source file > has > > a mask, but no mask materializes in the warped VRT. I have a WarpedVRT > > class in Rasterio that calls GDALAutoCreateWarpedVRT and is equivalent to > > the Python GDAL code you showed. It has a method that calls > > GDALGetMaskFlags and here's what that reports. > > > > with rasterio.open('https://oin-hotosm.s3.amazonaws.com/ > > 5a324a622553e6000ce5aaf5/0/3fa181a1-425c-4e53-b49f-ea72884da097.tif') as > > src, WarpedVRT(src, dst_crs=src.crs) as vrt: > > print(vrt.mask_flag_enums) > > > > # Output: > > # ([<MaskFlags.all_valid: 1>], [<MaskFlags.all_valid: 1>], > > [<MaskFlags.all_valid: 1>]) > > > > The source has a per-dataset mask, but this doesn't surface in the VRT. > It > > reports that all the pixels are valid. > > Hi Sean, > > OK I now understand what you meant. The warper in general in GDAL (so not > specific to the VRT warping) can use the mask of the input dataset, but > doesn't generate one in output. However it should be able to generate an > alpha > band if you call GDALCreateWarpedVRT() with psOptions->nDstAlphaBand = 4 > (couldn't test easily, but hopefully should work) > > Even > After setting that warp option and setting the color interpretation of the resulting band to GCI_AlphaBand, I'm in business! Thanks, Even! -- Sean Gillies
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