Thanks Brian. But this way you rewrite the whole image to disk. It uses lots of disk space and takes forever.
I want to avoid that and just get the mask out to a msk file as fast as possible. I don't want to convert my rgba vrt mosaic. The final objective is to get a msk file I can use with the simple rgb vrt mosaic. Then I'll be able to build overviews with jpeg/ycbcr compression which I can't do with rgba vrt because of the 4 bands. For now I have tried 3 ways: 1) use gdal_rasterize to create a mask directly from the mask polygon shapefile. Then just edit the rgb vrt mosaic and add a maskband to it. The problem here is gdaladdo does not honor the maskband. This is the fastest way I know, pitty it doesn't work in the end. 2) use gdal_translate like you suggested but use -scale to write all 0s in all 3 bands, and compress with deflate. You get a valid mask and a very, very small useless mosaic. This works but takes a while still. 3) use gdal_translate like you suggested but exaggerate the jpeg compression so it errors out (jpeg_quality=15). You get an invalid 1kb mosaic and an apparently good msk. But it's corrupted in some way. So doesn't work. I think #1 has potential. If there was a way to somehow turn the tif created by gdal_rasterize into a "true" mask file and have it honored by gdaladdo we would have a winner. Maybe there's a way to directly export the alpha band from the rgba vrt mosaic to a mks file without writing anything else? That I guess would be the fastest way of all. Duarte -----Mensagem original----- De: Brian Case [mailto:[email protected]] Enviada: quinta-feira, 6 de Fevereiro de 2014 21:51 Para: Duarte Carreira Cc: [email protected] Assunto: Re: [gdal-dev] how to create just the msk file from a rgba vrt file Duarte gdaltranslate -of outfrmt -b 1 -b 2 -b 3 -mask 4 infile outfile brian you can output to vrt's just dont try to mosaic masked or aphad files with vrts brian On Thu, 2014-02-06 at 13:20 +0000, Duarte Carreira wrote: > Hi there. > > > > Continuing with trying to cut processing times, I am trying to get a > msk file from a vrt mosaic, without converting the entire vrt to tif > just to get the msk file. > > > > In other words, how can we create a msk file from the alpha band > without rewriting the whole image? > > > > Thanks again. > > Duarte > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Duarte Carreira > Diretor | Dep. Informação Geográfica e Cartografia > > > www.edia.pt > > www.alqueva.com.pt > Tel. +351 284315100 > > > > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
