Thanks Even ;-) > Le 26 oct. 2018 à 10:11, Even Rouault <[email protected]> a écrit : > > On vendredi 26 octobre 2018 09:09:34 CEST Vincent Sarago wrote: >> Goal: I’d like to see if there could be a way to use VRT of COG to create a >> mbtile like system to read tiles. >> >> If I remember well when a VRT points to COG you still need to create >> external overviews for the whole VRT because it won’t fetch de overviews >> from the COG itself when trying decimated read. > > No, that's not exactly true. If a VRT contains more than one source, GDAL > won't be able to expose a proper overview externaly, but it will use the > overviews of sources, when present, for decimated read (*). However if your > VRT has a lot of sources (let's 1024x1024 tiles of 256x256 pixel each), if > you > ask for just a 1024x1024 output buffer of the whole extent, there is no > magic: > GDAL will have to open each source dataset to compute its contributed single > pixel. In that case, you may want to pregenerate an overview of the whole VRT. > > Even > > (*) and actually even if those don't expose overviews proper, it will let the > underlying driver handle that at best: so a VRT of VRT of COG would work > > -- > Spatialys - Geospatial professional services > http://www.spatialys.com
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