Hello Even, My map contains no overviews but a seamless collection of PNG tiles with zoom levels ranging from 13 to 17 (which I suppose is similar to overviews). Each tile is 256 x 256 pixels with the pixel being RGB888, a pretty much standard arrangement.
When reading I call each band's RasterIO this way: GDALRasterBand *b1 = DataSetIn->GetRasterBand(1); b1->RasterIO(GF_Read, x * MAP_TILE_SIZE, y * MAP_TILE_SIZE, MAP_TILE_SIZE, MAP_TILE_SIZE, red, MAP_TILE_SIZE, MAP_TILE_SIZE, GDT_Byte, 0, 0, NULL); having: MAP_TILE_SIZE defined to be 256 red - is the red band which I've allocated to be 256 x 256 byte-sized pixel array x & y are tile's id with respect to the main map's top-left corner at (0,0). But this would always return data in zoom-level 17. Deyan On Wed, Dec 29, 2021 at 8:50 PM Even Rouault <even.roua...@spatialys.com> wrote: > Deyan, > > you generally don't need to use that option. The driver should > automatically select the right overview level when you use the dataset or > band RasterIO() methods, according to the window of interest and the size > of the buffer you specify. > > Even > Le 29/12/2021 à 19:47, Deyan Vasilev a écrit : > > Hello, > I am trying to handle map zooming in a GDAL-based MBTiles windows app. The > only way I have found to control the raster's zoom level is through > GDALOpenEx's open options. > > Changing the zoom-level app-side would require closing the MBTiles db and > reopening it, passing the new zoom level as an open option. I made this to > work but it seems to me somehow clumsy as there is surely a significant > overhead for closing and reopening the db. > > Can you please share if there is a way to request specific zoom-levels > without doing the closing/reopening stuff? > > _______________________________________________ > gdal-dev mailing > listgdal-dev@lists.osgeo.orghttps://lists.osgeo.org/mailman/listinfo/gdal-dev > > -- http://www.spatialys.com > My software is free, but my time generally not. > >
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