Selon Jorge Arevalo <jorgearev...@libregis.org>: > Hello, > > I'm working with Mapserver, trying to serve images stored in PostGIS > Raster via WMS using the new version of GDAL PostGIS Raster driver > (I'm working to improve it). The images appears misplaced when > overview tables are used. The overviews were correctly created, but > the driver doesn't serve them in the right way. In other words: it > isn't a data problem. It's a driver problem. > > I've been re-reading the GDAL driver implementation tutorial, but it > only covers the default support in GDAL for external overviews stored > in TIFF files. My overviews are stored in PostGIS Raster tables, not > TIFF files. I'm looking at geotiff.cpp code. I guess the driver have > to fullfill some requirements, like geotiff driver does. My question > is: what are the most important parts in order to provide a good > overview support, based on the idea that the overviews are raster > tables? (Just reading support, so far)
Jorge, I'm not sure if there are very well formalized requirements documented somewhere, bu the ones I can think of are : 1) A few characteristics of the overview band should be the same as the base band, i.e. same data type (this is probably not a so strong requirement, because RasterIO() should do the translation to the requested data type), and same color table in the case the base band has a color table associated 2) The spatial extent of the overview band should be exactly the same as the one of the base band. This is really a strong requirement. And I feel this is the likely cause of the mis-placement you observe. I'm not sure how your PostGIS Raster overviews are built, but if they have a different extent that the full resolution table, you'll surely have an issue, unless the driver compensates for that by padding/cropping appropriately. Best regards, Even _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev