[gdal-dev] Implementing overview support apart from the default support

[Jorge Arevalo]

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)

Many thanks in advance,

-- 
Jorge Arevalo
http://www.krop.com/jorgearevalo