[postgis-devel] WKTRaster & overviews

[Mateusz Loskot]

Martin Daly wrote:
> >
> > One more question: How are you going to name the overview tables?
> 
> At the moment there is no provision for creating overviews, so there is
> no need for PostGIS Raster to have any rule(s) for naming them. In
> addition, the metadata (both alternatives) allow for discovery by query
> based on the base raster table name, schema, etc., rather than by
> naming convention.

As gdal2wktraster needs to name tables, I decided on simple convention
for that purpose, it is: ov_<RASTER TABLE>_<LEVEL> where
<RASTER TABLE> - name of table with original raster
<LEVEL> - number of overview level

Certainly, this convention sits on gdal2wktraster side only.

BTW, Since yesterday, gdal2wktraster provides support for loading overviews
as well as padding tiles (blocks) of right-most and bottom-most row with "garbage"
(nodata or zeros), if necessary.

For example, here are hex-encoded tiles of 5x5 pixels raster
(1 band, 1 byte of pixel type) tiled using 3x3 block size where
A0, B0, C0 are real pixel values and FF is nodata:

A0B0C0   A0B0FF
A0B0C0   A0B0FF
A0B0C0   A0B0FF

A0B0C0   A0B0FF
A0B0C0   A0B0FF
FFFFFF   FFFFFF

Client is supposed to ignore all FFs, as they are beyond spatial extent of raster.

Best regards,
--
Mateusz Loskot
Senior Programmer, Cadcorp
http://www.cadcorp.com