[postgis-devel] [gdal-dev] Re: [SoC] GDAL WKTRaster weekly report #9

[Mateusz Loskot]

Frank Warmerdam wrote:
> Is there any mechanism currently for creating overviews?  How have
> you been testing overviews?

Frank,

I suppose you are asking for the GDAL driver.
However, just to confirm, gdal2wktraster can generate
WKT Raster datasets with overviews (in regular blocking mode).

> Under DOUBTs you ask what happens if the bounding box of a block
> does not match any real block in the table, what should happen.  In this
> case IReadBlock() should fill the buffer with the nodata value (zero if
> nodata is not set).

This is exactly what gdal2wktraster does when tiles (blocks) of
downsampled rasters have to get some padding along right-most
or bottom-most column:

http://trac.osgeo.org/postgis/browser/spike/wktraster/scripts/gdal2wktraster.py#L801

Certainly, it's client's (or perhaps GDAL driver too) responsibility to
clip padded tiles and remove such areas of invalid raster data.

> You also mention a doubt about how to handle the 16BF type, which is
> apparently "16-bit float".  I have never seen such a thing before and I'm
> not sure why it is part of the WKTRaster specification. I would suggest
> removing it.

I had same impression and I simply don't use this data anywhere in
gdal2wktraster script.

I believe the right person to ask about this 16-bit float type is
Sandro (strk) - he is the author of original specification documents:

http://trac.osgeo.org/postgis/browser/spike/wktraster/doc

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org