[gdal-dev] GDAL Raster Attribute Tables.

[Frank Warmerdam]

On Tue, Apr 23, 2013 at 1:57 PM, Peter Bunting <petebunting at mac.com> wrote:

> Hi All,
>
> We were wondering if there is any interest in the GDAL community for
> improving the Raster Attribute Implementation? Within our group of
> collaborators we have been representing image segmentations as clump files
> often large attribute tables containing millions of rows and numerous
> columns of data used for classification. We are finding the current
> approach that reads a single value at a time with the whole attribute table
> in memory to be quite poor performance wise and resource (i.e., memory)
> hungry.
>

Peter,

You do seem to be pushing raster attribute tables well beyond the expected
use cases.


>
> We would like to propose a new implementation that allows reading and
> writing of whole chunks of a single column within the attribute table more
> like RasterIO.
>

> If we were to create a patch, would the GDAL community be receptive to
> this? We were thinking this would be incorporated within the interface
> changes in GDAL 2.0.
>

I would be receptive to additional read (and perhaps write) methods for
chunks of the attribute table at a time if it can be done with a minimum of
distruption of the existing api.


> It has been muted that OGR might be merged into GDAL in version 2.0 if
> this were to occurred how would attribute tables be dealt with and are the
> changes we proposing something that needs to be considered in that wider
> context also?
>

I had not been contemplating treating raster attribute tables as OGR layers.

I must confess that I'm still not certain that pushing raster attribute
tables to be very large is a good idea.

Best regards,
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Software Developer
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20130423/1d004c21/attachment.html>