[postgis-devel] [WKTRaster] Setting properties on a raster

David Zwarg dzwarg at avencia.com
Sun Feb 21 11:37:07 PST 2010


Sounds good to me, I'll change the spec.

z

On Sun, Feb 21, 2010 at 2:26 PM, Pierre Racine
<Pierre.Racine at sbf.ulaval.ca> wrote:
>>I'm looking at setting the properties of a raster.  I managed to
>>figure out how to set the SRID pretty easily:
>>http://trac.osgeo.org/postgis/ticket/423
>
> This is very great Zwarg!
>
>>I'm thinking about ST_SetPixelType now, and I'm wondering how you want
>>to handle the data conversions.  It seems like when the pixel type is
>>changed, the raster data will need to be processed and either
>>truncated or re-allocated, as the pixel type is changed.  Is that
>>correct?
>
>>A also noticed that ST_SetWidth and ST_SetHeight are not in the spec,
>>is that intentional?  Would it ever make sense to set the height and
>>the width?  In one sense, ST_SetPixelType is performing the same kind
>>of truncation/expansion on the bit depth as ST_SetWidth/ST_SetHeight
>>would perform the truncation/expansion in the spatial dimension.
>>Should ST_SetPixelType be dropped if ST_SetWidth and ST_SetHeight are
>>not implemented?  Or should ST_SetHeight and ST_SetWidth be
>>implemented as well?
>
> I agree that ST_SetPixelType does not really make sence... If I want to change the pixel type I would probably instead want to do something like:
>
> ST_MapAlgebra(raster, 'int(A)') on a float raster or ST_MapAlgebra(raster, 'float(A)') on a integer raster...
>
> Pierre
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