[Gdal-dev] Imagine overviews option

[Frank Warmerdam]

On 9/16/05, Garrett Potts <potts at cfl.rr.com> wrote:
> Hello FRank and others:
> 
> Actually it seems if anything were to be added it would be best to
> add it to the XML option string for the hfa dataset???
> I am not sure if frank likes this or not but this would give a
> generic way, without changing any current interfaces, of specifying
> writer specific overview dataset creation options.
> 
>    <Option name='HFA_USE_RRD' type='boolean' description='Use
> external rrd file for overview building, default NO'/>
> 
> Not sure if this is what the create options was intended?  If not
> then maybe some other metadata NAME could be added for the HFA
> specific way of creating an overview?

Garrett, 

The problem is that creation options are for information needed when
creating the .img file.  But creating overviews is not part of the Create()
or CreateCopy() methods.  It is a separate operation that might be
never be done, might be done later, or might be done in a separate
process run. 

If I were to allow this to be passed into the Create() method, then I 
would have to figure out somewhere in the .img file to stash this
preference so that I could find it again later when it is time to create
overviews.   That is possible, but it seems ... messy.  And it would not
extend well to other formats where I cannot just add arbitrary data
in the format. 

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent