[Qgis-developer] Raster Filters

Mark Coletti mcoletti at lychnobite.org
Wed Jun 20 13:19:50 EDT 2007

On Wed, Jun 20, 2007 at 01:13:44PM -0400, Peter Ersts wrote:

> Just after ending the raster refactoring chat, I had an idea, rather 
> than trying to integrate the QgsRasterFilter idea into rendering 
> processes itself, why not treat the QgsRasterFilter as if it were a data 
> provider?

  That's what I was hinting at during the IRC session:

(12:45:26) mcoletti: timlinux: So would the data pipeline for a chain
		     of filters look like this: first filter is
		     attached to raster data provider.  Then a second
		     filter gloms onto the first.  The second filter
		     does all data requests through the first filter,
		     which may or may not ultimately pass requests on
		     to the data provider.  The second filter doesn't
		     know it's not talking directly to the provider.

But I infer through my cold induced fuzzy thinking is that some of the
proposed filters would require a tighter coupling to the data
provider.  OTOH, maybe some of the information that those filters
would need from the data provider could just be propogated as needed
down the filter line?  (Although that might add unnecessary overhead.)



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