On Tue, Feb 28, 2012 at 11:09 PM, Andrea Aime
<[email protected]>wrote:
> On Tue, Feb 28, 2012 at 11:32 PM, Martin Davis <[email protected]> wrote:
> > So these need to be defined as parameters to the RenderingTransformation
> > process, and then specified in the SLD with values provided by calls to
> the
> > "env" function?
> >
> > Hmm... I think I like the invertQuery way better - more explicit, and
> fewer
> > lines of code for users to screw up.
> >
> > I can see that having access to rendering parameters in the SLD could be
> > very useful, however.
>
> In my mind a process is first and foremost a WPS process, its
> rendering transformation
> ability is something added on top, the process has to work even outside of
> that rendering context (when called striaight from WPS the rendering
> transformation
> methods are _not_ going to get called).
>
> A process that does vector to raster transformation obviously needs to know
> how big the output raster will be, thus it needs to have some simple and
> WPS bindable way to do that, the grid to world transformation is not a
> obvious
> candidate there, width and height are more natural.
>
> I see you are thinking about the process as something that makes sense
> to be used only as a rendering transformation instead, so hopefully it
> is not build as
> a process (since you'd have around a WPS process that cannot be used)
> but as a straight filter function?
>
> I did not cover that use case, but if you want to propose API changes that
> would make both approaches work I'm all ears :-)
>
> These are all good points, Andrea, and I agree with your reasoning that
it's nice to have a single implementation which can be used as both a
standalone process and as a rendering transformation.
I don't have any great ideas about another way of doing things at this
point. It does seem to me like it would be nice to avoid having all that
ugly boilerplate code in the SLD to pass in the rendering context
information. I guess there are various ways this might be done:
- well-known parameters that the Rendering pipeline could fill in
automatically
- a RenderingTransform-specific method on the process class to pass in this
information (but this would require ThreadLocal storage again, or creating
a new process object for each rendering use)
Anyway, for now I'll look at switching over to using the explicit
parameters.
--
Martin Davis
OpenGeo - http://opengeo.org
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