[mapserver-dev] RE: [mapserver-users] colorramp and datarange on the fly?

[Jan Hartmann]

If you allow two passes, you can have all sorts of summarized values in 
the template, to be used in the second pass, like Bart's actual extent 
used for coloring. Doesn't look to difficult to implement to me, as long 
as the two passes only get called when really necessary. I'm not sure if 
performance is an issue for MapServer itself: if you really want high 
performance, you should use the underlying format or database directly.

Jan

On 3-2-2010 17:02, Lime, Steve D (DNR) wrote:
> How big a change would depend on the implementation. The brute force approach where you simply loop through features once to compute ranges and then again to draw would be probably pretty straight forward and driver independent. Wouldn't be fast (but would be simple). Complexity would be added as you try and boost performance by:
>
>    - allowing drivers to compute stats in their own way (e.g. add to the layer API something like msLayerGetStats(...))
>    - caching geometries from a first pass through the shapes for the second
>
> Steve
>
> BTW The color ramp support needs to be cleaned up first. I think we scared the originator of that code away when an RFC was originally put together.
>
> -----Original Message-----
> From: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Bart van den Eijnden
> Sent: Wednesday, February 03, 2010 5:12 AM
> To: mapserver-users at lists.osgeo.org
> Subject: [mapserver-users] colorramp and datarange on the fly?
>
> Hi list,
>
> is it possible to have a colorramp in Mapserver based on the min and max value in the current extent?
>
> So instead of predefining the min and max in DATARANGE, have Mapserver use the min and max value of the dataset in the current extent?
>
> If not, would it be an easy change or a very complex one?
>
> Best regards,
> Bart_______________________________________________
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