[mapserver-dev] Rendering smoothed lines

Lime, Steve D (DNR) Steve.Lime at state.mn.us
Mon Sep 17 13:14:57 PDT 2012

I can't speak to supporting curves, but GEOMTRANSFORM's can apply to labels although there's probably still some work to do. For labels there are actually two geometries the label point and the label bbox. We probably need to extend the parser expression syntax to be able to pick between the two if doing GEOMTRANSFORM expressions. 

Don't know if this helps or not.

Smoothing as a GEOMTRANSFORM makes sense. Right now only a few GEOS-based operators are exposed (e.g. buffer) but there's no reason more can't be or that they have to be rooted in GEOS.


-----Original Message-----
From: mapserver-dev-bounces at lists.osgeo.org [mailto:mapserver-dev-bounces at lists.osgeo.org] On Behalf Of Daniel Morissette
Sent: Monday, September 17, 2012 12:39 PM
To: 'MapServer Dev List'
Subject: [mapserver-dev] Rendering smoothed lines

Hi Devs,

Has anyone been thinking about adding support for line smoothing (b-spline, Bezier curves, ?) in MapServer? I believe AGG supports this already, is this an option that we could enable easily for AGG rendering?

More specifically, we've been asked about the ability to smooth contour lines as we zoom out (probably more a combination of simplifying and smoothing). In the contour case it would not be sufficient to do the smoothing at the renderer level (i.e. in AGG) since we also want the contour labels to be positioned properly on top of the smoothed contour. 
For this reason we may instead want to implement smoothing as a GEOMTRANSFORM operation.

This raises another question: Do GEOMTRANSFORM operations also apply to labels? (RFC-72 suggests that this planned enhancement would not be in place yet)

Daniel Morissette
Provider of Professional MapServer Support since 2000

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