Hi Enzo,
I'd second Andy's recommendation of using PostGIS to render circles
with varying size based on some attribute. That sounds like the right
place to start.
As far as styling the circles once you've created them can find more
about the LineSymbolizer (which you can use to define the outline size
and color of the circle), and the PolygonSymbolizer (to define the
fill color) on the Mapnik wiki:
http://trac.mapnik.org/wiki/LineSymbolizer
http://trac.mapnik.org/wiki/PolygonSymbolizer
Also at the wiki is a page that has started to document some usage
specific to PostGIS:
http://trac.mapnik.org/wiki/PostGIS#Usage
And here is a sample script in python that shows buffering existing
polygon data into a larger polygon using PostGIS:
http://mapnik-utils.googlecode.com/svn/trunk/tutorials/postgis/postgis_geometry.py
You could likely borrow from some of the script ideas to approximate
the same effect with circles.
Where these references are incomplete or unclear I'll try to answer
further.
Dane
On Nov 16, 2008, at 7:40 PM, Enzo Losantas wrote:
Thanks Andy for replying.. somehow gave me an idea how it works.
although there are still things that im confused about. as for the
kind of circles, maybe circles that have dynamic
radius based on a certain parameter. Since these are varying radii,
I'll probably follow your advice regarding
drawing polylines in postgis.
As for the item on LineSymbolizer / PolygonSymbolizer, can you help
me with this? Are there any available
API or references that can be of help as well? How does this work
exactly?
thanks,
Enzo
On Wed, Nov 12, 2008 at 8:16 PM, Andy Allan <[EMAIL PROTECTED]>
wrote:
What kind of circles are you looking for? If you just want small
circles to mark point locations, then make a .png and use a
PointSymbolizer with it. But if you're trying to vary the size of the
circles, like for example "draw me a circle where the radius is
proportional to the population of the town", then you'd be better off
creating polylines in postgis (or shapefile) and then just
LineSymbolizer / PolygonSymbolizer depending on whether you want the
outline or it filled.
Cheers,
Andy
On Wed, Nov 12, 2008 at 2:54 AM, Enzo Losantas
<[EMAIL PROTECTED]> wrote:
> hello,
>
> im wondering if anyone here is familiar with rendering osm through
mapnik?
> Particularly, anyone knows how to render circles? is it through
node-ways or
> it can be done through the rules?
>
>
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