hey guys, i was wondering if anyone can help enlighten me on this? i was wondering how it would be possible to draw circles on mapnik? i was pointed earlier to using postgis and probably use buffer function?
im thinking of trying to create circles where the radius is dynamic, and is dependent on an attribute of a certain set of points. how could i go about this? by the way, thanks dave for pointing me to the right direction. Thanks. Enzo ---------- Forwarded message ---------- From: Enzo Losantas <[email protected]> Date: Wed, Jan 7, 2009 at 3:27 PM Subject: Re: [OSM-dev] help: drawing circles on mapnik To: Dane Springmeyer <[email protected]> can you point me to the mapnik-users list where i can join? as for the buffer function, the buffer distance value can be obtained by a field in the same table? would that be possible? also, im not familiar with the "speed bump", what would that mean? Thanks a lot. Enzo On Wed, Jan 7, 2009 at 3:02 PM, Dane Springmeyer <[email protected]> wrote: > Enzo, > Yes you would use the Buffer function in PostGIS but you can create them > dynamically in your select statement within your mapnik xml mapfile, so > there is no need to pre-calculate in another geometry field unless you need > a speed bump. As of r769 in svn trunk, mapnik's PostGIS plugin can support > multiple geometry fields. > > For more info consider posting to the mapnik-users list and reading: > http://trac.mapnik.org/wiki/PostGIS > > Dane > > On Jan 6, 2009, at 6:45 PM, Enzo Losantas wrote: > > Just a minor follow up, does this mean that im going to add another column > in my database, > use postgis to add shapefiles or buffers, then use mapnik and render the > circles properly with > the LineSymbolizer and PolygonSymbolizer? > > Thanks, > Enzo > > On Tue, Jan 6, 2009 at 5:13 PM, Enzo Losantas <[email protected]>wrote: > >> Anyone knowledgeable on how to go about this? >> >> Dane, i was thinking of maybe going about this with a buffer maybe? >> If i have a point, then i could use that point as the center of the >> buffer, >> then this buffer can be the circle that i am looking for. there seems to >> be a >> buffer function that postgis offers.. is that correct? >> >> Thanks, >> Enzo >> >> ---- >> Date: Sun, 16 Nov 2008 21:15:43 -0800 >> From: Dane Springmeyer <[email protected]> >> Subject: Re: [OSM-dev] help: drawing circles on mapnik >> To: Enzo Losantas <[email protected]> >> Cc: [email protected] >> Message-ID: <[email protected]> >> Content-Type: text/plain; charset="us-ascii" >> >> 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? >> > > > > -- > Check these out: > > http://ohm.ecce.admu.edu.ph/ > > http://smart.com.ph/ > > > -- Check these out: http://ohm.ecce.admu.edu.ph/ http://smart.com.ph/ -- Check these out: http://ohm.ecce.admu.edu.ph/ http://smart.com.ph/
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