[OpenLayers-Users] TileCache and KaMaps

[Tim Schaub]

> http://sigma.openplans.org/dev/test-meta.html
> 

If this is really meta tiles, I'd be interested to see how you're getting
transparency.  Has anybody else confirmed that PIL gets rid of transparency
when doing the image crop?

Tim

> The second uses metaTile for the tiger layers, the first 
> doesn't, everything else is the same.  Overlaid on the 
> bluemarble layer, however, everything in tiger is shifted 
> south, the outlines don't match.  Not sure if there was 
> something I configured wrong, but all I did was add metaTile=true.
> 
> When testing on its own it seemed to be working, definitely 
> less 'United States' labels on my page.  So the root concept 
> seems to be working, which is great news.
> 
> I'll also note that right now it seems to be having more 
> blank images. 
> It's not all pre-cached.  I've actually consistently had 
> problems with areas that aren't pre-cached, they tend to not 
> wait until the backend has returned, instead just return the 
> broken images.  It would be great if I could get it so 
> there's never the broken images, some just take a lot longer to load.
> 
> best regards,
> 
> Chris
> 
> 
> It also doesn't hook directly into mapscript (and
> > there aren't plans to, though it could in the future) to use added 
> > capabilities of MapServer like ka-map does. It also (due to lack of 
> > support in the Python Imaging library) doesn't support chopping up 
> > transparent tiles and maintaining transparency: this means that you 
> > can't metaTile transparent images.
> > 
> > TileCache is young. It hasn't been tested on dozens or hundreds of 
> > installs like ka-Map has been.
> > 
> > TileCache is written in Python. It doesn't require 
> mapscript. It can 
> > be run on a service which is far from your original service 
> (via WMS 
> > cascading). The code is clean. It runs under CGI or mod_python.
> > 
> > TileCache supports multiple request formats. WorldWind, WMS-C, TMS.
> > 
> > TileCache supports multiple data backends: mapserver (via 
> mapfiles), 
> > WMS cascading, mapnik, and is easy to extend to anything 
> else -- for 
> > example, one of the next additions I'm going to look into 
> is an ArcXML 
> > layer. This means that if you have a custom data source, 
> it's probably 
> > easy for you to wrap it in TileCache.
> > 
> > 
> > TileCache is, for the most part, a replacement for ka-Map. However, 
> > it's an immature project, and may not fit all the needs 
> that everyone has.
> > The metaTiling support, in particular, is not extremely 
> well tested, 
> > and that is the primary benefit that ka-Map offers. 
> However, based on 
> > empirical testing, I feel that it's likely that for many cases, 
> > TileCache will be much faster than ka-Map, and I think that 
> it's more 
> > likely to be maintained and extended in the future than ka-Map's 
> > rendering tool.
> > 
> > Personally, I'm working to migrate all my ka-Map based instances to 
> > TileCache. If TileCache doesn't do it, then my steps will 
> be to make 
> > TileCache do it, rather than setting up ka-Map. However, I have not 
> > yet migrated any projects which require metaTiling to TileCache, so 
> > I'm not yet convinced of its stability at that particular task. 
> > Anything which doesn't require metaTile support, I would absolutely 
> > recommend
> > TileCache: I'm not to the same point with anything which requires 
> > metaTile support yet.
> > 
> > Regards,
> 
> --
> Chris Holmes
> The Open Planning Project
> http://topp.openplans.org
>