[Tilesathome] Another preprocessor - OsmFilter

[Jiri Klement]

Hi,

I've made another preprocessor. It's in Java as osmosis plugin again,
but this time it doesn't change the resulting map.

It filters osm file based on osmarender stylesheet. Only nodes/ways
that will be selected by at least one rule are preserved in osm file,
all others are removed. It probably won't make z12-z17 rendering much
faster, but it can be useful for lowzoom tiles.

For example look at following image:
http://jttt.110mb.com/osmfilter.png

It's a map of road network in Czech Republic. Time needed to create
the image was only 6 minutes (I've already had 400MB extract of Czech
Republic available). When I've tried to do the same thing with orp
without tag filtering, I had to stop it after 25 minutes because orp
was eating all my memory. Osmosis have build-in caching support so it
should be possible to run it on the planet without running out of
memory.

Detailed time usage:
filter tags - 2:05
orp - 3:25
render - 1:45

I think this can be useful for making low zoom maps or for people who
wish to render they own layers which cover only small portion of osm
data in the area.

--
Jiri