please check: the patch ignores preserved points, so I think it
could break
routing.
You cannot route over polygons. So I don't expect that removing a point from a polygon can break routing?
The filter is also used in MapBuilder.processLines()
You are right. I thought my patch checks if the element is a MapShape like it is done in the RemoveEmpty. But it doesn't. So this has to be added and/or be extended to check for preserved points.
I would assume that straight lines are filtered by
DouglasPeuckerFilter ?
Probably not. Otherwise the file size of the img files should have been the same.
I don't understand. Your patch doesn't change the number of points on straigth lines, does it?
No, but it removes spikes from polygons. So the following polygon: a-b-c-d-c-e-a will become a-b-c-e-a I don't know if the DouglasPeuckerFilter does the same?
(at least now that I've committed the removeShortArcs patch) I did already look for other algos, eg. the VW algo http://www2.dcs.hull.ac.uk/CISRG/publications/DPs/DP10/DP10.html sounds like a possible alternative to DouglasPeucker. On the other hand, I assume that the input for the filters will change with the intended mp_cut changes, so we may end up solving the same
problem
at two different places.
Yes and no. The mp_cut changes will only affect how polygons are cut when they are part of a multipolygon. But there are many polygons that are not. On the other hand I also use the algorithm of the RoundCoordsFilter in the mp_cut branch (not yet committed) and therefore observe exactly the same problems. So improving the RoundCoordsFilter algo will also solve problems in the mp_cut branch.
OK. The RoundCoordsFilter really looks a bit brutal ;-)
Gerd