[mkgmap-dev] new branch low-res-opt to test improvements for filters

Wed May 5 02:42:32 BST 2021

I think the simplify 4 patch had some more improvements for contourlines -
but then I played around all the time with the DP values so it's hard to
compare. I do know that simplify v4  versus 3 back then was an improvement.
I think merging lines of different directions would be good too - with the
caveat that we would need an additional instruction in the lines style-file
to tell for lines not to merge (maybe make this a list - because then it's
not needed each occurrence in the lines file, but once per type. I feel
this is only important for any type that is either off center (e.g. I have
MTB routes on the right side of the center line, hiking routes on the left
- so you can see both if on the same way) or that have an arrow or similar
in the typ-file (i.e. I have arrows on my rivers so you can see the
direction of water flow). Oh and not sure if this is would be merged also
at level 0 or only >0. That would make a big difference in how many
line types I put on that list. I mean there are many types also at level 0
where I don't care about the direction. Of course any line with oneway that
is routable could not be merged too. On the other hand even quite a few
routable lines could be merged - but not all.
If this also applies to level 0, then that file needs to have one command
for level 0, and one command for level 1 and higher. At level 1 and onwards
it only depends on the typfile if merging is possible or not. At level 0 it
depends on both typfile and oneway attribute.

On Mon, 3 May 2021 at 23:28, Gerd Petermann <GPetermann_muenchen at hotmail.com>
wrote:

> Hi all,
>
> as a result of the thread about raster problems I've started this new
> branch.
>
> First commit implements experimental options to specify values for
> --reducePointError and --reducePointErrorPolygon for each resolution
> Options are --simplify-filter-line-errors as replacement for
> --reducePointError and --simplify-filter-polygon-errors as replacement for
> --reducePointErrorPolygon.
> If --simplify-filter-line-errors is given and
> ----simplify-filter-polygon-errors is not given the values for lines are
> also used for polygons.
> Meaning is similar to the --polygon-size-limits option, values are given
> in pairs <resolution,reduce-value>
> Note that in resolution 24 the filter is not used.
> Sample usage:
> --x-simplify-filter-line-errors=23:1.3,22:2.6,20:4,18:6
> --x-simplify-filter-polygon-errors=23:1.3,22:2.6,20:4
> The old options are still supported, --reducePointErrorPolygon=1.3 is
> treated like --x-simplify-filter-line-errors=23:1.3
>
> If none of the options is used the default is 2.6 for all resolutions.
>
> There are a few more things to change:
> - simplify4.patch with special code to improve rendering of contour lines
> - more-merge.patch to allow merging of roads at level > 0
> - Line merger could merge more lines if direction of the lines doesn't
> matter
> - maybe I find a way to merge dual-carriage ways into one line (again, if
> direction doesn't matter)
> - the --housenumber option should probably not assign numbers to trunk
> roads (similar to motorways), this can add lables to these roads and thus
> prohibit merging.
>
> None of these changes should change routing results. They can reduce img
> size and improve rendering.
>
> Gerd
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>

-- 
Felix Hartman - Openmtbmap.org & VeloMap.org
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