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

Mon May 3 16:28:26 BST 2021

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