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Allow filtering features by zoom level in conditional expressions

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This moves filtering from the serialization stage to the
tiling stage so that the zoom level can be known to the filter.

The side effect is to carry null attributes much further through
the pipeline than previously.
This commit is contained in:
Eric Fischer
2018-04-05 14:15:19 -07:00
parent 6b29966e4a
commit d01d8177a0
15 changed files with 13698 additions and 57 deletions
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README.md
+7 -1
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@@ -210,7 +210,7 @@ resolution is obtained than by using a smaller _maxzoom_ or _detail_.
### Filtering features by attributes
* `-j` *filter* or `--feature-filter`=*filter*: Check features against a per-layer filter (as defined in the [Mapbox GL Style Specification](https://www.mapbox.com/mapbox-gl-js/style-spec/#types-filter)) and only include those that match. Any features in layers that have no filter specified will be passed through. Filters for the layer `"*"` apply to all layers.
* `-j` *filter* or `--feature-filter`=*filter*: Check features against a per-layer filter (as defined in the [Mapbox GL Style Specification](https://www.mapbox.com/mapbox-gl-js/style-spec/#types-filter)) and only include those that match. Any features in layers that have no filter specified will be passed through. Filters for the layer `"*"` apply to all layers. The special variable `$zoom` refers to the current zoom level.
* `-J` *filter-file* or `--feature-filter-file`=*filter-file*: Like `-j`, but read the filter from a file.
Example: to find the Natural Earth countries with low `scalerank` but high `LABELRANK`:
@@ -219,6 +219,12 @@ Example: to find the Natural Earth countries with low `scalerank` but high `LABE
tippecanoe -z5 -o filtered.mbtiles -j '{ "ne_10m_admin_0_countries": [ "all", [ "<", "scalerank", 3 ], [ ">", "LABELRANK", 5 ] ] }' ne_10m_admin_0_countries.geojson
```
Example: to retain only major TIGER roads at low zoom levels:
```
./tippecanoe -o roads.mbtiles -j '{ "*": [ "any", [ ">=", "$zoom", 11 ], [ "in", "MTFCC", "S1100", "S1200" ] ] }' tl_2015_06001_roads.json
```
### Dropping a fixed fraction of features by zoom level
* `-r` _rate_ or `--drop-rate=`_rate_: Rate at which dots are dropped at zoom levels below basezoom (default 2.5).