Clipping is pretty context dependent, meaning, depending on how your clipping certain geometries, several different approachs may work more effecient. This repository contains two functions for clipping under with two pretty different contexts.
Belove is an example of the two different clipping methods on an Alaska geojson polygon feature.
package main
import (
"github.com/paulmach/go.geojson"
"github.com/murphy214/tileclip"
"github.com/murphy214/mercantile"
"fmt"
"io/ioutil"
)
func main() {
// reading alaka geojson file
bs,_ := ioutil.ReadFile("alaska.geojson")
feature,_ := geojson.UnmarshalFeature(bs)
// used for clipping a specific part of a feature into a single tile
tileid := mercantile.TileID{1,8,5}
about_tile_feature := tileclip.ClipTile(feature,tileid)
about_tile_feature.Properties = map[string]interface{}{"COLORKEY":"purple","TILEID":mercantile.Tilestr(tileid)}
fmt.Printf("About Tile: %+v Feature: %+v\n",tileid,about_tile_feature)
// return a tilemap (map[m.TileID]*geojson.Feature)
// keep_parents determines whether to keep previous zoom levels in the tileid:feature map
keep_parents := false
tilemap := tileclip.ClipFeature(feature,int(tileid.Z),keep_parents)
// collecting all features from map
feats := []*geojson.Feature{}
for k,v := range tilemap {
v.Properties = map[string]interface{}{"TILEID":mercantile.Tilestr(k),"COLORKEY":"white"}
feats = append(feats,v)
fmt.Printf("Tile: %+v Feature: %+v\n",k,v)
}
feats = append(feats,about_tile_feature)
tileclip.MakeFeatures(feats, "a.geojson")
}
ClipTile clips a single feature about a single tile returning a single feature.
func ClipTile(feature *geojson.Feature,mercantile m.TileID) *geojson.FeatureClipFeature clips a feature at a defined endzoom and then collects all tiles with that given endzoom created. Keep_parents is a bool that determines wheter or not to delete the parent or upper tile k/v sets for the returned tilemap.
func ClipFeature(feature *geojson.Feature,endzoom int,keep_parents bool) map[m.TileID]*geojson.Feature