blemoine · September 9, 2015 10:07 · Sep 9, 2015
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,119 @@
+/*
+ pour lancer :
+ node geoJsonMinifier.js <cheminDuFichierGeoJson> > <cheminDuFichierDeSorti>
+
+ */
+
+var fs = require('fs');
+var _ = require('lodash');
+
+var geoJsonPath = process.argv[2];
+if (!geoJsonPath) {
+  console.error("You must pass a path to a geoJson file", geoJsonPath);
+  return;
+}
+fs.readFile(geoJsonPath, function (err, geoJsonContent) {
+  if (err) {
+    console.error("Error while reading file", err);
+    return;
+  }
+
+  var geoJson = JSON.parse(geoJsonContent);
+
+  if (geoJson.type != 'FeatureCollection') {
+    console.error("The type of the geoJsonContent must be FeatureCollection", geoJson.type);
+    return;
+  }
+
+  console.log(JSON.stringify(minifyGeoJson(geoJson)));
+});
+
+function minifyGeoJson(geoJson) {
+
+  var minifiedFeatures = geoJson.features.map(function (feature) {
+    var minifyCoordinate = _.flow(decreasePrecision(3), removeDuplicatePoint);
+    var newCoordinates = minifyCoordinate(feature.geometry.coordinates);
+
+    return {
+      "type": "Feature",
+      "id": feature.id,
+      "properties": feature.properties,
+      "geometry": {
+        "type": feature.geometry.type,
+        "coordinates": newCoordinates
+      }
+    };
+  });
+
+  return {
+    "type": "FeatureCollection",
+    "features": minifiedFeatures
+  }
+}
+
+function isCoordinate(maybeCoordinates) {
+  return _.isArray(maybeCoordinates) && maybeCoordinates.length == 2 && _.isNumber(maybeCoordinates[0]) && _.isNumber(maybeCoordinates[1])
+}
+
+function removeDuplicatePoint(arr) {
+  var arrSize = arr.length;
+  return arr.map(function(el) {
+      if(_.isArray(el) ) {
+        if(el.every(isCoordinate)) {
+          var elSize = el.length;
+          return el.filter(function(coordinates, idx) {
+            //Minus 2 beacause we want at least 3 points
+            if(idx > 0 && idx < elSize - 2) {
+              return distanceBetweenCoordinates(coordinates, el[idx - 1]) > 100
+            } else {
+              return true;
+            }
+          });
+        } else {
+          return removeDuplicatePoint(el);
+        }
+      } else {
+        return el;
+      }
+  })
+}
+
+function decreasePrecision(precision) {
+  return function _decreasePrecision(arr) {
+    var tenFactor = Math.pow(10, precision);
+
+    return arr.map(function (el) {
+      if (_.isArray(el)) {
+        return _decreasePrecision(el);
+      } else if (_.isNumber(el)) {
+        return Math.round(el * tenFactor) / tenFactor;
+      } else {
+        return el;
+      }
+    })
+  }
+}
+
+function toRadians(n) {
+  return n * Math.PI / 180;
+}
+
+function distanceBetweenCoordinates(coord1, coord2) {
+  var lon1 = coord1[0];
+  var lat1 = coord1[1];
+  var lon2 = coord2[0];
+  var lat2 = coord2[1];
+
+  var R = 6371000; // earth radius in meters
+  var φ1 = toRadians(lat1);
+  var φ2 = toRadians(lat2);
+  var Δφ = toRadians(lat2-lat1);
+  var Δλ = toRadians(lon2-lon1);
+
+  var a = Math.sin(Δφ/2) * Math.sin(Δφ/2) +
+      Math.cos(φ1) * Math.cos(φ2) *
+      Math.sin(Δλ/2) * Math.sin(Δλ/2);
+  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
+
+  return R * c;
+}