Better handling of rings and holes not touched by the intersection

CHANGES.md

@@ -1,3 +1,10 @@
+# 0.0.11
+- Fix up some handling for those rings (outer and holes) that aren't intersected by the split line.
+- Add output geojson validation for test files
+
+# 0.0.10
+- Fix up packaging of dependencies
+
 # 0.0.9
 - Fix another infinite loop case with holes back to outer ring
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "polygon-splitter",
-  "version": "0.0.9",
+  "version": "0.0.11",
   "description": "Split a polygon using a polyline.",
   "main": "dist/polygonsplitter.js",
   "module": "dist/polygonsplitter.mjs",
@@ -31,7 +31,7 @@
     "@rollup/plugin-commonjs": "^21.0.1",
     "@rollup/plugin-node-resolve": "^13.0.6",
     "@rollup/pluginutils": "^4.1.2",
-    "@turf/rewind": "^6.5.0",
+    "@placemarkio/check-geojson": "^0.1.12",
     "@turf/turf": "^6.5.0",
     "@vitejs/plugin-vue": "^1.9.3",
     "ava": "^3.15.0",
@@ -48,7 +48,9 @@
     "write-json-file": "^4.3.0"
   },
   "dependencies": {
+    "@turf/rewind": "^6.5.0",
     "glob": "^8.0.3",
+    "point-in-polygon-hao": "^1.1.0",
     "robust-predicates": "^2.0.4"
   },
   "keywords": [

src/Contour.js

@@ -0,0 +1,8 @@
+export class Contour {
+
+  constructor(contourId, coords) {
+    this.id = contourId
+    this.rawCoords = coords
+  }
+
+}

src/Edge.js

@@ -1,11 +1,12 @@
 export class Edge {
 
-  constructor(p1, p2, edgeType, index) {
+  constructor(p1, p2, edgeType, index, contourId) {
     this.p1 = p1
     this.p2 = p2
     this.edgeType = edgeType
     this.originalIndex = index
 
+    this.polygonContourId = contourId
     this.interiorRing = false
 
     this.minX = Math.min(p1.p[0], p2.p[0])

src/fillQueue.js

@@ -1,7 +1,10 @@
 import {Edge} from './Edge'
 import {Point} from './Point'
+import {Contour} from './Contour'
 
 export function fillQueue(polygon, line, polyEdges, lineEdges, polylineBbox) {
+  let numberOfRingsInPolygon = 0
+  const contours = []
 
   const linegeom = line.type === 'Feature' ? line.geometry : line
   const linecoords = linegeom.type === 'LineString' ? [linegeom.coordinates] : linegeom.coordinates
@@ -19,7 +22,7 @@ export function fillQueue(polygon, line, polyEdges, lineEdges, polylineBbox) {
       p2 = new Point(linecoords[i][ii + 1])
       p1.nextPoint = p2
       p2.prevPoint = p1
-      const e = new Edge(p1, p2, 'polyline', edgeCount)
+      const e = new Edge(p1, p2, 'polyline', edgeCount, null)
       lineEdges.push(e)
       prevEdge.nextEdge = e
       e.prevEdge = prevEdge
@@ -48,8 +51,12 @@ export function fillQueue(polygon, line, polyEdges, lineEdges, polylineBbox) {
     let polyLenth2 = polycoords[i].length
 
     for (let ii = 0; ii < polyLenth2; ii++) {
+      numberOfRingsInPolygon = numberOfRingsInPolygon + 1
+
       let polygonSet = polycoords[i][ii]
       let polyLenth3 = polygonSet.length
+
+      contours.push(new Contour(numberOfRingsInPolygon, polygonSet))
 
       const firstPoint = new Point(polygonSet[0])
       let p1 = firstPoint
@@ -62,7 +69,7 @@ export function fillQueue(polygon, line, polyEdges, lineEdges, polylineBbox) {
         p1.nextPoint = p2
         p2.prevPoint = p1
 
-        e = new Edge(p1, p2, 'polygon', edgeCount)
+        e = new Edge(p1, p2, 'polygon', edgeCount, numberOfRingsInPolygon)
         prevEdge.nextEdge = e
         e.prevEdge = prevEdge
         if (iii === 1) firstEdge = e
@@ -82,6 +89,7 @@ export function fillQueue(polygon, line, polyEdges, lineEdges, polylineBbox) {
       firstPoint.prevPoint = p2.prevPoint
     }
   }
+  return contours
 }
 
 function edgeIntersectsBbox(edge, bbox) {

src/index.js

@@ -1,4 +1,5 @@
 import rewind from '@turf/rewind'
+import inside from 'point-in-polygon-hao'
 import {fillQueue} from './fillQueue'
 import {findIntersectionPoints} from './findIntersections.js'
 // import { _debugCandidatePoly, _debugIntersectionPoint, _debugLinePoints, _debugIntersectionPoints, _debugPolyStart } from './debug'
@@ -11,14 +12,25 @@ export default function (polygon, line) {
   const polylineEdges = []
   const polylineBbox = [Infinity, Infinity, Infinity, Infinity]
 
-  fillQueue(poly, line, polygonEdges, polylineEdges, polylineBbox)
+  const contours = fillQueue(poly, line, polygonEdges, polylineEdges, polylineBbox)
 
   findIntersectionPoints(polygonEdges, polylineEdges, intersections)
 
   if (intersections.length === 0) {
     return polygon
   }
 
+  // Track the number of intersections per contour
+  // This is useful for holes or outerrings that aren't intersected
+  // so that we can manually add them back in at the end
+  const numberIntersectionsByRing = {}
+  contours.forEach(c => numberIntersectionsByRing[c.id] = 0) //eslint-disable-line
+  intersections.forEach(i => {
+    const id = i.polygonEdge.polygonContourId
+    numberIntersectionsByRing[id] = numberIntersectionsByRing[id] + 1
+  })
+
+
   let infiniteLoopGuard = 0
   const outPolys = []
   // _debugIntersectionPoints(intersections)
@@ -119,15 +131,51 @@ export default function (polygon, line) {
     polyStart = nextPolyStart
   }
 
+  const outCoordinates = outPolys.map(poly => [poly])
+
+  const keys = Object.keys(numberIntersectionsByRing)
+  for (let index = 0; index < keys.length; index++) {
+    const key = keys[index]
+    const value = numberIntersectionsByRing[key]
+    if (value === 0) {
+      const edge = findFirstPolygonEdge(polygonEdges, parseInt(key))
+      const ring = findRingFromEdge(edge, contours)
+      createAsHoleOrAddAsNewOuterRing(ring, outCoordinates)
+    }
+  }
 
   return {
     type: 'Feature',
     properties: {},
     geometry: {
       type: 'MultiPolygon',
-      coordinates: outPolys.map(poly => [poly])
+      coordinates: outCoordinates
+    }
+  }
+}
+
+function findFirstPolygonEdge(polygonEdges, contourId) {
+  for (let index = 0; index < polygonEdges.length; index++) {
+    const edge = polygonEdges[index];
+    if (edge.polygonContourId === contourId) return edge
+  }
+}
+
+function findRingFromEdge(edge, contours) {
+  const contour = contours.find(c => c.id === edge.polygonContourId)
+  return contour.rawCoords
+}
+
+function createAsHoleOrAddAsNewOuterRing(unusedRing, outCoordinates) {
+  for (let index = 0; index < outCoordinates.length; index++) {
+    const existingRing = outCoordinates[index];
+    if (inside(unusedRing[0], [existingRing[0]])) {
+      existingRing.push(unusedRing)
+      return
     }
   }
+  // If no match is found push it as a new outer ring
+  outCoordinates.push([unusedRing])
 }
 
 // Walk around the polygon collecting vertices

test/harness/in/multi-with-hole.geojson

@@ -0,0 +1,105 @@
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "expected": 2
+        },
+        "geometry": {
+        "type": "MultiPolygon",
+        "coordinates": [
+          [
+            [
+              [
+                -125.827487,
+                44.831595
+              ],
+              [
+                -128.945652,
+                42.673378
+              ],
+              [
+                -125.459447,
+                38.967804
+              ],
+              [
+                -117.461429,
+                38.466534
+              ],
+              [
+                -121.17349,
+                44.386244
+              ],
+              [
+                -125.827487,
+                44.831595
+              ]
+            ],
+            [
+              [
+                -124.41171,
+                41.47705
+              ],
+              [
+                -126.605215,
+                42.74795
+              ],
+              [
+                -124.642412,
+                43.318244
+              ],
+              [
+                -123.576387,
+                42.246982
+              ],
+              [
+                -124.41171,
+                41.47705
+              ]
+            ],
+            [
+              [
+                -121.385261,
+                39.899593
+              ],
+              [
+                -119.430181,
+                40.946759
+              ],
+              [
+                -122.039683,
+                42.383191
+              ],
+              [
+                -121.385261,
+                39.899593
+              ]
+            ]
+          ]
+        ]
+      }
+    },
+    {
+      "type": "Feature",
+      "properties": {},
+      "geometry": {
+        "type": "LineString",
+        "coordinates": [
+          [
+            -123.478021,
+            46.254241
+          ],
+          [
+            -123.169157,
+            42.701512
+          ],
+          [
+            -123.834531,
+            37.504321
+          ]
+        ]
+      }
+    }
+  ]
+}