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- import { point } from "@turf/helpers";
- /**
- * Takes a {@link LineString|linestring}, {@link MultiLineString|multi-linestring},
- * {@link MultiPolygon|multi-polygon} or {@link Polygon|polygon} and
- * returns {@link Point|points} at all self-intersections.
- *
- * @name kinks
- * @param {Feature<LineString|MultiLineString|MultiPolygon|Polygon>} featureIn input feature
- * @returns {FeatureCollection<Point>} self-intersections
- * @example
- * var poly = turf.polygon([[
- * [-12.034835, 8.901183],
- * [-12.060413, 8.899826],
- * [-12.03638, 8.873199],
- * [-12.059383, 8.871418],
- * [-12.034835, 8.901183]
- * ]]);
- *
- * var kinks = turf.kinks(poly);
- *
- * //addToMap
- * var addToMap = [poly, kinks]
- */
- export default function kinks(featureIn) {
- var coordinates;
- var feature;
- var results = {
- type: "FeatureCollection",
- features: [],
- };
- if (featureIn.type === "Feature") {
- feature = featureIn.geometry;
- }
- else {
- feature = featureIn;
- }
- if (feature.type === "LineString") {
- coordinates = [feature.coordinates];
- }
- else if (feature.type === "MultiLineString") {
- coordinates = feature.coordinates;
- }
- else if (feature.type === "MultiPolygon") {
- coordinates = [].concat.apply([], feature.coordinates);
- }
- else if (feature.type === "Polygon") {
- coordinates = feature.coordinates;
- }
- else {
- throw new Error("Input must be a LineString, MultiLineString, " +
- "Polygon, or MultiPolygon Feature or Geometry");
- }
- coordinates.forEach(function (line1) {
- coordinates.forEach(function (line2) {
- for (var i = 0; i < line1.length - 1; i++) {
- // start iteration at i, intersections for k < i have already
- // been checked in previous outer loop iterations
- for (var k = i; k < line2.length - 1; k++) {
- if (line1 === line2) {
- // segments are adjacent and always share a vertex, not a kink
- if (Math.abs(i - k) === 1) {
- continue;
- }
- // first and last segment in a closed lineString or ring always share a vertex, not a kink
- if (
- // segments are first and last segment of lineString
- i === 0 &&
- k === line1.length - 2 &&
- // lineString is closed
- line1[i][0] === line1[line1.length - 1][0] &&
- line1[i][1] === line1[line1.length - 1][1]) {
- continue;
- }
- }
- var intersection = lineIntersects(line1[i][0], line1[i][1], line1[i + 1][0], line1[i + 1][1], line2[k][0], line2[k][1], line2[k + 1][0], line2[k + 1][1]);
- if (intersection) {
- results.features.push(point([intersection[0], intersection[1]]));
- }
- }
- }
- });
- });
- return results;
- }
- // modified from http://jsfiddle.net/justin_c_rounds/Gd2S2/light/
- function lineIntersects(line1StartX, line1StartY, line1EndX, line1EndY, line2StartX, line2StartY, line2EndX, line2EndY) {
- // if the lines intersect, the result contains the x and y of the
- // intersection (treating the lines as infinite) and booleans for whether
- // line segment 1 or line segment 2 contain the point
- var denominator;
- var a;
- var b;
- var numerator1;
- var numerator2;
- var result = {
- x: null,
- y: null,
- onLine1: false,
- onLine2: false,
- };
- denominator =
- (line2EndY - line2StartY) * (line1EndX - line1StartX) -
- (line2EndX - line2StartX) * (line1EndY - line1StartY);
- if (denominator === 0) {
- if (result.x !== null && result.y !== null) {
- return result;
- }
- else {
- return false;
- }
- }
- a = line1StartY - line2StartY;
- b = line1StartX - line2StartX;
- numerator1 = (line2EndX - line2StartX) * a - (line2EndY - line2StartY) * b;
- numerator2 = (line1EndX - line1StartX) * a - (line1EndY - line1StartY) * b;
- a = numerator1 / denominator;
- b = numerator2 / denominator;
- // if we cast these lines infinitely in both directions, they intersect here:
- result.x = line1StartX + a * (line1EndX - line1StartX);
- result.y = line1StartY + a * (line1EndY - line1StartY);
- // if line1 is a segment and line2 is infinite, they intersect if:
- if (a >= 0 && a <= 1) {
- result.onLine1 = true;
- }
- // if line2 is a segment and line1 is infinite, they intersect if:
- if (b >= 0 && b <= 1) {
- result.onLine2 = true;
- }
- // if line1 and line2 are segments, they intersect if both of the above are true
- if (result.onLine1 && result.onLine2) {
- return [result.x, result.y];
- }
- else {
- return false;
- }
- }
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