我正在尝试从Google Maps API V3多边形中实现多边形自相交算法。
目标只是检测是或否,用户绘制的简单多边形是自交叉。
我找到了this very interesting link,但它假定多边形顶点的坐标是以geoJSON格式给出的。但是,这不是我的情况;我只能使用polygon.getPath()
将多边形坐标检索到polygoncomplete
事件中。
这就是我检索坐标的方法:
google.maps.event.addDomListener(drawingManager, 'polygoncomplete', function(polygon)
{
var polygonBounds = polygon.getPath();
var coordinates = [];
for(var i = 0 ; i < polygonBounds.length ; i++)
{
vertice = {
"Latitude" : polygonBounds.getAt(i).lat(),
"Longitude" : polygonBounds.getAt(i).lng()
}
coordinates.push(vertice );
}
}
如何将polygon.getpath()
给出的坐标转换为 geoJSON 格式?
有没有更好的方法来检测Google地图多边形是否自相交?如果是这样,请你分享一些代码样本,而不仅仅是数学解释?
PS:我看过this链接,但没有任何代码示例,我有点迷失。
答案 0 :(得分:5)
您不需要将它们转换为GeoJSON以使用jsts library,您需要将它们从google.maps.LatLng对象转换为jsts.geom.Coordinates。而不是使用它:
var geoJSON2JTS = function(boundaries) {
var coordinates = [];
for (var i = 0; i < boundaries.length; i++) {
coordinates.push(new jsts.geom.Coordinate(
boundaries[i][1], boundaries[i][0]));
}
return coordinates;
};
使用此选项可将google.maps.Polygon路径中的坐标转换为JTS格式:
var googleMaps2JTS = function(boundaries) {
var coordinates = [];
for (var i = 0; i < boundaries.getLength(); i++) {
coordinates.push(new jsts.geom.Coordinate(
boundaries.getAt(i).lat(), boundaries.getAt(i).lng()));
}
return coordinates;
};
然后改变&#34; findSelfIntersects&#34;像这样:
/**
* findSelfIntersects
*
* Detect self-intersections in a polygon.
*
* @param {object} google.maps.Polygon path co-ordinates.
* @return {array} array of points of intersections.
*/
var findSelfIntersects = function(googlePolygonPath) {
var coordinates = googleMaps2JTS(googlePolygonPath);
var geometryFactory = new jsts.geom.GeometryFactory();
var shell = geometryFactory.createLinearRing(coordinates);
var jstsPolygon = geometryFactory.createPolygon(shell);
// if the geometry is aleady a simple linear ring, do not
// try to find self intersection points.
var validator = new jsts.operation.IsSimpleOp(jstsPolygon);
if (validator.isSimpleLinearGeometry(jstsPolygon)) {
return;
}
var res = [];
var graph = new jsts.geomgraph.GeometryGraph(0, jstsPolygon);
var cat = new jsts.operation.valid.ConsistentAreaTester(graph);
var r = cat.isNodeConsistentArea();
if (!r) {
var pt = cat.getInvalidPoint();
res.push([pt.x, pt.y]);
}
return res;
};
proof of concept fiddle (credit to HoffZ)
代码段
var mapOptions = {
zoom: 16,
center: new google.maps.LatLng(62.1482, 6.0696)
};
var drawingManager = new google.maps.drawing.DrawingManager({
drawingControl: false,
polygonOptions: {
editable: true
}
});
var googleMaps2JTS = function(boundaries) {
var coordinates = [];
for (var i = 0; i < boundaries.getLength(); i++) {
coordinates.push(new jsts.geom.Coordinate(
boundaries.getAt(i).lat(), boundaries.getAt(i).lng()));
}
coordinates.push(coordinates[0]);
console.log(coordinates);
return coordinates;
};
/**
* findSelfIntersects
*
* Detect self-intersections in a polygon.
*
* @param {object} google.maps.Polygon path co-ordinates.
* @return {array} array of points of intersections.
*/
var findSelfIntersects = function(googlePolygonPath) {
var coordinates = googleMaps2JTS(googlePolygonPath);
var geometryFactory = new jsts.geom.GeometryFactory();
var shell = geometryFactory.createLinearRing(coordinates);
var jstsPolygon = geometryFactory.createPolygon(shell);
// if the geometry is aleady a simple linear ring, do not
// try to find self intersection points.
var validator = new jsts.operation.IsSimpleOp(jstsPolygon);
if (validator.isSimpleLinearGeometry(jstsPolygon)) {
return;
}
var res = [];
var graph = new jsts.geomgraph.GeometryGraph(0, jstsPolygon);
var cat = new jsts.operation.valid.ConsistentAreaTester(graph);
var r = cat.isNodeConsistentArea();
if (!r) {
var pt = cat.getInvalidPoint();
res.push([pt.x, pt.y]);
}
return res;
};
var map = new google.maps.Map(document.getElementById("map"), mapOptions);
drawingManager.setDrawingMode(google.maps.drawing.OverlayType.POLYGON);
drawingManager.setMap(map);
google.maps.event.addListener(drawingManager, 'polygoncomplete', function(polygon) {
//var polyPath = event.overlay.getPath();
var intersects = findSelfIntersects(polygon.getPath());
console.log(intersects);
if (intersects && intersects.length) {
alert('Polygon intersects itself');
} else {
alert('Polygon does not intersect itself');
}
});
&#13;
#map {
width: 500px;
height: 400px;
}
&#13;
<script src="https://maps.google.com/maps/api/js?libraries=drawing"></script>
<script src="https://cdn.rawgit.com/bjornharrtell/jsts/gh-pages/1.4.0/jsts.min.js"></script>
<p>
Draw a polygon on the map
</p>
<div id="map">
</div>
&#13;