difference

difference是Turf中一个用于计算多边形之间异同的函数，它会将几何对象A和一个或多个几何对象B传入，返回A中不属于B的部分。即A与B的异形部分。

参数

• polygon: (Feature<Polygon>) 输入的多边形。
• subtractPolygons: (FeatureCollection<Polygon>) 需要减去的多边形集合。

返回值

• (FeatureCollection<Polygon>) 具有异形部分的多边形集合。

示例

var polygon = turf.polygon([[
  [-70.603637, -33.399918],
  [-70.614624, -33.395332],
  [-70.639343, -33.392466],
  [-70.659942, -33.394759],
  [-70.683975, -33.404504],
  [-70.697021, -33.419406],
  [-70.687408, -33.434306],
  [-70.668411, -33.444163],
  [-70.645370, -33.448467],
  [-70.622673, -33.446828],
  [-70.603637, -33.399918]
]]);
var subtractPolygons = turf.featureCollection([
    turf.polygon([[
      [-70.614624, -33.399918],
      [-70.663452, -33.395332],
      [-70.639343, -33.392466],
      [-70.614624, -33.399918]
    ]]),
    turf.polygon([[
      [-70.668411, -33.434306],
      [-70.622673, -33.446828],
      [-70.645370, -33.448467],
      [-70.668411, -33.444163],
      [-70.683975, -33.404504],
      [-70.668411, -33.434306]
    ]])
]);

var result = turf.difference(polygon, subtractPolygons);

//=result

依赖

• turf-flatten
• turf-erase

原理

该函数使用了turf-erase库和turf-flatten库的联合作用。该函数将几何A的坐标扁平化、和几何B中的每个坐标分别做比较，找出A中不属于B的部分进行生成新的多边形。

参考文献

• turf-difference - Github