Geometry 判断几何是否被另一个几何/线段分割成多段

如下图，如何判断几何多边形a被多边形b，切割为多段几何？

 几何a被几何b切割

1. 获取几何a与几何b的交集c

 var intersectgeometry = new combinedgeometry(geometrycombinemode.intersect, geometry1, geometry2); 

 

 

2.几何a排除交集c，得到余下空白区域d

 var combinedgeometry = new combinedgeometry(geometrycombinemode.exclude, geometry1, intersectgeometry); 

 

 3.判断几何d区域是否包含多段几何

几何d区分为俩段，获取域的边框近似点集，发现含有俩段线条的描述（俩段m->z的文本），与真实几何分段对应。

所以，可以通过线条终止字符"z"个数，来判断几何的分段数量。

• 获取几何的近似多边形值
• 获取其路径内的点集
• 判断点集中是否含有2个及以上的线条绘制结束字符"z"

1     var flattenedpathgeometry = combinedgeometry.getflattenedpathgeometry();
2     var outerpointsstring = flattenedpathgeometry.figures.tostring();
3     if (outerpointsstring.length > 2
4         && outerpointsstring.replace("z", string.empty).length == outerpointsstring.length - 2)
5     {
6         return true;
7     }

 完整函数见下方代码

 1     /// <summary>
 2     /// 检查几何是否被另一个几何分割成多段
 3     /// </summary>
 4     /// <param name="geometry1"></param>
 5     /// <param name="geometry2"></param>
 6     /// <returns></returns>
 7     private bool checkgeometryisdividedbyanothergeometry(pathgeometry geometry1, geometry geometry2)
 8     {
 9         var intersectgeometry = new combinedgeometry(geometrycombinemode.intersect, geometry1, geometry2);
10         var combinedgeometry = new combinedgeometry(geometrycombinemode.exclude, geometry1, intersectgeometry);
11         var flattenedpathgeometry = combinedgeometry.getflattenedpathgeometry();
12         var outerpointsstring = flattenedpathgeometry.figures.tostring();
13         var geometrylist = outerpointsstring.split(new[] { 'm' }, stringsplitoptions.removeemptyentries).where(i => i.contains("z")).select(i => $"m{i}").tolist();
14         if (geometrylist.count >= 2 && hintstrokepath.data == null)
15         {
16             var a = geometry.parse(geometrylist[0]); ;
17             var b = geometry.parse(geometrylist[1]); ;
18         }
19         if (outerpointsstring.length > 2
20             && outerpointsstring.replace("z", string.empty).length == outerpointsstring.length - 2)
21         {
22             return true;
23         }
24         return false;
25     }

4. 获取几何被分割后的多段几何内容

解析"m"、"z",分别获取俩段几何数据

1     var geometrylist = outerpointsstring.split(new[] { 'm' }, stringsplitoptions.removeemptyentries).where(i => i.contains("z")).select(i => $"m{i}").tolist();
2     if (geometrylist.count >= 2)
3     {
4         var geometry1 = geometry.parse(geometrylist[0]); ;
5         var geometry2 = geometry.parse(geometrylist[1]); ;
6     }

几何被直线分割

几何被线段分割，如何判断或者获取分割后的多段几何？

直接用线段与几何重复上面的步骤，是有问题的。

线段类似“m150,130l150,1300 150,170z”去与几何去交集，combinedgeometry中的数据是空的

需要给线条添加1的粗细：

  var geometry2 = linegeometry.getwidenedpathgeometry(new system.windows.media.pen(system.windows.media.brushes.black, 1)); 

结果如下图：