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"

     var flattenedPathGeometry = combinedGeometry.GetFlattenedPathGeometry();
     var outerPointsString = flattenedPathGeometry.Figures.ToString();
     if (outerPointsString.Length >
         && outerPointsString.Replace("z", string.Empty).Length == outerPointsString.Length - )
     {
         return true;
     }

完整函数见下方代码

     /// <summary>
     /// 检查几何是否被另一个几何分割成多段
     /// </summary>
     /// <param name="geometry1"></param>
     /// <param name="geometry2"></param>
     /// <returns></returns>
     private bool CheckGeometryIsDividedByAnotherGeometry(PathGeometry geometry1, Geometry geometry2)
     {
         var intersectGeometry = new CombinedGeometry(GeometryCombineMode.Intersect, geometry1, geometry2);
         var combinedGeometry = new CombinedGeometry(GeometryCombineMode.Exclude, geometry1, intersectGeometry);
         var flattenedPathGeometry = combinedGeometry.GetFlattenedPathGeometry();
         var outerPointsString = flattenedPathGeometry.Figures.ToString();
         var geometryList = outerPointsString.Split(new[] { 'M' }, StringSplitOptions.RemoveEmptyEntries).Where(i => i.Contains("z")).Select(i => $"M{i}").ToList();
         if (geometryList.Count >=  && HintStrokePath.Data == null)
         {
             var a = Geometry.Parse(geometryList[]); ;
             var b = Geometry.Parse(geometryList[]); ;
         }
         if (outerPointsString.Length >
             && outerPointsString.Replace("z", string.Empty).Length == outerPointsString.Length - )
         {
             return true;
         }
         return false;
     }

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

     var geometryList = outerPointsString.Split(new[] { 'M' }, StringSplitOptions.RemoveEmptyEntries).Where(i => i.Contains("z")).Select(i => $"M{i}").ToList();
     if (geometryList.Count >= )
     {
         var geometry1 = Geometry.Parse(geometryList[]); ;
         var geometry2 = Geometry.Parse(geometryList[]); ;
     }

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, ));

结果如下图：