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     }

View Code

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：