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 > 2
        && outerPointsString.Replace("z", string.Empty).Length == outerPointsString.Length - 2)
    {
        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 >= 2 && HintStrokePath.Data == null)
        {
            var a = Geometry.Parse(geometryList[0]); ;
            var b = Geometry.Parse(geometryList[1]); ;
        }
        if (outerPointsString.Length > 2
            && outerPointsString.Replace("z", string.Empty).Length == outerPointsString.Length - 2)
        {
            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 >= 2)
    {
        var geometry1 = Geometry.Parse(geometryList[0]); ;
        var geometry2 = Geometry.Parse(geometryList[1]); ;
    }

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：