在DXFReader中， 一般的多边形的面积计算绝对值
其中K表是顶点的数目，
它们的坐标，用于
在求和
和
，
所以用下面的代码就可以计算出一个封闭的多段线的区域：
| 01 | Dim Vertex As Object |
| 02 | Dim Entity As Object |
| 03 | Dim k As Long |
| 04 | Dim i As Long |
| 05 | Dim Area As Single |
| 06 |
| 07 | With DXFReader1 |
| 08 |
| 09 | For Each Entity In .Entities |
| 10 | If Entity.EntityType = "POLYLINE" Then |
| 11 |
| 12 | Area = 0 |
| 13 |
| 14 | For k = 1 To Entity.Vertexes.Count |
| 15 |
| 16 | If k = Entity.Vertexes.Count Then |
| 17 | i = 1 |
| 18 | Else |
| 19 | i = k + 1 |
| 20 | End If |
| 21 |
| 22 | Area = Area + _ |
| 23 | Entity.Vertexes(k).x0 * Entity.Vertexes(i).y0 - _ |
| 24 | Entity.Vertexes(i).x0 * Entity.Vertexes(k).y0 |
| 25 |
| 26 | Next k |
| 27 |
| 28 | Area = Abs(Area) / 2 |
| 29 |
| 30 | End If |
| 31 | Next Entity |
| 32 |
| 33 | End With |
