c#在ArCEngine中怎样根据中心点和两个半径来画出一个圆环？

[renchuang]

c#在ArCEngine中怎样根据中心点和两个半径来画出一个圆环？

[renchuang]

有大神吗，指点一下吧，谢了，

[weixin_42406391]

记得是GDI+

[HerryDong]

很简单的问题啊，圆环不就是拿大的圆擦除小的圆嘛~

using System;
using System.Windows.Forms;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.Display;
using ESRI.ArcGIS.Geometry;

namespace WinApp
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        // 绘制按钮
        private void btnDraw_Click(object sender, EventArgs e)
        {
            // 圆心
            IPoint pPoint = new ESRI.ArcGIS.Geometry.Point();
            pPoint.X = 400;
            pPoint.Y = 400;

            // 内部、外部半径
            double innerRadius = 200;
            double outerRadius = 300;

            // 内部、外部圆
            IGeometry pInnerCircleGeometry = CreateCircle(pPoint, innerRadius);
            IGeometry pOuterCircleGeometry = CreateCircle(pPoint, outerRadius);

            // 绘制圆环
            IGeometry pRingGeometry = Erase(pOuterCircleGeometry, pInnerCircleGeometry);
            CreateElement(axMapControl1.Object as IMapControlDefault, pRingGeometry);
        }

        // 根据圆心和半径创建一个圆
        private IGeometry CreateCircle(IPoint pPoint, double radius)
        {
            // 创建圆的边界线
            IConstructCircularArc pConstructCircularArc = new CircularArc() as IConstructCircularArc;
            pConstructCircularArc.ConstructCircle(pPoint, radius, false);
            ICircularArc pCircularArc = pConstructCircularArc as ICircularArc;

            // 转换为片段集合
            object missing = Type.Missing;
            ISegment pSegment = pCircularArc as ISegment;
            ISegmentCollection pSegmentCollection = new Ring() as ISegmentCollection;
            pSegmentCollection.AddSegment(pSegment, ref missing, ref missing);

            // 转换为环，闭合之
            IRing pRing = pSegmentCollection as IRing;
            pRing.Close();

            // 返回地理实体
            IGeometryCollection pGeometryCollection = new Polygon() as IGeometryCollection;
            pGeometryCollection.AddGeometry(pRing, ref missing, ref missing);
            IGeometry pGeometry = pGeometryCollection as IGeometry;
            return pGeometry;
        }

        // 利用小圆对大圆进行擦除操作
        private IGeometry Erase(IGeometry pSourceGeometry, IGeometry pEraseGeometry)
        {
            ITopologicalOperator pTopologicalOperator = pSourceGeometry as ITopologicalOperator;
            IGeometry pGeometry = pTopologicalOperator.Difference(pEraseGeometry);
            return pGeometry;
        }

        // 创建Element元素，添加到地图
        private void CreateElement(IMapControlDefault mapControl, IGeometry pGeometry)
        {
            // 创建颜色
            IRgbColor pRgbColor = new RgbColor();
            pRgbColor.Red = 255;
            pRgbColor.Green = 0;
            pRgbColor.Blue = 0;

            // 创建面符号
            ISimpleFillSymbol pSimpleFillSymbol = new SimpleFillSymbol();
            pSimpleFillSymbol.Color = pRgbColor;
            pSimpleFillSymbol.Style = esriSimpleFillStyle.esriSFSDiagonalCross;

            // 创建面要素
            IFillShapeElement pFillShapeElement = new PolygonElement() as IFillShapeElement;
            pFillShapeElement.Symbol = pSimpleFillSymbol;
            IElement pElement = pFillShapeElement as IElement;
            pElement.Geometry = pGeometry;

            // 添加至地图
            IActiveView pActiveView = mapControl.ActiveView;
            IGraphicsContainer pGraphicsContainer = pActiveView.GraphicsContainer;
            pGraphicsContainer.DeleteAllElements();
            pGraphicsContainer.AddElement(pElement, 0);
            pActiveView.PartialRefresh(esriViewDrawPhase.esriViewGraphics, null, null);
        }
    }
}

[ziqi0716]

这个使用要付费吧?所以大家用的少