ITransform2D.Scale 详解

在ArcGIS Engine下如何实现矩形外扩指定距离？其实已经提供了相关的接口 ITransform2D，里面有个scale方法可以进行多边形缩放 ，参数如下

ITransform2D.Scale(IPointOrigin，doublesx，doublesy);

其中 Origin为缩放基点、sx与sy分别是X、Y方向的缩放因子。在开发帮助中我们可以下面的描述：

where sX is the ratio of Old Width to New Width, and sY is the ratio of Old Height to New Height（sX是原始宽度与新宽度的比例，sY是原始高度与新高度的比例)

 

如果原始宽度和高度分别为dWidth、dHeight，将矩形外扩50米，新的宽度和高度分别为dWidth+100、dHeight+100,缩放传值为如下

ITransform2D.Scale(IPoint Origin，dWidth/(dWidth+100)，dHeight/(dHeight+100) );

但实际得出的结果与我们所期望的恰好相反，经反复实验正确的传值如下所示

ITransform2D.Scale(IPoint Origin，(dWidth+100)/dWidth，(dHeight+100)/dHeight );

                        IPolygon pPolygon = pFeature.ShapeCopy as IPolygon;
                        IPoint pCenter = new PointClass();
                        pCenter.PutCoords((pPolygon.Envelope.XMin+pPolygon.Envelope.XMax)/2,
                            (pPolygon.Envelope.YMin+pPolygon.Envelope.YMax)/2);
                        pCenter.SpatialReference = pPolygon.SpatialReference;
                        ITransform2D pTran = pPolygon as ITransform2D;
                        pTran.Scale(pCenter, (pPolygon.Envelope.Width + dis * 2) / pPolygon.Envelope.Width,
    (pPolygon.Envelope.Height + dis * 2) / pPolygon.Envelope.Height);
                        pPolygon = pTran as IPolygon;
                        pFeature.Shape = pPolygon;
                        pFeature.Store();
                        pFeature = pFeatureCursor.NextFeature();

转载：http://blog.csdn.net/me_dispose/article/details/36185401#