Point2f[] points=rotatedRect.Points();

///<Summary>
///利用向量運(yùn)算截取一個(gè)RotatedRect區(qū)域
///</Summary>
///<param name="img">類型為CV_U8C3的Mat</param>
///<param name="rotatedRect">RotatedRect</param>
public static Mat sliceRotetedImg8UC3(Mat img,RotatedRect rotatedRect){
 // Rect bounding=rotatedRect.BoundingRect();
 Point2f[] points=rotatedRect.Points();
 int topLeftIndex=0;
 double topLeftR=points[0].X*points[0].X+points[0].Y*points[0].Y;
 for(int i=1;i<4;i++){
  double r=points[i].X*points[i].X+points[i].Y*points[i].Y;
  if(r<topLeftR){
   topLeftIndex=i;
   topLeftR=r;
  }
 }
 double x1=points[(topLeftIndex+1)%4].X-points[topLeftIndex].X,y1=points[(topLeftIndex+1)%4].Y-points[topLeftIndex].Y;
 double x2=points[(topLeftIndex+3)%4].X-points[topLeftIndex].X,y2=points[(topLeftIndex+3)%4].Y-points[topLeftIndex].Y;
 double vX1=x1,vY1=y1,vX2=x2,vY2=y2;
 int width=(int)Math.Sqrt(vX1*vX1+vY1*vY1),height=(int)Math.Sqrt(vX2*vX2+vY2*vY2);
 Mat ret=new Mat(new Size(width,height),MatType.CV_8UC3);
 // Console.WriteLine($"width={width},height={height}");
 var indexer1=img.GetGenericIndexer<Vec3b>();
 var indexer2=ret.GetGenericIndexer<Vec3b>();
 for(int j=0;j<ret.Height;j++){
  for(int i=0;i<ret.Width;i++){
   double kx=(double)i/width,ky=(double)j/height;
   int x=(int)(points[topLeftIndex].X+kx*vX1+ky*vX2),y=(int)(points[topLeftIndex].Y+kx*vY1+ky*vY2);
   indexer2[j,i]=indexer1[y,x];
  }
 }
 return ret;
}