局部选择打印

实现在pictureBox控件中绘制了一系列的矢量图，然后实现部分的选择打印。
   1. 记录下选择区域的开始点和结束点的坐标；
   Point startPoint = Point.empty;
  Point EndPoint = Point.empyt;
  int zoom = 2;//图片的放大系数
  int xtrans = 0;//图片的x轴偏移
  int ytrans = 0;//图片的y轴偏移
  2.在Printdocument _PrintPages()中绘制选择区域的图
       private PrintDocument_PrintPages( object sender, PrintPageEventArgs e )
{
        PrintF p = new PointF( startPoint.x , startPoint.Y );
         p.x = ( startPoint.x / zoom ) - xtrans;
         p.y = ( startPoint.y / zoom ) - ytrans;
         Draw( p , e.Graphics );
}

  private void Draw( PointF org , Graphics g )
 {
          Matrix orgM = g.Transform.Clone();
          Matrix c = orgM.Clone();
          Matrix X = new Matrix();
          X.Scale( e.VisibleClipBounds.Width / Math.abs(endPoint.x - startPoint.x  ) * zoom , e.VisibleClipBounds.Height / Math.abs( endPoint.y - startPoint.y ) * zoom );
           Matrix y = new Matrix();
           y.Translate( -org.x , -org.y , MatrixOrder.Append);
          c.Multiply( x );
          c.Multiply( y );
          g.Transform = c;
      //
   绘制代理......
    //
  

}