C#图像画矩形框

//保存127*229的图片_S
//File.Copy(imagepath, temppath, true); //拷贝文件
bmp = new Bitmap(imagepath);
bmp_S = new Bitmap(bmp, 127, 229);
//bmp_S.Save(imagepath_S, ImageFormat.Jpeg);
g = Graphics.FromImage(bmp_S);
//gp = new GraphicsPath();
//rec = new Rectangle(new Point((total - height) / 2, (total - height) / 2), new Size(width, height));
//gp.AddRectangle(rec);

        pen = new Pen(Color.Red);
        pen.Width = penWidth;
        g.DrawRectangle(pen, new Rectangle(new Point((total - height) / 2, (total - height) / 2), new Size(width, height)));
        bmp_S.SetResolution(72, 72);   //设置分辨率
        bmp_S.Save(imagepath_S, ImageFormat.Tiff);
        bmp.Dispose();
        bmp_S.Dispose();
        
        //创建229*229的图片_M
        //创建图像
        //File.Copy(imagepath, temppath, true);
        bmp = new Bitmap(imagepath);
        rec = new Rectangle(0, 0, 229, 229);  //绘制整块区域
        bmp_M = new Bitmap(rec.Width, rec.Height,PixelFormat.Format24bppRgb);           //按指定大小创建位图
        
        //重画
        g = Graphics.FromImage(bmp_M);                   //从位图创建Graphics对象
        g.Clear(Color.FromArgb(0, 0, 0, 0));                    //清空
        g.DrawImage(bmp, rec, new Rectangle(5000, 5000, 229, 229), GraphicsUnit.Pixel);   //从pic的给定区域进行绘制
        bmp_M.SetResolution(72, 72);    //设置分辨率
        
        //绘制矩形框
        //gp = new GraphicsPath();
        //rec = new Rectangle(new Point((total - width) / 2, (total - height) / 2), new Size(width, height));
        //gp.AddRectangle(rec);

        pen = new Pen(Color.Red);
        pen.Width = penWidth;
        g.DrawRectangle(pen, new Rectangle(new Point((total - width) / 2, (total - height) / 2), new Size(width, height)));
        g.DrawLine(pen, new Point((total - width) / 2 + tempdist1, total / 2), new Point((total + width) / 2 - tempdist1, total / 2));
        g.DrawLine(pen, new Point(total / 2, (total - height) / 2 + tempdist1), new Point(total / 2, (total + height) / 2 - tempdist1));

        bmp_M.Save(imagepath_M, ImageFormat.Tiff); 
        bmp.Dispose();
        bmp_M.Dispose();