如何在DRAWING后的图片上加提示

if (PrevBitmap != null)
            {
                Rectangle rectDest = new Rectangle(PrevBitmapLocation, PrevBitmapSize);
                Rectangle rectSrc;                if (bIsMouseOverPrev)
                {
                    if (bIsMouseDown)
                        rectSrc = new Rectangle(new Point(PrevBitmapSize.Width * 2, 0), PrevBitmapSize);
                    else
                        rectSrc = new Rectangle(new Point(PrevBitmapSize.Width, 0), PrevBitmapSize);
                }
                else
                    rectSrc = new Rectangle(new Point(0, 0), PrevBitmapSize);                //MessageBox.Show(bIsMouseOverClose.ToString()+bIsMouseDown.ToString());
                grfx.DrawImage(PrevBitmap, rectDest, rectSrc, GraphicsUnit.Pixel);
            }我用这段代码在窗体上绘制了图片
如何在鼠标移动到那个图片区域的显示显示提示
      this.toolTip1.AutoPopDelay = 5000;
                toolTip1.InitialDelay = 1000;
                toolTip1.ReshowDelay = 1000;
                // Force the ToolTip text to be displayed whether or not the form is active.
                toolTip1.ShowAlways = true;
                this.toolTip1.IsBalloon = true;
                //this.toolTip1.
                toolTip1.SetToolTip(PrevBitmap, "是");因为PrevBitmap是图片不是控件所以执行不了