How to solve performance problem in rendering/Drawing of image (rectangle movement is very slow on image)

//OnPaint event to draw the image
protected override void OnPaint(PaintEventArgs e)
{
    base.OnPaint(e);
    Graphics g = e.Graphics;
    g.InterpolationMode = interMode;

    //draw image
    if (image != null)
    {
        Rectangle srcRect;
        Point pt = new Point((int)(hScrollBar1.Value / zoom),
            (int)(vScrollBar1.Value / zoom));
        if (canvasSize.Width * zoom < viewRectWidth &&
            canvasSize.Height * zoom < viewRectHeight)
        {
            // view all image
            srcRect = new Rectangle(0, 0, canvasSize.Width, canvasSize.Height);
        }
        else
        {
            // view a portion of image
            srcRect = new Rectangle(pt, new Size((int)(viewRectWidth / zoom),
                (int)(viewRectHeight / zoom)));
        }
        g.DrawImage(image, srcRect, srcRect, GraphicsUnit.Pixel);
    }
}

//Code to draw rectangle (class: Selection)
public Selection Selection
{
    get { return selection; }
    set { selection = value; Invalidate(); }
}
protected override void OnPaint(PaintEventArgs e)
{
    base.OnPaint(e);
    if (selection != null)
        selection.Draw(e.Graphics);
}

public void Draw(Graphics g)
{
    Pen p = new Pen(lineColor, lineWidth);
    g.DrawRectangle(p, new Rectangle(location, size));
    p.Dispose();
}
//Events of Mouse
private void YLScsPanel1_MouseDown(object sender, MouseEventArgs e)
{
    Point pt = new Point(e.X, e.Y);
    pt = YLScsPanel1.ConvertControlPointToCanvas(pt);
    if (selection.isHitting(pt) && e.Button == MouseButtons.Left && srcBmp != null)
    {
        isHit = true;
        YLScsPanel1.Cursor = Cursors.Hand;
    }
}
private void YLScsPanel1_MouseMove(object sender, MouseEventArgs e)
{
    if (isHit)
    {
        YLScsPanel1.Cursor = Cursors.Hand;
        Point pt = new Point(e.X, e.Y);
        pt = YLScsPanel1.ConvertControlPointToCanvas(pt);
        newLocation.X = Math.Max(0, Math.Min(pt.X, srcBmp.Width - newSize.Width));
        newLocation.Y = Math.Max(0, Math.Min(pt.Y, srcBmp.Height - newSize.Height));
        selection.Location = newLocation;
        YLScsPanel1.Selection = selection;
    }
}
private void YLScsPanel1_MouseUp(object sender, MouseEventArgs e)
{
    if (isHit)
    {
        isHit = false;
        YLScsPanel1.Cursor = Cursors.Default;
        showPanel2();
    }
}