How to draw rectangle when form is resized - opencv

Question

enter code hereI'm using OpenCv and displaying frames which i get from video file on the imagebox. Now I'm drawing multiple rectangles on the frame and trying to move and delete them. This is working fine. But, when i'm resizing the form...i can't draw,move or delete the rectangles at the correct position as the frame coordinates are not getting changed but only imagebox coordinates are being changed and the frame is fitted into it.Please help me out.
black rectangle is where i have drawn the rectangle after form is resized...red rectangle is where the rectangle is being drawn
private void imageBox1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
drawRect = true;
RectStartpt = e.Location;
if (count > 0)
{
foreach (Rectangle allRect in Rect_List)
{
rect_count++;
if (allRect.Contains(e.Location))
{
Cursor cursor = Cursors.Cross;
drawRect = false;
RectStartpt = new Point(e.X, e.Y);
rect = allRect;
break;
}
}
}
}this.Invalidate();}
private void imageBox1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left && e.Button != MouseButtons.Right)
{
return;
}
else if (e.Button == MouseButtons.Left)
{
Point EndPt = new Point(e.X, e.Y);
Size shift = new Size(Math.Abs(RectStartpt.X - EndPt.X), Math.Abs(RectStartpt.Y - EndPt.Y));
if (drawRect == true)
{
rect.Location = new Point(Math.Min(RectStartpt.X, EndPt.X), Math.Min(RectStartpt.Y, EndPt.Y));
rect.Size = shift;
count = 1;
}
else if (drawRect == false)
{
rect.X += e.X - RectStartpt.X;
rect.Y += e.Y - RectStartpt.Y;
RectStartpt = new Point(e.X, e.Y);
}
}
}
private void imageBox1_MouseUp(object sender, MouseEventArgs e)
{
if (frame != null)
{
if (drawRect == true)
{
frame.Draw(rect, new Bgr(Color.Red), 2);
Rect_List.Add(rect);
}
else if (drawRect == false)
{
frame.Draw(rect, new Bgr(Color.Red), 2);
Rect_List.RemoveAt(rect_count - 1);
Rect_List.Add(rect);
if (Timer_enabled == false)
{
frame = captureFrame.QueryFrame().ToImage<Bgr, Byte>();
foreach (Rectangle allRect in Rect_List)
{
frame.Draw(allRect, new Bgr(Color.Red), 2);
}
imageBox1.Image = frame;
imageBox1.Refresh();
rect = new Rectangle();
frame_no++;
}
}
imageBox1.Image = frame;
imageBox1.Refresh();
//rect = new Rectangle();
rect_count = 0;
}
}
private void Form1_Resize(object sender, EventArgs e)
{
formGraphics = null;
formGraphics = imageBox1.CreateGraphics();
frame = frame.Resize(imageBox1.Width, imageBox1.Height, Inter.Linear);
imageBox1.Image = frame;
}