Scroll an image with mouse

[JohnLM 14]

I am having trouble figuring this one out. 

 

I have a form with a tscrollbox and an timage.

 

In the image1MouseMove event of the timage I have the following code; 

procedure TForm2.im1MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  scrollbox1.vertScrollBar.Position := x;
  scrollbox1.horzScrollBar.Position := y;
end;

But it is not what I'd expect. 

 

What I am trying to do: 

 

1. Lets say I have screenshot of my desktop and inserted into the timage.

2. And I resize the app's form smaller

3. Using the mouse, I want to click on the image and drag (or pan) around inside the form's scrollbox area so that I can see other parts of the image.

 

What am I doing wrong and how can I fix this?  TIA