Author: Eber Irigoyen

Someone asked how to drag a TImage for example, and just playing with code I came 
up with this quick (and dirty?) solution.

Answer:

There's an article here on how to drag windowed controls "Dragging controls and 
forms the easy way", but that code doesn't work for TImages for example 

My solution for such thing is simply put the Image inside a TPanel and from the 
Image OnMouseDown call the code of the TPanel, thus resulting in being able to move 
the image, here's the code: 

1   procedure TForm1.Panel1MouseDown(Sender: TObject; Button: TMouseButton;
2     Shift: TShiftState; X, Y: Integer);
3   const
4     SC_DragMove = $F012; {this is magic (undocumented)}
5   begin
6     ReleaseCapture;
7     panel1.perform(WM_SysCommand, SC_DragMove, 0);
8   end;
9   
10  procedure TForm1.Image1MouseDown(Sender: TObject; Button: TMouseButton;
11    Shift: TShiftState; X, Y: Integer);
12  begin
13    panel1mousedown(Sender, Button, Shift, X, Y)
14  end;


The same would work for resizing, or all the other things that can be done changing the constant (given that the image is aligned using alClient)