procedure TForm1.ImageEnView1MouseWheel(Sender: TObject; Shift: TShiftState;
  WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
{ This procedure handles all the zooming. }
begin
  if ImageEnView1.Focused then
  begin
    if (WheelDelta > 0) and (ZoomLevel < 9) then
    begin
      ZoomLevel := ZoomLevel + 1;
      ImageEnView1.ZoomAt(MousePos.X, MousePos.Y,
        ImageEnView1.Zoom * 1.333333333);
    end;
    if (WheelDelta < 0) and (ZoomLevel > 1) then
    begin
      ZoomLevel := ZoomLevel - 1;
      ImageEnView1.ZoomAt(MousePos.X, MousePos.Y, ImageEnView1.Zoom * 0.75);
    end;
    Handled := True;
  end
  else
    Handled := False;
end;

procedure TForm1.ImageEnView1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  iPoint: TPoint;
begin
  { Handle mouse button zooming with 8 levels of zoom with zooming at the mouse
    cursor position }
  iPoint := Mouse.CursorPos;
  if (Button = mbLeft) and (ZoomLevel < 9) and
    (ImageEnView1.MouseInteract = []) then
  begin
    { Change the mouse cursor to zoom in }
    ImageEnView1.Cursor := 1779;
    { Set the zoom level }
    ZoomLevel := ZoomLevel + 1;
    ImageEnView1.ZoomAt(iPoint.X, iPoint.Y, ImageEnView1.Zoom * 1.333333333);
  end;
  if (Button = mbRight) and (ZoomLevel > 1) and
    (ImageEnView1.MouseInteract = []) then
  begin
    { Change the mouse cursor to zoom out }
    ImageEnView1.Cursor := 1778;
    { Set the zoom level }
    ZoomLevel := ZoomLevel - 1;
    ImageEnView1.ZoomAt(iPoint.X, iPoint.Y, ImageEnView1.Zoom * 0.75);
  end;
  { If the left button is held down and ZoomLevel > 1 then scroll the image and
    change the mousecursor to scroll }
  if (Button = mbLeft) and (ImageEnView1.MouseCapture) and (ZoomLevel > 1) and
    (ImageEnView1.MouseInteract = [miScroll]) then
    { Change the mouse cursor to scroll }
    ImageEnView1.Cursor := 1782;
end;

procedure TForm1.ImageEnView1MouseMove(Sender: TObject; Shift: TShiftState;
  X, Y: Integer);
begin
  { Toggle mouseinteract between scrolling and zooming }
  if (ssLeft in Shift) and (ImageEnView1.MouseCapture) and (ZoomLevel > 1) then
  begin
    ImageEnView1.MouseInteract := [miScroll];
  end
  else
  begin
    ImageEnView1.MouseInteract := [];
  end;
end;