procedure TForm1.Zoom(I: Single);
var
  NewW, NewH: Integer;
  NewX, NewY, SX, SY: Integer;
  A, B: Double;
begin
  FScale := FScale + Round(FScale * I);
  NewW := Trunc(ImgW * (FScale / 1000));
  NewH := Trunc(ImgH * (FScale / 1000));

  SX := Image1.Left;
  SY := Image1.Top;

  if (NewW < ClientWidth) and (NewH < ClientHeight) then begin
    // 图像小于窗口时，居中显示
    NewX := (ClientWidth - NewW) shr 1;
    NewY := (ClientHeight - NewH) shr 1;
  end else begin

    // 窗口显示不下时
    //NewX := SX;
    //NewY := SY;
    GetCursorPos(Mouse);
    Mouse := ScreenToClient(Mouse);
    //Mouse := Image1.ClientToParent(Mouse);
    A := (Mouse.X - SX) / Image1.Width;
    B := (Mouse.Y - SY) / Image1.Height;

    NewX := SX - Round((NewW - Image1.Width) * A);
    NewY := SY - Round((NewH - Image1.Height) * B);



  end;
  Image1.SetBounds(NewX, NewY, NewW, NewH);
end;