Class field lost value!

[alzaimar]

So why do you create another TBrighnessAdjustmentLayer then?
This should work (I removed the 'create' and got rid of some begin/end and other unimportant stuff):

Delphi-Quellcode:

var
  Index: Integer;
  Layer: TCustomFilterLayer;
begin
  Index := lbLayers.ItemIndex;

  if Index <> - 1 then
    if lbLayers.Items.Objects[Index] is TCustomFilterLayer then begin
      Layer := lbLayers.Items.Objects[Index] as TCustomFilterLayer;
      if Layer is TBrightnessAdjustmentLayer then
          SetAmount(vtInteger, -100, 100, TBrightnessAdjustmentLayer(Layer).Amount);
    end;
end;