anchor.diff:      FImageMouseDown: Boolean;
       FKeyModifierZoom: TShiftStateEnum;
       FKeyModifierHorzScroll: TShiftStateEnum;
  +    FInitScrollbarSize: integer;
   
       FOnScroll: TNotifyEvent;
       FOnScrollAlt: TATScrollAltEvent;
  
positive.code:   //Fit and recalculate ImageScale
    FImage.Left:= 0;
    FImage.Top:= 0;
  
    AWidth:= ClientWidth;
    AHeight:= ClientHeight;
  
    if FImageFit then
    begin
  
negative.code:   AScrollMaxX, AScrollMaxY: Integer;
    ARatio, AImageRatio,
    ACenterRatioX, ACenterRatioY: Double;
    NScrollbarSize: integer;
  begin
    AKeepPosition:= FImageKeepPosition and (not AResetPosition);
  
    if FImageFit then
      NScrollbarSize:= 0
    else
      NScrollbarSize:= FInitScrollbarSize;
  
    VertScrollBar.Visible:= not FImageFit;
    HorzScrollBar.Visible:= not FImageFit;
    AWidth:= Width-NScrollbarSize;
    AHeight:= Height-NScrollbarSize;
  
    //Save center position, need to restore it later
    ACenterRatioX:= 0;
  