'Declaration

Public Overrides ReadOnly Property IsVisibleWithoutImage As Boolean

public override bool IsVisibleWithoutImage { get; }

public: __property bool get_IsVisibleWithoutImage(); override;

public:
property bool IsVisibleWithoutImage {
   bool get() override;;
}

true - this visual tool will be always visible in image viewer;
false - this visual tool will be visible in image viewer only if image is painted in image viewer.