alpha_pen(const alpha_type &a = 1, const affine_func_type &func = affine_func_type()):alpha_(a),affine_func_(func) { }
alpha_pen(const PEN_ &x, const alpha_type &a=1, const affine_func_type &func=affine_func_type())
:PEN_(x),alpha_(a),affine_func_(func) { }
alpha_pen(const alpha_type &a = 1, const affine_func_type &func = affine_func_type()):alpha_(a),affine_func_(func) { }
alpha_pen(const PEN_ &x, const alpha_type &a=1, const affine_func_type &func=affine_func_type())
:PEN_(x),alpha_(a),affine_func_(func) { }