A method is provided for generating ink data including stroke objects. The method includes generally four steps. The first step receives device-dependent user-input data including either one of pen event data of Type 1, which includes indicator position data and indicator pressure data, or pen event data of Type 2, which includes indicator position data but does not include indicator pressure data. The second step determines whether the pen event data is Type 1 or Type 2. The third step derives one or both of radius data for defining a width of the stroke object and transparency data for defining a transparency of the stroke object, based on the pen event data of Type 1 or Type 2. The fourth step outputs the stroke object including said one or both of radius data and transparency data as device-independent common attribute value(s) of each of multiple points of the stroke object.