Collaborative Illustrator with Android Tablets

In this paper, we consider the collaborative editing of two-dimensional (2D) data such as handwritten letters and illustrations. In contrast to 1D case, overriding of objects can have a specific meaning in editing 2D data; e.g., we can represent the relative distance of two objects and the transparency by over-riding them. This paper considers the semantics of collaborative drawing by focusing on the overriding of objects, and proposes three editing modes based on users' strokes. Proposed editing modes are realized as a part of Android application with a careful selection of the information sharing model; e.g., we can switch the shared memory model realized by Firebase Realtime Database to a distributed shared memory realized by connecting replica nodes through WebRTC, depending on the use-case.