A sketch is a schematic representation of an image containing a set of objects or concepts. When people need to express and communicate a new idea, they often sketch a rough picture to represent it. Drawing a sketch helps to develop and explore new ideas and enables useful reflection on an idea, elaborating possible alternatives and promoting its evolution. The development of different interaction and communication tools has produced new attention to more natural interaction and communication modalities, including sketching. Hand-drawn sketching is easy and intuitive to use to communicate with others, and human-computer interaction is also simplified.