Reading 7#: Sketch Based Interfaces: Early Processing for Sketch Understanding

Comments:
Jonathan Hall
Summary:
The paper is to introduce a freehand sketch recognition system that allow users to draw in an unrestricted fashion. The system is suitable for unistroke sketch, and consists of three parts, approximation, beautification, and basic recognition.

Stoke Approximation: Vertex detection is implemented by detecting the minimum speed or the maximum absolute value of curvature. With both two sources, the system can generate hybrid fits. Then, Bezier curves are used for approximating curves sketch.
Beautification: Adjust the slopes of line segments, in order to have the same slope end up being parallel.
Basic recognition: It is implemented by template matching.

Overall, the system can get 96% accuracy.

Discussion:
It is a good idea to represent sketches by vertexes. Actually, vertexes are important features for recognition, because they means that some kind of changes happened. Changes are what we are concerned. For example, we are always concerned about what teachers say more loudly.

Robust to noise? In the paper, very few contents discussed how to deal with noise. Noise, I mean, is not the noise when detecting vertexes, but the noise when drawing. Users don't always draw a totally correct sketch. Recognition techniques should be improved to be more robust to kinds of noise.