PaleoSketch proposes a new low-level recognition and beautification system that can recognize eight primitives with recognition rates of around 98.56%. Two new features NDDE and DCR along with a new ranking algorithm which help in distinguishing polylines from curves is the major contribution of the paper.
The system returns multiple interpretations which allows recognition errors to be corrected as a simple pen-click could be used to switch to an alternative interpretation. This recognizer can distinguish circle from ellipse and also can recognize spirals and helix which has not been supported in any previous low level recognizers.
Implementation:
Prerecognition: After basic prerecognition steps a series of graphs and values are computed for the stroke including direction graph, speed graph, curvature graph etc. Corners are also identified at this step.
NDDE (normalized distance between direction extremes) : Stroke length between the point with the highest direction value (arctangent angle of the change of y over the change of x) and the point with the lowest direction value.
DCR(Direction change ratio) : Maximum direction change divided by the average direction change.
For a polyline NDDE is low and DCR is high, whereas for a curve NDDE is high(nearly 1) and DCR is low.
Hierarchy is needed to sort the interpretations. A new ranking algorithm was introduced which makes use of the corner finding algorithm.
My thoughts: The ranking algorithm introduced is a very good idea. This kind of algorithms can be used in different scenario. NDDE and DCR along with few other features can help in improving the accuracy.
The system returns multiple interpretations which allows recognition errors to be corrected as a simple pen-click could be used to switch to an alternative interpretation. This recognizer can distinguish circle from ellipse and also can recognize spirals and helix which has not been supported in any previous low level recognizers.
Implementation:
Prerecognition: After basic prerecognition steps a series of graphs and values are computed for the stroke including direction graph, speed graph, curvature graph etc. Corners are also identified at this step.
NDDE (normalized distance between direction extremes) : Stroke length between the point with the highest direction value (arctangent angle of the change of y over the change of x) and the point with the lowest direction value.
DCR(Direction change ratio) : Maximum direction change divided by the average direction change.
For a polyline NDDE is low and DCR is high, whereas for a curve NDDE is high(nearly 1) and DCR is low.
Hierarchy is needed to sort the interpretations. A new ranking algorithm was introduced which makes use of the corner finding algorithm.
My thoughts: The ranking algorithm introduced is a very good idea. This kind of algorithms can be used in different scenario. NDDE and DCR along with few other features can help in improving the accuracy.
Agree with, The ranking algorithm introduced is a very good idea.
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