Measurement of pest-damaged area of leaf based on auto-matching of representative leaf

In order to evaluate the pest-damaged extent of crop quantitatively, the anthors proposed a novel method based on auto-matching of representative whole leaf to measure leaf pest-damaged area. Firstly, the outer contour of leaf was extracted after image binary; secondly, the contour was approximated to a polygon and segmented to many sub-contours using polygon vertexes; thirdly, the mapping relationship between the whole leaf and the pest-damaged leaf was constructed by matching their sub-contours based on the shape context; finally, the pest-damaged leaf was reconstructed by mapping their sub-contour relationship for area calculation. The experiments on ten types of different leaves showed that the average process time for one leaf was 0.952 s, the maximum relative error was 8.22% and, the average relative error was 4.78%. As to leaves with high shape complexity, the average relative error was 7.48%, and to leaves with medium and low shape complexity, those were 5.99% and 1.84%, respectively. The proposed method has proved to be an accurate and efficient method for measurement of leaf pest-damaged area.