Fig. 1. Flow chart of image preprocessing for rice pests

Fig. 2. Step image of brown planthopper (a)-(e) and fusion image (f). Step displacement: (a) 0 mm; (b) 0.24 mm; (c) 0.48 mm; (d) 0.72 mm; (e) 0.96 mm

Fig. 3. Corner detection result of brown planthopper

Fig. 4. Composite image with step. Step displacement: (a) 0.12 mm; (b) 0.24 mm; (c) 0.32 mm; (d) 0.44 mm

Fig. 5. Analysis of composite image with different steps for brown planthopper.(a) Image entropy curve; (b) step number curve; (c) corners number curve

Fig. 6. Analysis of composite image under different magnifications.(a) Difference curve of image entropy; (b) corners number curve

Fig. 7. Magnification-optimum carry shift curve