Fig. 1. Rice gay image

Fig. 2. Three-dimension topographic image of rice

Fig. 3. One-direction grayscale wave curve

Fig. 4. Grayscale wave curve

Fig. 5. Local threshold segmentation curve of rice image. (a) Line 30 of the grayscale wave curve; (b) column 210 of the grayscale wave curve

Fig. 6. Four-direction one-dimension threshold segmentation of rice image. (a) Horizontal direction sub-image; (b) vertical direction sub-image; (c) left diagonal directional sub-image; (d) right diagonal directional sub-image; (e) segmentation results after an and operation

Fig. 7. Experimental results of various methods. (a)Raw images; (b) 2DOtsu method; (c) 2DTE method; (d) Niblack method; (e) our method