Fig. 1. Sketch of the edge detection system

Fig. 2. Top view of probe and moving textile. (a) Normal position; (b) left shift; (c) right shift

Fig. 3. Flow chart of detecting edge

Fig. 4. Pixel distribution

Fig. 5. Original image

Fig. 6. Gray scale response curve of textile and background

Fig. 7. Grayscale response curve with only edge information

Fig. 8. Flow chart for solving edge starting point xk

Fig. 9. Flow chart for solving edge terminating point xj

Fig. 10. Experimental platform

Fig. 11. Creamy white carpet edge detection result. (a) Original grayscale; (b) after median filtering; (c) after algorithm post-processing

Fig. 13. Edge detection result of dark gray cotton cloth with hollowed-out and white stripes. (a) Original grayscale; (b) after median filtering; (c) after algorithm post-processing

Fig. 14. Edge detection result of dark gray cotton cloth with hollowed-out and white stripes in a light gray background. (a) Original grayscale; (b) after median filtering; (c) after algorithm post-processing

Fig. 15. Contrast among OTSU algorithm, lattice Boltzmann algorithm, and designed algorithm for edge detection. (a) Original grayscale; (b) after median filtering; (c) after OTSU algorithm post-processing; (d) after lattice Boltzmann algorithm post-processing; (e) after designed algorithm post-processing