Refer to Fig. 10.22(c).FIGURE 10.22 (a) Original image of size 834 × 1114 pixels, with int...

Refer to Fig. 10.22(c).

FIGURE 10.22 (a) Original image of size 834 × 1114 pixels, with intensity values scaled to the range [0, 1]. (b) Results of Steps 1 and 2 of the Marr-Hildreth algorithm σ = 4 and n = 25 using and (c) Zero crossings of (b) using a threshold of 0 (note the closedloop edges). (d) Zero crossings found using a threshold equal to 4% of the maximum value of the image in (b). Note the thin edges.

(a) Explain why the edges form closed contours.

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(b) Does the zero-crossing method for finding edge location always result in closed contours? Explain.