Algorithm 1. Measuring the ambiguity threshold.

1 Initialize the value α and determine the shape of the membership function

2 Find the image histogram

3 Initialize the position of the membership function, and shift it along the range of the gray-level values

4 At each position (gray-level value g), find the upper and lower membership values μU(g) and μL(g) respectively

5 Using Eq. (9), find the amount of ultrafuzziness at each position

6 Determine the position gpos that has the maximum ultrafuzziness, and use this value to threshold the image (T = gpos)