$7\mathrm{.}2$ Based on the imageprocessing.c structure, write a small routine which can automatically calculate the global threshold value according to the iterative global threshold estimation algorithm we discussed in class.

Hint: you have to initialize a T; then read through the image several times to update the $T$; your iteration will stop when your newly updated $T_i$ is not much different from the previous $T_{i-1},$ i$.$e$.a=5T_{i}T$