The aim is to find the good class for a pixel. Of course, if the class of assignment is the true class of membership of the pixel, there is no cost: Tl/l=0.
On the other hand, each time there is an error, it is necessary to penalize the bad choice. As there is no reason to penalize a class l' () rather than a class l'' ( and ) (l being the true class), the cost of one error will be the same for all the errors:
Tl'/l = 1 |