For any pixel x of an image Ii, we must distribute the mass of belief on all the classes to recognize, to indicate with which degree the information contained in image Ii states that a pixel x is likely to belong to class c.
The mass allotted to uncertainty, denoted , is a tool which allows uncertainty of the source Ii on the choice of the class of membership of the pixel x, to be represented. We can consider that corresponds to any of the k possible classes: .
The difficulty thus lies in the distribution of the initial mass of evidence between all the classes, and especially in the calculation of the part which must return to uncertainty .
The distribution of the mass between each class consists in giving a proportion of this mass equivalent to the degree of possibility, allotted by the source, to the fact that the pixel x is an element of the class c.