Table 3.

The most implemented pre-processing techniques.

Computational Solution	References
Normalization/histogram equalization	[1,12,13,15,17,18,19,25,26,28,31,32,33,39,40,55,59,60,61,63,70,73,80,85,86,90,91,104]
Intensity-based/dimensional-based filtering	[3,6,12,17,28,54,70,86]