We show a numerical examples here too :
Gradient | N | E | S | W | NE | SE | NW | SW |
Value | 12 | 13 | 7 | 8 | 4 | 7 | 12 | 14 |
Here k_{1}*Min accounts for the case in which the gradients are all very similar, so that we wish to inclue all of them by setting a threshold that exceeds them. k_{2} * (Max - Min) accounts for the case in which there is a significant difference between the maximum and minimum gradient values.
consider the numerical example illustrated in table 1, Min = 4, Max
= 14 and T = 11 consequently. Therefore the selected subset of gradients
consists of those with value less than 11 :
Gradient subset = {S, W, NE, SE}
G | B | R | |
S | G18 | ( B17 + B19 ) / 2 | ( R13 + R23 ) / 2 |
W | G12 | ( B7 + B17 ) / 2 | ( R11 + R13 ) / 2 |
NE | ( G4 + G8 + G10 + G14 ) / 4 | B9 | ( R13 + R5 ) / 2 |
SE | ( G14 + G18 + G20 + G24 ) / 4 | B19 | ( R13 + R25 ) / 2 |