where AS(L) is the average colour value, L is the width of the
histogram.
L
f (Ci) is the summation of the hue value Ci of all
histogram with L width.
The strawberry colour gradation is implemented with a
threshold set according to the major colour value on a* channel.
According to a* value, the colour feature is divided into three
degrees:
a∗ ≥ 160, black-red
150 ≤ a∗ ≺ 160, bright-red
a∗ ≺ 150, light-red