Symbol	Description
s	Size of a square grid
smin	The minimum value of s
smax	The maximum value of s
M	Image size for a square image
G	Total number of gray levels in an image
gmax	Maximum gray level over a grid
gmin	Minimum gray level over a grid
nr	Total number of boxes at scale r, required to cover the rough surface over (i, j)th grid
Nr	Total number of boxes at scale r, required to cover the rough surface of an image
r	The scale of a square grid for an image
h	Height of a box
γ	Correlation coefficient
R2	Goodness of fit
$\widehat{b}$	The slope of LLS fitted line (for evaluation of FBM images)
ER	Equal ratio. Indicates that s is a divisor of the image size
CI	Consecutive integer. Indicates that the value of s is all integer from smin to smax.
CW	The “consecutive integer + weight method” strategy
OCI	Optimized consecutive integer. Indicates that the division of the xy plane is based on the improved consecutive integer method.
TFD	Theoretical fractal dimension refers to the fractal dimension used to generate FBM images
FD	Fractal dimension
DE	Distance error
FBM	Fractional Brownian motion