Algorithm 1. Feature pixel point screening based on eight-point scan path detection

Input: scene map and robot’s pose

Output: coordinates and pixel values of the set of feature pixels

Calculate the robot’s coordinate $\left(j,i\right)$ based on the scene map and robot’s pose;

N←1;

Δ There are 11 rays in total in one area;

while N ≤ 11 do

for y←i to 0 by −1 do

Calculate coordinate $\left(x,y\right)$ according to the Nth ray’s slope and robot’s coordinate $\left(j,i\right);$

if ($\left(x,y\right)$ in the map) then

if (pixel value of $\left(x,y\right)$ = 100) then

Record the coordinate and pixel value of feature pixel $\left(x,y\right)$;

exit;

else

Record the coordinate and pixel value of feature pixel $\left(x,y\right)$;

end if

else

exit;

end if

end for

N←N+1;

end while