in julia code: Similarly, define a new subtype EdgeStencil which applies the same operation as maxabsgradfilter in the lecture notes.

function image$\_$maxabsgradfilter$($A$)$

B $=0*$A

for i $=2$:size$($A$,1)-1,$ j $=2$:size$($A$,2)-1$

a $=$ A$[$i$-1$:i$+1,$ j$-1$:j$+1]$

B$[$i$,$j$]=$ max$($abs$($a$[3,2]-$ a$[1,2]),$ abs$($a$[2,3]-$ a$[2,1]))$

end

return B

end

already have

abstract type AbstractStencil end