Canny edge detector: Difference between revisions

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unique =: 3 : 'y*i.$y'

connect =: 3 : 'attach^:_ unique y'

octant =: 3 : '4|(>.(_0.5+((4%(o. 1))*(12&o. y))))' NB. eighth of circle

canny =: 3 : 0

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NB. Step 3 - edge detection

NB. find the octant (eighth of circle) in which the gradient lies

octant =: 3 : '4|(>.(_0.5+((4%(o. 1))*(12&o. y))))'

NB. test pattern <(i:6)(4 : 'octant (x j. y)')"0/(i:6)

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NB. is this gradient the greatest of immmediate colinear neighbore?

greatestOf =: 4 : '(x greaterThan y) *. ((-x) greaterThan y)'

NB. find the octant (eighth of circle) in which the gradient lies

NB. relative address of neighbor ~~relevant~~ ~~to grad~~ direction

krnl0 =: _1 0

krnl1 =: _1 _1

krnl2 =: 0 _1

krnl3 =: 1 _1

og =: octant image2

NB. relative address of neighbor, per gradient direction

nbr =: 4 2 $ _1 0, _1 _1, 0 _1, 1 _1

NB. mask for maximum ~~gradient~~ colinear ~~with~~ gradient

NB. mask for maximum colinear gradient

ok0 =: (0=og) *. ~~krnl0~~ greatestOf image2

ok0 =: (0=og) *. (0{nbr) greatestOf image2

ok1 =: (1=og) *. ~~krnl1~~ greatestOf image2

ok1 =: (1=og) *. (1{nbr) greatestOf image2

ok2 =: (2=og) *. ~~krnl2~~ greatestOf image2

ok2 =: (2=og) *. (2{nbr) greatestOf image2

ok3 =: (3=og) *. ~~krnl3~~ greatestOf image2

ok3 =: (3=og) *. (3{nbr) greatestOf image2

image3 =: image2 *. (ok0 +. ok1 +. ok2 +. ok3)

NB. Step 4 - Weak edge suppression