Xử lý ảnh số - Phân đoạn ảnh part 4 pot

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(a)

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ρmin

ρmax

θmin θmax

(b)

H`ınh 7.15: (a) Biˆe˙’u diˆe˜n to.a d¯ˆo. cu.

. c cu˙’a d¯u.

`o.

ng thˇa˙’ng; (b) lu.

o.

. ng tu.

˙’ ho´a mˇa.t phˇa˙’ng

θρ th`anh c´ac ˆo.

Thuˆa.t to´an tˇang c1, c2 v`a t`ım c3 tu.

o.

ng ´u.

ng; sau d¯´o cˆa.p nhˆa.t gi´a tri. t´ıch lu˜y mˆo.t c´ach

th´ıch ho.

. p v´o.

i bˆo. (c1, c2, c3). Hiˆe˙’n nhiˆen, d¯ˆo. ph´u.

c ta.p cu˙’a biˆe´n d¯ˆo˙’i Hough phu. thuˆo.c

nhiˆe` u v`ao sˆo´ c´ac to. a d¯ˆo. v`a c´ac hˆe. sˆo´ trong biˆe˙’u diˆe˜n h`am d¯u.

o.

. c cho.

Tro.

˙’ la.i b`ai to´an liˆen kˆe

´t biˆen. Phu.

o.

ng ph´ap du.

. a trˆen biˆe

´n d¯ˆo˙’i Hough bao gˆo`m:

(1) t´ınh gradient cu˙’a a˙’nh; (2) phˆan hoa.ch mˇa.t phˇa˙’ng tham sˆo´ ρθ; (3) kiˆe˙’m tra c´ac ˆo

t´ıch lu˜y c´o su.

. tˆa.p trung nhiˆ`eu pixel; v`a (4) kiˆe˙’m tra mˆo´i liˆen hˆe. (d¯ˇa. c biˆe.t, t´ınh liˆen

tu. c) gi˜u.

a c´ac pixel trong ˆo d¯u.

o.

. c cho.n. Kh´ai niˆe.m t´ınh liˆen tu. c trong tru.

`o.

ng ho.

. p n`ay

thu.

`o.

ng du.

. a trˆen khoa˙’ng c´ach gi˜u.

a c´ac pixel khˆong liˆen thˆong d¯u.

o.

. c x´ac d¯i.nh suˆo´t qu´a

tr`ınh duyˆe.t trong tˆa.p c´ac pixel tu.

o.

ng ´u.

ng mˆo.t ˆo t´ıch lu˜y. Mˆo.t khe ho.

˙’ ta.i d¯iˆe˙’m bˆa´t

k`y d¯u.

o

.

. c ch´u ´y nˆe

´u khoa˙’ng c´ach gi˜u.

a d¯iˆe˙’m n`ay v`a lˆan cˆa.n gˆa`n nhˆa´t cu˙’a n´o vu.

o.

.t qu´a

mˆo.t ngu.

˜o

.

ng cho tru.

´o

.

c (xem Phˆa`n 2.3 vˆe` c´ac kh´ai niˆe.m liˆen thˆong, lˆan cˆa.n v`a khoa˙’ng

c´ach).

7.2.3 Phu.

o.

ng ph´ap d¯ˆo` thi.

Phu.

o.

ng ph´ap trong phˆa`n tru.

´o

.

c du.

. a trˆen mˆo.t tˆa.p c´ac d¯iˆe˙’m biˆen nhˆa.n d¯u.

o.

. c thˆong qua

to´an tu.

˙’ gradient. V`ı vˆa.y n´o ´ıt khi d¯u.

o.

. c su.

˙’ du.ng trong bu.

´o

.

c tiˆe` n xu.

˙’ l´y d¯ˆo´i v´o.

i c´ac

a˙’nh c´o nhiˆe˜u. Phˆa`n n`ay tr`ınh b`ay thuˆa.t to´an to`an cu. c d¯ˆe˙’ x´ac d¯i.nh c´ac d¯u.

`o.

ng biˆen

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