ch04 - phat hien bien

7/30/2019 Ch04 - Phat Hien Bien

1/45

Cc phng php pht hin bin

11/01/2013Phm Vit Hng Nhp mn x l nh 1


2/45

Nhm trch chncimnhmhiunh

Cha c nhngha chnh xc v bin

Thay itngt trong mc xm

Nu l nhentrng th im bin l imen c t nht 1

imtrng bn cnh

Tphp cc im bin l ng bin bao quanh itng

C 2 cch cbn Pht hin bin trctip

Pht hin bin gin tip

11/01/2013 Phm Vit Hng Nhp mn x l nh 2


3/45

Nibinda vo bin thin cp xm

Chyu l lyo hm

Bcnht (Gradient)

Bc hai (Laplace)

Tngihiuqunubinimc xm l t

ngt. Ktqu l nh bin



4/45

Nunh c thc phn vng th ranh giigia

cc vng l bin.

D bin v phn vung l hai bi ton ingu

nhau.

C th dng c trong trnghpbin thin

camc xm khng tngt. Ktqu l ng bin.



5/45

Gradient l mt vector c thnh phnhinthtc

thay i gi trimnh:

dxv dyl khong cch theo hng x, y y l gi trgnng v trong tn hiurirc, o hm

khng tnti. M phngbng nhn chp.


dy

yxfdyyxffy

y

yxfdx

yxfydxxf

fxx

yxf

),(),(),(

),(),(),(


6/45

Vidx=dy=1 ta c:

Ma trn nhn chp l


),()1,(

),(),1(

yxfyxffyy

f

yxfyxffxx

f

1

1

11

B

A


7/4511/01/2013 Phm Vit Hng Nhp mn x l nh 7

3330

3330

3330

0000

I

****

*003

*003

*000

AI

****

*000

*000

*330

BI

****

*003

*003

*330

BIAI


8/45

Sdng ma trn nhn chp m hnh o hm

theo hai hng


101

101

101

xH

111

000

111

xH



000000

000000

005555

005555

005555

000000

I

******

*5500*

*101000*

*151500*

*101000*

******

xHI



000000

000000

005555

005555

005555

000000

I

******

*5151515*

*5101515*

*0000*

*5101515*

******

yHI



******

*10151515*

*15201515*

*151500*

*501515*

******

yx HIHI


12/45

Tngt Prewitt kthut Sobel c 2 ma trn

nhn chp theo 2 hng


101

202

101

xH

121

000

121

xH


13/45

Sdng 8 mtn nhn chp theo 8 hng


333

305

355

333

303

555

333

503

553

533

503

533

555

303333

335

305

335

553

503

333

355

305

333


14/45

Kthut gradient thnghiuquvi thay iln

Vi thay ichm, minchuyntiprng th k

thuto hm bc hai l lachntthn



15/45


2

2

2

2

2

y

f

x

ff

)),(),1((2

2

yxfyxfxx

f

xx

f

),1(),(2),1(

)],1(),([)],(),1([

yxfyxfyxf

yxfyxfyxfyxf

)1,(),(2)1,(2

2

yxfyxfyxf

y

f


16/45

Vyo hm bc hai trong tn hiurircxpx:

tngng


)1,(),1(),(4)1,(),1(2 yxfyxfyxfyxfyxff

010141

010

H


17/45

Thctngi ta c th dng mtsbinth

xpxrirco hm bc hai


111

181111

H

010

141

010

H

121

242

121

H


18/45

y l thut ton cinnhngn nay vn rt

hiuqu v csdngrng ri

C khnnga ra ng bin mnh v pht

hin chnh xc vinh c nhiu

Bao gmnmbc

Sau khi p dng, nh c thc m ha thnhcc ng cong vi cng thc ton hc



19/45

Bc 1: Lm trnnh (ma trn Gaussian)


24542

491294

51215125

49129424542

115

1H

HIB


20/45

Bc 2: Tnh gradient bng ma trn Prewitt

C th dng cc php pht hinbcmt khc

(gradient ngin, Sobel..)

Ktqu l 2 nh gradient theo hai hng x v y


yy

xx

HBG

HBG


21/45

Bc 3: Tnh gradient hngtimiim (i,j)

Hngsc nguyn ha nm trong 8

hng [0..7] Tngng 8 im ln cncamtimnh


x

y

yx

GG

GGG

arctan

22


22/45

Bc 4: Loibnhngim khng phi l cc

i xa bnhngim khng phi l bin

Xt (i,j), l gradient hngti (i,j), G1, G2 l hai im

ln cn theo hng.

Nu G(i,j) G1 v G(i,j) G2 th migili (i,j) ((i,j) l

cciaphng)

Ngcli th xa (i,j) v (i,j) l imnn



23/45

Bc 5: Phn ngng tm bin

im c gradient lnhnthng c khnng l bin

cao hnim c gradient nhhn.

Vicchnngng phn loi l rt kh.

Canny sdng phn ngngvitr

C hai ngng cao v thp

Ginh l bin quan trngthngnm trong nhngnglin tc trong bcnh.



24/45

Bc 5: Phn ngng

u tin p dngngng cao tm ra cc im bin

quan trng v chcchn

T cc im ny theo du cc ng bin sdng

thng tin vhng bc 3

Khi i theo cc bin ny sdngngngthp c th

theo du cc ng bin mchvimtimbtutt



25/45



26/45

Xc nh bin khng theo sbini m da vo

trung bnh gi tr cc im ln cn

Vicas m x n vi tm l (i,j) th nu

th imnh I(i,j) s l im bin v ngclis l imnn


),(*

),(jiI

nm

jiW


27/45



28/45



29/45

Xt nh I vi kch thc M x N.

imnhtiv tr (i,j) c gi tr I(i,j)

Chng ta tm xt nhentrng (0,1) cho n

gin.



30/45

Viim (i,j) th im:

4 lng ging l im ln cn trn, di, tri v phi

(P2,P4,P6,P8)

8 lng ging l im ln cnc tm hng.


P1 P2 P3

P8 P P4

P7 P6 P5


31/45

Chu tuyncaitng l tphp cc im

trong nh sao cho:

Pi v Pi+1 l 8-lng gingvi nhau

P1 v Pn l 8-lng gingvi nhau

Vimi i th tntimtim Q khng thucitng

sao cho Q l 4-lng gingca Pi



32/45

Hai chu tuyn C= v

C= l ingunu:

Vimi i tnti j sao cho Pi v Pj l 4 lng gingca

nhau

Pi l nn th Qj l itnghocngcli



33/45

Thut ton gm cc bc

Xc nhimxut pht

D bo v xc nhim bin tip theo

Lpbc 2 cho n khi gpimxut pht

Vic xc nhimxut pht squytnh tnh

chtca cc ng bin thu c

tnghiuqucathut ton ta c thsdng

cpnn vng thay v chmtim bin



34/45

Thut ton tng qut snh sau

Xc nhcpnn-vng xut pht

Xc nhcpnn-vng tip theo

Lachnim bin vng

Thchintiptbc 2 cho n khi gpcpnn-vng

xut pht

tm cpnn-vng xut pht c thduytnh

t trn xungdi, t tri qua phi.



35/45

Ton t d bin

Xc nhcpxut pht

Xc nhcptip theo



36/45

Nghin cucu trc hnh hccaitngnh

C cc php ton chyugin n (dilation) v

co(erosion).

Cc php ton cnhnghada vo cc iu

kin:

itng l X

Phntcu trc B

Bx l php dchchuyn B tiv tr x



37/45

Hpca cc Bx vi x thuc X


Xx

B

xBX

01110

01010

00110

0110111010

X

011110

011110

001110

011111

111110

BX

1B


38/45

Tphp cc im x sao choBx nm trong X


XBxX x :B

01110

01010

00110

0110111010

X

00110

00000

00010

00100

01000

BX

1B


39/45

Da vo nh co v gin

EG( A)=( AB)( AB)

Nn tch ngng trong huhtthi gian


0 1 0

1 1 1

0 1 0


40/45

Php m l co ri gin n


BB)(),( XBXOPEN

01110

01010

00110

0110111010

X

01110

00000

00110

01100

11000

),( BXOPEN

1B


41/45


42/45

CLOSE(X,B) cha X c th coi l xpxtrn

OPEN(X,B) thuc X c th coi l xpxdi


BXBB)( X

BXBB)( X


43/45

Thut ton tm bin sdng php ton xpxtrn

di:

Tnh X Bii=1,n

Tnh (X Bi)


n

i 1


44/45



45/45

tch ngng = 128

ch04 - phat hien bien

Documents