ch04 - phat hien bien
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7/30/2019 Ch04 - Phat Hien Bien
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Cc phng php pht hin bin
11/01/2013Phm Vit Hng Nhp mn x l nh 1
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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
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Nibinda vo bin thin cp xm
Chyu l lyo hm
Bcnht (Gradient)
Bc hai (Laplace)
Tngihiuqunubinimc xm l t
ngt. Ktqu l nh bin
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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.
11/01/2013 Phm Vit Hng Nhp mn x l nh 4
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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.
11/01/2013 Phm Vit Hng Nhp mn x l nh 5
dy
yxfdyyxffy
y
yxfdx
yxfydxxf
fxx
yxf
),(),(),(
),(),(),(
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Vidx=dy=1 ta c:
Ma trn nhn chp l
11/01/2013 Phm Vit Hng Nhp mn x l nh 6
),()1,(
),(),1(
yxfyxffyy
f
yxfyxffxx
f
1
1
11
B
A
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7/30/2019 Ch04 - Phat Hien Bien
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3330
3330
3330
0000
I
****
*003
*003
*000
AI
****
*000
*000
*330
BI
****
*003
*003
*330
BIAI
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Sdng ma trn nhn chp m hnh o hm
theo hai hng
11/01/2013 Phm Vit Hng Nhp mn x l nh 8
101
101
101
xH
111
000
111
xH
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000000
000000
005555
005555
005555
000000
I
******
*5500*
*101000*
*151500*
*101000*
******
xHI
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000000
000000
005555
005555
005555
000000
I
******
*5151515*
*5101515*
*0000*
*5101515*
******
yHI
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7/30/2019 Ch04 - Phat Hien Bien
11/4511/01/2013 Phm Vit Hng Nhp mn x l nh 11
******
*10151515*
*15201515*
*151500*
*501515*
******
yx HIHI
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Tngt Prewitt kthut Sobel c 2 ma trn
nhn chp theo 2 hng
11/01/2013 Phm Vit Hng Nhp mn x l nh 12
101
202
101
xH
121
000
121
xH
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Sdng 8 mtn nhn chp theo 8 hng
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333
305
355
333
303
555
333
503
553
533
503
533
555
303333
335
305
335
553
503
333
355
305
333
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Kthut gradient thnghiuquvi thay iln
Vi thay ichm, minchuyntiprng th k
thuto hm bc hai l lachntthn
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11/01/2013 Phm Vit Hng Nhp mn x l nh 15
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
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Vyo hm bc hai trong tn hiurircxpx:
tngng
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)1,(),1(),(4)1,(),1(2 yxfyxfyxfyxfyxff
010141
010
H
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Thctngi ta c th dng mtsbinth
xpxrirco hm bc hai
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111
181111
H
010
141
010
H
121
242
121
H
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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
11/01/2013 Phm Vit Hng Nhp mn x l nh 18
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Bc 1: Lm trnnh (ma trn Gaussian)
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24542
491294
51215125
49129424542
115
1H
HIB
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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
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yy
xx
HBG
HBG
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Bc 3: Tnh gradient hngtimiim (i,j)
Hngsc nguyn ha nm trong 8
hng [0..7] Tngng 8 im ln cncamtimnh
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x
y
yx
GG
GGG
arctan
22
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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
11/01/2013 Phm Vit Hng Nhp mn x l nh 22
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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.
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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
11/01/2013 Phm Vit Hng Nhp mn x l nh 24
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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
11/01/2013 Phm Vit Hng Nhp mn x l nh 26
),(*
),(jiI
nm
jiW
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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.
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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.
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P1 P2 P3
P8 P P4
P7 P6 P5
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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
11/01/2013 Phm Vit Hng Nhp mn x l nh 31
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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
11/01/2013 Phm Vit Hng Nhp mn x l nh 32
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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
11/01/2013 Phm Vit Hng Nhp mn x l nh 33
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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.
11/01/2013 Phm Vit Hng Nhp mn x l nh 34
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Ton t d bin
Xc nhcpxut pht
Xc nhcptip theo
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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
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Hpca cc Bx vi x thuc X
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Xx
B
xBX
01110
01010
00110
0110111010
X
011110
011110
001110
011111
111110
BX
1B
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Tphp cc im x sao choBx nm trong X
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XBxX x :B
01110
01010
00110
0110111010
X
00110
00000
00010
00100
01000
BX
1B
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Da vo nh co v gin
EG( A)=( AB)( AB)
Nn tch ngng trong huhtthi gian
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0 1 0
1 1 1
0 1 0
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Php m l co ri gin n
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BB)(),( XBXOPEN
01110
01010
00110
0110111010
X
01110
00000
00110
01100
11000
),( BXOPEN
1B
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CLOSE(X,B) cha X c th coi l xpxtrn
OPEN(X,B) thuc X c th coi l xpxdi
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BXBB)( X
BXBB)( X
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Thut ton tm bin sdng php ton xpxtrn
di:
Tnh X Bii=1,n
Tnh (X Bi)
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n
i 1
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tch ngng = 128
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