timhieundvantay
TRANSCRIPT
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I.K THUT NHN DNG VN TAY:K thut nhn dng vn tay u da trn nguyn tc i snh
cc im c trng trn mi vn tay.
V vy, vic xc nh cc im c trng trn vn tay l vn
c bn nht v then cht nht trong k thut nhn dng vn tay.
1.CC C TRNG TRN VN TAY:Trn cc vn tay c cc im c trng (Nhng im c bit m v
tr ca n khng trng lp trn cc vn tay khc nhau) c phn
thnh 2 loi: Cc chi tit (Minutiae) v cc im k d(singularity)a)Singular (nhng vng k d): L nhng vng c cu trc khc
thng so vi nhng vng khc.
C 2 loi Singular: Core v Delta
Core thng c mt s loi nh sau
Core
Delta
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Whorl Right Loop Twin loop Left loop
b)Minutiae (cc chi tit): Khi d theo tng ng vn, ta s thyc nhng im ng vn kt thc (Ridge Ending) hoc r nhnh
(Bifurcation), nhng im ng vn kt thc. Nhng im ny
c gi l chi tit trn vn tay (Minutiae)
im kt thc cang vn
im r nhnh
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2.XC NH CC IM C TRNG:nh vn tay u vo l cc nh chp t cc my chp vn tay. Mi my c c trng
hnh nh khc nhau. V vy, mun xc nh c chnh xc cc chi tit th chng ta phi x l nh
d liu u vo:
Cc kthut xl nh u vo gm c:
- Chun ha mc xm ca nh: a nh vxm ng u thuntin cho vic x l
- Tng cng nh: Lm ni bt cc ng vn ci thin cht lngnh vn tay
- Nhphn ha nh: a nh vnh en/trng vi 2 gi tr xm xcnh (0/255) phc v cho vic lm mnh v tm chi tit ca vn tay.
- Tm xng nh (lm mnh ng vn): Lm mnh ng vn v dng1 im nh phc v cho vic tm cc chi tit.
- Tm cc chi tit: Tm ra cc im cui ca mi ng vn, cc imgiao nhau trn cc ng vn a vo khu xl i snh.
3.I SNH VN TAYPhng php i snh c s dng trong chng trnh l phng
php Minutiae-base : Da trn vic i snh gia cc chi tit(Minutiea) tm c trn cc vn tay.
C 2 phng php gip xl v tm kim cc chi tit (Minutiea) trn vn tay:
- Trch cc chi tit da vo nh nhphn ha v lm mnh- Trch cc chi tit trc tip tnh xm s dng k thut: D tm theo ng vn da trn
mc xm.
Trong chng trnh ny, nhm DST la chn phng php th nht: c th tn dng ccthut ton trong mn ha my tnhng vi t tng chung ca Ging vin a ra khihng dn lm bi tp ln.
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II.CC K THUT XL DLIU U VO:1.M HA NH VN TAY V DLIU CHNG
TRNH:
a) Dliu u vo:- D liu u vo ca chng trnh thng l nh 24bit RGB. V vy ta
phi chuyn nh vnh xm.
- nh trong my tnh c m ha v dng ma trn im (2 chiu) ccim nh
- 1 im nh trong my tnh (24bit) c c trng bi 3 mu: Red,Green, Blue.
b)Chuyn 1 im nh vnh xm:Mc xm ca 1 im nh c tnh theo cng thc:
Grayij = 0.299*Rij + 0.587*Gij + 0.114*Bij
c) Lu trdliu cho cc bc xl ca chng trnh:S dng mng 2 chiu lu mc xm tng ng ca tng im nh.
- Trong bo co ny, d liu mc xm ca nh a vo x l k hiu limage[,] v image[i,j] l mc xm ca nh ti im nh dng
th i, ct th j.
2.XC NH MA TRN NH HNG:a) Mc tiu:
To ra ma trn nh hng, l tp hp hng ca tng pixel trong nh.
b)T tung:- Tm hng ca tng im, sau tp hp li thnh ma trn nh
hng.- Tnh hng ca tng im ph thuc vo min ln cn (ma trn
W*W im vi i v j l im gia ca khi)
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c) Phng php:- Chia nh thnh cc khi nhhn kch thc WxW
- Tnh Gradient theo 2 hng x,y l Gx, Gy ti mi im pixel trong khi
- Khi hng ca im chnh gia ca khi c xc nh theo cng thc:
=
w
i
w
j yx
w
i
w
j yx
jiGjiG
jiGjiG
1 1
22
1 1
),(),((
),(),(2arctan
2
1
d)Cch tnh: tnh (x,y) Ta phi tnh tng cc Gx(i,j) v Gy(i,j), vi i : (x-wS) -> (x+wS) ,j: (y-
sW)->(y+sW)
x
y
i,j
(x,y)
widthS uare widthS uare
widthSquar
widthSquar
y
i,j
(x,y)
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Vi mi (i,j) ta tnh Gx,Gy theo Cng thc Sobel:
Gx = ((image[i + 2, j] + 2 * image[i + 2, j + 1] + image[i + 2, j + 2] - image[i, j] - 2 *
image[i, j + 1] - image[i, j + 2]));
Gy = ((image[i, j + 2] + 2 * image[i + 1, j + 2] + image[i + 2, j + 2] - image[i, j] - 2 * image[i
+ 1, j] - image[i + 2, j]));
Trong : image[i,j] l xm ca im [i,j]
Sau tp tc chy bin i,j v ly tng ca cc 2xG ,2
yG ,
xG xGy , n khi ht khong bao
Sau khi hon tt vng lp,ly cc gi tr p dng vo cng thc tnh
=
w
i
w
j yx
w
i
w
j yx
jiGjiG
jiGjiG
1 1
22
1 1
),(),((
),(),(2arctan
2
1
Sra c hng ca 1 im (x,y), gn gi tr ny vo 1 mng 2 chiu
(i,j)
-1 1
2
1
-2
-1
Gx
(i,j)
-1
1 2 1
-2 -1
Gy
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Tip tc chy vng lp n khi tnh ht hng ca tt ccc im x,y tas c ma trn nh hng
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3.K THUT CHUN HA MC XM:a)Mc tiu:
o V d vnh sau khi chun ha mc xm
Vic thu nhn nh khng phi lc no ta cng thu c nh c cht lng
tt.V vy trc khi thut ton x l nh ta phi ci thin cht lng nh
nhm gia tng hiu qu x l. Chun ha nh v mc xm slm ng u
cng xm trong bn thn nh .
b) T tng :Xt ln lt cc im nh trong nh, tm ra xm ca tng im
trong nh, sau rt ra xm trung bnh ca nh. Sau chuyn
mc xm ca cc im nh ca nh v mc xm trung bnh.
nh trc khi chun ha nh sau khi chun ha
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c) Cc hm sdng :- u tin ta dng hm GetM() tm xm trung bnh ca nh :
m : xm trung bnh ca nh
width : rng ca nh
heigth : chiu cao ca nh
Tng sim nh = width * heigth
: xm ti im (i,j)- Tip theo s dng hm GetV() tm sai stng i tng i
ca mt im nh :
( )
: sai stng i ca im nh ti (i,j)m : xm trung bnh ca nh
width : rng ca nh
heigth : chiu cao ca nh
Tng sim nh = width * heigth
: xm ti im (i,j)
- Sau ta xt ln lt tng im nh trong nh v a chng vmc xm trung bnh :
+ Nu xm ti (i,j) < xm trung bnh
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+ Nu xm ti (i,j) > = xm trung bnh
: xm ti im (i,j)
: sai stng i ca im nh ti (i,j)
m : xm trung bnh ca nh
, : cc tham s truyn voTri qua thc nghim ca mt s dn i trc th gi tr v
l ti u nht
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4.TNG CNG CHT LNG NH VN TAY:a) Mc tiu:Cc nh vn tay thng c ly bng hai phng php : t mc hoc t cc sensor (cm
bin ).Cc nh vn tay c ly t mc thng c cht lng thp v khng ng u.Mc tiuca phng php Gabor l ci thin cht lng nh ca vn tay.
nh gc nh c tng cng
b) T tng:Sdng hm lc Gabor: l mt cng c hu dng cho vic x l nh.N c c tnh chn lc
trong min khng gian ln tn s. Hm Gabor 2D c dng nh sau:
g(x,y;T,)=exp
2
2
2
2
2
1
yxcos
T
x2
x=xcos+ysin
y=-xsin+ycos
Trong
+ l hng ca b lc
+ T l chu k ca hm cos (trong thc nghim thng c chn c gi tr t[0,1]).Ta c : T=1/f.
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+ x ; y l cc lch chun (trong thc nghim thng c chn c gi tr t[0,4])
c) Gii thut tng cng nh:+ Xc nh trng nh hng ca im (x,y)
+ S dng hm lc gabor cho nh chun ha trong min tn s
- Chia nh cn lc thnh tng khi nhkch thc WxW
- Xc nh hng ca khi ( da theo trng nh hng)
- Hng l hng ca khi
Tnh G ti (i,j) theo hng ca (i,j),W,f,fi,G c thdng hay m theo cos
T
x2
Sau xm ca (x,y) bng tng ca cc G(i,j) nhn vi xm ca (i,j)
- Nu kt qu> 255 th xm ca (x,y) =255 v tr v mu trng
- Nu kt qu< 0 th xm ca (x,y) = 0 v tr vmu en
`
ij
widthSqure widthSqure
x,y
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d) Cc hm c bn trong tng cng nh:+ Hm GetMaskFilter : l hm tnh Gabor. p dng cng thc Gabor ta tnh c G (x,y)
+ Hm ToFiltring: Tng cng mc sang ti im (x, y).Trong hm ToFiltring cho 2 bin i, jchy t 0 -> 2widthsquare +1 tnh G(i, j).Sau ta tnh G(i,j) * image(i+x,j+y).Kt qu tnhc s so snh vi on [0;255].
- Nu = kt qu >= 255 th chuyn im (x, y) thnh mu trng
- Nu = kt qu 2ws +1 tnh G(i,j).Sau ta tnh G(i,j) * image(i+x,j+y).Kt qutnh c s sosnh vi on [0;255].
- Nu =kt qu >= 255 th chuyn im (x,y) thnh mu trng- Nu =kt qu
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o Bin i nh xm c x l bc trc thnh nh nhphn (en trng)di dng bit 0, 1
o nh sau khi c nh phn ha sc a vo khu x l tiptheo (lm mnh ng vn tay, trch tm cc im Minutiae)
b)THUT TON Local Threshold:- Mc tiu ca thut ton:
o Bn cht ca vic nh phn ha nh l da vo xm ca 1 imnh ang xt xc nh im nh sl mu en hay mutrng.
o Nu xm nhhn doXamth ta gn im nh thnh mu trng
Vy, thut ton Local Threshold c p dng xc nh ngng doXamnh ni pha
trn.
- Cng thc tnh ThresholdThreshold = x
vi
F(x)=max(
)
gT(x) = Tng sim nh c xm
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6.LM MNH NG VN:a. Mc tiu:
o Lm mnh nh nh phn v 1 pixel ( tc l xng) thun tincho vic tm chi tit ca vn tay.
b. T tng chnh ca gii thut tm xng:o Thc hin duyt qua tt ccc im nh trong nh nh phno Kim tra im nh ang c xt c mu l en (0) v l im
bin hay khng ( dng hm IsBoder(int x, int y) )? Nu l im binth kim tra xem im nh c thc xa trng hay khng (dng hm IsDelete(int x, int y) )? Nu c th xa trng th st mu
ti im l trng (255).o Qu trnh lp li cho ti khi khng cn im bin no c xa
.nh nh phn lc ny sc bc dn lp bin cho ti khi ch cnli cc im bin to thnh xng nh.
c. Cc hm c bn trong gii thut tm xng:o Kim tra bin IsBoder(intx, inty)
- im nh ang xt c mu l mu en v c 1 trong scc imnh cn tri, cn phi, cn trn, cn di c mu l mu trng thim nh l im bin.
o Kim tra xa trng IsDelete(intx, inty)
im nh ang xt ( k hiu mu en vin ) l im bin vn c mu en v im nh cn tri l mu trng.
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Xt 8 im nh kcn xung quanh im nh cn kim tra ( c mu en).
- So snh mu ca cp 3 im nh trn k nhau (cng 1 mu) nukhc mu so vi mu ca cp 3 im nh trn k nhau (cng 1mu) i xng qua im nh ang c kim tra th im nh nyl im cn xa trng.
im nh ang xt ( k hiu mu en vin ) l im cn xa trng
o To xng c bn MakeBone()- St thuc tnh isBone = false.- Trong khi isBone = false th duyt qua tt ccc im nh trong
nh nh phn.- Kim tra im nh ang c xt c mu l en (0) v l im
bin hay khng ( dng hm IsBoder(intx, inty) )? Nu l im binth kim tra xem im nh c thc xa trng hay khng (dng hm IsDelete(intx, inty) )? Nu c thxa trng th st muti im l trng (255) v st thuc tnh isBone = true. Kt thcto xng.
o Xa chi tit tha ClearBone()- Duyt qua tt ccc im nh trong nh nh phn.
P1 P2 P3
P4 P5
P6 P7 P8
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- Nu im nh ang c xt mu l en th kim tra trongs4 im nh cn cho vi n c l im nh mu en haykhng? Nu cc im nh cn cho vi im nh ang xt l mu en th 2 im nh cn chung gia n v im
nh ang xt sst mu l mu trng.
III. PHNG PHP I SNH:1.PHNG PHP:Phng php i snh c s dng trong chng trnh l phng php Minutiae-base : Da trn
vic i snh gia cc chi tit (Minutiea) tm c trn cc vn tay.
a) Xl dliu u vo:- Mc ch x l d liu u vo l gip tm chnh xc cc chi tit trn vn tay.
C 2 phng php gip xl v tm ki
m cc chi ti
t (Minutiea) trn vn tay:
- Trch cc chi tit da vo nh nhphn ha v lm mnh- Trch cc chi tit trc tip tnh xm s dng k thut: D tm theo ng vn da trn
mc xm.
Trong chng trnh ny, nhm DST la chn phng php th nht: c th tn dng ccthut ton trong mn ha my tnhng vi t tng chung ca Ging vin a ra.
Cc bc xl dliu u vo:
- Chun ha mc xm ca nh: a nh vxm ng u thun tin cho vic x l- Tng cng nh: Lm ni bt cc ng vn ci thin cht lng nh vn tay- Nhphn ha nh: a nh vnh en/trng vi 2 gi trxm xc nh (0/255)
phc v cho vic lm mnh v tm chi tit ca vn tay.
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- Tm xng nh (lm mnh ng vn): Lm mnh ng vn v dng 1 im nh phcv cho vic tm cc chi tit.
- Tm cc chi tit: Tm ra cc im cui ca mi ng vn, cc im giao nhau trn ccng vn a vo khu xl i snh.
b) Cc trng hp gy nhiu cho vic i snh:- nh vn tay khng lin nt hoc xut vng b nhe, hoc cc ng vn chp b m
- nh chp vn tay c v tr sai lch so vi mu i snh
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- nh chp vn tay c gc lch so vi nh mu i snh
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c) Cc bc i snh 2 vn tay:- Tm ra cc chi tit trn 2 vn tay. Mi chi tit c trng bi 3 thng s (xi, yi, )
- 2 vn tay phi c khp mu: Cc mu vn tay cn i snh sc t 1 v tr saocho c s ph hp gia chng theo 1 ngng. Nhm DST s dng php bin i Hough
tnh ton. (Quay vn tay a vo i snh 1 gc v dch 1 on (x1, y1) avn tay cn i snh v dng tng ng vi vn tay gc)
- Khi tm ra c lch v gc lch tiu chun, ta t li v tr v cc chi tit trn vntay mt cch hp l v thc hin php i snh trc tip trn cc chi tit tm c trn 2
vn tay.
- Tnh ton slng chi tit trng khp- So snh slng chi tit trng khp vi s chi tit trn 1 vn tay => T da vo t l
v kt lun s ging/khc nhau gia cc vn tay
2.GII THUT KHP MU V I SNH VN TAY:a)Khp mu vn tay:
- S dng php bin i Hough tm ra 1 gc lch v onlch (x1, y1) ti u nht.
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o Cho php lch gc gia 2 vn tay ti a l 60o : Tachia khong lch thnh 20 + 1 phn v lu cc gi trca gc lch tng ng angelSet[] = {-30, -27, -24, ,24, 27, 30}.
o Chia lch v v tr gia 2 nh vn tay thnh n on(n = chiu cao hoc n = rng ca nh vn tay). Mion hn km nhau 2n v. V lu cc gi trtngng vo 2 mng deltaXSet[] v deltaYSet[]
V d: vi nh 200x300: deltaXSet[] = {-200, -198, -196, , 194, 196, 198, 200} deltaYSet[] = {-300, -298, -296, , 294, 296, 298, 300}
- Vi 2 vn tay em i snh: Ta tm c tp cc chi tittng ng
{ } { } { }
Duyt trn tng cp chi tit tm c gia 2 vn tay: (gi 2
chi tit l mx, my
o Thc hin php bin i trn vn tay cn i snh: Tnh tin tng on trn gii hn cho php
Quay tng gc trong gii hn cho php
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Trong , gi tr ca vn tay mi sc tnh tin n ta (deltaXSet[i], deltaYSet[j]) v c quay 1 gc angelSet[k] vii, j, k l cc ch s ca cc mng tng ng.
o Tm ra mt gii hn v lu vo mng 3 chiuA[][][] sao cho vi gii hn l nh nht cho 2chi tit mx, my
o Tm nh nht trong mng ch sA[][][]- Ta gi cp l ngng bin i cc chi tit trong 2 vn
tay ph hp cho vic i snh.
b)i snh 2 vn tay:- Vi 2 vn tay em i snh: Ta tm c tp cc chi tit
tng ng
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{ }
{
} { }
- Bng cch so snh tng ng cc cp mi , mi ca 2 tp V1,V2
o Nu cp chi tit mi , mi lch nhau mt ngng