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I HC QUC GIA TP. H CH MINH
TRNG I HC KHOA HC TNHIN
KHOA CNG NGH THNG TI N
NGUYN DUY NGHA - 0012612
NGHIN CU K THUT XL VIDEO S, NG DNG VO THEO
VT V PHN LOI I TNG
LUN VN CNHN TIN HC
GIO VIN HNG DN
TH.S NGUYN TRI TUN
NI N KHA 2000 - 2004
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LI CM N
Trc tin ti xin cm n thy Nguyn Tri Tun ngi hng dn ti
thc hin ti ny. Nhc s tin tng, ch bo tn tnh ca thy ti lun vn
ny hon thnh.
Con xin gi tt c lng bit n, qu trng n ng b, cha m v cc ngi
thn trong gia nh ht lng nui con n hc v lun lun bn cnh con
ng vin con khi con gp kh khn
Em xin cm n tt c cc thy c trong trong trng Khoa Hc T Nhin
v c bit l cc thy c trong Khoa Cng Ngh Thng tin nhit tnh ging
dy v truyn t nhiu kin thc qu bu cho em.
Ti xin chn thnh cm n bn b trong lp cng nh cc anh ch kha
trc cho gip ch bo tn tnh, c bit l anh Trng Thin nh gip
ti nhiu mt v thit b cng nh ti liu
y l mt hng nghin cu mi v rt kh, vi thi gian tip cn kh
ngn trong vng 6 thng v nng lc ca ngi lm ti cho nn ti chc
chn cn nhiu thiu st. Huy vng s nhn c nhiu li ng gp ti
ny hon thin hn
Tp HCM thng 7 nm 2004Sinh vin thc hin
Nguyn Duy Ngha
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CHNG 1_____________________________________________ 1
MU_________________________________________________ 1
1.1 Tng quan____________________________________________ 1
1.2 Yu cu bi ton ______________________________________ 2
1.3 B cc lun vn_______________________________________ 2
CHNG 2_____________________________________________ 4
TNG QUAN V VIDEO V CC K
THUT XL VIDEO CBN____________ 4
2.1 Khi nim v video ______________________________________ 5
2.2 Khi nim v video tun t____________________________ 5
2.2.1 Tn hiu video tun t _________________________________ 5
2.2.2 Cc chun video tng t ______________________________ 8
2.2.3 Cc thit b video tng t _____________________________ 8
2.3 Khi nim v video s _________________________________ 9
2.3.1 Tn hiu Video s _____________________________________ 9
2.3.2 Cc chun video s ____________________________________ 9
2.3.3 Nhc im ca video s ______________________________ 11
2.3.4 u im ca video s _________________________________ 11
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2.3.5 Cc phng php xl trn video s ____________________ 12
2.3.5.1 Pht hin chuyn ng ______________________________ 12
2.3.5.2 c lng chuyn ng _____________________________ 19
CHNG 3____________________________________________ 25
THEO VT V PHN LOII TNG 25
3.1 Bi ton theo vt v phn loi i tng_______________ 26
3.2 M hnh xl bi ton________________________________ 27
3.3 Tin xl____________________________________________ 28
3.4 Pht hin chuyn ng _______________________________ 28
3.5 Theo vt i tng ___________________________________ 37
3.5.1 Don v tr ca i tng trong tng lai ______________ 38
3.5.2 So khp i tng____________________________________ 38 3.5.3 Theo vt i tng ___________________________________ 41
3.5.4 Cp nht i tng___________________________________ 45
3.6 Phn loi i tng __________________________________ 45
CHNG 4____________________________________________ 48
CIT CHNG TRNH____________________ 48
4.1 Mi trng ci t ___________________________________ 49
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4.2 Cu trc chng trnh _______________________________ 49
4.2.1 Cu trc dliu _____________________________________ 49
4.2.2 Cu trc chng trnh ________________________________ 51
CHNG 5____________________________________________ 52
KT QUV HNG PHT TRIN_______ 52
5.1 Kt qut c ____________________________________ 53
5.1.1 Dliu thnghim___________________________________ 53
5.1.2 Kt qut c ____________________________________ 53
5.2 Hng pht trin ____________________________________ 54
TI LIU THAM KHO _________________________ 55
PHLC 1____________________________________________ 56
MT VI HNHNH VKT QUT
C___________________________________________________ 56
1. Mt vi mt n chuyn ng____________________________ 56
2. Kt qu theo vt i tng _____________________________ 63 3. Kt qu theo vt i tng l ngi _____________________ 66
PHLC 2____________________________________________ 69
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VI NT VTHVIN INTEL OPENCV69
1. OpenCV l g? _________________________________________ 69
2. Cc chc nng ca thvin OpenCV ___________________ 69
2.1 Cc kiu dliu cbn _______________________________ 69
2.2 Cc hm xl trong OpenCV __________________________ 71
2.2.1 Cc hm x l cc kiu d liu cbn _____________________ 71
2.2.2 Cc hm v x lnh __________________________________ 72
2.2.3
Cc hm v phn tch vn ng v theo vt i tng _________ 73
2.2.4 Cc hm v nhn dng i tng _________________________ 73
2.2.5 Cc hm v giao din v thu nhn video ___________________ 73
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1
CHNG 1
MU
1.1 Tng quan
Hin nay phn ln lng thng tin con ngi thu vo l di dng hnh
nh. Thng tin di dng hnh nh l thng tin trc quan nn con ngi d dng
tip nhn n. Vi s ra i ca nhiu my mc k thut hin i nh l my nh
s, my quay s, cc my thu hnh, my vi tnh ... th lng thng tin con ngi
thu c ngy cng nhiu. Con ngi khng ch mun tip thu thng tin mt
cch thng m phi bit x l n, lm cho n hu ch hn. Do con ngi
tin hnh nghin cu cc phng php x l trn thng tin trc quan ny chng ta c th tip nhn ti a lng thng tin trc quan ny. Vic x l nh s
ra i vo nhng nm 1960 vi nhiu hng khc nhau nh l nn nh, nhn
dng ..., trong khi vic x l video ch xut hin vo cc thp k gn y cng
vi s ra i ca nhiu trang thit b k thut mi v hin i. Ngy nay trn th
gii vic nghin cu vnh s v video s pht trin rng ri. Cc trng i
hc u c mt ngnh ring nghin cu vn ny gi l ngnh th gic mytnh( computer vision ). Tuy vy vn ny vn cn mi Vit Nam v thiu
cc thit b h trv ti liu, v y l mt hng pht trin mnhiu ha hn
v cng nhiu thch thc. Hin nay Vit Nam cc h thng gim st Vit
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2
Nam cha pht trin lm v ch yu vn da vo con ngi. Tuy nhin trong vi
nm na khi kinh t v khoa hc k thut pht trin th cc h thng gim st ny
cng s pht trin theo. Vic nghin cu v x l video strong khoa c tin
hnh cch y mt nm vi cc ti v gim st giao thng v theo vt i
tng bng li... Vi mong mun tham gia vo hng nghin cu cn mi ny
v gip cc h thng gim st t hiu qu cao hn v gim c chi ph con
ngi chng ti thc hin ti nghin cucc kthut xl trn video s
ng dng vo theo vt v phn loi i tng.
1.2 Yu cu bi ton
Bi ton theo vt v phn loi i tng c chia thnh hai phn.
y chng ti tp trung vo nghin cu phn mt l phn theo vt i tng.
V theo vt i tng ta cn phi thc hin cc phn sau:
Rt trch i tng chuyn ng. Trong phn ny ta phi tch cc
i tng chuyn ng ra khi khung cnh.
Theo vt i tng. Vi tng i tng ta phi lu li c quo
ca chng khi chng vo vng quan st ca taV phn loi i tng, chng ta phi phn bit c cc loi i tng
trong khung cnh quan st ca chng ta. y l phn loi i tng l ngi i
b v cc i tng khc nh l xe...
1.3 B cc lun vn
Da vo cc yu cu trn chng ti chia lun vn thnh 5 chng
Chng 1: MuChng 2: Tng quan v video v cc kthut xl video s: nhm gip
chng ta hiu r hn v video s v cc kthut cbn nht trong x l video s.
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3
Chng 3: ng dng vo bi ton theo vt v phn loi i tng:
trong phn ny ta s p dng cc kkin thc nghin cu c vo gii mt
bi ton trong x l video d l theo vt i tng.
Chng 4: Ci t thnghim
Chng 5: Cc kt qut c v hng pht trin: chng ny trnh
by cc kt qut c trong vic gii quyt bi ton trn v hng pht trin
trong tng lai.
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4
CHNG 2
TNG QUAN V VIDEO V CC K
THUT XL VIDEO CBN
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5
2.1 Khi nim v video
Video hay cn gi l chui nh( image sequence ) tng trng cho
thng tin hnh nh. l mt chui cc hnh nh truyn lin tc theo thi
gian
S = f(x,y,t)
trong :
x,y R: l ta ca im nh (thng tin v khng
gian)
t R: thng tin v thi gian
Da trn cng thc trn ta thy nh tnh l mt trng hp c bit ca
Video. Khi n l mt chui cc nh khng thay i theo thi gian.
f(x,y,t1) = f(x,y,t2); i,j R, x,y R
Video thng c thu, lu tr, v chuyn i dng tun t (analog)
nn chng ta s bt u t video tun t.
2.2 Khi nim v video tun t
2.2.1 Tn hiu video tun t
Tn hiu video tun tc xem nh l tn hiu in 1 chiu theo thi
gian f(t) v c ly mu theo chiu dc.
Vic ly mu theo chu k ny c gi l qut( scanning ). Cc
phng php qut thng c s dng nht l qut lin tc (progressive
scanning) v qut xen k (interlace scanning)
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6
Qut lin tc(progressive scanning)
H1: Qut lin tc. Cc dng qut bt u t A n B, tip tc n C v c
th cho n D ri quay trli D
o Mi nh hay cn c gi l frame l d liu c ly mu
theo thi gian.
o Mi nh ny c qut lin tc tng dng ngang v t trnxung di vi tc l t giy.
o Phng php qut ny thng c dng trong cng nghip
my tnh vi tc t = 1/72 giy.
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Qut xen k
H2: Qut xen k. Dng qut bt u t A n B, chuyn qua C v tip tc cho
n khi ti D s trv E v tip tc qut n F
V mt ngi pht hin ra hnh nh chp khi tn s qut di
50Hz nn tn s qut ca my bao gicng phi ln hn 50Hz. Tuy nhin
khi p dng trong cc nghnh cng nghip khc nh l nghnh truyn thng
th gp kh khn v vn bng thng do kch thc qu ln. T xut
hin phng php qut xen k. Phng php ny chia dng qut thnh dng
chn v dng l ( gi l field ) v qut cc dng chn trong khong t richuyn qua qut cc dng l. V th tn s qut s gim i mt na.
Mt vi thng s quan trng ca tn hiu video l :
o phn gii theo chiu dc ( vertical resolution ): thng s
ny c lin quan n s dng qut trn 1 frame.
o T l co ( aspect ratio ): t l gia chiu rng v chiu cao ca
frame.
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2.2.2 Cc chun video tng t
Component Analog Video: chun video ny s dng cc thnh phn
mu RGB hoc l YCrCb( YIQ hoc l YUV )
Composite Video:
o NTSC ( National Television Standards Committee ): xut
hin vo nm 1952, hin ti c s dng Bc M v Nht.
C 262.5 dng trn 1 field hay l 525 dng trn 1 frame, 60
field trn 1 giy v c t l co l 4:3
o PAL ( Phase Alternating Line ) v SECAM ( SEquential
Color And Memory ): c pht trin vo nhng nm 1960
v ngy nay thng c s dng Chu u. Vit Nam
cng dng chun ny. Cc thng s k thut: 625 line trn 1
frame, 50 field trn 1 giy.
2.2.3 Cc thit b video tng t
Cc thit b video tng t c thc chia lm 3 loi. Loi dnh cho
truyn thng. Loi c cht lng chuyn nghip. Loi dnh cho ngi tiudng.
Video c quay bi my quay thng thng v c lu trong bng
hoc c quay bi cc my quay dng trong phim trng v to thnh
phim ( 24 frame/giy ).
Hu ht tn hiu video tng tc lu da trn k thut t ngoi tr
a laser l dng k thut quang.
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2.3 Khi nim v video s
2.3.1 Tn hiu Video s
Tn hiu video sc lu tr di dng s. Do chng c ly
mu v lng t ha. Tn hiu video s l mt thng tin 3 chiu gm 2 chiu
khng gian v 1 chiu thi gian hay cn c gi l chui nh s vi mi nh
s l mt nh c ly mu v lng t ha.
chiu thi gian
chiu dc
chiu ngang
H3: chui nh
2.3.2 Cc chun video s
Vic trao i gia cc ng dng v cc sn phm video s a ra
cc chun video s. Cc chun ny bao gm :
Chun nn: dng trao i thng tin trong dng nn ca
video
Chun cc phn gii hin th: c dng trong cng
nghip my tnh.
Chun studio s: c dng trong ngnh cng nghip ti vi
Chun vgiao tip mng c dng trong cng nghip
truyn thng
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H4: cc chun v studio s
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H5: Cc chun vnh v video s nn2.3.3 Nhc im ca video s
Nhc im ca video s l n i hi khi lng lu tr ln v bng
thng rng truyn ti. Chng ta hy th lm mt php tnh. Vi tn hiu TV
cht lng tt ta cn 1440 im nh trn mt dng, 1050 dng cho mt frame
sng, 720 im trn mt dng v 525 dng trn mt frame sc mu. Bi v mi
giy c 30 frame v 8 bit/ pixel nn kt qu cui cng l xp x545 Mps. y l
mt yu cu qu ln. Do hin nay ngi ta ang nghin cu cc phng php
nn video gim kch thc khi truyn ti.
2.3.4 u im ca video s
Tuy c nhc im v yu cu b nhln nhng video s li c nhiu u
im quan trng. Video tun t cung cp cho chng ta mt s rt gii hn cc
hot ng tng tc nh l : chn knh, chnh ti lui hay l quay chm trn bng
video. Ngoi ra hin th tn hiu theo chun ny v d NTSC trn mt h my
dng chun khc v d PAL ta cn c mt b chuyn i tn hiu t tin. Vi tn
hiu s ta khng cn phi chuyn i cc tn hiu ny. Ngoi ra ta cn c th
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chnh sa, to cc hiu ng p trn tn hiu video s. Video s khng ch c vai
tr gii tr m n cn cung cp cho chng ta nhiu thng tin quan trng trong
nhiu lnh vc nh l cc nh gim st qun s, iu khin giao thng, v rt
trch thng tin t cc d liu nh v video.
2.3.5 Cc phng php xl trn video s
Video s c nhiu thng tin trc quan hn l nh s. L do chnh l do
video s c cha thng tin v chuyn ng trong khi nh s ch l nh chp mt
cnh tnh. Cc chui nh ng lun hm cha cc thng tin v chuyn ng, cc
chuyn ng ny l mt tn hiu nhy cm i vi th gic con ngi. Con ngi
c th d dng nhn bit c cc i tng ngay khi chng chuyn ng thm
ch chng rt kh thy khi ng yn. V th cc phng php x l video s cng
khc so vi cc phng php x lnh s. Vn ng l thng tin quan trng
trong x l video s bi v vn ng mang rt nhiu thng tin v mi quan h
khng gian v thi gian gia cc i tng trong nh. Cc phng php cbn
trong x l video s l pht hin chuyn ng v c lng chuyn ng. Pht
hin chuyn ng thng c p dng trong cc h quan st( pht hin itng di chuyn hoc l ng yn ), cn c lng chuyn ng thng c p
dng trong nn video s. Ngoi ra cn c cc phng php x l khc c p
dng vo mc tin x l nh l lc nhiu... cc phng php ny p dng trn
tng frame ging nh trong x lnh s.
2.3.5.1 Pht hin chuyn ng
a. Snt v chuyn ng
Chuyn ng theo cc khi nim trong vt l l s thay i v tr
gia vt ny v vt kia. Tc l khi xt ti s chuyn ng th ta phi xt l n
chuyn ng so vi ci g. Khi xt ti chuyn ng ta thng t n vo mt h
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quy chiu qun tnh. Mt vt c thng yn trn h quy chiu ny nhng li
chuyn ng khi xt n vi h quy chiu khc. V d khi ta ng yn th c th
coi l ta ng yn so vi h quy chiu gn vi tri t, nhng khi a vo h
quy chiu gn vi mt tri th ta li chuyn ng. iu ny c ngha rt quan
trng khi ng dng vo camera ng. Chuyn ng trong thc t l chuyn
ng 3D nhng khi con ngi tip nhn th n trthnh chuyn ng 2D. Ni
chung hnh nh m mt ngi nhn c u l 2D ht. V php ton chuyn i
nh 3D thnh nh 2D m mt con ngi cm nhn c l php chiu phi cnh.
H6 Php chiu phi cnh ca mton thng
Chuyn ng trong th gii thc 3D qua php chiu phi cnh s
bin thnh chuyn ng trong mt phng 2D. Tuy nhin con ngi nhn bit
chuyn ng qua s thay i sng ca im nh. Do c nhng chuyn
ng m con ngi khng c cm nhn c nh l chuyn ng ca qu cu
ng mu. T ta c phng php pht hin chuyn ng u tin l so
snh skhc bit theo thi gian.
z
x
y
mt phng chiu
P1
P2O
Tm chiu
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b. Phng php so snh skhc bit
Chng ta xc nh sai khc Dk,k-1 gia frame th k v th k-1 nh
sau :
Dk,,k-1 = Fk Fk-1
trong : Fk l frame ti thi im k
Nu camera tnh, s thay i nh sng rt nh v nhiu khng ng
k th mt im c coi l chuyn ng nu khc bit ca n ln hn 0 v
ngc li sng yn.
Tuy nhin trong thc t cc iu kin trn kh c th xy ra. Do
loi b cc im m chng ta pht hin sai do nhiu gy ra, ta c th dng
mt ngng T thch hp.
Mk,k-1( x, y ) = >
laiNguoc
neu
0
T|)yx,1(-k,Dk,|1
Vi Mk,k+1c gi l mt n chuyn ng thi im k, nu bng
1 th im c coi l chuyn ng v bng 0 th im l ng yn. T
l ngng thch hp c th l mt gi tr c thc xc nh trong qu trnhthc nghim hoc da trn cc thut ton. c gi c th tham kho mt
thut ton xc nh ngng ph lc B ca [1].
frame th k frame th k-1
mt n chuyn ng
H7: Kt qu ca phng php so snh skhc bit
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u im ca phng php ny l n gin v d ci t do tc
s nhanh. Tuy nhin nhc im ca n l nhng vng tht s chuyn ng
nhng do ng mu nn sc hiu l ng yn v nhng vng tht sng
yn th li cho l chuyn ng.
khc phc nhc im trn ta c mt thut ton so snh khc
bit ci tin:
Bc 1: To mt cu trc Pyramid Gaussian trong mi frame
c c trng bi nhiu phn gii khc nhau. Bt u x lmc phn gii
thp nht.
Bc 2: Vi mi im mc phn gii hin ti, tnh ton khc
bit chun ha:
FDNk,r( x, y ) =
+
yx
yx
cryxf
ryxfryxfkyxf
,
2
,
,,(
,,(),,(),,(
trong :
N: l cc im trong ln cn ca x
),,( ryxf : l gradient ca mt nh ti im (x, y)
),,( kyxf : l frame thi im k
c: l hng s
Nu khc bit chun ha ny cao hn khc bit phn gii
trc th thay th khc bit trc bng khc bit mc hin ti. Nu
khng th vn gi nguyn gi tr trc .
Bc 3 : Lp li bc 2 cho tt c phn gii
Bc 4 : Ly ngng vi s khc bit chun ha mc phn gii
cao nht.
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c. Phng php trnn
Phng php trn cng da trn s so snh gia 2 nh, nhng
khng phi l 2 nh lin tip trong chui nh m l gia cc nh trong chui nh
vi mt nh tham chiu gi l nh nn. nh nn l cnh thu c khi khng c
i tng chuyn ng no ht. Gi B l nh nn thu c, ta c khc bit
gia nh nn v nh th k trong chui nh
Dk= Fk B
Nu nhiu t v khng c s thay i ca nh sng th im c ta
( x, y ) c xem l tnh nu Dk( x, y ) = 0 v ngc li. Tuy nhin trong thc
t lun c nhiu v vy ta phi dng ngng hn ch nhiu
1 Nu Dk( x, y ) > T
Mk( x, y ) =
0 ngc li
Vi Mk l mt n chuyn ng, im ( x, y ) c xem l chuyn
ng khi Mk( x, y ) = 1 v ng yn khi Mk( x, y ) = 0.
Trong thc tnh nn lun lun bin i do s thay i sng dogi, cc m my bay qua v th ta phi lun cp nhp nn li. Gi Bk l nn
thi im k. Ta c nn thi im k + 1 c cp nht nh sau:
*Bk( x, y ) + ( 1 - ) Fk( x, y ) nu Mk( x, y ) = 0
Bk+1( x, y ) =
Bk( x, y ) nu Mk( x, y ) = 1
Vi l mt hng sc gi l t l hc phn nh mc cp nht nn
nhanh hay chm.
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nh nn nh thk
bng ma mt n chuyn ng
H8 : bng ma trong phng php tr nn
Phng php tr nn cho kt qu tt hn phng php so snh skhc bit khi x l cc i tng ng mu, tuy nhin n c mt nhc im khi
nh nn cha mt i tng ng yn, sau i tng ny chuyn ng th
phng php trn s pht hin ra 2 i tng chuyn ng ch khng phi l 1.
i tng b pht hin sai ny c gi l bng ma. gii quyt vn trn
ngi ta phi s dng nh nn khng c i tng chuyn ng no trong ht
hoc c th da vo cc thut ton to nh nn.Ngoi ra cn mt hng tip cn mi trong phng php tr nn
l da trn m hnh xc sut thng k. tng chnh y l a ra mt m
hnh thng k cho nn. Thng c hai m hnh thng k chnh l n phng
thc ( unimodal ) v a phng thc ( multimodal ). Trong m hnh n phng
thc mi im c m hnh vi phn phi xc sut n thng l phn phi
Gaussian ( x, y, k, k ), trong k l gi tr trung bnh v k l ma trn hip
phng sai ca phn phi frame t. Nhng im m mu quan st c gn
( hay cn gi l khp ) vi phn phi nn th c phn thnh im nn hay l
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im ng yn v ngc li l im chuyn ng. V nn lun lun thay i nn
ta phi cp nhp li m hnh nn nh sau:
t+1 = ( 1 - )*t + *dt
t+1 = ( 1 - )*t + *dt*dtT
Vi l hng s ch mc iu chnh m hnh nn nhanh hay
chm.
i vi m hnh nn a phng thc ( multimodal ), chng ta cn
n nhiu phn phi xc sut c lp vi nhau m hnh mi im nh. Mi
phn phi c gn vi mt trng sc trng cho mc u tin ca chng.
Ch mt vi phn phi u tin vi trng s ln mi c dng m hnh cho
nn. Mt phn phi mi ca s quan st sc cp nhp vo m hnh nn nu
nh n khng khp bt c phn phi no c trng cho m hnh nn, ngc li
n trng s ca cc phn phi sc cp nhp li nh sau:
( 1 - ) wt+1,i + i = m
wt+1,i =
( 1 - )wt+1,i i m
Vi m l ch s ca phn phi khp vi phn phi mi ca s quan st,
c gi l t l hc trng s
d. Phng php da trn Optical Flow
y l mt phng php phc tp v i hi cc phn cng t tin
chy real-time nn chng ta ch ni khi qut v n.
Cc chuyn ng ca i tng trong 3D c gy ra chuyn ng2D trong mt phng nh c gi l Optical Flow. Optical Flow tng ng vi
s cm nhn chuyn ng ca mt ngi.
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H9: Hnh nh cc xe v Optical Flow ca chng
Optical Flow c ng dng nhiu trong nhn dng hot ng. Khi mi
vn ng c m hnh ha bng m hnh chuyn ng l t hp tuyn tnh ca
cc vn ng cbn. Cc vn ng cbn ny l cc Optical Flow c hc
trong qu trnh hun luyn.
2.3.5.2 c lng chuyn ng
Nh ni, thng tin v chuyn ng rt quan trng trong x l v
nn video. Nn nh l cc phng php nhm lm gim s bit cn thit c
trng video. Trong khi cc k thut x l video l cc phng php bin i
trn chui nh nh l nng cao cht lng chui nh. Vic phn lp nh trn c quan trng trong vic a ra ch ca vic c lng chuyn ng tc l lin
quan n vic chn m hnh x l sao cho ph hp. V d nh trong nn video
th cc tham s chuyn ng c c lng u dn n mt vic l t c
t l nn cao nht. Do cc chuyn ng c tnh ton khng cn phi ging
vi cc chuyn ng tht ca im nh min l ta t c mt t l bit ti thiu.
Tuy nhin, trong x l video th cc chuyn ng tht ca cc im nh li l
iu ta quan tm. pht trin mt thut ton c lng chuyn ng th theo
Janusz Konrad ta cn c 3 yu t sau: M hnh, tiu chun v chin thut tm
kim.
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a. Cc m hnh chuyn ng
C 2 m hnh cn thit trong c lng chuyn ng: m
hnh chuyn ng ( l cch c trng vn ng trong mt chui nh ) v m
hnh quan st ( l m hnh m c s lin quan ca cc tham s chuyn ng vi
mt nh ). Trong m hnh chuyn ng ta li c m hnh chuyn ng theo
khng gian v theo thi gian.
M hnh chuyn ng theo khng gian
Hu ht cc chuyn ng u l s kt hp ca php chiu
cc chuyn ng ca i tng trong cnh 3D v chuyn ng ca camera.
Trong khi chuyn ng ca camera nh hng n chuyn ng ca ton b hay
hu ht cc im nh th chuyn ng ca i tng chnh hng ti cc im
tng ng vi hnh chiu ca i tng. Trong lun vn ny chng ti nghin
cu trn camera tnh v th chng ti s khng nghin cu chuyn ng ca
camera. Ni chung chuyn ng ph thuc rt nhiu yu t nh l cc php
chiu, m hnh ca i tng 3D... Ta xt trng hp ng gin nht l chuynng tnh tin ca i tng 3D. Khi vector vn tc tc thi ca im x trong
mt phng nh s l
v(x) =
2
1
b
b
Trong cc tham s b = (b1, b2)T = (v1,v2)
T ph thuc vo
gc quay ca camera v cc tham s trong chuyn ng tnh tin 3D. M hnh
tnh tin 2D ny ng dng rt nhiu trong thc tc bit l trong nn video v
n a ra mt xp x gn ng vi hu ht nh trong t nhin. Khi chuyn ng
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ca vt th 3D c thm cc chuyn ng affine th ta c m hnh chuyn ng
affine vi 6 tham s
v(x) =
2
1
b
b
+ xbbbb
65
43
R rng m hnh chuyn ng tnh tin l trng hp c bit
ca m hnh chuyn ng affine. Hu ht cc m hnh chuyn ng phc tp u
a ra rt tt nhng ty vo tng ng dng. Khng phi lc no chng cng ci
thin c s chnh xc trong c lng chuyn ng. Ni chung, s tham s
cng nhiu th vic m t chuyn ng cng chnh xc hn.
M hnh chuyn ng theo thi gianQuo ca mt im nh ring bit c v trong khng
gian (x, y, t) ca mt chui nh c thc xem nh l ty bi v chng ph
thuc vo vn ng ca i tng. Trong trng hp n gin nht, quo
ca chng l tuyn tnh. Gi s chng ta c vn tc vt(x) gia thi gian t = tk-1 v
thi gian ( > t ) l mt hng s, mt quo tuyn tnh c thc trnh by
nh sau:x() = x(t) + vt(x)( - t ) = x(t) + dt,(x)
Trong dt,(x) = vt(x)( - t ) l mt vector dch chuyn c
o theo hng thi gian. Cho nn i vi chuyn ng tuyn tnh, nhim v ca
chng ta l tm 2 thnh phn ca vector vn tc v hay vector dch chuyn d ca
mi im x.
Mt s mrng trong t nhin ca m hnh quo tuyn
tnh l m hnh ng cong bc 2. Khi ta c thm mt i lng mi l gia
tc ca mt im.
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x() = x(t) + vt(x)( - t ) +2
1 at(x)( - t )2
Trong gia tc at l o hm ca vn tc vt. Cc m hnh
trn i hi 2 ( i vi tuyn tnh ) hoc 4 ( i vi bc 2 ) ti mi im x.
gim gnh nng tnh ton, m hnh tham s theo khng gian c th kt hp vi
cc m hnh trn.
Vng htr
Tp im x m trong cc m hnh khng gian v thi gian
p dng c gi l vng h tr. S la chn ca mt m hnh v vng h trl
mt trong cc yu t quyt nh n tnh chnh xc ca c lng cc tham schuyn ng. Thng thng khi cho mt m hnh chuyn ng, vng h tr
cng nh th vic xp x cng tt hn, bi v vi vng h trln th chuyn ng
c th phc tp v do ta phi c m hnh chuyn ng phc tp hn. Thng
thng vng h tr() c th thuc 1 trong 4 loi sau:
1. l ton bnh: Mt m hnh chuyn ng
c p dng cho ton bnh. M hnh ny
thch hp cho vic c lng chuyn ng
ca camera.
2. l mt im nh: M hnh ny p dng cho
mt im nh. Trong trng hp ny ta
thng s dng m hnh khng gian t nh tin
kt hp vi m hnh tuyn tnh hoc bc 2.
3. l mt khi im hnh ch nht: Cc m
hnh vn ng sc p dng trn mt khi
im nh hnh ch nht. Trong trng hp
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n gin nht, cc khi ny khng ph ln
nhau v hp ca chng s bao ph ton b
nh. Trong trng hp ny m hnh chuyn
ng khng gian tnh tin kt hp vi m
hnh chuyn ng thi gian tuyn tnh c
xem l m hnh hiu qu nht v c p
dng trong cc chun nn video nh l
MPEG-1, MPEG-2...
4. l mt vng bt k: Cc m hnh vn ng
s p dng trn cc im thuc vo . y
vng s tng ng vi cc i tng. K
thut ny c p dng trong chun nn
MPEG-4.
M hnh quan st
Khi chuyn ng c c lng ( v c quan st bng
mt ngi ) da trn s thay i ca cng sng, mu hoc c hai, cc miquan h ginh gia cc tham s chuyn ng v mt nh ng mt vai tr
rt quan trng. Gi thuyt hp l v thng thy l cng sng vn khng
i theo quo chuyn ng (i tng khng thay i sng khi di chuyn).
i vi cc nh c ly mu theo thi gian iu ny c ngha l
Ik(x(tk)) = Ik-1(x(tk-1))
S dng cng thc trong m hnh chuyn ng theo thi gian vi t = tk-1, = tkv gi thuyt rng chng ta ly mu nh theo khng gian, ta c:
Ik(n) = Ik-1(n-d).
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Tuy nhin chng ta khng th s dng cng thc trn tm d trong thc t v
nhiu q. Cng thc trn c vit li nh sau:
Ik(n) = Ik-1(n-d) + q(n)
Do d c tnh bng cch ti thiu hm li gia Ik(n) v Ik-1(n-d).
b. Tiu chun c lng
C rt nhiu tiu chun c lng ty thuc vo yu cu ca bi
ton. Trong nn nh th li don ca bc lng l rt quan trng. Cn
trong php ni suy b p chuyn ng th li ni suy cc i li l mi quan
tm. Ngoi ra ty thuc vo kh nng x l m vic c lng chuyn ng thc
hin trn . Ni chung cc tiu chun c lng u c mc ch chung l cc
tiu ha hm li:
k(n) = Ik(n) k(n) n
Trong k(n) = Ik-1(n d(n) ) c gi l c lng b p chuyn ng ca
Ik(n).
c. Chin thut tm kim
Mt khi m hnh chuyn ng c xc nh v kt hp vimt tiu chun c lng, bc cui cng l pht trin mt chin lc hiu qu
c v tnh phc tp v cht lng li gii c lng cc tham s chuyn ng.
i vi mt s t cc tham s vn ng yu cu khng gian trng thi nh th
chin lc thng dng nht khi ti thiu hm li l so khp. Trong hng ny,
cc c lng b p chuyn ng Ik-1( n d(n) ) cho cc ng vin chuyn ng
d c so snh vi nh gc Ik(n) trong vng h trca m hnh vn ng. ng
vin no khp nht i vi tiu chun a sc chn c lng. Ngoi
ra ta cn c nhiu phng php c lng na m chng ta s khng ni ti: k
thut da trn gradient, thut ton tin cy cao nht c chn u tin...
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CHNG 3
THEO VT V PHN LOI I TNG
Trong chng ny chng ta s p dng cc thut ton x l video
c nghin cu phn trn vo bi ton theo vt v phn loi
i tng.
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3.1 Bi ton theo vt v phn loi i tng
Vic theo vt v phn loi i tng ang c nghin cu trong nhngnm gn y. Trong ng dng theo vt v phn loi i tng chng ta phi
phn loi c i tng v ch theo vt i tng chng ta quan tm. Theo vt
i tng l chng ta lu li c ng i ca cc i tng ang vo vng
quan st ca camera. Ta c thng dng vo cc h quan st gim c chi
ph lu tr cc d liu thc t cc camera quan st. Hnh nh t camera
truyn vo my tnh, sau my tnh x l. Nu trong c cc i tng m
chng ta quan tm th my tnh s lu on phim ny li sau ny chng ta x
l. Nh cp trong chng I, kch thc ca d liu video l rt ln v th
vic lu tr c chn lc ny s gim c chi ph cho vic lu tr rt nhiu.
Trong bi ton ny chng ti s theo vt nhng i tng no l ngi. Thng
thng khi theo vt i tng ngi ta thng dng 4 phng php sau:
Phng php 1: Theo vt i tng da theo cc c im ring ca i
tng. Phng php ny cho kt qu kh tt v c th p dng c i vi
camera ng nhng i hi chng ta phi c tri thc vi tng cn theo di,
tc l chng ta phi c c cc danh sch cc c im ring ca i tng.
Phng php 2: Phng php ny s dng phn b mu ca i tng
theo vt. Tiu biu ca phng php ny l MeanShift v CamShift. Phng
php ny thng c ng dng trong tracking ngi da vo s phn b mu
da.Phng php 3: Phng php ny xem cc i tng chuyn ng nh l
cc vng lin thng v theo vt cc i tng bng cch so khp cc vng lin
thng tm vng khp nht.
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Phng php 4: Phng php ny theo vt i tng da vo ng bin
ca chng. Phng php ny tng t vi phng php 3 v chng ta theo vt
bng cch cp nhp ng bin ca i tng.
3.2 M hnh xl bi ton
Trong bi ton trn, d liu m chng ti x l s l on video c quay
t camera v ghi li vi chun AVI. M hnh x l bi ton c thc trnh by
nh sau:
D liu thu c t camera c t cnh sc truyn vo my tnh.
D liu ny qua mt b tin x l lc nhiu.... Sau n s qua b pht hin
chuyn ng. B pht hin chuyn ng s pht hin im no l im tnh (
im nn ) v im no l chuyn ng. T ta dng php phn tch connected
component rt trch cc i tng chuyn ng v truyn danh sch cc i
tng rt trch c qua bc lng chuyn ng. Bc lng chuyn ng
sc lng chuyn ng ca cc i tng c trong danh sch i tng v so
khp vi cc i tng mi . Ty vo cc trng hp m ta s cp nhp li v tr
ca i tng, loi bi tng ra khi danh sch i tng hay l thm mt itng vo danh sch i tng. Sau cc i tng ny sc chuyn qua b
phn loi chn lc cc i tng l ngi v theo vt Vic theo vt l lu li
v tr ca cc i tng ang trong vng quan st v cui cng ta sc qu
o chuyn ng ca i tng. Trong phn ny biu din vic theo vt i
tng chng ti s v khung bao quanh i tng. Sau y l s tm tc qu
trnh theo vt v phn loi i tng ca chng ti.
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H10: S x l bi ton
3.3 Tin xl
D liu t my camera lu vo my tnh di dng file AVI. Trong chun
file ny h mu m n dng l RGB vi phn b mu l BGR. Sau khi kho st
cc h mu RGB, HSV, YUV chng ti chn thnh phn Y ca h mu YUV.
Do cc frame nh t file AVI phi c chuyn sang h mu YUV v ly
thnh phn Y x l. Sau frame nh ny s qua b lc lc nhiu. B lc
thng dng l Median v Gaussian. Vi cc b lc ny chng ta s gim bt
cc chuyn ng khng cn thit nh l cc chuyn ng ca l cy...
3.4 Pht hin chuyn ng b pht hin chuyn ng, u vo l nh qua b tin x l, v v th
chng ta ch s dng thnh phn Y x l. y l bc cbn nhng cng l
bc quan trng nht. Nu ta x l khng tt bc ny th kt qucc bc sau
s khng cao. trong phn ny d liu vo l cc frame ca on video thu
c t camera tnh qua giai on tin x l, v chng ta s tch cc i tng
chuyn ng. Cc i tng chuyn ng c hnh dng, mu sc khc nhaunhng c cng chung c im l chuyn ng. li dng tnh cht trng lp
thng tin gia cc frame nn phng php ch yu trong phn ny l trnh.
Nh trnh by trong chng I, hai phng php c s dng ch yu trong
Tin x l Pht hin chuyn ngcapture
Theo vt i tngPhn loi itng
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pht hin chuyn ng l so snh s khc bit v tr nn. Nhc im ca
phng php tr nn l nhy cm vi nn v nhc im ca phng php so
snh s khc bit l khng pht hin c chuyn ng ca phn bn trong cc
i tng ng mu. [3] ra mt phng php rt hay, l kt hp gia 2
phng php trn. Trong khi phng php so snh s khc bit ca 3 frame lin
tip c thc hin xc nh cc vng chuyn ng hp l th phng php
tr nn c thc hin tip sau s lp y cc phn cn li m phng php
so snh s khc bit khng pht hin ra. Xem xt chui nh c truyn vo
t camera tnh. Gi In(x) t trng cng ti v tr x v thi gian t = n.
Nguyn l trong so snh 3 frame khc bit l : Mt im c coi l chuyn
ng nu cng ca n thay i ng k gia frame hin ti v frame trc
n , gia frame hin ti v frame trc na. Tc l im x l chuyn ng
nu:
( | In(x) In-1(x) | > Tn(x) ) v ( | In(x) In-2(x) | > Tn(x) ).
Trong Tn(x) l ngng m t s thay i cng ng kv tr x. Vn
chnh ca phng php so snh s khc bit l nhng im nm bn trong itng ng mu th khng nm trong tp cc im chuyn ng. Tuy nhin, sau
khi phn cc im chuyn ng thnh cc vng chuyn ng th cc im nm
bn trong c thc lp y bng cch p dng phng php tr nn ly ra tt
c cc im chuyn ng nm bn trong hp R bao quang vng chuyn ng.
Gi Bn(x) c trng cho cng nn hin ti im x. Vng bn c thc
lp y bng cc im nm trong R m c cng khc bit ng k so vi
nn.
bn = { x: | In(x) Bn(x) | > Tn(x), x R }
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Tuy nhin phng php ny c mt nhc im l phn kt qu cui cng
bao gicng ph thuc vo lng thng tin m phng php tr nn c c.
Khi p dng phng php ny vo theo vt i tng l ngi s gp mt kh
khn l phng php tr nn s cho ra kt qu khng tt thng l c s ngn
cch gia u ngi v thn ngi v v th s cho ra hai i tng ch khng
phi l mt i tng. Mc khc khi chng ti p dng phng php trn th gp
mt li nh m chng ti nghl do b th vin OpenCV gy ra. Khi s dng b
th vin OpenCV captrure on video v ly tng frame nh ra, th c sau 5
frame chng ta li c mt frame trng vi frame trc. Do phng php so
snh 3 frame lin tip s cho kt qu sai. Cui cng chng ti chn phng
php tr nn. Phng php ny nhy cm vi nn v cho kt qu khng tt lm
v th chng ti s dng cc b lc tuyn tnh v b lc morphology kh
nhiu v lp y khong trng gia u ngi v thn ngi.
Gi B(x) l nh nn, I(x) l nh hin ti, D(x) l khc bit gia nh nn
v nh hin ti
D(x) = | B(x) I(x) |Khi ta c mt n chuyn ng l
0 nu D(x) < T(x)
M(x) =
1 ngc li
Trong T(x) l ma trn ngng ch sai khc ng k gia nh hin ti
v nh nn. C hai nh nn Bn v ngng Tnu l thuc tnh thng k
ca cng im nh c quan st t chui nh Ik (k < n ). B0(x) l nh
u tin trong chui nh, B0(x) = I0(x) v T0(x) c cho mt gi tr mt
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nh khc khng. B(x) v T(x) c cp nhp theo thi gian theo cng
thc sau.
Bn(x) + ( 1 - )In(x) nu x ng yn
Bn+1(x) =
Bn(x) nu x ng
Tn(x) + ( 1 - )(5*|In(x) Bn(x)|) nu x ng yn
Tn+1(x) =
Tn(x) nu x ng
Trong l gi tr ch mc p ng ca nn i vi s thay i ca
mi trng. c th l 1 hng sc chn theo kinh nghim hoc c thc
cp nht nh sau: Gi Q l tp hp cc im c chn ngu nhin v khng
thuc vo phn chuyn ng frame trc. Chng ta tnh ton mt t s thay i
sng (t) tng ng vi cc im trong Q.
(t)=
Qq qB
qI
)(
)(1
Vi I(q) l cng ca im q ti frame hin ti, v B(q) l cng
ca im q ti nh nn.
Trong trng hp t s thay i sng ny ln hn ngng cho trc th
chng ta siu chnh li tham s cp nhp nn nh sau:
= 0.01 +c
t)( nu (t) >
Vi c l mt hng s cho trc, c c xc nh bng thc nghim.
Sau y l s ton b qu trnh trong b pht hin chuyn ng.
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H11 : S x l trong b pht hin chuyn ng
By gichng ta si chi tit mt s thut gii trong s trn. l
thut gii tr nn, thut gii cp nhp nn, thut gii cp nhp ngng v
thut gii rt trch i tng chuyn ng.
a. Thut gii tr nn
input: nh nn B, nh hin ti I v ma trn ngng T
output: nh M l mt n chuyn ng
Ngng
Tr nn
Rt trch i tngchuyn ng
Cp nhtngng
Cpnht nn
frame knh nn
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m := getHeight(M);
n := ge tWid th(M);
for x := 1 to m dofor y := 1 to n do
if | B[x,y] I[x,y] | > T[x,y] then
M[x,y] := 255;
else
M[x,y] := 0;
y chng ti s dng nh xm lm mt n chuyn ng thayv dng nh nh phn do M[x,y] s nhn mt trong hai gi tr l 255 ch
mu trng( im chuyn ng ) v 0 ch mu en ( im ng yn )
b. Thut gii cp nht nn
input: nn B, nh hin ti I v mt n chuyn ng M
output: nn B c cp nht li
m := getHeight(B);
n := getWid th(B);
for x := 1 to m do
for y := 1 to n do
if M[x,y] = 0 then
B[x,y] := *B[x,y] + ( 1 - )*B[x,y];
c. Th tc cp nht ngng
input: ma trn ngng T, nn B, nh hin ti I, mt n chuyn ng M
output: ma trn ngng c cp nht.
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Med ian( M, temp );
Close( temp , M );
L := getConnec tedCom ponent( M ); Thut gii trch ly i tng chuyn ng
Input: L danh sch cc thnh phn lin thng
Output: A danh sch cc i tng chuyn ng
j := 1;
For i:= 1 to getSize(L) do
If getObjec tSize( L[i] ) > c then
Begin
Initia lOb jec t( A[ j], L[i] );
j := j +1;
End
Sau y chng ta xem kt qu thc hin ca gii thut rt trch cc
i tng chuyn ng.
frame hin ti
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Mt n chuyn ng khi dng phng php tr
nn. Vn cn nhiu v c s phn cch nh giaxe my, thn mnh v u
Mt n chuyn ng khi ci tin phng php tr
nn. Cc phn nhiu c lc b v cc phn
xe my, thn mnh v u c lin kt vi
nhau
Khi th nghim phng php pht hin chuyn ng trn chng ti thu
c kt qu sau:
Tng s frame th nghim l 2010
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Thi gian x l l 145 giy
Tc x l trung bnh l 13.6 giy
Cc i tng chuyn ng u c pht hin
3.5 Theo vt i tng
Sau khi cc i tng c pht hin, chng ta s tin hnh theo vt
i tng. Hu ht cc h thng hin nay u theo vt i tng da vo b lc
Kalman. y chng ti cng s dng b lc Kalman nhng c mt s sa i.
Nh bit theo vt i tng c ngha l chng ta phi phn tch v ghi li qu
o ca i tng. c th theo vt tt chng ta phi c lng c chuyn
ng ca i tng. Mi i tng sc c trng bi mt s tham s sau:
1. p = V tr trong ta nh. Ta ca trng tm ca i tng
s chnh l ta ca i tng.
2. p = l khng chc chn ca v tr. Khng bao gichng ta
c thc lng chnh xc c v th khng chc chn ny
chnh l sai s trong c lng.
3.>v = tc ca i tng. y chng ta s dng dch
chuyn thay cho tc v chng ta ang xt l cc im ri rc
ch khng phi l cc im lin tc.
4. >
v = khng chc chn ca vn tc.
5. = hnh ch nht bao quanh i tng.
6. d : l mt s ch tin cy ca i tng. tin cy ny s dng
quyt nh loi b hay theo vt i tng.
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3.5.1 Don v tr ca i tng trong tng lai
Vic c lng v tr ca i tng trong mi frame l rt quan
trng. N gip cho vic tnh ton n gin hn v vic theo vt s chnh xc hn.
V trc lng sc s dng la chn s cc i tng cn phi xem xt
trong qu trnh theo vt. Vic c lng s gim c rt nhiu thi gian v vi
mi i tng chng ta khng cn phi xem xt trn ton bnh m ch xt
trong vng c don m thi. Gi t l thi gian gia 2 frame, theo m hnh
chuyn ng tuyn tnh th ta c
pn+1 = pn + v*t
V khng chc chn c cho l bng khng chc chn ca v tr hin ti
cng vi khng chc chc ca vn tc nhn cho thi gian.
pn+1 = pn + vn*t
Nhng v tr ny sc chn c lng v tr mi ca i tng trong frame
tip theo. Mi i tng trong frame hin ti sc don v tr mi bng
cch cng hnh ch nht bao quanh i tng mt khong l vn*t sau m
rng ra mt khong pn+1. Do d nu c vng chuyn ng mi no thuc vovng don ny th ta s tin hnh so khp.
3.5.2 So khp i tng
Cho mt vng i frame hin ti, chng ta tm vng khp vi
vng ny frame tip theo bng phng php so khp tng quan nh. Hm
tng quan gia vng frame hin ti vi vng ng vin frame tip theo v
cch vng ny mt khong d l:
C(d) =
++
Rx
nn
W
dxxjiW II )()(),( 1
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Trong : In l mt im nh ti frame hin ti, In+1 l mt im nh ti
frame tip theo. W l hm trng s v ||W|| c tnh bng cng thc sau:
= Rx xWW )( y W(x) l hm trng s th hin mc u tin ca im x. Cc i tng
m chng ta quan st c c th di chuyn t xa ti hoc i ra xa. Khi kch
thc ca chng frame tip theo s ln hn hoc nh hn. V th hm trng s
ny phi c tnh lm sao cc im gn tm ca i tng s c u tin
cao hn. V gim chi ph tnh ton th hm trng s ny ch p dng i vi
cc im nh no c xem l chuyn ng, do cc im c xem l ng
yn s c hm trng s bng 0. Nu x l im chuyn ng ta c:
+=
r
xrxW
max
)(1
2
1
2
1)(
Trong r(x) l khong cch bn knh t x ti tm ca vng , v rmax l khong
cch bn knh ln nht trong . gim chi ph tnh ton ta c thc lng
tm ca i tng chnh l tm ca hnh ch nht bao quanh i tng v
khong cch ln nht trong vng bng mt na ng cho ca hnh ch nht
bao quanh i tng. Khi so khp vng i tng c kch thc m*n th chi ph
tnh ton s l O(m2n2). Nu kch thc ca vng i tng ln th chi ph s
tng ln rt ln kh m kim sot c. V th chng ti cnh mt ngng
m chi tnh ton s khng vt qua ngng . y chng ti chn ngng l
25 im nh. Kch thc ca vng nh theo mi chiu s b gim i mt na nu
n ln hn 25 v chng ti sm s ln gim kch thc la chn cc im
khi so khp. V d nh mt vng c kch thc 80*45 th kch thc s gim i
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2 ln theo chiu x v 1ln theo chiu y. Do trong qu trnh so khp, theo
chiu x c 4 im th s chn mt im so khp v c 2 im theo chiu y th
s chn 1 im. Vi cch x l nh trn th phc tp ca thut ton khng bao
giqu O(254). Sau y l thut gii so khp i tng
Input: i tng frame hin ti currentObject, i tng frame tip
theo targetObject, 2 frame nh In v In+1.
Ouput: C(d)
x1 := c urrentOb jec t.ob jec tRec t.x;
y1 := currentOb jec t.ob jec tRec t.y;
x2 := c urrentOb jec t.ob jec tRec t.x +
currentObject.objectRect.width;
y2 := currentOb jec t.ob jec tRec t.y +
currentObject.objectRect.height;
xStep := 1;
yStep := 1;
while( m > 25 )
yStep := yStep + 1;
while( n > 25 )
xStep := xStep + 1;
Cd := 0;
for y := y1 to y2 do
for x := x1 to x2 do
begin
if M[x,y] > 0 then
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begin
Wx := ( )rrx
max
1
2
1
2
1+ ;
Cd := Cd + ],[].[* 1 dyydxxyxWx II nn +++ + ;
end
x := x + xStep ;
y := y + yStep;
end
3.5.3 Theo vt i tng
Theo vt i tng th rng ln hn l so khp i tng. Chng ta
phi lu vt c quo chuyn ng ca i tng. chnh y l so
khp i tng c c vi cc i tng m ta thu c frame tip
theo. Cc i tng frame tip theo sau khi qua b pht hiu chuyn
ng s rt trch ra c cc vng chuyn ng. Chng ta s to mt
danh sch cc vng chuyn ng thun tin cho vic theo vt. Sau chng ta c lng v tr mi ca cc i tng frame hin ti. Khi
vic so khp s d dng hn. Chng ta ch so khp cc i tng vi vng
chuyn ng mi m v trc lng ca cc i tng ny thuc vo
vng chuyn ng mi . Ty trng hp so khp m chng ta c cc
quyt nh theo vt khc nhau. Sau y l s thut gii theo vt i
tng.
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H12: S theo vt i tng
N
Y
Rt trch cc vngchuyn ng
Don v tr mi cacc i tng A
Duyt A tm cc
i tng j khp vivng chuyn ng i
i = 1
i Bi
Stop
Tm i tng trongkhp vi i i = i + 1
Cc i tngang lu tr
Frame j
Danh sch cc
vng Bi
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Khi so khp cc i tng trong j vi i tng i s xy ra cc trng hp
sau:
1. Khng c i tng no khp vi vng chuyn ng ht. y
ta c 2 trng hp xy ra: mt l vng chuyn ng ny mi vo
vng quan st. Khi ta to mt i tng mi thit lp cc
tham s ban u nh l v tr, vn tc , .... v cho tin cy
mc thp nht. Trng hp hai l ta don sai. Khi ny ta c
th mrng vng tm kim v so khp cc i tng.
2. Ch c mt i tng khp vi vng chuyn ng. y l trng
hp tt nht trong theo vt. Lc ny ta s cp nht i tng theo
vng chuyn ng mi ny.
3. Mt i tng khp vi nhiu vng chuyn ng. iu ny c
th do i tng tch ra thnh nhiu i tng. y ta s cp
nht i tng hin ti theo i tng khp nht. Cc i tng
cn li s tng ng vi i tng mi v chng ta thit lp cc
tham s ban u cho cc i tng.4. Trng hp nhiu i tng cng khp vi mt vng chuyn
ng. Trng hp ny l do cc i tng giao nhau. y
chng ti ch xt 2 i tng giao nhau thi. Khi 2 i tng
giao nhau chng ti s xt v tr ca 2 i tng ny vi v tr
ca i tng m cp nht li v tr mi ca cc i tng. y
mi i tng sc c mt hnh ch nht bao quanh i
tng. Chng ti s so snh gc tri trn v gc phi di ca
cc hnh ch nht bao quanh i tng a ra cc quyt nh
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cp nht li v tr hnh ch nht bao ny theo gc tri trn hay
gc phi di ca vng mi. V d
Frame In Frame In+1
H13: v d thut ton so cp nhp v tr khi 2 i tng giao nhau
v d trn ta thy x21 < x11 do x21 = x1 cn x12 > x22 nn
x12 = x2, do dch chuyn theo phng x ca i tng 1 l
x1 = x2 x12 cn ca i tng 2 l x2 = x1 x12. Thnh phn
theo phng y c tnh tng t.
5. Trng hp cc i tng khng khp vi vng chuyn ng
no ht. Trng hp ny c th do i tng ra khi vng quan
st hoc l i tng ny bi tng khc che khut, v th
trong trng hp ny tin cy ca i tng s gim xung.
Khi tin cy gim xung di ngng cho php th ta s loi
bi tng ny ra khi danh sch.
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3.5.4 Cp nht i tng
Cc tham s ca i tng sc cp nht theo cc tham s ca
i tng mi. Gi d l dch chuyn ca i tng gia 2 frame In v frame
In+1. ta c
d =t
ppnn
+1
Vi pn+1 l v tr mi ca i tng.
Khi ta c vn tc ca i tng c cp nhp nh sau:
( )
vv nnd *1*
1
+=+
v khng chc chn ca vn tc c cp nhp nh sau:
( ) vvv nnn d *1* 11 += ++
3.6 Phn loi i tng
Phn loi i tng l mt cng vic rt kh v tn rt nhiu thi gian.
phn loi i tng chng ta cn phi bit cc c trng ring ca i tng.
l cc c trng ring ca i tng m i tng khc khng c. C rt nhiu
phng php tm c trng v phn loi i tng, tuy nhin c hai phng
php chung, ph bin thng c s dng l:
1. Sdng Heuristics. Phng php ny a ra cc c trng ca i
tng m t kinh nghim hoc cc phn tch l thuyt vi tng
. Tc l ta da vo cu trc, hnh dng, mu sc ca i tng ...
Phng php ny c u im l cho kt qu tt v nhanh, tuy nhinn da vo trc gic ca con ngi nn nhiu lc kt qu li khng
tt lm, v c nhiu bi ton khi s dng phng php ny s lm
phc tp thm.
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2. Phng php thng k. Phng php ny tm cc c trng ca i
tng da trn kt qu quan st c ca mt tp mu. T kt qu
quan st ny chng ta s rt ra c cc c im chung, cc quy
lut chung ca tp mu. Phng php ny thng cho kt qu kh
tt v chng da trn cc quan st thc t. Tuy nhin phng php
c nhc im l i hi tp mu quan st phi ln v cng vic thu
thp tp mu rt kh khn v tn thi gian. Nu chng ta thu thp d
liu cho tp mu khng tt th kt qu s khng tt. Mt trng hp
in hnh ca phng php ny l mng neuron. Hin nay vi s
pht trin ca tc my tnh ngy cng nhanh th phng php ny
ang c s dng rng ri.
y v thi gian c hn v khng c iu kin thc hin phng
php thng k cho nn chng ti chn phng php Heuristics. y
chng ti s phn loi ngi i b vi cc i tng khc nh l xe, ngi
i xe my ... Vic phn loi ny da vo hnh ch nht bao i tng. i
vi ngi i b th chiu rng ca hnh ch nht rt ngn cn chiu cao thdi hn cn i vi cc phng i tng khc v d nh xe t th chiu
rng thng di hn chiu di. V th chng ti chn t l gia chiu rng
vo chiu di lm mt c trng phn loi.
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ta c:
nu
3
3)30( 0 =< tg
height
widthth i tng c xem l ngi
chuyn ng. Trong width l chiu rng ca khung bao i tng cn height
l chiu cao. Thuc tnh hnh ch nht bao quanh i tng cha s dng n
hnh dng ca i tng do ta c mt hng khc phn loi i tng.
width
Np =
p T i tng chuyn ng l ngip < T i tng chuyn ng khng phi l ngi
Trong N l sim chuyn ng trong hnh bao i tng, width l
chiu rng ca ng bao.
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CHNG 4
CI T CHNG TRNH
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4.1 Mi trng ci t
Chng ti ci t th nghim chng trnh bng ngn ng C++ v trin
khai trn mi trng Window bng b cng c Visual Studio 6.0. Chng ti s
dng thm th vin Intel OpenCV h trx l. y l mt th vin m ngun
mca Intel v x l th gic my tnh.
4.2 Cu trc chng trnh
4.2.1 Cu trc dliu
Ngoi cc d liu cbn trong C++ chng ti cn s dng cc cu
trc ca th vin Intel OpenCV nh l IplImage lu tr cu trc nh. Cu trc
ny tha k t th vin IPL( Intel Image Processing Library ). Do cu trc ny
kh phc tp nn chng ti khng trnh by trong lun vn ny. Chi tit cc bn
c th xem trong ti liu ca th vin Intel OpenCV
m t mt i tng chuyn ng chng ti xy dng cu trc
MovingObject
typedef struct tagMovingObject
{
int objectConfidence;
CvRect objectRect;
CvPoint2D32f objectVelocity;
CvPoint objectCentroid;
CvPoint2D32f objectVelocityUncertainty;
CvPoint2D32f objectPositionUncertainty;
CArray< int , int > arrTargetObjectIndex;
BOOL objectUpdated;
}MovingObject, *pMovingObject;
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Trong cu trc MovingObject trn ta c mt vi cu trc khc :
typedef struct CvPoint
{
int x; /* x-coordinate, usually zero-based */
int y; /* y-coordinate, usually zero-based */
}
CvPoint;
typedef struct CvPoint2D32f
{
float x; /* x-coordinate, usually zero-based */
float y; /* y-coordinate, usually zero-based */
}
CvPoint2D32f;
typedef struct CvRect
{
int x; /* x-coordinate of the left-most rectangle corner[s] */
int y; /* y-coordinate of the top-most or bottom-most
rectangle corner[s] */
int width; /* width of the rectangle */
int height; /* height of the rectangle */
}
CvRect;
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4.2.2 Cu trc chng trnh
Chng trnh c xy dng da trn hai phn: phn giao din v
phn x l.
Trong phn giao din chng ti c s dng mt s lp v giao din
nh l CXPStyleButtonST, CbuttonST...
Trong phn x l chng ti xy dng mt lp x l video
CSequenceProcessing . Mt vi hm x l cbn trong lp ny nh sau:
/ / H m ly d liu t file AVI
void GetFile( const char* szFileName );
/ / H m khi to cc gi t r cn t h it
int Proces s AVI();
/ / H m t rnn r t r a i tng chu yn n g
void Ba ckgroun dSu btra ct ion( IplIm age *ba ckgroun dImage,
IplImage *currentImage,
IplIm a ge *foregrou n dIma ge,
IplIm a ge *th resh oldIma ge );
/ / H m thc h in cc cng vic x l
void Next ();
/ / H m s o khp i tn g
dou ble Mat ch ingObject( Movin gObject* cu rren tObject,
MovingOb ject* ta rgetOb ject);
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CHNG 5
KT QU V HNG PHT TRIN
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5.1 Kt qut c
5.1.1 Dliu thnghim
D liu m chng ti th nghim c quay trn mt con ng
gn cng vin Gia nh vo lc 5h chiu. D liu dc lu vo my qua cng
IEEE 1394 v dng phn mm Unlead Video Studio DV 5.0 x l v lu di
dng file AVI. y tit kim b nhchng ti lu di dng AVI nn. Cc
thng s nh sau:
Chun nn l Cinepak Codec.
Kch thc ca file AVI l 56,7Mb
Thi gian ca on film l 10 pht 07 giy
T l frame 30frame/giy
Chiu rng ca tng frame l 320 pixel
Chiu cao ca tng frame l 240 pixel
5.1.2 Kt qut c
Vi d liu trn chng ti tch c cc i tng chuyn ng.
X lc cc chuyn ng khng cn thit nh l chuyn ng ca l cy, cc
i tng chuyn ng c kch thc nhc loi b. Tuy nhin khi khung
cnh c qu nhiu i tng chuyn ng th thut ton cho kt qu khng tt
lm. Vic theo vt i tng kh tt, tuy nhin khi hai i tng gp nhau th
vic theo vt gp kh khn. V phn loi i tng cc i tng l ngi th
c nhn dng rt tt, tuy nhin v thut ton phn loi cn rt th nn khi cc
i tng khc khng phi l i tng ngi chuyn ng, chuyn ng phaxa camera th h thng nhn dng sai v cho rng l i tng ngi.
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5.2 Hng pht trin
Vi kt qut c hin ti, chng ti ra hng pht trin trong tng
lao:
1. H thng pht hin chuyn ng hin ti vn cn yu v chng da
trn thut ton tr nn rt nhy cm vi nhiu v s thay i ca
nn. Mc khc thut ton ny ch p dng vi camera tnh thi. Do
chng ti s pht trin mt h thng mi tt hn da trn cc m
hnh ton hc mi.
2. Xy dng mt h thng phn loi nhiu i tng. C th da trn
m hnh thng k c th l mng nron phn loi i tng.
3. T h thng phn loi ny ta c th xy dng cc h thng chng
trm bng cch a ra cc c trng ring h thng nhn dng
trm v a ra bo ng.
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TI LIU THAM KHO
[1] A.M.Tekalp , Digital Video Processing , Prentice Hall , 1995
[2] Hand Book of Image & Video Processing, Academic Press, pp.207-226 ,
2000
[3]Robert T.Collins , Alan J.Lipton and Takeo Kamade , A System for
VideoSurveillance and Monitoring , 1999
[4] LIU Ya, AI Haizou, XU Guangyou, Moving Object Detection and
Tracking Based on Background Subtraction, 2001.
[5] Fatih Poriki and Oncel Tuzel, Mitsubishi Research Laboratory, Human
Body Tracking by Adaptive Background Models and Mean-Shift Analysis,
7-2003
[6] Mathew Price, Video Classification and Tracking with Colour
Technical Report, 14-11-2002
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PH LC 1
MT VI HNH NH V KT QUT
C
1. Mt vi mt n chuyn ng
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Sau y l mt s frame m c i tng l ngi i b
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2. Kt qu theo vt i tng
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3. Kt qu theo vt i tng l ngi
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PH LC 2
VI NT V THVIN INTEL OPENCV
1. OpenCV l g?
OpenCV l vit tt ca Intel Open Source Computer Vision. l mt
th vin gm nhiu hm C v mt s lp C++ da trn cc thut ton ph bin
trong x lnh v th gic my tnh.
OpenCV l mt th vin m ngn mv min ph.
OpenCV l mt nn tng giao din lp trnh t cp trung ti cao. N chn 300 hm C cho php x l tng im nh cng nh ton bnh hay on
video. Khi kt hp vi th vin IPP (Intel Intergrated Performance Primitives)
trn cc CPU Intel s ti u ha x l nhvn dng kin trc ca CPU. y l
mt th vin c th s dng c trn Window v Linux.
2. Cc chc nng ca thvin OpenCV
2.1 Cc kiu dliu cbn
OpenCV cung cp rt nhiu kiu d liu c cu trc nhm h trti a
vic x l. Cc kiu d liu c thc chia ra lm 2 loi:
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Cc kiu d liu gip : y l cc kiu d liu gip cho thao
tc vi cc d liu nh d dng hn nh l :
o IplImage: dng lu cu trc file nh
o CvPoint: dng lu v tr ca im nh
o CvRect:
o CvBox
o V nhiu kiu d liu khc
Cc kiu d liu ng: y l cc kiu d liu c OpenCV
pht trin gip vic x lc ti u:
o CvMemStorage: y l mt cu trc d liu cp thp
dng lu tr cc cu trc d liu tng ng nh l
sequences, graphs...
typedef struct CvMemStorage
{
struct CvMemBlock* bottom;/* first allocated
block */
struct CvMemBlock* top; /* the current memory
block - top of the stack */
struct CvMemStorage* parent; /* borrows new
blocks from */
int block_size; /* block size */
int free_space; /* free space in the top
block (in bytes) */
} CvMemStorage;
o CvSeq : y l cu trc nn tng ca tt c cu trc ng
c s dng trong OpenCV. OpenCV cng cho php
chng ta to cc cu trc d liu mi t cu trc ny.
o CvSet : y l cu trc k tha t cu trc CvSeq.
o CvGraph : Cu trc ny li k tha t cu trc CvSet.
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V cn nhiu kiu d liu khc na. bit thm chi tit c gi hy
tham kho trong file help ca OpenCV.
2.2 Cc hm xl trong OpenCV
V cc hm x l trong OpenCV ta c th chia ra nh sau:
2.2.1 Cc hm x l cc kiu d liu cbn
y l cc hm h tr cho vic x l cc cu trc d liu
trong OpenCV bao gm:
Khi to:
cvCreateImage : hm khi to mt cu trc IplImage
cvMat: hm khi to mt cu trc CvMat
cvCreateMemStorage: hm khi to mt cu trc
CvMemStorage.
CvCreateSeq: hm khi to cu trc CvSeq.
.......
Cc hm hy
cvReleaseImage: gii phng b nh ginh cho cu trcIplImage c cp pht bng hm cvCreateImage.
cvReleaseMat: gii phng b nhginh cho cu trc CvMat
c khi to bng hm cvMat.
cvReleaseMemStorage: gii phng b nhginh cho cu trc
CvMemStorage c khi to bng hm
cvCreateMemStorage.
.....
Ni chung cc cu trc c khi to t hm cvCreateXXX
th sc gii phng bng hm cvReleaseXXX
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Ngoi ra cn cc hm sao chp, ly thng tin t cc phn t trong
bn trong cu trc v cc ton t trn cc cu trc.
2.2.2 Cc hm v x lnh
Cc hm x lnh c thc phn thnh cc loi sau:
Cc hm vn gin: y cc hm thc hin cc thao tc v
n gin trn nh nh l v elip, hnh ch nht.... hay l vit
ch trn nh.
Cc hm v tm cnh v gc trong nh: cc hm ny s dng
cc thut ton thng dng trong tm cnh nh l cc mt n
Sobel, Laplace, Candy.....
Cc hm v ly mu, ni suy, bin i hnh hc.
Cc php bin i morphological: ngoi cc php bi n i c
bn nh l Erode, Dilate cn c cc php bin i phc tp
hn bng cc kt hp 2 php bin i Erode v Dilate nh l :
o Open: open(A,B) = dilate(erode(A,B),B)
o Close: close(A,B) = erode(dilate(A,B),B)o Morphological gradient:
morp_grad(A,B) = dilate(A,B) erode(A,B)
o Top hat: tophat(A,B) = A erode(A,B)
o Black hat: blackhat(A,B) = dilate(A,B) A
Cc b lc nhiu: s dng cc b lc thng dng nh l
Median, Gausian.... Cc php chuyn i cc khng gian mu: cc khng gian
mu m OpenCV h trl: Gray, RGB, HSV, YCrCb, XYZ,
Lab, Bayer.
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Cc php bin i c bit nh l : php bin i Hough,
Fourier...
Cc hm v Histogram
Ni chung cc hm x lnh ca OpenCV l mt phn trong th
vin IPL.
2.2.3 Cc hm v phn tch vn ng v theo vt i tng
Cc hm dng trong phng php tr nn.
Cc hm v theo vt i tng da theo thut ton
MeanShift, Camshift, v Snake.
Cc hm dng tnh ton Optical Flow da vo cc thut
ton ph bin: Horn & Schunck, Lucas & Kanade, ...
Cc hm c lng trng thi da vo b lc Kalman
2.2.4 Cc hm v nhn dng i tng
Cc hm v nhn dng i tng theo phng php PCA nh
l: tnh ma trn tng quan, tnh cc vector ring.....
Cc hm v nhn dng i tng theo m hnh Makp n.2.2.5 Cc hm v giao din v thu nhn video
Cc hm ny nm trong th vinHighgui v th khi s dng cc
hm ny bn phi khai bo : #include highgui.h v thit lp
cc lin kt ti cc file th vin cn thit l highgui.lib v
highgui.dll. Cc hm cbn trong th vin ny l:
Cc hm v Window: to ca s mi, hy mt ca s, lyHandle ca mt ca s, ly tn ca mt ca s....
Cc hm v x l file nh: nh l c mt nh t file v lu
vo cu trc IplImage, hm hin mt nh ln mn hnh, lu
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mt nh xung mt file, hay chuyn i khng gian mu ca
nh....
Cc hm v nhp xut video: bao gm cc hm ly d liu t
mt file AVI, ly d liu t camera v lu vo cu trc
CvCapture, hm ly mt Frame t cu trc CvCapture, hm
lu d liu video xung mt file AVI..
Ngoi ra trong th vin highgui cn c cc lp c vit di
dng hng i tng d dng s dng nh l lp
CvvImage..
Cc hm c gii thiu trn l cc hm cbn trong OpenCV.
Ngoi ra cn c mt s hm c bit c mrng sau mi phin bn ci tin
ca n. OpenCV cn cung cp cho chng ta rt nhiu cc v d rt hu ch. Nu
cc bn quan tm th vin ny v mi bt u lm quen th c th tham kho
bi vit: A step-by-step guide to the use of the Intel OpenCV library
and the Microsoft DirectShow technology ca Robert Laganiere a
chhttp://www.site.uottawa.ca/~laganier/tutorial/opencv+directshow/ . Hoc l
tham gia vo nhm OpenCV ti a chhttp://groups.yahoo.com/group/opencv .
http://www.site.uottawa.ca/~laganier/tutorial/opencv+directshow/http://groups.yahoo.com/group/opencvhttp://groups.yahoo.com/group/opencvhttp://www.site.uottawa.ca/~laganier/tutorial/opencv+directshow/