Do Tim Va Cat Anh Mat Nguoi Su Dung Thuat Toan PCA

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B CNG THNGTRNG I HC CNG NGHIP TP. HCM KHOA CNG NGH IN T

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D TM V CT NH MT NGI DNG PCA

GVHD: Ths. o Th Thu Thy SVTH : Nguyn Trung Hiu -06052461Bi Ngc Lim -06054491 Lp:DHDT2B1

TP. H Ch Minh, thng 7 nm 2010

Hin nay, cng vi s pht trin ca x hi, vn an ninh bo mt ang c yu cu kht khe ti mi quc gia trn th gii. Cc h thng nhn dng con ngi c ra i vi tin cy ngy cng cao. Mt trong cc bi ton nhn dng con ngi rt c quan tm hin nay l nhn dng khun mt. V nhn dng khun mt l cch m con ngi s dng phn bit nhau. Bn cnh , ngy nay vic thu thp, x l thng tin qua nh nhn bit i tng ang c quan tm v ng dng rng ri. Vi phng php ny, chng ta c th thu nhn c nhiu thng tin t i tng m khng cn tc ng nhiu n i tng nghin cu. S pht trin ca khoa hc my tnh to mi trng thun li cho bi ton nhn dng khun mt ngi t nh s. Cc h thng nhn dng offline ra i v c tin cy cao, tuy nhin cc h thng nhn dng online li cha p ng c nhiu.Bi ton nhn dng khun mt ngi l mt bi ton hp dn, khng gii hn gii php s dng, vn dng linh hot kin thc trong nhiu lnh vc, thch thc nhiu ngi nghin cu v tnh ng dng to ln trong thc t. y l mt ch c th ni cn tng i mi vi nhng ng dng mang tnh cng ngh cao nh: robot, cc thit b camera,cc h thng bo mt, nhn dng, v ang c cc hng, cng ty p dng vo nhm nng cao cc tnh nng sn phm ca mnh trong qu trnh cnh tranh trn th trng hin nayVi mong mun tip cn cc cng ngh mi, ng thi b sung kin thc v khoa hc k thut hin i, cng nh tng kt li nhng k nng, kin thc trong sut qu trnh hc tp ti trng, chng em xin chn ti D tm v ct nh mt ngi dng PCA. y c th l mt bi ton nh, nhng n cng gip chng em c mt ci nhn khi qut v bi ton, to c s tin cho s tm ti v pht trin cc hng cao hn trong s nghin cu cc cng ngh mi...Bi lun ny c trnh by bao gm c 5 chng: Chng 1: Gii thiu Matlab v khi qut v nh. Chng 2: Cc phng php xc nh khun mt. Chng 3: Phn tch thnh phn chnh PCA.

LI M U

Chng 4: Chng trnh m phng. Chng 5: Kt lun. Ni dung ca ti: Tm hiu phng php nhn din nh. Nghin cu PCA. D tm nh mt ngi c khng gian (1=>4). Ct nh mt v lu vo 1 file. X l nh ng qua webcam.Trong bi lun ny chng em xin cp ti vn d tm v nhn dng mt ngi qua mt nh tnh cho trc, ng thi m rng hn l x l nh thu c qua mt thit b thu nh, v d nh: camera, webcam,

Sau mt thi gian hc tp v nghin cu, cui cng chng em cng hon thnh bi lun nghin cu ca mnh. y l thi im tt nht chng em c dp c by t lng bit n ca mnh n nhng ngi thn gip ng vin trong sut qu trnh chng em thc hin bi lun ny.Trc tin, chng em xin cm n BGH trng i Hc Cng Nghip Thnh Ph H Ch Minh, Qu Thy C trong khoa Cng ngh in T to iu kin cho chng em thc hin bi lun ny. c bit l C o Th Thu Thy, C khng ch l ngi hng dn khoa hc mt cch ti tnh, m cn l ngi du dt chng em, ng vin v nh hng cho chng em c nhng bc i u i v mt cch nhn khoa hc v tr thc, cuc sng, v s c gng phn u trong tng lai, iu ny c ngha rt su sc i vi chng em, gip chng em t tin v n lc hon thnh bi lun ny ng thi hn. Mt ln na, chng em xin by t lng bit n su sc n vi C.ng thi chng con xin cm n cha m, anh ch ht sc thng cm, chia s v ng vin chng con trong nhng kh khn trong qu trnh lm n tt nghip ny.Xin cm n nhng ngi bn thn yu, nhng ngi yu mn, chia s, gip chng ti trong lc chng ti thc hin bi lun ny.Kt qu ca bi lun ny l mn qu m chng em dnh tng cho tt c mi ngi thn yu, vi tt c tm lng mnh!Sinh vin thc hinNguyn Trung Hiu Bi Ngc Lim

LI CM N

NHN XT CA GIO VIN HNG DN..........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

Ch k ca gio vin

NHN XT CA GIO VIN PHN BIN.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

Ch k ca gio vin

MC LC

Chng 1: GII THIU MATLAB V KHI QUT V NH

Trang

............................................................................................................................. 11.1 Gii thiu chung v phn mm Matlab21.1.1 Khi nim v Matlab21.1.2 Tng quan v cu trc d liu Matlab, cc ng dng21.1.2.1 D liu31.1.2.2 ng dng31.1.2.3 Toolbox l mt cng c quan trng trong Matlab31.1.3 H thng Matlab31.1.4 Lm quen vi Matlab41.1.5 Cc ca s lm vic ca Matlab51.2 Gii thiu khi qut v nh s71.2.1 Cc khi nim c bn v nh71.2.2 Cc cch phn loi nh81.3 X l nh vi Matlab91.3.1 X l nh91.3.2 Cc giai on x l nh101.3.3 X l nh vi Matlab111.3.3.1 Cc kiu nh trong Matlab111.3.3.2 Cc hm x l nh c bn trong Matlab131.3.3.3 Bin i khng gian nh20Chng 2: CC PHNG PHP XC NH KHUN MT........................................................................................................................... 362.1 nh ngha bi ton xc nh khun mt ngi372.2 ng dng ca phng php xc nh khun mt372.3 Phng php xc nh khun mt392.3.1 Hng tip cn da trn tri thc402.3.2 Hng tip cn da trn c trng khng thay i412.3.2.1 Cc c trng khun mt42

2.3.2.2 Kt cu452.3.2.3 Sc mu ca da452.3.2.4 a c trng452.3.3 Hng tip cn da trn so khp mu452.3.4 Hng tip cn da trn din mo462.4 Kh khn v th thch trong bi ton xc nh khun mt ngi47Chng 3: PHN TCH THNH PHN CHNH PCA (PRINCIPAL COMPONENT ANALYSIS)........................................................................................................................... 483.1 S lc v phn tch thnh phn chnh PCA493.2 Thut ton PCA v ng dng trong nhn dng khun mt ngi503.2.1 Thut ton503.2.2 Phn tch thnh phn chnh PCA503.2.3 Hnh nh minh ha533.3 ng dng Eigenfaces trong vic nhn dng mt ngi563.3.1 Tnh ton Eigenfaces593.3.2 Dng Eigenfaces phn loi nh mt ngi.613.3.3 ng dng Eigenfaces pht hin gng mt623.3.3.1 Xem xt li khng gian mt633.3.3.2 Nhn dng theo thi gian thc643.4 Nhn xt653.4.1 u im ca phng php PCA653.4.2 Nhc im ca PCA65Chng 4: CHNG TRNH M PHNG........................................................................................................................... 674.1 Chng trnh m phng684.1.1 C s d liu nh6841.1.1 Tp nh hun luyn684.1.1.2 Tp nh mu694.1.2 Cc bc thc hin chng trnh70

4.1.3 Lu gii thut724.1.3.1 Lu gii thut chnh724.1.3.2 Lu gii thut chi tit724.1.4 Kt qu m phng.774.1.5 Tc thc hin.804.2 Nhn xt kt qu t c81Chng 5: KT LUN855.1 Kt lun855.2 Hng pht trin ti85PH LC .............................................................................................................TI LIU THAM KHO ..................................................................................

MC LC HNHTrangHnh 1.1 Ca s khi khi ng Matlab4Hnh 1.2 Ca s Command History6Hnh 1.3 Ca s Workspace6Hnh 1.4 Ca s Array Editor7Hnh 1.5 Cc bc c bn trong x l nh9Hnh 1.6 nh trc v sau khi imresize23Hnh 1.7 nh trc v sau khi imrotate26Hnh 1.8 nh c quay theo chiu ngang27Hnh 1.9 nh trc v sau khi imcrop28Hnh 1.10 nh trc v sau khi imcrop theo 1 ta cho trc30Hnh 1.11 nh trc v sau khi imtransforms32Hnh 1.12 nh trc v sau khi imtransformsvi 1 cng nh35Hnh 2.1 phn gii ca 1 nh41Hnh 2.2 Mt loi tr thc ca ngi nghin cu phn tch trn khun mt. 41Hnh 2.3 Mt mu khun mt, c 16 vng v 23 quan h (cc mi tn) 46Hnh 3.1 Eigenfaces53Hnh 3.2 Bc nh kim tra v hnh chiu ca n54Hnh 3.3 nh ban u55Hnh 3.4 Face map ca bc nh ban u55Hnh 3.5 Face map nh ban u vi khng gian khng phi l khun mt 56Hnh 3.6 Nhng gng mt dng hun luyn57Hnh 3.7 By Eigenfaces c tnh ton t dy hun luyn ca hnh 4.6,phng nn c loi b58Hnh 3.8 nh v hnh chiu ca n vo khng gian mt ngi xc nh bicc Eigenfaces t hnh 3.761Hnh 3.9 nh gc v bn mt ngi, vng ti ch ra hnh dngkhun mt63Hnh 3.10 V d n gin th hin 4 hnh chiu ca nh ln khng gian mt ngi. Trong trng hp ny s dng 2 eigenfaces l 1, 2 v 3 lp mt ngi (c th) bit trc (1, 2, 3)63

Hnh 3.11 H thng d tm v nh v mt ngi64Hnh 4.1 Tp nh Face68Hnh 4.2 Tp nh nface69Hnh 4.3 Tp nh mu70Hnh 4.4 Lu gii thut chnh72Hnh 4.5 Lu gii thut chn nh73Hnh 4.6 Lu gii thut chng trnh d tm nh mt ngi74Hnh 4.7 Lu gii thut chng trnh nhn dng75Hnh 4.8 Lu gii thut PCA76Hnh 4.9 Giao din chnh77Hnh 4.10 Giao din chng trnh 1 (nh tnh)77Hnh 4.11 Giao din chng trnh 2 (nh ng)78Hnh 4.12 Giao din kt qu chng trnh 1 (nh tnh) vi 1 khun mt 78Hnh 4.13 Giao din kt qu chng trnh 2 (nh ng)vi 1 khun mt 79Hnh 4.14 Giao din kt qu chng trnh 1 (nh tnh) vi 2 khun mt 79Hnh 4.15 Giao din kt qu chng trnh 1 (nh tnh) vi 4 khun mt n .. 80 Hnh 4.16 Giao din kt qu chng trnh 1 (nh tnh) vi 4 khun mt nam 80 Hnh 4.17 nh li do qu nhiu chi tit khng phn bit c83Hnh 4.18 Li do nh khng c sc nt84

Chng 1GII THIU MATLAB V KHI QUT V NH

1.1 Gii thiu chung v phn mm Matlab1.2 Gii thiu khi qut v nh s1.3 X l nh vi Matlab

Chng 1: Gii thiu Matlab v khi qut v nh2


GVHD: Ths. o Th Thu ThySVTH: Nguyn Trung Hiu Bi Ngc Lim

GVHD: Ths. o Th Thu ThySVTH: Nguyn Trung Hiu Bi Ngc LimChng 1GII THIU MATLAB V KHI QUT V NH1.1 Gii thiu chung v phn mm Matlab1.1.1 Khi nim v MatlabMatlab l mt ngn ng lp trnh thc hnh bc cao c s dng gii cc bi ton v k thut. Matlab tch hp c vic tnh ton, th hin kt qu, cho php lp trnh, giao din lm vic rt d dng cho ngi s dng. D liu cng vi th vin c lp trnh sn cho php ngi s dng c th c c nhng ng dng sau y. S dng cc hm c sn trong th vin, cc php tnh ton hc thng thng. Cho php lp trnh to ra nhng ng dng mi. Cho php m phng cc m hnh thc t. Phn tch, kho st v hin th d liu. Vi phn mm ho cc mnh. Cho php pht trin, giao tip vi mt s phn mm khc nh C++, Fortran.1.1.2 Tng quan v cu trc d liu ca Matlab, cc ng dngMatlab l mt h thng tng giao, cc phn t d liu l mt mng (mng ny khng i hi v kch thc). Chng cho php gii quyt cc vn lin quan n lp trnh bng my tnh, c bit s dng cc php tnh v ma trn hay vect v c th s dng ngn ng C hc Fortran lp trnh ri thc hin ng dng lp trnh bng cc cu lnh gi t Matlab. Matlab c vit tt t ch MATrix LABoratory tc l th vin v ma trn, t phn mm Matlab c vit nhm cung cp cho vic truy cp vo phn mm ma trn mt cch d dng, phn mm ma trn ny c pht trin bi cc cng trnh Linpack v Eispack. Ngy nay Matlab c pht trin bi Lapack v Artpack to nn mt ngh thut phn mm cho ma trn.

1.1.2.1 D liuD liu ca Matlab th hin di dng ma trn (hoc mng - tng qut), v c cc kiu d liu c lit k sau y: Kiu n single, kiu ny c li v b nh d liu v n i hi t byte nh hn, kiu d liu ny khng c s dng trong cc php tnh ton hc, chnh xc km hn. Kiu double kiu ny l kiu thng dng nht ca cc bin trong Matlab. Kiu Sparse. Kiu uint8, uint8, uint16, uint64... Kiu char v d Hello. Kiu cell. Kiu Structure.Trong Matlab kiu d liu double l kiu mc nh s dng trong cc php tnh s hc.1.1.2.2 ng dngMatlab to iu kin thun li cho: Cc kho hc v ton hc. Cc k s, cc nh nghin cu khoa hc. Dng Matlab tnh ton, nghin cu to ra cc sn phm tt nht trong sn xut.1.1.2.3 Toolbox l mt cng c quan trng trong MatlabCng c ny c Matlab cung cp cho php bn ng dng cc k thut phn tch, thit k, m phng cc m hnh.Ta c th tm thy toolbox trong m trng lm vic ca. Mng nron. Logic m. Simulink.1.1.3 H thng MatlabH thng giao din ca Matlab c chia thnh 5 phn: Mi trng pht trin.

y l ni t cc thanh cng c, cc phng tin gip chng ta s dng cc lnh v cc file, ta c th lit k mt s nh sau.+ Desktop.+ Command Window.+ Command History.+ Browsers for viewinghelp. Th vin, cc hm ton hc bao gm cc cu trc nh tnh tng, sin cosin atan, atan2 etc..., cc php tnh n gin n cc php tnh phc tp nh tnh ma trn nghich o, tr ring, chuyn i fourier, laplace, symbolic library. Ngn ng Matlab. l cc ngn ng cao v ma trn v mng, vi cc dng lnh, cc hm, cu trc d liu vo, c th lp trnh hng i tng. ho trong Matlab. Bao gm cc cu lnh th hin ha trong mi trng 2D v 3D, to cc hnh nh chuyn ng, cung cp cc giao din tng tc gia ngi s dng v my tnh. Giao tip vi cc ngn ng khc. Matlab cho php tng tc vi cc ngn ng khc nh C, Fortran 1.1.4 Lm quen vi MatlabTrc tin khi ng Matlab bn kch click vo biu tng file Matlab.exe, trn mn hnh xut hin ca s sau. (Xem hnh v 1.1) Ca s cha cc thanh cng c (Giao din ngi v my) cn thit cho vic qun l cc files, cc bin, ca s lnh, c th coi desktop l cc panel gm cc , vng, qun l v tc dng ca tng ca s nh c qun l bi desktop.

Hnh 1.1 Ca s khi khi ng Matlab

n.

Trn hnh v ta thy ca s desktop (ca s ln nht), v cc ca s ph ca

1.1.5 Cc ca s lm vic ca Matlaba) Ca s Command WindowL ca s giao tip chnh ca Matlab bi y l ni nhp gi tr cc bin, hin th gi tr, tnh ton gi tr ca biu thc, thc thi cc hm c sn trong th vin (dng lnh), hoc cc hm (dng function) do ngi dng lp trnh ra trong M-file.Cc lnh c nhp sau du nhc >>, v nu c sai st trong qu trnh g (nhp) lnh th hy nhn phm Enter cho n khi nhn c du nhc >>. Thc thi lnh bng nhn phm Enter.G cc lnh sau:>> A= pi/2 ;>> B= sin(A) B=1Hoc chng trnh son tho trong M-file di y:% Chuong trinh trong M-file x= 0:pi/6:2*pi;y=sin(x);plot(x, y);% chuong trinh c lu vi tn file l ve_sin.mb) Ca s command HistoryCc dng m bn nhp vo trong ca s Command Window (cc dng ny c th l dng nhp bin, hoc c th l dng lnh thc hin hm no ) c gi li trong ca s Command History, v ca s ny cho php ta s dng li nhng lnh bng cch click chut ln cc lnh hoc cc bin, nu nh bn mun s dng li bin . Xem hnh 1.2

Click chut ln lnh hoc bin s dng li

c) Ca s Workspace

Hnh 1.2 Ca s Command History

L ca s th hin tn cc bin bn s dng cng vi kch thc vng nh (s bytes), kiu d liu(lp), cc bin c gii phng sau mi ln tt chng trnh. (xem hnh 1.3)

Click chut ln bin xem d liu (hoc thay i gi tr)

Hnh 1.3 Ca s Workspace

Ngoi ra n cho php thay i gi tr, cng nh kch thc ca bin bng cch click chut ln cc bin. Hoc click vo nt bn tri ngay cnh nt save. V d khi chn bin (gi s l bin b) ri click (hoc click chut vo nt cnh nt save) ta c ca s sau gi l Array Editor (xem hnh 1.4)

Hnh 1.4 Ca s Array EditorTiu l tn bin b, nh dng d liu c tn l: Numeric format, mc nh l dng short, kch thc size l 1 by 3 (tc l mt hng v 3 ct) ta c th thay i kch thc ny bng cch thay i gi tr c trong kch thc size.Dng ca s ny lu cc bin di l d liu ca bin b, ta c th thay i chng bng cch thay i gi tr trong cc . Tt c cc bin u c lu trong Workspace trong th hin c kch thc (Size), s Bytes v kiu d liu (class) (8 bytes cho mi phn t d liu kiu double c th l 24 bytes dnh cho b v 8 bytes dnh cho a).d) Ca s M-fileL mt ca s dng son tho chng trnh ng dng, thc thi chng trnh vit trong M-file bng cch g tn ca file cha chng trnh trong ca s Commandwindow.Khi mt chng trnh vit trong M-file, th tu theo ng dng c th, tu theo ngi lp trnh m chng trnh c th vit di dng sau: Dng Script file: Tc l chng trnh gm tp hp cc cu lnh vit di dng lit k, khng c bin d liu vo v bin ly gi tr ra. Dng hm function: c bin d liu vo v bin ra.e) ng dn th mc: Ni lu gi cc files chng trnh.1.2 Gii thiu khi qut v nh s1.2.1 Cc khi nim c bn v nhnh s l tp hp hu hn cc im nh vi mc xm ph hp dng m t nh gn vi nh tht. S im nh xc nh phn gii ca nh. nh c phn

gii cng cao th cng th hin r nt cc t im ca tm hnh cng lm cho tmnh tr nn thc v sc nt hn.a) im nh (Picture Element)im nh (Pixel) l mt phn t ca nh s ti to (x, y) vi xm hoc mu nht nh. Kch thc v khong cch gia cc im nh c chn thch hp sao cho mt ngi cm nhn s lin tc v khng gian v mc xm (hoc mu) ca nh s gn nh nh tht. Mi phn t trong ma trn c gi l mt phn t nh.b) Mc xm ca nhMc xm: L kt qu ca s bin i tng ng 1 gi tr sng ca 1 im nh vi 1 gi tr nguyn dng. Thng thng n xc nh trong [0, 255] tu thuc vo gi tr m mi im nh c biu din.Cc thang gi tr mc xm thng thng: 16, 32, 64, 128, 256 (Mc 256 l mc ph dng. L do: t k thut my tnh dng 1 byte (8 bit) biu din mc xm. Mc xm dng 1 byte biu din: 28=256 mc, tc l t 0 n 255).c) phn gii ca nhnh ngha: phn gii (Resolution) ca nh l mt im nh c n nh trn mt nh s c hin th.Theo nh ngha, khong cch gia cc im nh phi c chn sao cho mt ngi vn thy c s lin tc ca nh. Vic la chn khong cch thch hp to nn mt mt phn b, chnh l phn gii v c phn b theo trc x v y trong khng gian hai chiu.V d: phn gii ca nh trn mn hnh CGA (Color Graphic Adaptor) l mt li im theo chiu ngang mn hnh: 320 im chiu dc * 200 im nh (320*200). R rng, cng mn hnh CGA 12 ta nhn thy mn hn mn hnh CGA 17 phn gii 320*200. L do: cng mt mt ( phn gii) nhng din tch mn hnh rng hn th mn (lin tc ca cc im) km hn.1.2.2 Cc cch phn loi nhnh nh phn: Gi tr xm ca tt c cc im nh ch nhn gi tr 1 hoc 0 nh vy mi im nh trong nh nh phn c biu din bi 1 bit.nh xm: Gi tr xm nm trong [0, 255] nh vy mi im nh trong nh nh phn c biu din bi 1 byte.

nh mu: H mu RGB:Mt pixel c biu din bng 3 gi tr (R, G, B) trong R, G, B l mt gi tr xm v c biu biu din bng 1 byte. Khi ta c mt nh 24 bits.P(x, y) = (R, G, B) H mu CMY: l phn b ca h mu RGB(C, M, Y) = (1, 1, 1) - (R, G, B) HayC+R=M+G=Y+B=1=> H mu ny thng c dng trong my in. H mu CMYK: trong K l m nht ca mu K= min(C, M, Y)P(x, y) = (C-K, M-K, V-K, K).V d:Vi (C1, M1, Y1) ta s c K=min(C1, M1, Y1)vy CMYK=(C1-K, M1-K, Y1-K, K)1.3 X l nh vi Matlab1.3.1 X l nh

Thu nhnnhTin x l nhPhnon nhBiu din v m tNhn dng v ni suyC s trithcCc bc cn thit trong x l nh. u tin, nh t nhin t th gii ngoi c thu nhn qua cc thit b thu (nh Camera, my chp nh). Trc y, nh thu qua Camera l cc nh tng t (loi Camera ng kiu CCIR). Gn y, vi s pht trin ca cng ngh, nh mu hoc en trng c ly ra t Camera, sau n c chuyn trc tip thnh nh s to thun li cho x l tip theo. My nh s hin nay l mt th d gn gi. Mt khc, nh cng c th tip nhn t v tinh; c th qut t nh chp bng my qut nh. Hnh di y m t cc bc c bn trong x l nh.

Hnh 1.5 Cc bc c bn trong x l nh

1.3.2 Cc giai on x l nha) Thu nhn nh (Image Acquisition) nh c thu t nhiu ngun khc nhau:my nh, my quay phim, my qut,nh v tinh Mc ch: bin i thng tin hnh nh v cc cu trc c lu tr trong my tnh, c th hin th ra cc thit b ngoi vi nh l my in, mn hnh Gm hai tin trnh:+ Bin i nng lng quang hc thnh nng lng in.+ Tng hp nng lng in thnh nh hoc ma trn s.b) Tin x l (Image Processing) L qu trnh s dng cc k thut x l nh lm nh tt ln theo mc ch s dng. Mc ch:+ iu chnh chiu sng khc phc hu qu ca vic chiu sng khng



u.

mun.

+ Gim nh thnh phn nhiu ca nh tc l cc i tng xut hin ngoi

+ Hiu chnh gi tr sng gia nn v i tng.+ Chun ho ln, mu, dng ca nh.+iu chnh b lc khuych i v nn cc tn s.c) Phn on (Segmentation)

L qu trnh phn chia ni dung cc i tng cn kho st ra khi nh. Phn chia cc i tng tip gip nhau. Phn tch cc i tng ring bit thnh cc i tng con.d) Biu din nh (Image Representation)u ra nh sau phn on cha cc im nh ca vng nh (nh phn on) cng vi m lin kt vi cc vng ln cn. Vic bin i cc s liu ny thnh dng thch hp l cn thit cho x l tip theo bng my tnh. Vic chn cc tnh cht th hin nh gi l trch chn c trng (Feature Selection) gn vi vic tch

cc c tnh ca nh di dng cc thng tin nh lng hoc lm c s phn bit lp i tng ny vi i tng khc trong phm vi nh nhn c.V d: trong nhn dng k t trn phong b th, chng ta miu t cc c trng ca tng k t gip phn bit k t ny vi k t khc.e) Nhn dng v ni suy nh (Image Recognition and Interpretation)Nhn dng nh l qu trnh xc nh nh. Qu trnh ny thng thu c bng cch so snh vi mu chun c hc (hoc lu) t trc. Ni suy l phn on theo ngha trn c s nhn dng.V d: mt lot ch s v nt gch ngang trn phong b th c th c ni suy thnh m in thoi. C nhiu cch phn loai nh khc nhau v nh. Theo l thuyt v nhn dng, cc m hnh ton hc v nh c phn theo hai loi nhn dng nh c bn: Nhn dng theo tham s. Nhn dng theo cu trc.Mt s i tng nhn dng kh ph bin hin nay ang c p dng trong khoa hc v cng ngh l: nhn dng k t (ch in, ch vit tay, ch k in t), nhn dng vn bn (Text), nhn dng vn tay, nhn dng m vch, nhn dng mt ngif) C s tri thc (Knowledge Base)Nh ni trn, nh l mt i tng kh phc tp v ng nt, sng ti, dung lng im nh, mi trng thu nh phong ph ko theo nhiu. Trong nhiu khu x l v phn tch nh ngoi vic n gin ha cc phng php ton hc m bo tin li cho x l, ngi ta mong mun bt chc quy trnh tip nhn v x l nh theo cch ca con ngi. Trong cc bc x l , nhiu khu hin nay x l theo cc phng php tr tu con ngi. V vy, y cc c s tri thc c pht huy.1.3.3 X l nh vi Matlab1.3.3.1 Cc kiu nh trong Matlaba) nh c nh ch s (Indexed Images)Mt nh ch s bao gm mt ma trn d liu X v ma trn bn mu map. Ma trn d liu c th c kiu thuc lp uint8, uint16 hoc kiu double. Ma trn bn mu l mt mng mx3 kiu double bao gm cc gi tr du phy ng nm

gia 0 v 1. Mi hng ca bn ch ra cc gi tr m: red, green v blue ca mt mu n. Mt nh ch s s dng nh x trc tip gia gi tr ca pixel nh ti gi tr trong bn mu. Mu sc ca mi pixel nh c tnh ton bng cch s dng gi tr tng ng ca X nh x ti mt gi tr ch s ca map. Gi tr 1 ch ra hng u tin, gi tr 2 ch ra hng th hai trong bn mu Mt bn mu thng c cha cng vi nh ch s v c t ng np cng vi nh khi s dng hm imread c nh. Tuy nhin, ta khng b gii hn khi s dng bn mu mc nh, ta c th s dng bt k bn mu no.b) nh cng (Intensity Images)Mt nh cng l mt ma trn d liu nh I m gi tr ca n i din cho cng trong mt s vng no ca nh. Matlab cha mt nh cng nh mt ma trn n, vi mi phn t ca ma trn tng ng vi mt pixel ca nh. Ma trn c th thuc lp double, uint8 hay uint16. Trong khi nh cng him khi c lu vi bn mu, Matlab s dng bn mu hin th chng.Nhng phn t trong ma trn cng i din cho cc cng khc nhau hoc xm. Nhng im c cng bng 0 thng c i din bng mu en v cng 1,255 hoc 65535 thng i din cho cng cao nht hay mu trng.c) nh nh phn (Binary Images)Trong mt nh nh phn, mi pixel ch c th cha mt trong hai gi tr nh phn 0 hoc 1. Hai gi tr ny tng ng vi bt hoc tt (on hoc off). Mt nh nh phn c lu tr nh mt mng logic ca 0 v 1.d) nh RGB (RGB Images)Mt nh RGB - thng c gi l true-color, c lu tr trong Matlab di dng mt mng d liu c kch thc 3 chiu mxnx3 nh ngha cc gi tr mu red, green v blue cho mi pixel ring bit. nh RGB khng s dng palette. Mu ca mi pixel c quyt nh bi s kt hp gia cc gi tr R, G, B (Red, Green, Blue) c lu tr trong mt mt phng mu ti v tr ca pixel. nh dng file ho lu tr nh RGB ging nh mt nh 24 bits trong R, G, B chim tng ng 8 bit mt. iu ny cho php nhn c 16 triu mu khc nhau.Mt mng RGB c th thuc lp double, uint8 hoc uint16. Trong mt mng RGB thuc lp double, mi thnh phn mu c gi tr gia 0 v 1. Mt pixel m



thnh phn mu ca n l (0, 0, 0) c hin th vi mu en v mt pixel m thnh phn mu l (1, 1, 1 ) c hin th vi mu trng. Ba thnh phn mu ca mi pixel c lu tr cng vi chiu th 3 ca mng d liu. Chng hn, gi tr mu R, G, B ca pixel (10, 5) c lu tr trong RGB(10, 5, 1), RGB(10, 5, 2) v RGB(10,5, 3) tng ng. tnh ton mu sc ca pixel ti hng 2 v ct 3 chng hn, ta nhn vo b ba gi tr c lu tr trong (2, 3, 1:3). Gi s (2, 3, 1) cha gi tr 0.5176; (2, 3, 2)cha gi tr 0.1608 v (2, 3, 3) cha gi tr 0.0627 th mu sc ca pixel ti (2, 3) sl (0.5176, 0.1608, 0.0627).1.3.3.2 Cc hm x l nh c bn trong Matlaba) c v ghi d liu nh c mt nh ho Hm imread c mt nh t bt k nh dng no c tr gip trong bt k chiu su bit no c tr gip. Hu ht cc file nh s dng 8 bit cha gi tr ca pixel. Khi chng c c vo b nh, Matlab cha chng di dng uint8. Vi cc file tr gip 16 bt d liu, PNG v TIFF, Matlab cha chng di dng uint16.Ch : Vi nh ch s, imread lun lun c bn mu vo trong mt chui thuc lp double, thm ch mng nh t n thuc lp uint8 hay uint16 Chng hn, on m sau s c mt nh RGB vo khng gian lm vic ca Matlab lu trong bin RGB.RGB=imread(football.jpg);Trong v d ny, imread s nhn ra nh dng file s dng t tn file. Ta cng c th ch ra nh dng file nh mt tham s trong hm imread. Matlab tr gip rt nhiu nh dng ho thng dng chng hn: BMP, GIF, JPEG, PNG, TIFF bit thm cc kiu gi hm v tham s truyn vo, xem tr gip online ca Matlab../ c nhiu nh t mt file ho- Matlab tr gip mt s nh dng file ho chng hn nh: HDF v TIFF, chng cha nhiu nh. Theo mc nh, imread ch tr gip nh u tin trong file. nhp thm cc nh t file, s dng c php c tr gip bi

nh dng file. Chng hn, khi c s dng vi TIFF, ta c th s dng mt gi tr ch s vi imread ch ra nh m ta mun nhp vo.V d sau y c mt chui 27 nh t mt file TIFF v lu nhng nh ny trong mt mng 4 chiu. Ta c th s dng hm iminfo xem bao nhiu nh c lu tr trong file:mri = uint8(zeros(128,128,1,27)); % preallocate 4-D array for frame=1:27[mri(:,:,:,frame),map] = imread('mri.tif',frame); End Khi file cha nhiu nh theo mt s kiu nht nh chng hn theo th t thi gian, ta c th lu nh trong Matlab di dng mng 4 chiu. Tt c cc nh phi c cng kch thc. Ghi mt nh ho Hm imwrite s ghi mt nh ti mt file ho di mt trong cc nh dng c tr gip. Cu trc c bn nht ca imwrite s yu cu mt bin nh v tn file. Nu ta gp mt phn m rng trong tn file, Matlab s nhn ra nh dng mong mun t n.V d sau ti mt nh ch s X t mt file Map vi bn mu kt hp vi n map sau ghi nh xung mt file bitmap.load clown whosNameSizeBytes ClassX200x320512000 double array caption2x14 char arraymap81x31944 double arrayGrand total is 64245 elements using 513948 bytes imwrite(X,map,'clown.bmp')./ Ch ra nh dng ph - Tham s c bit Khi s dng imwrite vi mt s nh dng ho, ta c th ch ra cc tham s ph. Chng hn, vi nh dng PNG ta c th ch ra su bit nh mt tham s ph. V d sau s chi mt nh cng I vi mt file nh 4 bit PNG.

imwrite(I,'clown.png','BitDepth',4 ); bit thm cc cu trc khc ca hm xem phn tr gip trc tuyn ca Matlab../ c v ghi nh nh phn theo nh dng 1 bit Trong mt s nh dng file, mt nh nh phn c th c lu trong mt nh dng 1 bit. Nu nh dng file tr gip n, Matlab ghi nh nh phn nh nh 1 bit theo mc nh. Khi ta c mt nh nh phn vi nh dng 1 bit, Matlab i din n trong khng gian lm vic nh mt mng lgic. V d sau c mt nh nh phn v ghi n di dng file TIFF. Bi v nh dng TIFF tr gip nh 1 bit, file c ghi ln a theo nh dng 1 bit:BW = imread('text.png'); imwrite(BW,'test.tif'); kim tra chiu su bit ca file test.tif, gi hm iminfo v kim tra trng BitDepth ca n:info = imfinfo('test.tif'); info.BitDepthans =1Ch : Khi ghi file nh phn, Matlab thit lp trng ColorType thnh grayscale../ Xem lp lu tr ca file . Hm imwrite s dng lut sau y quyt nh lp lu tr c s dng trong nh kt qu:+ logical: Nu nh dng nh ra (Output Image) c ch r l tr gip nh 1 bit, hm imwrite to mt file nh 1 bit. Nu nh dng nh ra c ch r l khng tr gip nh 1 bit (nh JPEG), hm imwrite chuyn nh ti mt nh thuc lp uint8.+ uint8: Nu nh dng nh ra c ch r l tr gip nh 8 bit, hm imwriteto mt nh 8 bit+ uint16: Nu nh dng nh ra c ch r tr gip nh 16 bit (PNG hoc TIFF), hm imwrite to mt nh 16 bit. Nu nh dng nh ra khng tr gip nh 16 bit, hm chuyn i d liu nh ti lp uint8 v to mt nh 8 bit.

+ double: Matlab chuyn d liu nh ti dng uint8 v to mt nh 8 bit bi v hu ht cc file nh s dng nh dng 8 bit. Truy vn mt file ho Hm imfinfo cho php ta c th nhn c thng tin v mt file nh c tr gip bi toolbox.C php: imfinfo(filename,fmt)Cc thng tin c cung cp bi hm imfinfo l: filename, filemodedate, filesize, format, formatversion, width, height, bitdepth, colortype Thng tin m ta nhn c ph thuc vo kiu ca file nhng n lun bao gm nhng thng tin sau:+ Tn ca file nh.+ nh dng file nh.+ S version ca nh dng file.+ Ngy sa i file gn nht.+ Kch thc file tnh theo byte.+ Chiu rng nh tnh theo pixel.+ Chiu cao nh tnh theo pixel.+ S lng bt trn mt pixel.+ Kiu nh: RGB, ch s b) Hin th nh Dng hm imview hin th mt nh s dng hm imview, dng hm imview, ch r nh m ta mun hin th. Ta c th s dng imview hin th mt nh m c nhp vo trong khng gian lm vic ca Matlab.moonfig = imread('moon.tif'); imview(moonfig);Ta cng c th ch nh tn ca file nh nh trong v d sau:imview('moon.tif'); File nh phi c mt trong th mc hin ti hoc trong ng dn ca Matlab. Cu trc ny c th hu ch cho vic qut qua nhiu nh. Tuy nhin, lu , khi s dng cu trc ny, d liu nh khng c lu trong khng gian lm vic ca Matlab.

Nu ta gi hm imview m khng ch ra mt k tham s no, n s hin th mt hp chn file cho php ta ch ra tn file mun hin th../ Xem nhiu nh Nu ta ch ra mt file m cha nhiu nh, hm imview ch hin th nh u tin trong file . xem tt c cc nh trong file, s dng hm imread nhp mi nh vo trong khng gian lm vic ca Matlab sau gi hm imview nhiu ln hin th mi nh ring bit. Dng hm imshow xem nh, ta c th s dng hm imshow thay cho imview. Ta s dng imshow hin th mt nh c nhp vo trong khng gian lm vic nh v d sau:moon = imread('moon.tif'); imshow(moon);Ta cng c th ch ra tn ca file nh nh mt tham s truyn vo cho hm nh v d sau: imshow('moon.tif');Khi s dng cu trc ny th d liu nh khng c nhp vo trong khng gian lm vic. Tuy nhin, ta c th mang nh vo trong khng gian lm vic bng cch s dng hm getimage. Hm ny s nhn d liu nh t handle ca mt i tng nh hin ti. Chng hn: moon = getimage; S gn d liu nh t moon.tif vo bin moon.c) Cc hm chuyn i kiu nh Vi cc thao tc nht nh s tht hu ch khi c th chuyn i nh t dng ny sang dng khc. Chng hn, nu ta mun lc mt mu nh c lu tr di dng nh ch s u tin ta nn chuyn i n thnh dng nh RGB. Khi ta p dng php lc ti nh RGB, Matlab s lc gi tr cng trong nh tng ng. Nu ta c gng lc nh ch s, Matlab n gin ch p t php lc ti ma trn nh ch s v kt qu s khng c ngha.Ch : Khi chuyn i mt nh t dng ny sang dng khc, nh kt qu c th khc nh ban u. Chng hn, nu ta chuyn i mt nh mu ch s sang mt nh cng , kt qu ta s thu c mt nh en trng. Danh sch sau y s lit k cc hm c s dng trong vic chuyn i kiu nh:

+ dither: To mt nh nh phn t mt nh cng en trng bng cch trn, to mt nh ch s t mt nh RGB bng cch trng (dither).+ gray2id: To mt nh ch s t mt nh cng en trng.+ grayslice: To mt nh ch s t mt nh cng en trng bng ccht ngng.+ im2bw: To mt nh nh phn t mt nh cng , nh ch s hay nh RGB trn c s ca ngng nh sng.+ ind2gray: To mt nh cng en trng t mt nh ch s.+ ind2rgb: To mt nh RGB t mt nh ch s.+ mat2gray: To mt nh cng en trng t d liu trong mt ma trn bng cch ly t l gi liu.+ rgb2gray: To mt nh cng en trng t mt nh RGB.+ rgb2ind: To mt nh ch s t mt nh RGB. Ta cng c th thc hin cc php chuyn i kiu ch s dng c php ca Matlab. Chng hn, ta c th chuyn i mt nh cng sang nh RGB bng cch ghp ni 3 phn copy ca ma trn nh gc gia 3 chiu: RGB=cat(3,I,I,I ); nh RGB thu c c cc ma trn ng nht cho cc mt phng R, G, B v vy nh hin th ging nh bng xm. Thm vo nhng cng c chuyn i chun ni trn, cng c mt s hm m tr li kiu nh khc nh mt phn trong thao tc m chng thc hin../ Chuyn i khng gian mu Toolbox x l nh biu din mu sc nh cc gi tr RGB ( trc tip trong nh RGB hoc gin tip trong nh ch s ). Tuy nhin, c cc phng php khc cho vic biu din mu sc. Chng hn, mt mu c th c i din bi cc gi tr hue, saturation v cc gi tr thnh phn (HSV). Cc phng php khc cho vic biu din mu c gi l khng gian mu. Toolbox cung cp mt tp cc th tc chuyn i gia cc khng gian mu. Cc hm x l nh t chng coi d liu mu sc di dng RGB tuy nhin, ta c th x l mt nh m s dng cc khng gian mu khc nhau

bng cch chuyn i n sang RGB sau chuyn i nh c x l tr li khng gian mu ban u.

d) Chuyn i nh dng cc file nh thay i nh dng ho ca mt nh, s dng hm imread c mtnh v sau lu n vi hm imwrite ng thi ch ra nh dng tng ng. minh ho, v d sau y s dng hm imread c mt file BMP vo khng gian lm vic.Sau , hm imwrite lu nh ny di nh dng PNG bitmap = imread('mybitmap.bmp','bmp'); imwrite(bitmap,'mybitmap.png','png');e) S hc nh S hc nh s ng dng ca cc php ton s hc chun nh: cng, tr, nhn, chia ln nh. S hc nh c s dng nhiu trong x l nh trong c cc bc ban u ln cc thao tc phc tp hn. Chng hn, tr nh c th c s dng pht hin s khc nhau gia hai hoc nhiu nh ca cng mt cnh hoc mt vt. Ta c th thc hin s hc nh s dng cc ton t s hc ca Matlab. Toolbox x l nh bao gm mt tp hp cc hm ng dng cc php ton s hc trn tt c cc con s khng lp y. Hm s hc ca toolbox chp nhn bt k kiu d liu s no bao gm uint8, uint16 hay double v tr li nh kt qu trong cng nh dng. Cc hm thc hin cc php ton vi chnh xc kp trn tng phn t nhng khng chuyn i nh ti gi tr chnh xc kp trong khng gian lm vic ca Matlab. S trn s c iu khin t ng. Hm s ct b gi tr tr v va vi kiu d liu. Lut ct b trong s hc nh Kt qu ca s hc nguyn c th d dng trn s dng cho lu tr. Chng hn, gi tr cc i ta c th lu tr trong uint8 l 255. Cc php ton s hc c th tr v gi tr phn s - khng c biu din bi mt chui s nguyn. Cc hm s hc nh s dng nhng lut ny cho s hc nguyn:+ Gi tr vt qu khong ca kiu s nguyn b ct b ti khong + Gi tr phn s c lm trn

Chng hn, nu d liu c kiu uint8, kt qu tr v nu ln hn 255 ( bao gm Inf ) th c gn l 255. Li gi lng nhau ti hm s hc nh Ta c th s dng cc hm s hc nh kt hp thc hin mt chui cc php ton. Chng hn tnh gi tr trung bnh ca hai nh:C=(A+B) /2Ta c th nhp vo nh sau:I = imread('rice.png');I2 = imread('cameraman.tif');K = imdivide(imadd(I,I2), 2); % not recommended- Khi c s dng vi kiu uint8 hay uint16, mi hm s hc ct kt qu ca n trc khi truyn n cho hm thip theo. S ct b ny c th gim ng k lng thng tin trong nh cui cng. Mt cch lm tt hn thc hin mt chui cc tnh ton l s dng hm imlincomb. Hm ny thi hnh tt c cc php ton s hc trong s kt hp tuyn tnh ca chnh xc kp v ch ct b kt qu cui cng:K = imlincomb(.5,I,.5,I2); % recommended1.3.3.3 Bin i khng gian nhBin i khng gian nh l thc hin nh x gia v tr cc pixel trong nh vo vi cc pixel trong nh ra.a) Bng thut ng

Tn thut ngDin gii

AliasingRng ca - xut hin khi gim kch thc nh. Khi kch thc ca mt nh b gim, cc pixel gc b ly mu gim to ra t pixel hn. Aliasing xy ra nh kt qu ca vic gim kch thc nh thng xut hin di dng bc thang ( c bit trong cc nh c tng phn cao )

AntialiasingCc bin php chng rng ca cho nh

Bicubic interpolationGi tr ca cc pixel ra c tnh ton t



gi tr trung bnh ca 4x4 pixel ln cn

Bilinear interpolationGa tr ca pixel ra c tnh ton t gi tr trung bnh ca 2x2 pixel ln cn

Geometric operationMt thao tc sa i quan h hnh hc ga cc pixel trong mt nh. Chng hn thay i kch thc nh, quay nh v xn nh

InterpolationQu trnh c s dng c lng gi tr nh mt v tr gia cc pixel

Nearest-neighbor interpolationCc gi tr pixel ra c gn gi tr ca pixel nm trong mt vng gn pixel .

b) Ni suyNi suy l qu trnh s dng c lng mt gi tr nh mt v tr gia cc pixel. Chng hn, nu ta thay i kch thc mt nh, n s cha nhiu pixel hn nh gc, toolbox s dng s ni suy tnh gi tr cho cc pixel thm vo. Hm imresize v imrotate s dng ni suy hai chiu thc hin thao tc ca mnh. Hm improfile cng s dng s ni suy ho../ Cc phng php ni suy- Toolbox s l nh cung cp 3 cch ni suy ho+ Ni suy cc pixel gn nht ( nearest neighbor interpolation )+ Ni suy song tuyn tnh ( Bilinear interpolation )+ Ni suy song khi ( Bicubic interpolation )Cc phng php ni suy lm vic theo mt cch ging nhau. Trong mi trng hp, tnh gi tr ca mt pixel c ni suy, chng tm im trong nh ra m pixel nm ti . Sau , chng gn mt gi tr ti cc pixel ra bng cch tnh ton gi tr trung bnh c trng s ca mt s pixel ln cn. Trng s da trn c s khong cch ti im ang xt.- Cc phng php ny khc nhau tp cc pixel m chng xem xt:+ Vi ni suy cc pixel gn nht: pixel ra c gn gi tr ca cc pixel gn n nht. Cc pixel khc khng c xem xt.+ Ni suy song tuyn tnh, gi tr ca pixel ra l gi tr trung bnh theo trng s ca 2x2 pixel ln cn.

+ Ni suy song khi: gi tr ca pixel ra l trung bnh c trng s ca 4x4 pixel ln cn.S lng cc pixel c xem xt nh hng n phc tp tnh ton. V vy, phng php song tuyn tnh mt nhiu thi gian hn phng php th nht v phng php song khi mt nhiu thi gian hn song tuyn tnh. Tuy nhin, s lng pixel ln hn, chnh xc s tt hn../ Kiu nh Cc hm s dng tuyn tnh yu cu mt tham s ch ra phng php ni suy. Vi hu ht cc hm, phng php mc nh c s dng l nearest-neighbor interpolation. Phng php ny to ra mt kt qu c th chp nhn c cho hu ht cc nh v l phng php duy nht thch hp vi nh ch s. Vi nh cng hay RGB, tuy nhin ta thng ch ra kiu song tuyn tnh hoc song khi bi v nhng phng php ny cho kt qu tt hnVi nh RGB, ni suy thng c thc hin trn mt phng R,B,G mt cch ring bitVi nh nh phn, ni suy gy ra nhng nh hng m ta c th nhn thy c. Nu s dng ni suy song tuyn tnh hoc song khi, gi tr tnh ton c cho pixel trong nh ra s khng hon ton l 0 hoc 1. nh hng trn nh kt qu ph thuc vo lp ca nh vo:+ Nu lp nh vo l double, nh ra l mt nh en trng thuc lp double.nh ra khng l nh nh phn bi v n bao gm cc gi tr khc 0 v 1.+ Nu nh vo l uint8, nh ra l mt nh nh phn thuc lp uint8. Gi tr ca cc pixel c ni suy c lm trn thnh 0 hoc 1. V vy , nh ra thuc lp uint8.Nu s dng phng php nearest-neighbor interpolation, nh ra lun l nh nh phn bi v nhng gi tr ca pixel c ni suy c ly trc tip t nh vo.c) Thay i kch thc nh thay i kch thc ca mt nh, s dng hm imresize. S dng hm ny ta c th:+ Ch ra kch thc ca nh kt qu.+ Ch ra phng php ni suy c s dng.+ Ch ra b lc c s dng ngn nga hin tng rng ca.



./ Ch ra kch thc cho nh kt qu- S dng hm imresize, ta ch th ch ra kch thc ca nh kt qu theo hai cch:+ Bng cch ch ra h s phng i c s dng trn nh.+ Bng cch ch ra chiu ca nh kt qu../ S dng h s phng i nh- m rng mt nh, ch ra h s phng i ln hn 1. thu nh mt nh, ch ra h s phng i nm gia 0 v 1. Chng hn, lnh sau tng kch thc ca nh I ln 1.25 ln:

Hnh 1.5 nh trc v sau khi imresize

I = imread('circuit.tif'); J = imresize(I,1.25); imshow(I)figure, imshow(J)./ Ch nh kch thc ca nh ra- Ta c th ch ra kch thc ca nh ra bng cch truyn mt vc t cha s lng hng v ct ca nh sau cng. Nhng lnh sau y to mt nh ra Y vi 100 hng v 150 ct.Y = imresize(X,[100 150])

Ch : Nu kch thc c ch ra khng c cng t l vi nh vo, nh ra s b bin dng./ Ch nh phng php ni suy c s dng.- Theo mc nh, hm imresize s dng phng php ni suy cc pixel gn nht (nearest neighbor interpolation) tnh gi tr cc pixel ca nh ra. Tuy nhin, ta c th ch nh cc phng php ni suy khc. Bng sau y lit k cc phng php ni suy c tr gip theo th t ca phc tp.

Gi tr tham sPhng php ni suy

nearestNi suy cc phixel gn nht ( mc nh )

bilinearNi suy song tuyn tnh

biculicNi suy song khi

Trong v d sau, hm imresize s dng phng php ni suy song tuyn tnh:Y=imresize(X, [100 150],bilinear);./ S dng b lc ngn chn hin tng rng ca Vic gim kch thc (hnh hc) ca mt nh c th gy ra nhng nh hng nht nh ln nh chng hn nh hin tng xut hin rng ca ti bin ca nh . iu ny l do thng tin lun b mt khi ta gim kch thc mt nh. Rng ca xut hin nh nhng gn sng trong nh sau cng. Khi gim kch thc ca nh s dng ni suy song tuyn tnh hoc song khi, hm imresize t ng p t mt b lc thng thp ln nh trc khi ni suy. iu ny gim nh hng ca rng ca trong nh ra. Ta c th ch ra kch thc ca b lc ny hoc ch ra mt b lc khc thay th.Ch : Thm ch s dng mt b lc thng thp, cht lng ca nh vn b nh hng do thng tin lun b mt trong qu trnh ni suy Hm imresize khng p t mt b lc thng thp ln nh nu phng php ni suy cc pixel gn nht c s dng. Phng php ni suy ny ban u c s dng vi cc nh ch s v b lc thng thp khng thch hp cho kiu nh ny. Ta cng c th ch ra mt b lc t to thay cho cc b lc c sn.Hm imresizeC php ca hm ny nh sau:B = imresize(A,m)

B = imresize(A,m,method)B = imresize(A,[mrows ncols],method) B = imresize(...,method,n)B = imresize(...,method,h)./ Din gii+ B=imresize(A,m): Tr li mt nh B ln gp m ln nh A (kch thc hnh hc) s dng phng php ni suy mc nh (nearest - neighbor interpolcation). A c th l mt nh ch s, nh en trng, RGB hoc nh nh phn. Nu m nm gia 0 v 1, B s nh hn A. Nu m ln hn 1, B s ln hn A.+ B=imresize(A,m,method): Tr li mt nh ln gp m ln nh A s dng phng php ni suy method. method l mt chui ch ra phng php ni suy no c s dng chng hn: nearest,bilinear,bicubic.+ B=imresize(A, [mrows ncols],method): Tr li mt nh vi kch thc c ch ra bi vector [mrows ncols]. Nu kch thc c ch ra khng cng t l vi nh vo, nh s b bin dngKhi kch thc ca nh ra nh hn kch thc ca nh vo v phng php ni suy c s dng l bilinear hoc bicubic, hm imresize p t mt b lc thng thp trc khi tuyn tnh ho gim hin tng rng ca. Kch thc mc nh l 11x11.Ta c th ch ra mt th t khc cho b lc mc nh s dng cu trc:B=imresize(,method,n): n l mt s nguyn ch ra kch thc ca b lc nxn. Nu n=0, hm imresize b qua bc lc. Ta cng c th ch ra b lc ring s dng c php:B=imresize(,method,h): Trong h l mt b lc FIR hai chiu ( c th c tr v bi cc hm ftrans2, fwind1, fwind2 hoc fsamp2 ).d) Quay nh- quay mt nh, s dng hm imrotate. Hm ny chp nhn hai tham s

chnh:

+ nh cn quay+ Gc quay- Gc quay tnh theo . Nu ta ch ra mt gi tr dng, hm imrotate quay

nh theo chiu ngc chiu kim ng h. Nu ch ra gi tr m, hm quay nh theo

chiu kim ng h. V d sau quay mt nh 35 theo chiu ngc chiu kim ng h:J=imrotate(I,35 ) ;- Mt s tham s tu chn ta c th truyn vo cho hm bao gm:+ Phng php ni suy c s dng+ Kch thc ca nh ra./ Ch nh phng php ni suy c s dng- Theo mc nh, hm imrotate s dng phng php ni suy th nht (nearest-neighbor interpolation) tnh gi tr cc pixel trong nh ra. Tuy nhin, ta c th ch ra cc phng php ni suy khc nh: bilinear ,bicubicV d sau quay mt nh 35 ngc chiu kim ng h s dng ni suy song tuyn tnh:I = imread('circuit.tif');J = imrotate(I,35,'bilinear'); imshow(I)figure, imshow(J)

Hnh 1.7 nh trc v sau khi imrotate./ Ch nh kch thc ca nh raTheo mc nh, hm imrotate to mt nh ra ln c th bao gm ton b cc pixel ca nh gc. Cc pixel nm ngoi bin ca nh gc c gn gi tr 0

nh th nn mu en trong nh ra. Nu ta ch ra chui crop nh mt tham s, hmimrotate s xn nh ra ti kch thc nh nh vo../ Hm imrotateC php ca n nh sau:B = imrotate(A,angle)B = imrotate(A,angle,method)B = imrotate(A,angle,method,bbox)./ Din gii+ B=imrotate(A,angle): Quay nh A mt gc angle theo chiu ngc chiu kim ng h, s dng phng php ni suy cc pixel gn nht. quay theo chiu kim ng h hy truyn gi tr m cho tham s angle+ B=imrotate(A,angle,method): Quay nh A mt gc angle theo chiu kim ng h s dng phng php ni suy c ch ra trong method.+ B=imrotate(A,angle,method,bbox): Quay nh A mt gc angle . Tham s bbox ch ra hp bin ca nh tr v. bbox l mt chui c th nhn cc gi tr sau:crop: nh ra B ch bao gm phn trung tm ca nh c quay v c cng kch thc vi nh Aloose: ( Mc nh ): nh ra B bao gm ton b nh c quay v ln hnnh A. Hm imrotate thit lp gi tr 0 cho cc pixel ngoi bin ca nh gc.V d- V d ny c mt nh quang ph nh sng mt tri c lu trong nh dng FITS v quay n v cn n theo chiu ngang.I = fitsread('solarspectra.fts'); I = mat2gray(I);J = imrotate(I,-1,'bilinear','crop'); imshow(I)figure, imshow(J)

Hnh 1.8 nh c quay theo chiu ngange) Xn nh (image cropping)- trch mt vng ch nht ca mt nh, s dng hm imcrop. Hmimcrop chp nhn hai tham s chnh:+ nh cn xn+ Cc gc ca hnh ch nht xc nh vng xn- Nu ta gi hm imcrop m khng ch ra hnh ch nht, ta c th xn nh theo cc tng tc. Trong trng hp ny, ta s dng tr chut chn vng ch nht cn xn bng cch nhn v gi phm chut tri v di chuyn chn vng xn. Khi chn xong th nh chut. Trong v d sau, ta hin th mt nh v gi hm imcrop. Hm imcrop hin th nh trong mt hnh v i ta v vng ch nht cn xn trn nh.imshow circuit.tif I=imcrop; Imshow(I);

Hnh 1.9 nh trc v sau khi imcrop

chut

./ Hm imcrop- C php ca n nh sau:I2 = imcrop(I)X2 = imcrop(X,map) RGB2 = imcrop(RGB) I2 = imcrop(I,rect)X2 = imcrop(X,map,rect) RGB2 = imcrop(RGB,rect) [...] = imcrop(x,y,...) [A,rect] = imcrop(...)[x,y,A,rect] = imcrop(...)./ Din gii Hm imcrop xn mt nh theo mt hnh ch nht c ch nh.I2=imcrop(I) ; X2=imcrop(X,map); RGB2=imcrop(RGB);Hm imcrop s hin th nh I v i ta ch ra hnh ch nht cn xn bng

Nu ta b qua cc tham s, hm imcrop thao tc trn nh ca trc hin ti. ch nh mt hnh ch nht ta dng tr chut nh ni trn Ta cng c th ch ra kch thc ca hnh ch nht m khng thao tc trc

tip nh cc c php sau:I2 = imcrop(I,rect)X2 = imcrop(X,map,rect) RGB2 = imcrop(RGB,rect)Trong : rect l mt vector bn phn t dng [xmin ymin width height], nhng gi tr ny c ch ra trong to khng gian. ch nh cc to khng theo to khng gian cho nh vo, t trc cc tham s khc vi 2 vector hai phn t ch ra Xdata v Ydata. Chng hn:[]=imcrop(x,y,)- Nu ta cung cp cc tham s ra ph, hm imcrop s tr li thng tin v vng ch nht c chn v h to ca nh vo. Chng hn:

[A,rect] = imcrop(...)[x,y,A,rect] = imcrop(...)A l nh ra, x v y l Xdata v Ydata ca nh vo./ Ch :- Do rect l mt tp hp cc to khng gian, cc phn t width v height trong rect khng lun lun tng ng chnh xc vi kch thc ca nh ra. Chng hn, gi s rect l [20 20 40 30], s dng h to khng gian theo mc nh. Gc trn tri ca vng ch nht c chn l tm ca pixel (20,20) v gc di phi ca vng ch nht l tm ca pixel (50,60). nh ra l mt nh c kch thc 31x41 ch khng phi 30x40. iu ny l do nh ra bao gm tt c cc pixel trong nh vo hon ton hoc mt phn c bao bc bi vng ch nht trn.V dI = imread('circuit.tif');I2 = imcrop(I,[75 68 130 112]);imview(I), imview(I2)

Hnh 1.10 nh trc v sau khi imcrop theo 1 ta cho trcf) Cc bin i nh thng dng- thc hin cc bin i khng gian nh 2 chiu, s dng hmimtransform. Hm ny chp nhn hai tham s chnh:+ nh cn bin i



+ Mt cu trc bin i c gi l TFORM ch ra kiu bin i ta mun thc hin./ Ch ra kiu bin i- Ta ch ra kiu bin i trong cu trc TFORM. C hai cch to mt cu trc TFORM:+ S dng hm maketform+ S dng hm cp2tform./ S dng hm maketform- Khi s dng hm ny, ta ch ra kiu bin i ta mun thc hin. Cc kiu bin i m maketform tr gip bao gm:+ affine: Bin i c th bao gm: translation ( dch ), rotation ( quay ), scaling, stretching v shearing. Cc ng thng vn l ng thng, ng song song vn song song nhng hnh ch nht c th b bin i+box: Mt trng hp c bit ca affine khi mi chiu c di v nh t l c lp+ composite : Bao gm t hp ca hai hay nhiu php bin i+ custom : Bin i do ngi dng t nh ngha, n cung cp cc hm thun hoc nghch c gi bi hm imtransform+ projective : Bin i trong cc ng thng vn gi nguyn nhng ccng song song ng quy li thnh mt im../ S dng cp2tform Ta s dng hm ny to ra cu trc TFORM khi ta mun thi hnh mt bin i cn kht vi cc im d liu nh mt bin i a thc.Ch : Khi s dng vi hm imtransform, cu trc TFORM phi nh ngha mt bin i 2 chiu. Nu mt nh cha nhiu hn mt chiu chng hn nh nh RGB, cng mt bin i 2 chiu s c p t ti tt c cc mt phng 2 chiu theo chiu cao hn. nh ngha mt bin i n chiu s dng hm imformarrray./ Thc hin bin i Khi ta nh ngha mt cu trc TFORM, ta c th thi hnh mt s bin i bng cch gi hm imtransform. Chng hn, on m sau s dng hm ny thi hnh mt bin i projective cho mt nh bn c:I = checkerboard(20,1,1);

figure; imshow(I)T = maketform('projective',[1 1; 41 1; 41 41; 1 41],...[5 5; 40 5; 35 30; -10 30]);R = makeresampler('cubic','circular');K = imtransform(I,T,R,'Size',[100 100],'XYScale',1); figure, imshow(K)

Hnh 1.11 nh trc v sau khi imtransforms- Cc tu chn ca hm imtransform cho php ta iu khin nhiu kha cnh ca vic bin i. Chng hn, ch rng nh b bin i xut hin nhiu bn copy ca nh gc. iu ny nhn c bi tu chon size.Xem thm Help Online

./ Hm imtransform p t mt bin i khng gian 2 chiu ln mt nh./ C phpB = imtransform(A,TFORM)B = imtransform(A,TFORM,INTERP) [B,XDATA,YDATA] = imtransform(...)[B,XDATA,YDATA] = imtransform(...,param1,val1,param2,val2,...)./ Din gii+ B=imtransform(A,TFORM ): bin i nh A theo cu trc c nh ngha trong TFORM. Cu trc ny c tr v t hm maketform hoc cp2tform. Nu ndims(A)>2 nh cc nh RGB th cng mt bin i khng gian 2 chiu c p t ti tt c cc mt phng theo chiu cao hn.Khi s dng c php ny, hm imtransform t ng dch gc ca nh ra nh ra c th c hin th nhiu nht c th.



+ B=imtransform(A,TFORM, INTERP): ch ra dng ca php ni suy c s dng. INTERP c th l mt trong cc gi tr nearest, bicubic hoc bilinear.Tng t, INTERP c th l mt cu trc c tr v t hm makeresampler. Tu chn ny cho php iu khin nhiu hn ln vic ly mu li (resampling).+ [B,XDATA,YDATA]= imtransform(): tr v v tr ca nh ra B trong khng gian X-Y. XDATA v YDATA cc vector hai thnh phn. Nhng thnh phn ca XDATA ch ra to x ca ct u v cui ca B. Nhng thnh phn ca YDATA ch ra to y ca ct u v cui ca B. Bnh thng, hm imtransform tnh ton XDATA v YDATA t ng v vy B cha ton b nh bin i A. Tuy nhin, ta c th chng tnh ton t ng ny xem di y:+ [B,XDATA,YDATA] = imtransform(...,param1,val1,param2,val2,...): Ch ra cc tham s iu khin nhiu kha cnh khc nhau ca bin i khng gian. Bng sau lit k cc tham s m ta c th ch ra.Tham sDin gii

UData VDataC hai tham s ny l cc vector hai phn t thc. Udata v Vdata ch ra v tr khng gian ca nh A trong khng gian vo 2 chiu U-V. Hai phn t ca Udata cho to u (honh ) ca ct u tin v cui cng ca A. Hai phn t ca Vdata cho to v ( tung ) ca hng u tin v cui cng ca A.Gi tr mc nh cho Udata v Vdata tng ng l [1 size(A,2) ] v [1 size(A,1) ]

Xdata YdataC hai tham s ny l cc vector hai phn t thc ch ra v tr khng gian ca nh ra B trong khng gian ra 2 chiu X-Y. Hai phn t ca Xdata ch ra honh x ca ct u tin v cui cng ca B. Hai phn t ca Ydata ch ra tung ca hng u tin v cui cng ca B.Nu Xdata v Ydata khng c ch ra, hm imtransform c lng gi tr cho chng c th cha ton b nh ra b bin i

XYScaleL vector vi mt hoc hai phn t thc. Phn t u tin ca XYScale ch ra chiu rng ca mi pixel vo trong khng gian X-Y. Phn t th hai (nu tn ti) ch ra chiu cao ca mi pixel ra. Nu XYScale ch c mt phn t, gi tr ny s c dng cho c chiu rng v chiu cao.Nu XYScale khng c ch nh nhng Size c ch ra th XYScale c tnh ton t Size,Xdata v Ydata.

SizeMt vector hai phn t nguyn khng m. Size ch ra s hng v ct trong nh ra B. Vi chiu cao hn, kch c ca B c ly trc tip t A. Ni cch khc, size(B,k) tng ng vi size(A,k) vi k>2. Nu Size khng c ch nh, n s c tnh t Xdata,Ydata v XYScale

FillValuesMt mng cha mt hoc nhiu gi tr t (fill values). Fill values c s dng cho cc pixel trn nh ra khi v tr c bin i tng ng trn nh vo hon ton l vin ngoi ca nh ra. nu A l 2 chiu, Fillvalues phi v hng. Tuy nhin, nu chiu ca A ln hn 2, FillValues c th l mt mng m kch thc ca n tho mn rng buc sau: size(fill_values,k) phi bng size(A,k+2) hoc 1.Chng hn, nu A l mt nh RGB unit8 c kch thc 200x200x3 th cc kh nng ca FillValues bao gm:+ 0: T vi mu en+ [0;0;0]: T vi mu en+ 255: T vi mu trng+ [255;255;255]: T vi mu trng+ [0;0;255]: T vi mu xanh+ [255;255;0]: T vi mu vngNu A l 4 chiu 200x200x3x10 th FillValues c th l 1 v hng 1x10,3x1,3x10

V dp mt php dch chuyn ngang ti mt nh cng ;I = imread('cameraman.tif');

tform = maketform('affine',[1 0 0;.5 1 0; 0 0 1]); J = imtransform(I,tform);imshow(I), figure, imshow(J)

Hnh 1.12 nh trc v sau khi imtransformsvi 1 cng nh

Chng 2CC PHNG PHP XC NH KHUN MT

2.1 nh ngha bi ton xc nh khun mt ngi2.2 ng dng ca phng php xc nh khun mt2.3 Phng php xc nh khun mt2.4 Kh khn v th thch trong bi ton xc nh khun mt ngi

Chng 2: Cc phng php xc nh khun mt36

Chng 2: Cc phng php xc nh khun mt37



Chng 2CC PHNG PHP XC NH KHUN MT

Hn mt thp k qua c rt nhiu cng trnh nghin cu v bi ton xc nh khun mt ngi t nh en trng, xm n nh mu nh ngy hm nay. Cc nghin cu i t bi ton n gin, mi nh ch c mt khun mt ngi nhn thng vo thit b thu hnh v u t th thng ng trong nh en trng. Cho n ngy hm nay bi ton m rng cho nh mu, c nhiu khun mt trong cng mt nh, c nhiu t th thay i trong nh. Khng nhng vy m cn m rng c phm vi t mi trng xung quanh kh n gin (trong phng th nghim) cho n mi trng xung quanh rt phc tp (nh trong t nhin) nhm p ng nhu cu tht s v rt nhiu ca con ngi.2.1 nh ngha bi ton xc nh khun mt ngiXc nh khun mt ngi (Face Detection) l mt k thut my tnh xc nh cc v tr v cc kch thc ca cc khun mt ngi trong cc nh bt k (nh k thut s). K thut ny nhn bit cc c trng ca khun mt v b qua nhng th khc nh: ta nh, cy ci, c th, 2.2 ng dng ca phng php xc nh khun mtC rt nhiu ng dng v ang c nghin cu, sau y chng em xina ra 1 vi ng dng trong thc t: H thng tng tc gia ngi v my: gip nhng ngi b tt hoc khim khuyt c th trao i. Nhng ngi dng ngn ng tay c th giao tip vi nhng ngi bnh thng. Nhng ngi b bi lit thng qua mt s k hiu nhy mt c th biu l nhng g h mun, . l cc bi ton iu b ca bn tay (hand gesture), iu b khun mt,

Nhn dng ngi A c phi l ti phm truy n hay khng? Gip c quan an ninh qun l tt con ngi. Cng vic nhn dng c th trong mi trng bnh thng cng nh trong bng ti (s dng camera hng ngoi). H thng quan st, theo di v bo v. Cc h thng camera s xc nh u l con ngi v theo di con ngi xem h c vi phm g khng, v d xm phm khu vc khng c vo, . Lu tr (rt tin ATM, bit ai rt tin vo thi im ), hin nay c tnh trng nhng ngi b ngi khc ly mt th ATM hay mt m s PIN v nhng ngi n cp ny i rt tin, hoc nhng ngi ch th i rt tin nhng li bo cho ngn hng l mt th v mt tin. Cc ngn hng c nhu cu khi c giao dch tin s kim tra hay lu tr khun mt ngi rt tin sau i chng v x l. Th cn cc, chng minh nhn dn (Face Identification). iu khin vo ra: vn phng, cng ty, tr s, my tnh, Palm,. Kt hp thm vn tay v mng mt. Cho php nhn vin c ra vo ni cn thit, hay mi ngi s ng nhp my tnh c nhn ca mnh m khng cn nh tn ng nhp cng nh mt khu m ch cn xc nh thng qua khun mt. An ninh sn bay, xut nhp cnh (hin nay c quan xut nhp cnh M p dng). Dng xc thc ngi xut nhp cnh v kim tra c phi l nhn vt khng b hay khng. Trong tng lai s pht trin cc loi th thng minh c tch hp sn c trng ca ngi dng trn , khi bt c ngi dng khc dng truy cp hay x l ti cc h thng s c yu cu kim tra cc c trng khun mt so vi th bit nay c phi l ch th hay khng. Tm kim v t chc d liu lin quan n con ngi thng qua khun mt ngi trn nhiu h c s d liu lu tr tht ln, nh internet, cc hng truyn hnh, V d: tm cc on video c tng thng Bush pht biu, tm cc phim c din vin L Lin Kit ng, tm cc trn banh c Ronaldo ,

Hin nay c nhiu hng tip cn xc nh mt nh c phi l nh kha thn hay khng? Khun mt ngi c xem nh mt yu t xc nh cho mt hng tip cn m c dng gn y. ng dng trong video phone. Phn loi trong lu tr hnh nh trong in thoi di ng. Thng qua bi ton xc nh khun mt ngi v trch c trng, ri da vo c trng ny sp xp lu tr, gip ngi s dng d dng truy tm khi cn thit. Kim tra trng thi ngi li xe c ng gt, mt tp trung hay khng, v h tr thng bo khi cn thit. Phn tch cm xc trn khun mt. Trong lnh vc thit k iu khin robot. Hng my chp hnh Canon ng dng bi ton xc nh khun mt ngi vo my chp hnh th h mi cho kt qu hnh nh p hn, nht l khun mt ngi.2.3 Phng php xc nh khun mtC nhiu nghin cu tm phng php xc nh khun mt ngi, t nh xm n ngy nay l nh mu. Da vo tnh cht ca cc phng php xc nh khun mt, cc phng php ny c chia lm bn hng tip cn chnh: Hng tip cn da trn tri thc: M ha cc hiu bit ca con ngi v cc loi khun mt ngi thnh cc lut. Thng thng cc lut m t quan h ca cc c trng. Hng tip cn da trn c trng khng thay i: Mc tiu cc thut ton i tm cc c trng m t cu trc khun mt ngi m cc c trng ny s khng thay i khi t th khun mt, v tr t thit b thu hnh hoc iu kin nh sng thay i. Hng tip cn da trn so khp mu: Dng cc mu chun ca khun mt ngi (cc mu ny c chn la v lu tr) m t cho khun mt ngi hay cc c trng khun mt (cc mu ny phi chn lm sao cho tch bit nhau theo tiu chun m cc tc gi nh ra so snh). Cc mi tng quan gia d liu nh a vo v cc mu dng xc nh khun mt ngi.

Hng tip cn da trn din mo: Tri ngc hn vi so khp mu, cc m hnh (hay cc mu) c hc t mt tp nh hun luyn trc . Sau h thng (m hnh) s xc nh khun mt ngi. Hay mt s tc gi cn gi hng tip cn ny l hng tip cn theo phng php hc.2.3.1 Hng tip cn da trn tri thcTrong hng tip cn ny, cc lut s ph thuc rt ln vo tri thc ca nhng tc gi nghin cu v bi ton xc nh khun mt ngi. y l hng tip cn dng top-down. D dng xy dng cc lut c bn m t cc c trng ca khun mt v cc quan h tng ng. V d, mt khun mt thng c hai mt i xng nhau qua trc thng ng gia khun mt v c mt mi, mt ming. Cc quan h ca cc c trng c th c m t nh quan h v khong cch v v tr. Thng thng cc tc gi s trch c trng ca khun mt trc tin c c cc ng vin, sau cc ng vin ny s c xc nh thng qua cc lut bit ng vin no l khun mt v ng vin no khng phi khun mt. Thng p dng qu trnh xc nh gim s lng xc nh sai.Mt vn kh phc tp khi dng hng tip cn ny l lm sao chuyn t tri thc con ngi sang cc lut mt cc hiu qu. Nu cc lut ny qu chi tit (cht ch) th khi xc nh c th xc nh thiu cc khun mt c trong nh, v nhng khun mt ny khng th tha mn tt c cc lut a ra. Nhng cc lut tng qut qu th c th chng ta s xc nh lm mt vng no khng phi l khun mt m li xc nh l khun mt. V cng kh khn m rng yu cu t bi ton xc nh cc khun mt c nhiu t th khc nhau.C hai tc gi Yang v Huang dng mt phng thc theo hng tip cn ny xc nh cc khun mt. H thng ca hai tc gi ny bao gm ba mc lut. mc cao nht, dng mt khung ca s qut trn nh v thng qua mt tp lut tm cc ng vin c th l khun mt. mc k tip, hai ng dng mt tp lut m t tng qut hnh dng khun mt. Cn mc cui cng li dng mt tp lut khc xem xt mc chi tit cc c trng khun mt. Mt h thng a phn gii c th t c dng xc nh (hnh 2.1).

(a)(b)(c)(d)Hnh 2.1 phn gii ca 1 nh; (a) nh ban u c phn gii n=1; (b),(c), v (d) nh c phn gii n=4, 8, v 16.Cc lut mc cao nht tm ng vin nh: vng trung tm khun mt (phn ti hn trong hnh 2.2) c bn phn vi mt mc u c bn, phn xung quanh bn trn ca mt khun mt (phn sng hn trong hnh 2.2) c mt mc u c bn, v mc khc nhau gia cc gi tr xm trung bnh ca phn trung tm v phn bao bn trn l ng k. phn gii thp nht (mc m) ca nh dng tm ng vin khun mt m cn tm cc mc phn gii tt hn. mc hai, xem xt biu histogram ca cc ng vin loi bt ng vin no khng phi l khun mt, ng thi d ra cnh bao xung quanh ng vin. mc cui cng, nhng ng vin no cn li s c xem xt cc c trng ca khun mt v mt v ming. Hai ng dng mt chin lc t th n mn hay lm r dn gim s lng tnh ton trong x l. Mc d t l chnh xc cha cao, nhng y l tin cho nhiu nghin cu sau ny.

Hnh 2.2 Mt loi tr thc ca ngi nghin cu phn tch trn khun mt.2.3.2 Hng tip cn da trn c trng khng thay iy l hng tip cn theo kiu bottom-up. Cc tc gi c gng tm cc c trng khng thay i ca khun mt ngi xc nh khun mt ngi. Da trn nhn xt thc t, con ngi d dng nhn bit cc khun mt v cc i tng trong cc t th khc nhau v iu kin nh sng khc nhau, th phi tn ti cc thuc tnh hay c trng khng thay i. C nhiu nghin cu u tin xc nh cc c trng khun mt ri ch ra c khun mt trong nh hay khng. Cc c trng nh: lng

my, mt, mi, ming, v ng vin ca tc c trch bng phng php xc nh cnh. Trn c s cc c trng ny, xy dng mt m hnh thng k m t quan h ca cc c trng ny v xc nh s tn ti ca khun mt trong nh. Mt vn ca cc thut tan theo hng tip cn c trng cn phi iu chnh cho ph hp iu kin nh sng, nhiu, v b che khut. i khi bng ca khun mt s to thm cnh mi, m cnh ny li r hn cnh tht s ca khun mt, v th nu dng cnh xc nh s gp kh khn.2.3.2.1 Cc c trng khun mtMt s phng php xc nh cc c trng ca khun mt c t l chnh xc cao:+ Phng php xc nh khun mt t mt nh c hnh nn phc tp. Phng php ny da trn cnh (dng phng php Candy v heuristics) loi b cc cnh cn li duy nht mt ng bao xung quanh khun mt. Mt hnh ellipse dng bao khun mt, tch bit vng u v hnh nn. T l chnh xc ca thut ton l 80%.+ Phng php xc nh khun mt trong nh xm. Dng b lc lm ni cc bin, cc php ton hnh thi hc (morphology) c dng lm ni bt cc vng c cng cao v hnh dng chc chn (nh mt). Thng qua histogram tm cc nh ni bt xc nh cc ngng chuyn nh xm thnh hai nh nh phn. Cc thnh phn dnh nhau u xut hin trong hai nh nh phn th c xem l vng ca ng vin khun mt ri phn loi xem c phi l khun mt khng. Phng php c kim tra trn cc nh ch c u v vai ca ngi. Tuy nhin cn vn , lm sao s dng cc php ton morphology v lm sao xc nh khun mt trn cc vng ng vin.+ Phng php xc nh khun mt da m hnh xc sut xc nh khun mt trong nh c hnh nn phc tp trn c s mt b xc nh c trng cc b v so khp th ngu nhin. chnh l xem bi ton xc nh khun mt nh l bi ton tm kim vi mc tiu l tm th t cc c trng chc chn ca khun mt to thnh ging nht mt mu khun mt. Dng nm c trng (hai mt, hai l mi, phn ni gia mi v ming) m t mt khun mt. Lun tnh quan h khong cch vi cc c trng cp (nh mt tri, mt phi), dng phn b Gauss

m hnh ha. Mt mu khun mt c a ra thng qua trung bnh tng ng cho mt tp a hng, a t l ca b lc o hm Gauss. T mt nh, cc c trng ng vin c xc nh bng cch so khp tng im nh khi lc tng ng vi vector mu (tng t mi tng quan), chn hai ng vin c trng ng u tm kim cho cc c trng khc ca khun mt. Ging nh xy dng mt th quan h mi node ca th tng ng nh cc c trng ca mt khun mt, a xc sut vo xc nh. T l xc nh chnh xc l 86%.+ Phng php xc nh khun mt dng l thuyt xc sut thng k v hnh dng. Dng hm mt xc sut (Probility Density Function- PDF) qua N im c trng, tng ng (xi, yi) l c trng th i vi gi s da vo phn b Gauss c 2N- chiu. Cc tc gi p dng phng thc cc i kh nng (Maximum Likelihood- ML) xc nh v tr khun mt. Mt thun li ca phng php ny l cc khun mt b che khut vn c th xc nh c. Nhng phng php khng xc nh c a khun mt trong nh.+ Phng php xc nh khun mt da vo c trng, dng s lng ln cc du hiu t nh v c du hiu v ng cnh. u tin dng b lc o hm Gauss th hai, xc nh cc im mu cht ti cc i a phng trong b lc, ri ch ra ni c th l c trng. Giai on hai, kim tra cc cnh xung quanh im mu cht v nhm chng li thnh cc vng. Tiu chun nhm cc cnh l gn v tng t hng v cng . o lng cc c tnh vng nh: chiu di cnh, cng cnh, v bin thin cng c lu trong mt vector c trng. T d liu c trng khun mt c hun luyn, s tnh c gi tr trung bnh v ma trn hip phng sai ca mi c trng khun mt. Mt vng l ng vin khun mt khi khong cch Mahalanobis gia cc vector c trng u di mt ngng. Ri thng qua mng Bayes xc nh ng vin c phi l khun mt khng. T l chnh xc l 85%, tuy nhin mc sai l 28%, v ch hiu qu vi hnh khun mt c kch thc 60x60 im nh. Phng php ny c dng thm vi m hnh ng vin linh hot.+ Phng php xc nh khun mt da trn tch c trng vng mc v c ng theo dao ng nh ca mt. Thut ton hot ng trn bn hay vng ca cc mu cht, m hnh ha li vng mc. u tin tnh ton c lng th vng

khun mt trn c s b lc. Giai on th hai tinh ch trn phn gii mn hn. T l sai l 4.69%.+ Phng php xc nh khun mt da trn c s hnh thi hc (morphology) trch cc on ging mt (eye-analogue) xc nh khun mt ngi. Phng php ny cho rng mt v lng my l c trng ni bt nht v n nh nht ca khun mt con ngi, v n rt hu dng xc nh khun mt ngi. Cc on ging mt nh l cc cnh trn ng vin ca mt. u tin, cc php ton morphology nh ng, ct b sai khc, v phn ngng trch cc im nh c gi tr cng thay i ng k. Cc im nh ny s tr thnh cc im nh ging mt. Sau mt tin trnh gn nhn sinh cc on ging mt. Cc on ny c dng ch dn tm kim cc vng tim nng c th l khun mt qua kt hp cc c tnh hnh hc ca mt, mi, lng my, v ming. Cc vng ny s c mt mng neural xem xt c phi l khun mt khng. T l chnh xc l 94%.+ Phng php xc nh khun mt da trn hnh dng v p dng cho cc khun mt chp thng. C hai giai on xc nh khun mt ngi: tp trung v phn loi chi tit. Lm c th t cc mnh cnh, cc mnh ny c trch t b xc nh cnh n gin thng qua s khc bit cng l qu trnh tp trung. Khi c cc ng vin t qu trnh trn, dng thut ton CART xy dng mt cy phn loi t cc nh hun luyn, xem xt ng vin no l khun mt ngi.+ Phng php xc nh khun mt dng cu trc hnh hc ca khun mt ngi tm ng vin khun mt trong nh xm v hnh nn khng phc tp. Mi nh ch c mt khun mt ngi, nhng t th iu kin nh sng, khng c nh. T l chnh xc khang 94.25% v thi gian kh nhanh.+ Phng php xc nh khun mt dng sc mu ca da ngi tm ng vin, bng cch dng m hnh mu da ngi trn tng phn nh ri x l phn on trn . Sau khi c ng vin khun mt, dng mt s c tnh v hnh dng xc nh khun mt ngi. T l chnh xc l 85%.2.3.2.2 Kt cuKhun mt con ngi c nhng kt cu ring bit m c th dng phn loi so vi cc i tng khc. C mt s nh nghin cu cho rng hnh dng ca

khun mt dng lm kt cu phn loi, gi l kt cu ging khun mt (face-like texture). Tnh kt cu qua cc c trng thng k th t th hai (SGLD) trn vng c kch thc 16x16 im nh. C ba loi c trng c xem xt: mu da, tc, v nhng th khc.2.3.2.3 Sc mu ca daThng thng cc nh mu khng xc nh trc tip trn ton b d liu nh m cc tc gi dng tnh cht sc mu ca da ngi (khun mt ngi) chn ra c cc ng vin c th l khun mt ngi (lc ny d liu thu hp ng k) xc nh khun mt ngi.2.3.2.4 a c trngGn y c nhiu nghin cu s dng cc c trng ton cc nh: mu da ngi, kch thc, v hnh dng tm cc ng vin khun mt, ri sau s xc nh ng vin no l khun mt thng qua dng cc c trng cc b (chi tit) nh: mt, lng my, mi, ming, v tc.2.3.3 Hng tip cn da trn so khp muTrong so khp mu, cc mu chun ca khun mt (thng l khun mt c chp thng) s c xc nh trc hoc xc nh cc tham s thng qua mt hm. T mt nh a vo, tnh cc gi tr tng quan so vi cc mu chun v ng vin khun mt, mt, mi v ming. Thng qua cc gi tr tng quan ny m cc tc gi quyt nh c hay khng c tn ti khun mt trong nh. Hng tip cn ny c li th l rt d ci t, nhng khng hiu qu khi t l, t th, v hnh dng thay i ( c chng minh). Nhiu phn gii, a t l, cc mu con, v cc mu bin dng c xem xt thnh bt bin v t l v hnh dng.Hnh chiu c dng nh cc mu xc nh khun mt ngi. Dng PCA (phn tch thnh phn chnh - Principal Component Analysis - PCA) c mt tp hnh chiu c bn t cc mu khun mt, hnh chiu c m t nh mt mng cc bit. Dng c trng hnh chiu ring kt hp bin i Hough xc nh khun mt ngi. Sau mt phng php xc nh da trn a loi mu xc nh cc thnh phn ca khun mt c trnh by. Phng php ny nh ngha mt s gi thuyt m t cc kh nng ca cc c trng khun mt. Vi mt khun mt s c mt tp gi thuyt, l thuyt DepsterShafer. Dng mt nhn t tin cy kim

tra s tn ti hay khng ca cc c trng ca khun mt, v kt hp nhn t tin cy ny vi mt o xem xt c hay khng c khun mt trong nh.

Hnh 2.3 Mt mu khun mt, c 16 vng v 23 quan h (cc mi tn).

2.3.4 Hng tip cn da trn din moTri ngc vi cc phng php so khp mu vi cc mu c nh ngha trc bi nhng chuyn gia, cc mu trong hng tip cn ny c hc t cc nh mu. Mt cch tng qut, cc phng php theo hng tip cn ny p dng cc k thut theo hng xc sut thng k v my hc tm nhng c tnh lin quan ca khun mt v khng phi l khun mt. Cc c tnh c hc trong hnh thi cc m hnh phn b hay cc hm bit s nn dng c th dng cc c tnh ny xc nh khun mt ngi. ng thi, bi ton gim s chiu thng c quan tm tng hiu qu tnh ton cng nh hiu qu xc nh.Cc tip cn khc trong hng tip cn da trn din mo l tm mt hm bit s (nh: mt phng quyt nh, siu phng tch d liu, hm ngng) phn bit hai lp d liu: khun mt v khng phi khun mt. Bnh thng, cc mu nh c chiu vo khng gian c s chiu thp hn, ri sau dng mt hm bit s (da trn cc o khong cch) phn loi, hoc xy dng mt quyt nh phi tuyn bng mng neural a tng. Hoc dng SVM (Support Vector Machine) v cc phng thc kernel, chiu hon ton cc mu vo khng gian c s chiu cao hn d liu b ri rc hon ton v ta c th dng mt mt phng quyt nh phn loi cc mu khun mt v khng phi khun mt.

2.4 Kh khn v th thch trong bi ton xc nh khun mt ngiVic xc nh khun mt ngi c nhng kh khn nht nh nh sau: Hng (pose) ca khun mt i vi my nh, nh: nhn thng, nhn nghing hay nhn t trn xung. Cng trong mt nh c th c nhiu khun mt nhng t th khc nhau. S c mt ca cc chi tit khng phi l c trng ring ca khun mt ngi, nh: ru quai nn, mt knh, . Cc nt mt (facial expression) khc nhau trn khun mt, nh: vui, bun, ngc nhin, . Mt ngi b che khut bi cc i tng khc c trong nh. iu kin nh, c bit l v sng v cht lng nh, cht lng thit b thu hnh. Trc to ca my nh so vi nh. Kch thc khc nhau ca cc khun mt ngi, v c bit l trong cng mt nh. Mu sc ca mi trng xung quanh, hay mu sc qun o ca ngi c chp ly nh. Xut hin thnh phn khun mt hay khng. Nhiu khun mt c vng da dnh ln nhau.Cc kh khn trn chng t rng bt c phng php gii quyt (thut ton) bi ton xc nh khun mt ngi s khng th trnh khi mt s khim khuyt nht nh. nh gi v so snh cc phng php xc nh mt ngi, ngi ta thng da trn cc tiu ch sau: T l xc nh chnh xc l t l s lng cc khun mt ngi c xc nh ng t h thng khi s dng mt phng php xy dng so vi s lng khun mt ngi tht s c trong cc nh (detection rate). S lng xc nh nhm l s lng vng trong nh khng phi l khun mt ngi m h thng xc nh nhm l khun mt ngi (false positives). Thi gian thc hin l thi gian my tnh xc nh khun mt ngi trongnh (running time).

Chng 3PHN TCH THNH PHN CHNH PCA (PRINCIPAL COMPONENT ANALYSIS)

3.1 S lc v phn tch thnh phn chnh PCA3.2 Thut ton PCA v ng dng trong nhn dng khun mt ngi3.3 ng dng Eigenfaces trong vic nhn dng mt ngi3.4 Nhn xt

Chng 3: Phn tch thnh phn chnh PCA (Principal Component Analysis)52

Chng 3: Phn tch thnh phn chnh PCA (Principal Component Analysis)53



Chng 3PHN TCH THNH PHN CHNH PCA

3.1 S lc v phn tch thnh phn chnh PCAPhn tch thnh phn chnh (Principal Component Analysis - PCA) c trnh by theo nhiu quan im khc nhau. Vi cc nh thng k c in th PCA l tm cc trc chnh ca ellipsoid nhiu chiu bao hm m my s liu phn phi chun nhiu chiu, cc trc c c lng t mt mu n c th, trn mi c th ngi ta o p ch tiu. Ngi u tin a ra k thut ny l H.Hotelling (1933), sau l T.W.Anderson (1958) v A.M.Kshirsagar (1972).Vi cc nh nhn t hc c in th k tht ny l phng php phn tch nhn t trong trng hp c bit, khi cc phng sai ny bng khng hoc xp x bng khng. Phng php ny thng c s dng trong phn tch tm l, do Horst (1965) v Harman (1966) xut.Sau cng, theo quan im ph bin hn c ca cc nh phn tch s liu th PCA l mt k thut biu din cc s liu mt cch ti u theo mt tiu chun i s v hnh hc c bit. khi s dng k thut ny ngi ta khng i hi mt gi thuyt thng k hoc mt m hnh c bit no. Quan im ny tr nn ph bin t khi c my tnh in t, v l quan im mi nht. Nhng t tng ca phng php ny do K.Pearson (1901) xut. Trong cng trnh ca C.R Rao (1964) ni dung l thuyt ca phng php PCA c trnh by kh n gin v r rng.Lnh vc ng dng ca phng php PCA rt rng trong cng nghip, nng nghip, kinh t, khoa hc c bn vi bng s liu m cc ct l cc bin v cc dng l cc c th, trn o gi tr ca bin.

3.2 Thut ton PCA v ng dng trong nhn dng khun mt ngi3.2.1 Thut tonKhun mt con ngi c rt nhiu nt nhn bit, nu nh ta gp li mt ngi bn sau mt thi gian di, ta c th nhn ra ngay ngi d nhng chi tit c th trn mt c th thay i nh da, mi tc. Ta nhn ra khng phi v nh i mt, hay mi hay mi hay tc, lng my ngi m ta nhn ra v nh din mo ca ngi . Tc l trn khun mt tn ti mt nt tng th no c th nhn din, thut ton ca ta bt u t tng ny .Phn tch thnh phn chnh (Principal Component Analysis ) gi tt l PCA l thut ton nhn dng nh da trn nhng nt tng th ca khun mt, ta s p dng thut ton ny thc hin hai cng vic sau : Th nht l xc nh v tr nhng khun mt ngi trong mt bc nh. Th hai l tm mt khun mt ging vi khun mt cho trc.Ban u ta c mt tp nh khun mt gi l tp nh hun luyn (training set). Gi s mi nh c kch thc M*N, ta coi mi bc nh ny l mt vector trong khng gian M*N chiu. By gi mi khun mt l mt vector, ta thy nhng vector ny khng phn b ngu nhin trong khng gian nh m phn b theo mt quy lut tng i no , ta c th ni nhng vector ny nm trong mt khng gian con gi l khng gian khun mt. T nhng vector trong tp hun luyn, ta s tm mt c s trc chun cho khng gian khun mt. Nhng vector thuc c s ny c th coi l nhng vector mang nhng nt tng th c trng v khun mt.3.2.2 Phn tch thnh phn chnh PCAGi s tp hun luyn c P nh, khi ta s c P vector: T1, T2, , TP.Tnh vector nh trung bnh :

p 1 pm Tii1

S khc bit gia nhng khun mt vi nh trung bnh l nhng vector:

Ai Ti m

, i=1P

tng ca vic phn tch thnh phn chnh l tm mt tp nhng vector trc chun uk sao cho nhng vector ny m t tt nht s phn b nhng vector khun mt trong khng gian. Nhng vector uk c chn sao cho:

ui / uj

1, i j0, i j

pk i1

2uk / Ai

ln nht .

Nhng vector uk v gi tr v hng ktng ng ca ma trn AAT.

chnh l nhng vector ring v tr ring

u / v l tch v hng gia hai vector u, v.

A A1

A2 ...

Ap

Ta thy ma trn A c kch thc M*N P, cn ma trn AAT c kch thc M*NM*N, do kch thc ma trn ny qu ln nn ta khng th tm c nhng vector ring v nhng tr ring trc tip c, thay vo ta s tm nhng vector ring ca ma trn ATA c kch thc PP .Nu v l mt vector ring ca ATA v l tr ring tng ng, khi ta c:ATA v = v ATA Av = Avtc l Av l mt tr ring ca ma trn AAT.Thng thng ta ch ly mt s Q vector ring ng vi Q tr ring c gi tr ln

nht.

Sau khi c cc vector ring ca ma trn AAT, ta s chun ha chng thu c

mt c s trc chun ca khng gian khun mt .t L= ATA , tm V l tp hp cc vector ring ca L, D l tp hp cc tr ring tng ng .V bao gm Q vector ring ng vi nhng tr ring ln hn mt gi tr no hoc ng vi Q tr ring ln nht trong D.

E = AV l tp cc vector ring ca AAT. Do y l nhng vector ring, m n li c dng khun mt nn cn uc gi l Eigenfaces. E l ma trn M*NQ, mi ct l mt vector ring.Chun ha cc vector ct trong E (chia mi vector cho di ca vector ). By gi, ta c th coi E l mt c s trc chun ca khng gian khun mt.Vi H l bc nh c cng kch thc vi nhng bc nh trong tp hun luyn. Ta s xt n c phi l bc nh khun mt hay khng, cng nh tm bc nh ging vi n nht trong tp hun luyn .H c xem l mt vector trong khng gian M*N chiu.t K= H - m vi m l vector nh trung bnh.Cho V l mt khng gian c tch v hng hu hn chiu v W l mt khng gian con ca V. Gi s W c mt c s trc chun l {u1, , uQ}. Khi hnh chiu trc giao ca vector u bt k ln W c xc nh nh sau:

Qprwu u0 i1

u / ui ui

di

u u0

c gi l khong cch t u n W .

Tp hp ci

u / ui

, i=1,, Q c gi l ta ca u0 trong khng gian W.

Tm C=ETK l ta ca hnh chiu Kf ca K ln khng gian khun mt. C l vector ct Q1

QK f cieii1

vi ci = C( i , 1) ; ei= E( : , i) .

Vi Ai l mt ct trong ma trn A (tng ng vi bc nh Ti trong tp hun luyn). Ta

tnh C

ET A

l ta ca hnh chiu Ai f ca Ai ln khng gian khun mt.

ii

Ta tnh hai i lng sau:

S

Si

K K fC Ci

xem nh khong cch t bc nh H n khng gian mt.

xem nh khong cch t H n bc nh Ti trong tp hun luyn.

Xt v l hai ngng no . s < th H l bc nh khun mt (do H gn vi khng gian mt).

si < th Ti l bc nh ca cng mt ngi vi H ( H gn vi Ti).Vy l ta c th tm bc nh trong tp hun luyn ging vi bc nh H hay xc nh c phi l bc nh khun mt hay khng. Tuy nhin nh H phi c cng kch thc vi nhng bc nh trong tp hun luyn. By gi trong mt bc nh ln H c nhiu khun mt, ta s xc nh v tr nhng khun mt trong bc nh.Ti mi v tr (x,y) trong H, t H(x,y) l mt vng trong nh H c kch thc MNti (x,y), ta xem nh con H(x,y) l mt vector M*N chiu.K(x,y) = H(x,y) mTm Kf(x,y) l hnh chiu ca K(x,y) ln khng gian khun mt .

Tnh

s(x, y)

K (x, y) K f (x, y)

Tp hp cc gi tr s(x,y) to thnh mt bn khun mt (face map) ca H, t ta c th xc nh v tr nhng khun mt trong nh.3.2.3 nh nh minh haTrong v d ny ta c mt tp hun luyn gm nhng bc nh khun mt kch thc 180x200 pixel, di y l mt s hnh nh ca nhng eigenfaces thu c (lu l y ch l cc vector trc giao, nhng eigenfaces thc s chnh l nhng vector ny c chun ha).

Hnh 3.1 EigenfacesBy gi ta chiu hai bc nh ln khng gian khun mt ny :

Hnh 3.2 Bc nh kim tra v hnh chiu ca nNh ta thy nu bc nh l khun mt ngi th hnh chiu s kh ging vi nh gc, cn khi bc nh khng phi l khun mt th hnh chiu s khc nh gc rt nhiu, do khong cch t bc nh mt ngi ti khng gian mt s nh hn rt nhiu so vi khong cch t bc nh khng phi mt ngi ti khng gian mt.Di y l mt v d khc, ta c mt tp hun luyn gm nhng bc nh kch thc 18x27 pixel, ta cng tm cc Eigenface v sau tm face map ca mt bc nh kim tra. Trong v d ny th nh con H(x,y) vng hnh ch nht c tm ti (x,y) trn bc nh v c kch thc 18x27 pixel.

Hnh 3.3 nh ban u

Hnh 3.4 Face map ca bc nh ban u.Ta thy v tr ca mi khun mt chnh l nhng vng cc tiu a phng trn bc nh (l nhng m en trong nhng vng trng hnh ch nht).By gi nu ta c mt c s d liu nhng nh khng phi khun mt (ta thng tp trung vo nhng hnh nh xung quanh khun mt nh c o, mt phn ca khun mt ). Tm face map ca bc nh ban u vi khng gian khng phi khun mt ny, ta thu c kt qu sau:

Hnh 3.5 Face map nh ban u vi khng gian khng phi l khun mtHnh trn cng kh ging vi face map ng vi khng gian khun mt nhng ti mi vng sng hnh ch nht th khng h c tm gia.Thc ra t face map ng vi khng gian khun mt, nu ta c mt thut ton tt tm nhng v tr cc tiu a phng th c th xc nh v tr cc khun mt. Face map ng vi khng gian khng phi khun mt ch l mt cch n gin gip ta tm chnh xc hn thi.Tt c nhng iu thu c trn ch l kt qu hon ton da trn l thuyt, trong thc t nhng thut ton nhn dng mt ngi pht trin ln rt nhiu t tng ca PCA mi c c chnh xc yu cu.3.3 ng dng Eigenfaces trong vic nhn dng mt ngiHu ht vic lm trc y trong h thng t nhn dng gng mt u cho rng vic nhn ra cc gc cnh ca gng mt trong cc trng thi khc nhau l rt quan trng trong vic nhn dng, tha nhn rng vic xc nhn trc cc khong cch l rt quan trng v cn thit. iu xut chng ti a ra phng php l thuyt thng tin cho vic m ha v gii m nhng nh mt ngi, a ra bn cht ni dung thng tin ca nhng nh mt ngi, nhn mnh nhng c trng cc b v ton cc. Nhng c trng c hoc khng c lin quan trc tip n cch quan st bng trc gic ca chng ta v cc c trng ca gng mt nh cp mt, mi, mi hoc mi tc.

Trong ngn ng ca l thuyt thng tin, chng ta mun trch xut cc thng tin quan trng ca nh mt ngi, m ha mt cch hiu qu trong phm vi c th, v so snh gng mt m ha vi kho d liu ca cc mu c m ha mt cch tng t. Mt cch d dng trch xut thng tin cha ng trong bc nh mt ngi l bng cch no ch ra s khc bit trong tp hp nh mt ngi, c lp trong phn tch cc nt mt, v s dng nhng thng tin ny m ha v so snh cc nh gng mt c th.V mt ton hc, chng ta tm ra cc thnh phn chnh trong s phn b ca mt ngi, hoc cc vect ring (eigenvectors) t ma trn tng quan ca dy nh mt ngi. Nhng vect ring ny c th c xem nh l dy nhng im c trng, chng lin kt nhau m t s khc nhau gia cc nh mt ngi. Mi v tr ca nh gp phn to ra mi vect ring, v vy ta c th trnh by vect ring bng mt loi mt ma ghostly face m ta cn gi l eigenface. Mt s mt loi ny c trnh by trong hnh 3.7.

Hnh 3.6 a) Nhng gng mt dng hun luynb) nh trung bnh

Hnh 3.7 By Eigenfaces c tnh ton t dy hun luyn ca hnh 4.6, phng nn c loi bMi nh mt ngi trong dy hun luyn c th c ti hin chnh xc thng qua eigenfaces. S lng eigenfaces tng ng vi s nh mt ngi c a vo hun luyn. Tuy nhin cc gng mt c th xp x bng cch ch s dng best eigenfaces, c to ra t cc gi tr ring ln nht v t c th tnh ton sai bit ln nht vi chui nh mt ngi. L do chnh cho vic s dng t eigenfaces l nh s hiu qa trong qu trnh tnh ton. M eigenfaces s m rng ra khng gian con M chiu - khng gian mt ngi- ca tt c nh c th. ng hnh sin biu th cc pha v tn s khc nhau l hm c bn ca phn b Fourier (l hm ring ca h thng tuyn tnh). tng s dng eigenfaces c thc y bi s pht trin k thut ca Sirvokick v Kirby - nhng bc hnh miu t hiu qa cc gng mt s dng phng php phn tch cc thnh phn chnh (principal component analysis - PCA). H chng minh rng cc b su tp nh mt ngi c th c to li mt cch gn ng bng vic lu tr b trng s cho mi gng mt v mt chui nh bc hnh chun (c th nh hn rt nhu so vi b su tp ban u).

Qu trnh nhn dng c th tm tt nh sau: Chun b: Thu thp dy hun luyn ca nh mt ngi v tnh ton cc eigenfaces, xc nh khng gian mt ngi. Khi nhn c bc nh mi, tnh ton dy trng s da vo nh u vo v M eigenfaces bng cch chiu nh u vo vi tng eigenface. C th xc nh nh u vo c phi l gng mt hay khng da vo vic kim tra nh c gn khng gian mt ngi hay khng. Nu l gng mt thi phn loi cc trng s xem c phi ngi bit trc hay cha. (khng bt buc) Nu gng mt cha bit xut hin vi ln th tnh ton cc trng s thnh phn v st nhp vo nhng gng mt bit (hc nhn dng).3.3.1 Tnh ton EigenfacesLy bc nh mt ngi I(x,y) l ma trn 2 chiu NN (cc gi tr trong ma trn th hin mc xm ti tng im nh), hoc l vect N2. Bc nh chun c kch thc 256x256 m t vect c 65536 chiu, hoc c th xem mi bc nh l mt im trong khng gian 65536 chiu. Vi mt chui nh th ta s c mt bn m t tp hp cc im (mi im c trng cho 1 nh) trong khng gian rng ln ny.nh ca cc gng mt, c th xem nh tng t nhau trong dng tng qut, ch khng phi s phn b ngu nhin trong khng gian nh rng ln do ta c th m t chng trong khng gian con t chiu hn. tng chnh ca phng php phn tch cc thnh phn chnh (PCA) l tm kim cc vect tnh ton s phn b nh mt ngi theo hng tt nht i vi vng nh u vo cho trc. Nhng vect ny xc nh khng gian con ca nh mt ngi, chng cn c gi l khng gian mt (face space).Nhng vect ny c chiu di l N2, m t bc nh NN, v n l s kt hptuyn tnh t cc nh gc u vo. Bi v cc vect l cc eigenvect ca ma trn tng quan (covariance matrix) thu c t cc nh gc u vo, bi v chng cng c hnh dng nh gng mt, nn thng c gi l eigenfaces. Mt s v d v eigenfaces c ch ra hnh 3.7.

Ly mt chui hun luyn ca nh mt ngi l

1 , 2 , 3 , 4 ,..., n . Mi bc nh

khc vi nh trung bnh theo vect c tnh bng cng thc.

i i . Gng mt trung bnh ca chui

1 M

Mnn1

Hnh 3.6 th hin dy hun luyn, nh trung bnh ch ra hnh 3.6b. Dy ny l cc vect c kch thc ln c tnh ton PCA, tm kim dy M cc vect trc giao v cc gi tr ring thch hp. Cc vect v thang o l cc vect ring v tr ring tng ng ca ma trn tng quan.

1 MTT

2C nn AA M n1

Trong ma trn

A 1 , 2 , 3 ,..., n , ma trn C c kch thc l N

x N2 v

phi xc nh N vect ring v tr ring, l nhim v rt kh lm i vi kch thc ca mt nh chun. Chng ta cn phi c phng php tnh ton hp l tm ra cc vect ring ny. Tht may mn khi ta c th xc nh cc vect ring bng vic tnh ton trong ma trn c kch thc nh hn nhiu M x M, sau dng kt hp tuyn tnh ca cc vect tnh c trn.Vi s phn tch trn th vic tnh ton c gim bt rt nhiu, t bc ca cc im nh N2 chuyn sang bc ca cc nh trong dy hun luyn M. Thc t nhng nh gng mt trong dy hun luyn s tng i nh (MD1 )LeigV = [LeigV V(:,i)]; endendE = A * LeigV; sovector=size(E,2); for i=1:sovectordodai=norm(E(:,i));E(:,i)=E(:,i)/dodai; end

*****on code nhandien1 ca chuong trnh nhn dng khun mt*************

function anhtim = nhandien1(anhtest, m, A, E)toado = [];%Tp ta hnh chiu ca cc bc nh trong csdlsovector = size(E,2);%s vector ring trong E l s for i = 1 : sovectortam = E'*A(:,i);%ta hnh chiu ca bc nh Ai toado = [toado tam];endtam = rgb2gray(anhtest);% chuyn nh mu thnh nh trng en [dong cot] = size(tam);InImage = reshape(tam',dong*cot,1); dolech = double(InImage)-m; toadoKT = E'*dolech;khoangcach = [];% tnh khong cch ca tm nh so vi cc nh mufor i = 1 : sovector% xc nh khong cch ngn nht q = toado(:,i);tam = ( norm( toadoKT - q ) )^2; khoangcach = [khoangcach tam];

end[minKC , vitri] = min(khoangcach); if minKC50000000 anhtim =100;end

%%********on code lin quan*******%%******* on code lu nh*********if s==255% kim tra nh chn lu c phi l nh hay khng selection = questdlg(['No la anh trang do ban co luu khong?'],...['Luu ' 'anh da chon!'],...'Yes','No','Yes');%a ra bn thng bo nu n l nh trng if strcmp(selection,'No')% chn No quay li chng trnhreturn;elseif strcmp(selection,'Yes') [filename,pathname]=uiputfile({'*.jpg','JPEG Files(*.jpg)';...'*.bmp','Bitmap Files(*.bmp)';'*.gif','GIF Files(*.gif)';... '*.tif','TIFF Files(*.tif)';...'*.*','all image file'},'Luu anh da chon!','anhkq/'); imwrite(s,[pathname,filename]);endelse% nu nh lu khng phi l nh trng[filename,pathname]=uiputfile({'*.jpg','JPEG Files(*.jpg)';... '*.bmp','Bitmap Files(*.bmp)';'*.gif','GIF Files(*.gif)';...'*.tif','TIFF Files(*.tif)';...%t tn v chn loi nh mun lu '*.*','all image file'},'Luu anh da chon!','anhkq/');%thc hin lu nhimwrite(s,[pathname,filename]); end

********* on code chn nh *******[filename,pathname]=uigetfile({'*.jpeg;*.jpg;*.gif;*.tif;*.tiff;*.bmp;*.png',...'all image file';'*.jpg;*.jpeg','JPEG Files(*.jpg,*.jpeg)';...% chn ng dn ni cha nh test '*.gif','GIF Files(*.gif)';'*.tif;*.tiff','TIFF Files(*.tif,*.tiff)';...'*.bmp','Bitmap Files(*.bmp)';'*.png','PNG Files(*.png)'},'Chon anh kiem tra! ','anhtest/1.png'); anhchon=imread([pathname,filename]);% c nh chnaxes(handles.axes1);imshow(anhchon);% hin nh chn a=strcat('anhluu/anh_goc.jpg');imwrite(anhchon,a);

**********on code xa nh ********a=255;% to ra nh trnga1=strcat('anhluu/anh_goc.jpg'); imwrite(a,a1);% bin tt c cc nh ang hin thnh nh trng a1=strcat('anhluu/anh1.jpg'); imwrite(a,a1);a1=strcat('anhluu/anh2.jpg'); imwrite(a,a1); a1=strcat('anhluu/anh3.jpg'); imwrite(a,a1); a1=strcat('anhluu/anh4.jpg'); imwrite(a,a1); a1=strcat('anhluu/anh_face.jpg'); imwrite(a,a1); a1=strcat('anhluu/anh_kq.jpg'); imwrite(a,a1); a1=strcat('anhluu/anhtest.jpg'); imwrite(a,a1); a1=255;axes(handles.axes1); imshow(a1);% hin nh trng ln cc nh axes(handles.axes2); imshow(a1);axes(handles.axes3); imshow(a1); axes(handles.axes4); imshow(a1); axes(handles.axes5); imshow(a1);

axes(handles.axes6); imshow(a1); axes(handles.axes7); imshow(a1);set(handles.ten,'string',' ');% xa cc dng d liu thng tin nhn dng set(handles.ns,'string',' ');set(handles.mssv,'string',' ');set(handles.lop,'string',' ');set(handles.quequan,'string',' ');

******* on code thot********

selection = questdlg(['Close ' get(handles.figure1,'Name') '?'],...% a ra cu hi ['Close ' get(handles.figure1,'Name') '...'],...'Yes','No','Yes');% to bn lu chn c hai nt hi Yes, No if strcmp(selection,'No')% nu chn No quay la chng trnhreturn;end% Nu chn Yes thot khi chng trnhdelete(handles.figure1)

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