Tom Tat - Watermarking_DCT.pdf (Nguyen Anh Duc)

7/30/2019 Tom Tat - Watermarking_DCT.pdf (Nguyen Anh Duc)

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1

M U

Vic trao i thng tin, xut bn thng tin trnInternet c nhiu nguy c khng an ton do thng tin c

th b l hay b sa i hay b vi phm bn quyn. Ni

chung, bo v cc thng tin trn khi s truy cp, s

dng tri php cn phi kim sot c nhng vic chnh

sau: thng tin c to ra, lu tr v truy nhp nh thno, u, bi ai v vo thi im no. Nh vy vic

qun l bn quyn s ang l bi ton khng d dng ca

nh qun l.

Trn thc t, nhu cu v bo v quyn tc gi,

quyn s hu cho cc thng tin s l rt ln. Phng php

Thy Vn s (digital watermarking) ha hn l mt

phng php hiu qu bi v n cho php ch s hu ni

dung s c th nhng v giu nhng bng chng v bn

quyn ca mnh, t c th xc nh c quyn s hu,pht hin ra vic s dng tri php m vn khng lm nh

hng n ni dung ca ni dung s. Vi cc tnh cht

c th ca mnh Digital watermarking rt thch hp vi

vic bo v bn quyn tc gi.


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2

Xut pht t yu cu ca thc t, nhm mc ch

hng ti mt phn nhim v nhim v bo v bn quyn

thng tin s, Lun vn c ta : Nghin cu xc nh

bn quyn nh s bng k thut Thy vn s (Digital

Watermarking)

Lun vn gm c 3 chng:

Chng 1: Tng quan v Thy vn s v cc chunnn Multimedia

Chng 2: Mt s k thut Thy vn trong nh s:

Chng 3: Xy dng phn mm thc hin k thut

thy vn trn nh s

Trong qu trnh thc hin Lun vn, do thi gian

cng nh trnh ca tc gi cn c nhng hn ch nht

nh nn khng th trnh khi nhng sai st. Rt mong

nhn c s gp ca cc thy, c gio v cc bn

Lun vn hon thin hn. Ti xin chn thnh cm n s

hng dn, v gip tn tnh ca GS.TS Nguyn Bnh,

cc thy trong Khoa K thut in t, khoa Quc t v

o to sau i hc Hc vin Cng ngh BC-VT gip

ti trong qu trnh hc tp cng nh trong qu trnh

lm Lun vn.


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3

CHNG 1- TNG QUAN V

WATERMARKING V CC CHUN NN

MULTIMEDIA

Trong chng ny, lun vn gii thiu tng quan

v k thut watermarking v nn d liu multimedia, cc

phng php nh gi cht lng phc v cho qu trnh

nghin cu v thc hin cc k thut ny

1.1. Watermarking1.1.1.Tng quan v Watermarking

Digital watermark c rt nhiu ng dng v c

p dng rt nhiu vo cc lnh vc khc nhau trong thc

t. Do c tnh mnh ca thut ton watermarking trong

min DCT, ti la chn watermarking trong min DCT

nghin cu v pht trin cho ng dng xc nh bn

quyn nh s.

1.1.2.Php bin i sng con dng trongWatermarking

1.1.3.ng dng ca watermarking cho cc nhdng audio, video

1.2. Nn d liu Multimedia


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1.2.1.Tng quan v multimedia1.2.2.Hiu qu nn d liu multimedia

1.2.2.1. T l nn v s bit trn mt mu

1.2.2.2. Cc thc o cht lng

- Thc o cht lng ch quan

- Thc o cht lng khch quan

(1.1)

Trong i,j ch v tr ca pixel trong nh.

SNR theo n v decibel c tnh theo biu thc

sau:

(1.2)Trong trng hp mt nh 8 bit, th PSNR tng

ng c tnh theo dB l:

(1.3)

M

i

N

j

jiIjiIMN

RMSE1

2

1

)],('),([1

M

i

M

j

M

i

N

j

M

i

N

j

jiIjiI

jiI

RMSE

jiIMN

SNR

1 1

2

1 1

2

10

1 1

2

2

)],('),([

),(

log10

),(1

log20

RMSEPSNR

255log20 10


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5

Trong 255 l gi tr pixel c th ln nht trong 8

bit.

1.2.2.3. Tr m ha

1.2.2.4. phc tp m ha.

1.2.3.Tng quan v nn nh1.2.4.Cc chun nn d liu multimedia

1.2.4.1.

Chun m ha nh tnh.

1.2.4.2. Cc chun m ha video

1.2.4.3. Chun m ha audio


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CHNG 2 - MT S K THUT THY VN

TRONG NH S

Chng ny cp n mt s khi nim c bn vtn hiu hnh nh v cc c tnh ca h thng th gic

ngi HVS. Ni dung chng cng nn ra cc k thutThy vn trn nh s ang c nghin cu ph bin. Ty

theo lnh vc p dng, cc yu cu c th m la chn mtphng php thch hp. Nhng nhn chung, C th chiacc k thut thu vn theo hai hng tip cn chnh:

Hng th nht da trn min khng gian nh c k thutm bt t quan trng nht LSB,Hng th hai l s dngcc phng php kho st gin tip khc thng qua cc k

thut bin i bao gm cc bin i DCT hay DWT.2.1. nh s2.1.1.nh tng t v nh s2.1.2.Cc loi nh s

2.1.2.1. nh nh phn

2.1.2.2. nh a cp xm

2.1.2.3. nh RGB (True Colour)

2.2. Cc c tnh ca h thng th gic HVS nhhng n qu trnh Thy vn

2.3. Cc k thut Thy vn trong nh s


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C th chia cc k thut thu vn theo hai hng

tip cn chnh:

Hng th nht da trn min khng gian nh tc

l tin hnh kho st tn hiu v h thng ri rc mt cch

trc tip trn min gi tr ri rc ca cc im nh gi l

trn min bin s c lp t nhin. Sau , tm cch nhng

cc thng tin bn quyn vo nh bng cch thay i ccgi tr im nh sao cho khng nh hng nhiu n cht

lng nh v m bo s bn vng ca thng tin nhng

trc nhng tn cng c th c i vi bc nh nhng

thu vn. in hnh cho cch tip cn ny l phng php

tch bit t quan trng nht (LSB-Least Significant Bit) v

phng php s dng chui s gi ngu nhin.

Hng th hai l s dng cc phng php kho

st gin tip khc thng qua cc k thut bin i. Cc k

thut bin i ny lm nhim v chuyn min bin s c

lp sang cc min khc v nh vy tn hiu v h thng ri

rc s c biu din trong cc min mi vi cc bin s

mi. Sau , tm cch nhng thu vn vo nh bng cch

thay i cc h s bin i trong nhng min thch hp

m bo cht lng nh v s bn vng ca thu vn sau


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khi nhng. Cc php bin i c s dng ph bin l

DCT, DFT (Discrete Fourier Transform) v DWT.

K thut thu vn s dng php bin i DCT

thng chia nh gc thnh cc khi, thc hin php bin

i DCT vi tng khi nh gc c min tn s thp,

min tn s gia v min tn s cao. a s k thut thu

vn n bn vng s chn min tn s gia ca mi khi nhng bit thu vn theo mt h s k no gi l h s

tng quan gia cht lng nh sau khi nhng thu vn

(tnh n ca thu vn) v bn vng ca thu vn.

K thut thu vn s dng php bin i DWT

thng phn tch nh gc thnh cc min tn s LL, LH,

HL v HH sau nhng thng tin thu vn vo mt hoc

mt s min tn s vi cc h s tng quan khc nhau.

nh cha thu vn sau c th qua cc php bin i

nh thng thng ri tm li thu vn. Kt qu, thu vn

trong cc bng th hin tnh bn vng khc nhau trc cc

php bin i.

2.3.1.K thutthy vn da trn min khng giannh


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K thut ny c s dng nhiu trong k thut

giu tin, s dng cc bit t quan trng nht ca im nh

(gi l LSB - Least Significiant Bit). K thut LSB l k

thut s dng cc bt t quan trng v th gic nht trong

cc bt mang gi tr im nh giu tin.

2.3.2.K thut thy vn da trn min tn s sdng bin i DCT

2.3.2.1. Bin i Cosine ri rc (DCT)

Bin i cosine ri rc l mt cng c ton hc x

l cc tn hiu nh nh hay video. N s chuyn i cc

tn hiu t min khng gian sang min tn s v bin i

ngc li t min tn s quay tr li min khng gian m

khng gy tn hao n cht lng.

L do chn bin i cosine cho x l nh s l bin

i cosine ri rc yu cu t s phc tp tnh ton v ti

nguyn hn.Bin i cosine ri rc mt chiu:


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y, C(u) l h s bin i cosine ri rc, f(x) l

bin tn hiu, N l s cc phn t, u=0,1,2,..,N-1

Bin i cosine ri rc hai chiu:

Do nh s l cc ma trn hai chiu, do bin icosine ri rc hai chiu c s dng, phng trnh bin

i nh sau:

y C(u,v) l h s bin i cosine ri rc. )(u ,

)(v c nh ngha theo (2.3), f(x,y) l phn t ma trn

Nvy

NuxvuCvuyxf

N

vy

N

uxyxfvuvuC

N

u

N

v

N

y

N

x

2)12(cos

2)12(cos),()()(),(

2

)12(cos

2

)12(cos),()()(),(

1

0

1

0

1

0

1

0

vi u = 0

vi u 0

1

0

1

0

2

)12(cos)()()(

2

)12(cos)()()(

N

u

N

x

N

uxuCuxf

N

uxxfuuC

N

Nu

2

1

)(


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hai chiu u vo, N l s hng hay s ct u vo.C th

thc hin 2-DCT thng qua 1-D DCT.

2.3.2.2. Thy vn s nh ti min DCT

Phng trnh nhng Watermark:

Trong , Cw(i,j) l h s DCT (i,j) sau khi nhng

thy vn v l cc ch s mnh thy vn, cc ch s ny

c th xc nh liu Thy vn l hu hnh hay v hnh;

C(i,j) l h s DCT ban u trc khi thc hin Thy vn

s; W(i,j) l h s DCT Thy vn.

2.3.2.3. K thut thy vn ca Chris ShoemarkerChris Shoemarker s dng php bin i DCT

phn tch khi c chn t nh gc thnh cc min

tn s, sau chn mt cp hai h s trong min tn s

gia thc hin qu trnh nhng mt bit thy vn. Qutrnh nhng m bo: nu bit cn nhng l 0 th sau khi

nhng F(u,v)>F(p,q), cn nu bit cn nhng l 1 th F(u,v)

F(p,q) ng thi sau khi nhng th khong cch gi tr

gia hai h s c chn lun ln hn hoc bng k(k l

s t nhin c chn trc) gi l h s tng quan gia

),(),( jiWjiCCw


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tnh n v tnh bn vng ca thu vn. Cc khi DCT sau

khi nhng thu vn c bin i bng php bin i

ngc IDCT, ri ghp cc khi nh kt qu theo th t

c nh cha thu vn.

Qu trnh tch thu vn c thc hin theo cc

bc: c vo theo th t khi nh nhng thu vn, s

dng DCT bin i khi sang min tn s, ly hai h s v tr chn trong qu trnh nhng thu vn ri tnh

k=F(u,v)-F(p,q). Nu k>0 th c bit thu vn tng ng

l 0, ngc li c bit 1. Ghp cc bit c thu vn

y .

H s k cng ln th cht lng nh sau khi nhng

thu vn cng gim, ng thi tnh bn vng ca thu vn

trong nh cha trc cc tn cng li cng tng. Vic s

dng mt h s k v qu trnh nhng thu vn lun m

bo tho mn iu kin v lch gia hai h s chn ln

hn hoc bng k l yu t quan trng quyt nh tnh bn

vng v tnh n ca thu vn. Cng vi c im chung

ca cc h thu vn, ln ca k t l nghch vi cht

lng nh sau khi nhng (tnh n ca thu vn) ng thi


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t l thun vi tnh bn vng ca thu vn trong nh gc

trc cc tn cng thng thng.

Vic chn mt cp hai h s trong min tn s gia

thc hin qu trnh nhng mt bit thy vn c th l ty

. Tuy nhin tng bn vng ca thy vn trc tn

cng ca php nn nh JPEG th ta nn la chn cp h s

ny theo bng lng t JPEG.2.3.3.K thut thy vn s dng php bin i sng

con (Wavelet)

2.3.3.1. K thut thy vn ca Mehul R. v Priti R

Trong k thut cc tc gi s dng php bin di

sng con hai chiu phn tch nh gc thnh cc min

tn s LL, LH, HL v HH sau nhng thng tin thu vn

th nht vo min tn s LL, nhng tn hiu thy vn khc

vo min tn s HH. nh cha thu vn sau c th

qua cc php bin i nh thng thng ri tm li thu

vn. Kt qu, thu vn trong cc bng th hin tnh bnvng khc nhau trc cc php bin i.

2.3.3.2. K thut thy vn ca Tao P. v Eskicioglu

A.M.


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Trong k thut ny cc tc gi nhng tn hiu

thy vn vo c 4 bng tn trong php phn tch sng con,

mi bng tn c th s dng cc h s khc nhau.


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- Cho nh cha thy vn chu tc ng ca

php thy vn nhiu ln

3.3.2. Kt qu thc hin thut ton trn minDCT vi nh mu RGB

Theo nghin cu v m hnh th gic ngi HVS

mt ngi km nhy cm vi thnh phn mu B, do

phn mm tin hnh nhng thy vn trn min ny gim s nhn bit ca mt ngi i vi thay i trn nh

c cha thy vn. M hnh ny l do tc gi t xut ra

tin hnh vit phn mm trn nn matlab. Kt qu th

nghim nh sau

3.3.2.1. So snh nh trc v sau nhng thy vn

vi cc h s K khc nhau

3.3.2.2. nh gi bn ca thy vn khi cho

nh c cha thy vn chu cc bin i

-

Cho nh cha thy vn chu tc ng caphp ct


php nn JPEG


php thy vn nhiu ln


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Kt lun

Chng 3 trnh by c th cc bc thit k

phn mm s dng k thut Thy vn s bo v bn

quyn nh s. Phn mm thnh cng theo yu cu t

ra. Cht lng hnh nh sau khi nhng thy vn vn

trong ngng chp nhn c, v c tnh bn vng

tng i cao i vi cc thao tc bin i, x l nhthng thng.

Da trn kt qu th nghim, a ra mt s nhn

xt:

- Thut ton trn min DCT cho php nhng v

tch thng tin mt cch d dng, thi gian thc hin thut

ton nhanh.

- Thut ton trn min DCT cho Thy vn bn

vng vi nhng bin i nh nn JPEG, hay ct nh.


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KT LUN V KIN NGH

1. Kt lunSau mt thi gian lm vic, vi s n lc ca bn

thn v c s hng dn tn tnh ca cc thy gio, ti

hon thnh Lun vn ca mnh. Ni dung ch yu ca

Lun vn l nghin cu cc thut ton Thy vn s thc

hin trn nh s. Qua qu trnh tm hiu v phn tch cc

cng ngh hin c, Lun vn t c mt s kt qu

sau:

Nhng ni dung chnh c gii quyt

trong Lun vn

Tng hp cc thut ton Thy vn s ang c s

dng ph bin trong nh s.

Tin hnh vit phn mm trn MATLAB s dng

K thut Thy vn s trn min DCT.

nh gi kt qu t c thng qua thc nghim.

Nhng ng gp khoa hc v thc tin ca

Lun vn


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Cc kt qu nhn c cho thy m hnh giu tin

xut thnh cng khi nhng mt chui tin cho trc vo

mt nh s m khng lm thay i cht lng hnh nh.

Vic s dng thut ton Thy vn s trn min DCT

dung ho c hai yu cu c bn l tnh bn vng v

dung lng tin mt cch tt nht. Do vy, Lun vn hon

ton c tnh kh thi, v c ngha rt quan trng tronglnh vc bo v bn quyn, s hu tr tu, khng nhng

c p dng trong thng mi m cn m ra mt hng

tip cn mi cho vn bo v thng tin lin lc.

Nhng hn ch ca Lun vn

Lnh vc a phng tin nhiu nh dng khc ngoi

nh nh m thanh, video... cn c bo v bn quyn tc

gi. Lun vn mi ch khai thc c k thut Thu vn

trn nh s.

2. Kin nghDa vo nhng kt qu t c pht trin tip

phn mm c th ng dng vo bt k d liu a

phng tin no, tng cng c tnh bn vng ca thy

vn.

Documents

Tom Tat - Watermarking_DCT.pdf (Nguyen Anh Duc)