Báo cáo XLA - nhóm 11 -đề tài 41 - Trần Danh Tùng
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TRNG I HC BCH KHOA H NI
VIN CNG NGH THNG TIN V TRUYN THNG
Bo co BTL Mn: X L NH
Ti: TM HIU PHNG PHP NN NH JPEG 2000
nh gi thc nghim bng chng trnh cht lng nh JPEG2000 so vi nhJPEG trong cc trng hp c th
Ging Vin Hng Dn : PGS-TS Nguyn Th Hong Lan
Nhm sinh vin thc hin: Nhm 11
1. Trn Danh Tng - 20073350
2. Duy c - 20070837
H Ni, thng 12 nm 2010
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MC LC
I Gii Thiu Chung............ 2
1.1 Lch s ra i v pht trin ca chun JPEG2000...2
1.2 Cc tnh nng ca JPEG2000...4
II Cc bc thc hin nn nh theo chun JPEG2000.....4
2.1 X l trc bin i .4
2.2 Bin i lin thnh phn....4
2.3 Bin i ring thnh phn ....5
2.4 Lng t ha v gii lng t ha....6
2.5 - M ha v kt hp dng d liu sau m ha .....6
2.6 Phng php m ha SPIHT.7
2.7 - Phng php m ha EZW ...8
III- So Snh chun JPEG v JPEG2000, Kt qu thc nghim.......10
3.1- So snh chun JPEG v JPEG2000..10
3.2 Kt qu thc nghim, nh gi...........15
3.3 - Cc ng dng ca JPEG2000..........19
IV- Ti Liu Tham Kho20
Phn cng cng vic20
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I- GII THIU CHUNG
1.1- Lch s ra i v pht trin ca chun JPEG2000
Cng ngh JPEG - Joint Photographic Experts Group (Hip hi cc chuyn gia
hnh nh): L mt cng ngh nn nh tng i hiu qu c th lm vic vi ccnh kch c ln, nhiu mu. K thut ny c th t c h s nn hn tm miln so vi nh gc. Tuy nhin, h s nn cng cao th hnh nh sau khi gii nn scng b sai lch nhiu hn, n ch gn ging nh ban u ch khng t hon tonnh hnh nh gc. D sao th vi mt thng rt kh nhn ra iu khc bit.
Nguyn l ca phng php nn JPEG l: Ct hnh nh thnh tng khi nh,phn tch tt c cc d liu v mu sc, sng m cc khi cha bng cc
phng trnh ma trn. nh mu trong khng gian RGB (Red, Green, Blue) cchuyn i qua h YUV. Trong khi th gic ca con ngi li rt nhy cm vi hY, t nhy cm hn nhiu vi h U, V. H thng s nn thnh phn Y ca nh mc t hn nhiu so vi U v V. K tip l dng bin i Cosin ri rc, sau nal m ha theo phng php Hoffman. (Khi gii nn nh, cc bc thc thi s lmngc li qu trnh ni trn)
V phng php ny thc hin vi cc vng nh (thng thng l 8 x 8 pixel) nnhay xut hin s mt mt thng tin trn vng bin ca cc vng (block) ny.
Nh vy chng ta c th thy, mc d s ra i ca JPEG mang li nhiu lich to ln v nhiu mt nh: Lm gim nh kch thc nh, gim thi gian truynv lm gim chi ph x l nh vi mt cht lng nh kh tt nhng vic k thutnn JPEG s lm mt thng tin lc gii nn (cng nn vi h s cao th thng tincng mt nhiu khi bung) l mt hn ch khng nh ca phng php ny. V th gii quyt vn ny, thng 12/1999 mt bn phc tho tiu chun nn hnh nhtheo cng ngh mi JPEG2000 - Vi tiu ch dung lng nh hn nhng cht
lng hnh nh cao hn c ra i.Cho n thng 8/2000, bn phc tho ny c lu hnh trong gii chuyn giav hnh nh. Sau n c cng nhn l tiu chun quc t vo thng 12/2000v c ISO hp thc ha vo nm 2004 cho php ng dng vo cc h x l ,
phn phi.
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Vi JPEG2000 k thut x l hnh nh s t c nhng kt qu tht s ngkinh ngc v c th nn nh t 100-200 ln m hnh nh khng sai st bao nhiu so
vi hnh nh gc.
Khi Qut chung v JPEG2000:
JPEG2000 l h thng m ha hnh nh m k thut nn da trn k thut sngngn (wavelet). L mt tin ch ton hc cho php m t bng mt cng thc ngin nhng g xy ra ti mt thi im chnh xc ca tn hiu. Vi mt chui sngngn, ch cn biu din bng vi cng thc, ng biu din khng u m khng
cn phi m t c tnh ca tng im mt. Nh vy, ta c th nhn thy c vaitr c lc ca cng ngh ny trong khi phn tch t m mt file nh k thut s.
Thut ton trong k thut JPEG2000 l chn mt s nh cc sng ngn, ccsng ny c lp li nhng ni khc nhau, t l khc nhau m t chnh xctn hiu ca hnh nh. File nh nn khng cha nhiu hn s lng ch v tr vgin n ca tng sng ngn. Vic p dng k thut m ha theo tng khi, theotng khu vc u tin ca hnh nh (ROI -Regional Of Interest) cng l mt s tin
b ng k trong thut ton m ha JPEG2000.
Vi vic c ISO cng nhn, chng ta c th tin tng rng trong mt tng laign JPEG2000 s c thng mi ha thng qua nn cng nghip k thut s mli ch mang li ph hp nht l chn on hnh nh t xa trong Y khoa, hnhnh trn Internet, thm ch c th l phim nh k thut s thng qua nh dngMotion JPEG2000. V chc chn cc thit b di ng nh my tnh cm tay v inthoi di ng cng s khng b qua chun nn hnh nh ny
1.2- Cc tnh nng ca JPEG2000
JPEG2000 c nhiu chc nng c bit hn mi chun nn nh tnh khc nhJPEG hay GIF. Ta c th im qua mt s chc nng u vit caJPEG2000 so vicc chun nn nh tnh khc nh:- Cho cht lng nh tt nht khi p dng nn nh tnh c tn tht.
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- S dng c vi truyn dn v hin th lu tin v cht lng, phn gii, ccthnh phn mu v c tnh nh v khng gian.- S dng cng mt c ch nn nh cho c hai dng thc nn.- Truy nhp v gii nn ti mi thi im trong khi nhn d liu.- Gii nn tng vng trong nh m khng cn gii nn ton b nh.- C kh nng m ho nh vi t l nn theo tng vng khc nhau.- Nn mt ln nhng c th gii nn vi nhiu cp cht lng tutheo yu cu cangi s dng.
II CC BC THC HIN NN NH THEO CHUN JPEG2000
Chng ta c th hnh dung trnh t m ha v gii m JPEG2000 trong m hnhdi y:
Hnh 1 Trnh t m ha(a) v gii m JPEG2000 (b)
2.1 X l trc bin i:
Do s dng bin i Wavelet, JPEG2000 cn c d liu nh u vo dng ixng qua 0. X l trc bin i chnh l giai on m bo d liu a vo nnnh c dng trn. pha gii m, giai on x l sau bin i s tr li gi tr gc
ban u cho d liu nh.
2.2 Bin i lin thnh phn:
Giai on ny s loi b tnh tng quan gia cc thnh phn ca nh. JPEG2000s dng hai loi bin i lin thnh phn l bin i mu thun nghch (ReversibleColor Transform -RCT) v bin i mu khng thun nghch ( Irreversible ColorTransform -ICT) trong bin i thun nghch lm vic vi cc gi tr nguyn,cn bin i khng thun nghch lm vic vi cc gi tr thc. ICTvRCTchuynd liu nh t khng gian muRGB sang YCrCb.RCTc p dng trong c hai
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dng thc nn c tn tht v khng tn tht, cnICTch p dng cho nn c tntht. Cng thc ca bin i thun v ngc ca hai php bin i. ICT v RCTcho phn ph lc. Vic p dng cc bin i ny trc khi nn nh khng nmngoi mc ch lm tng hiu qu nn. Cc thnh phn Cr, Cb c nh hng rt tti s cm nhn hnh nh ca mt trong khi thnh phn chi Yc nh hng rtln ti nh. Chng ta c th thy r iu ny trong hnh 2
Hnh 2 Hnh minh ha nh vi RGB v YCrCb
2.3. Bin i ring thnh phn (bin i Wavelet)
- Bin i ring thnh phn c p dng trong JPEG2000 chnh l bin iWavelet. m bo tnh ton vn thng tin cng phi p dng cc php bin ithun nghch hoc bt thun nghch. Do php bini Waveletkhng phi l mt
php bin i trc giao nh bin iDCTm l mt php bin i bng con nncc thnh phn s c phn chiathnh cc bng tn s khc nhau v mi bng sc m ha ring r.
- JPEG2000 p dng bin i Waveletnguyn thun nghch 5/3 (IWT) v bini thc khng thun nghch Daubechies 9/7. Vic tnh ton bin i trong
JPEG2000 ny s c thc hin theo phng php Lifting(Cng thc c th caphng phpLiftingv bin i WavelettrongJPEG2000 cho phn ph lc). S ca phng php Lifting 1D p dng trongJPEG2000 trn hnh 4.3.Vic tnhton bin i Wavelet 2D suy ra t bin i Wavelet 1D theo cc phng php
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phn gii nh tu chn. TrongJPEG2000 c 3phng php phn gii nh nhngphng php c s dng nhiu nht chnh lphng php kim t thp.
Hnh 3 Phng php Lifting 1D dng tnh ton bin i wavelet
Do bin i Wavelet 5/3 l bin i thun nghch nn c th p dng cho nnnh theo c hai phng php, c tn tht v khng tn tht trong khi bin i 9/7
ch p dng cho nn nh theo phng php c tn tht thng tin.
2.4 Lng t ha v gii lng t ha
Cc h s ca php bin i s c tin hnh lng t ho. Qu trnh lngt ho cho php t t l nn cao hn bng cch th hin cc gi tr bin i vi chnh xc tng ng cn thit vi mc chi tit ca nh cn nn. Cc h s bin is c lng t ho theo php lng t ho v hng. Cc hm lng t hokhc nhau s c p dng cho cc bng con khc nhau v c thc theo biu
thc:
Vi:
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l bc lng t, U ( x, y) l gi tr bng con u vo; V( x, y) l gi tr saulng t ho. Trong dng bin i nguyn, t bc lng t bng 1.Vi dng
bin i thc th bc lng t s c chn tng ng cho tng bng con ringr. Bc lng t ca mi bng do phi c trong dng bt truyn i phathu c th gii lng t cho nh. Cng thc gii lng t ho l:
Vi:rl mt tham s xc nh du v lm trn, cc gi tr U(x,y);V(x,y) tng ng lcc gi tr khi phc v gi tr lng t ho nhn c. JPEG2000 khng chotrc rtuy nhin thng chn 1 r= 2.
2.5 M ha v kt hp dng d liu sau m ha
Theo khuyn ngh ca u ban JPEG quc t th JPEG2000 c th s dngnhiu phng php m ho khc nhau cng nh nhiu cch bin i Waveletkhcnhau c th thu c cht lng nh tng ng vi ng dng cn x l. iuny gip cho JPEG2000 mm do hn nhiu so vi JPEG. Vic p dng cc
phng php m ho khc nhau cng c m rng sang lnh vc nn nh ngbng bin i Wavelet. Trong thc t cc phng php m ho nh c p dng
khi nn nh bng bin i Waveletcng nh JPEG2000 th c hai phng phpc coi l c s v c p dng nhiu nht: phng php SPIHTv phngphpEZW.
Hin nayJPEG2000 vn c p dng m ho bng hai phng php ny vmt phng php pht trin t hai phng php ny l phng php m ho mt
phng bt. V th y chng ta s xem xt hai phng php ny. Vic kt hpdng d liu sau m ho caJPEG2000 thc chtl thc hin cc tnh nng c
bit caJPEG2000 nh tnh nngROI
2.6 - Phng php m ho SPIHT
C th thy rng d p dng bin i Waveletno hay cng vi n l mt php phn gii nh no th trong cc bng con c s th t thp cng l nhngthnh phn tn s cao (mang thng tin chi tit ca nh) trong khi nhng bng conc s th t cao hn th s cha nhng thnh phn tn s thp (mang thng tinchnh v nh). iu ngha l cc h s chi tit s gim dn t bng con mc
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thp (HH1 chng hn) (ng vi thnh phn tn s cao) xung bng con mc cao(ng vi thnh phn tn s thp) v c tnh tng t v khng gian gia cc bngcon, v d nh mt ng bin ca hnh v trong nh s tn ti cng mt v trtrn cc bng con (tng ng vi mc phn gii ca bng con y). iu ny dn ti s ra i ca phng php SPIHT(Set partitioning inhierarchical trees- phng php m ho phn cp theo phn vng). Phng php SPIHTc thitk ti u cho truyn dn lu tin. iu ny c ngha l ti mi thi im trong qutrnh gii nn nh theo phng php m ho ny th cht lng nh hin th ti thiim y l tt nht c th t c vi mt s lng bt a vo gii m tnh choti thi im y. Ngoi ra, phng php ny s dng k thut embeddedcoding;iu c ngha l mt nh sau nn vi kch c (lu tr) ln (t l nn thp) scha chnh d liu sau nn ca nh c kch c (lu tr) nh (t l nn cao). B mho ch cn nn mt ln nhng c th gii nn ra nhiu mc cht lng khc nhau.Gi s gi cc pixeltrong mt nhp cn m ho l pi, j. p dng mt php bin
i Wavelet Tno cho ccpixeltrong nh to ra cc h s ca php bin iWaveletl ci, j. Cc h s ny to ra mt nh bin i l C. Php bin i ny cvit di dng ton t nh sau: C=T(p). Trong phng php truyn dn lu tinvi nh th b m ho s bt u qu trnh khi phc (gii nn) nh bng cch tcc gi tr ca nh khi phc t cc h s bin i l c . S dng cc gi tr giim ca cc h s bin i to ra mt nh khi phc (vn cha p dng bin ingc Wavelet) l c v sau p dng bin i ngc Wavelet to ra nh cuicng l p . Chng ta c th vit di dng ton t nh sau:p = T 1 (c) .Nguyntc quan trng ca phngphp truyn dn nh theo kiu lu tin chnh l phng
php ny lun truyn i cc gi tr mang thng tin quan trng hn ca nh itrc. S d lm nh vy l do cc thng tin chnh l cc thng tin s lm gimthiu nhiu nht mo dng ca nh (s sai khc gia nh gc v nh khi phc).y chnh l l do ti sao phng php SPIHTlun truyn i cc h s ln trcv cng l mt nguyn tc quan trng ca phng php ny. Mt nguyn tc na lcc bt c trng s ln bao gi cngmang thng tin quan trng nht trong d liunh phn. Phng php SPIHTs dng c hai nguyn tc ny; n sp xp cc h s
bin i v truyn i cc bt c trng s ln nht. Qu trnh gii m c th dng li bt k mt bc no ng vi gi tr nh cn m ho yu cu. y chnh l cchm phng php m ho SPIHTlm tn tht thng tin.
2.7- Phng php m ho EZW
Phng php m ho EZW (Embedded Zerotree Wavelet Encoder) cng datrn c s php m ho lu tin (progressive coding) ging nhphng php mho SPIHT. Phng php ny ch yu da trn khinim v cyzero (zerotree).V c bn, thut ton ny da trn hainguyn tc nh trnh by phn phng
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php m ho SPIHT. Sau ychng ta s xem xt cc khi nim c bn ca thutton:
Cy t phn:Sau khi p dng bin i Waveletng vi cc mc phn gii khc nhau chng
ta c th biu din cc h s bin i di dng mt cy. Ta thy rng vi cy biudin ny c mi nt cha th c 4 nt con. Kt qu ny l do qu trnh bin iWavelet cc t l khc nhau. Cc cy ny c gi l cc cy t phn (quadtree).S cy t phn:
Hnh 4 cy t phn (a) v s phn mc (b)
Cy zero (zerotree): Cyzero l mt cy t phn, trong tt c cc nt ca nu nh hn nt gc. Mt cy nh vy khi m ho s c m ho bng mt itng duy nht v khi gii m th chng ta cho tt c cc gi tr bng khng. Ngoira c th m ho c cc h s Wavelettrong trng hp ny, gi tr ca ntgc phi nh hn gi tr ngng ang c xem xt ng vi h s WaveletSau khi c cc khi nim cn thit v cy t phn v cy zero, chng ta c th
trnh by nguyn l hot ng ca thut ton. Thut ton s m ho cc h s theoth t gim dn. Chng ta s dng mt gi tr gi l ngng (threshold) v s dngngng ny tin hnh m ho cc h s bin i. Cc h s c m ho theoth t t vng tn s thp n vng tn s cao. V ch nhng h s c gi tr tuyti ln hn hoc bng ngng th mi c m ho. Tip theo gim ngng vtip tc lm nh vy cho ti khi ngng t ti mt gi tr nh hn gi tr ca h
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s nh nht. Cch gim gi tr ngng y thc hin tng i c bit, gi trca ngng gim xung mt na so vi trc . B gii m phi bit cc mcngng ny th mi c th gii m nh thnh cng. Nhng khi ta i t nt cha nnt con trong cy t phn th n vn c 3 nt con. Vy ta phi i theo nhnh c ntcon no trc. Hay ni mt cch y hn ta di chuyn t h s ny n h skhc theo th t nh th no. C nhiu cch di chuyn khc nhau, tuy nhin haicch di chuyn trn hnh 5 l c s dng nhiu nht.
Hnh 5 - Hai cch sp xp th t cc h s bin i
Vic sp xp ny cn cn phi c quy c thng nht gia qu trnh m hov qu trnh gii m vic gii m nh c thnh cng. Hin nay phng phpm ho ny c p dng ngy cng nhiu trong vic x l nn nh ng. Phng
php ny cho t l nn v tin cy gii m cao. Ngoi ra phng phpEZWrt dtrin khai trn my tnh bi phng php ny khng yu cu vic lp trnh qu
phc tp.
III So Snh chun JPEG2000 v JPEG, Kt qu thc nghim :
Mt tnh nng quan trng v l u im r nt nht ca JPEG2000 so viJPEG cng nh cc chun nn nh khc nh MPEG 4 VTC hay JPEG - LS v. v....l JPEG2000 a ra c hai k thut nn c tn tht v khng tn tht theo cngmt c ch m ho ngha l JPEG2000 thc hin tt c cc dng thc ca JPEGch bng mt c ch m ho duy nht.
Nu xt v s tn ti ca hai k thut ny thJPEG cng c kh nng nnnhc tn tht v khng tn tht thng tin. Tuy nhin viJPEG th cch m ho vi
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hai dng ny l khc nhau v rt kh s dng c hai dng ny cng lc cho cngmt ng dng. Do , c th thy rng JPEG2000 c tnh mm do hn bt kchun nn nh tnh no trc y. Hn th, chng ta thy rng tt c cc
phng php thit k cho chunJPEG2000 u u vit v c nhiu tnh nng hnso viJPEG; ngoi ra nhng thng k v thc t cho thy vi cng mt t l nnv mt loi nh th nh c nn bi JPEG2000 hu nh lun c cht lng tthn so viJPEG. Chng ta c th quan st hai nh trong hnh 6 thy r iuny, nh bn tri c nn theoJPEG cn nh bn phi c nn theo
JPEG2000.
Hnh 6: So snh JPEG v JPEG2000
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Tnh nng u vit th hai ca JPEG2000 so vi JPEG chnh l trong dngthc nn c tn tht thng tin, JPEG2000 c th a ra t l nn cao hn nhiu sovi JPEG.
Cc phn mm nn nhJPEG hin ti (k cPhotoshop) cng ch thit k c th nn c ti t l 40:1 nhng vi JPEG2000 th t l nn c th ln ti200:1. Theo cng thc tnh PSNR trong n v dB, chng ta c: (b l s bt dng
biu din mtpixeltrn nh gc)
Vi hai nh hnh 6, s so snh v tham sPSNR cho trong bng pha di. cth so snh d dng hn, ta xt nh c nn vi cc t l khc nhau (o lng bih s bt/pixelhay bpp). Tt c cc s liu trn bng u cho thy JPEG2000 nnnh tt hn l JPEG; hn th h s PSNR m chng ta xt trong bng c otrong h n v logarit
Bng So snh JPEG v JPEG2000
- Tnh nng u vit th 3 ca JPEG2000 so vi JPEG l chun nn nh ny cth hin th c cc nh vi phn gii v kch thc khc nhau t cng mtnh nn.
Vi JPEG th iu ny l khng th thc hin c. S d c iu ny l doJPEG2000 s dng k thut phn gii nh v m ho nh km m chng ta niti phn m ho nh theoJPEG2000. Tnh nng ny l mt li th c bit quantrng caJPEG2000, trong khiJPEG cng nh cc chun nn nh tnh trc y
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phi nn nhiu ln thu c cht lng vi tng ln nn khc nhau th viJPEG2000 ta ch cn nn mt ln cn cht lng nh th s c quyt nh tutheo ngi s dng trong qu trnh gii nn nh theoJPEG2000. Mt tnh nng uvit na ca JPEG2000 l tnh nng m ho nh quan trng theo vng (ROI -
Region of Interest) m chng ta cp trong phn m ho nh theo JPEG2000.Cht lng ca ton b nh cng c thy r trn hnh 7.
Chng ta c th hiu r hn v u im ca cng ngh JPEG2000 so vi cc chunnn nh tnh khc thng qua bng ph lc di y:
Hnh 7:
Minh ha
tnh nng
ROI
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Ph Lc:
Bng so snh chun nn JPEG2000 v cc chun nn khc:
T bng trn chng ta c th thy cc tnh nng vt tri v kh nng u vit caJPEG2000 so vi cc chun nn nh tnh trc y
3.4- Mt s kt qu thc nghim
Gii thiu phn mm
Trong bo co ny nhm s dng cng c phn mm Morgan JPEG ToolBoxV2 x l so snh gia nh nn JPEG (Jpg) v JPEG2000 (JP2). Phn mm cdownload ti a ch http://www.morgan-multimedia.com/buyitJPEGTBOXV2.htm
Giao din chnh chng trnh:
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Cc nh dng m phn h tr (c th open thng qua phn mm v lu li sau khix l): .JP2, .J2C, .bmp, .png, .jpg, .tif, .gif, .pcx, .pga
Mt s kt qu b sung:
1, So snh t s nn gia JPEG2000 v JPEG trong dng nn c tn tht thng tin
2, Chng minh: vi cng mt t l nn v mt loi nh th nh c nn biJPEG2000 hu nh lun c cht lng tt hn so vi JPEG.
Thc hin thc t:
Input: File nh ngun little_boy.bmp
Ouput: nh c nn theo chun JPEG2000 v JPEG1. open file:
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Nn nh theo chun JPEG:
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X l trong giao din settings:
Chn t s nn 39: Cht lng nh:
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Chn t s nn 40: Cht lng nh:
T s nn JPEG t n t l 39:1 (xp x l thuyt 40:1)
2. Chun nn (s dng tnh cht ROI) chn t l nn 40:1, kt qu cho hnh nh nthn nhiu so vi nh JPEG cng t s nn
JPEG2000 JPEG
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nh gi:
nh nn theo chun JPEG2000 cho mt kt qu tt hn nhiu so vi nh nn theochun JPEG, mc d dung lng c ln hn mt cht (45.8KB v 4.53 KB) nhng
u nh hn nhiu so vi nh gc (183KB). Kt qu ny st vi thc t tm hiuca nhm.
3.2 Cc ng dng ca JPEG2000:
Hin nay, JPEG 2000 c ng dng trong 1 s lnh vc nh:- Chn on hnh nh t xa trong Y khoa.- Hnh nh trn Internet: Tng tc phn phi vi JPIP (JPEG2000 InternetProtocol) thm ch c th l phim nh k thut s thng qua nh dng MotionJPEG2000.
- My nh k thut s: Khng gim cht lng hnh nh thu hoch, h tr choInternet.- My qut / my in: Chip cho cc th trng ny xut hin.
- Thit b di ng: Hiu qu tng tc duyt hnh nh ln.
- in nh k thut s v cc Video: Sn xut / lu tr / phn phi, YahooMessenger
IV TI LIU THAM KHO:
1. Slides X l nh C Nguyn Th Hong Lan B Mn TT&MMT VinCNTT &TT Trng HBKHN.2. Jin Li - Image Compression - the Mechanics of the JPEG2000 (2001)3. Satish Kumar - An Introduction to Image Compression (10/2001)5. Ti liu tham kho trn mng internet.
Phn cng cng vic:
1. Tm, Phn loi ti liu: c + Tng.2. Dch ti liu: c + Tng.3. Vit bo co, slides + demo: Tng
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