View
230
Download
0
Category
Preview:
Citation preview
8/3/2019 Nhan Dang Va Xu Li Anh
1/17
Bi ging mn hc Nhn Dng v X L nh
BI 1TNG QUAN V X L NH
1. Gii thiu chungNhn dng v x l nh l mt trong nhng lnh vc c nhiu ng dng trong
thc tin nh: h thng tin a l (GIS Geographic Information System), qun s,y hc.
C th, x l nh s c rt nhiu ng dng nh:- Lm ni cc nh trong y hc.- Khi phc li nh do tc ng ca kh quyn trong thin vn hc.- Chuyn ti, nn nh khi truyn i xa hoc lu tr.
2. Cc giai on ca qu trnh x l nh- Nhn dng v X l nh bao gm 2 giai on chnh:
- Giai on bin i nh (Image Transformation) hay lm p nh(Image Enhancement): trong giai on ny, nh ca i tng trong t nhin cthu li thnh nh s (s ha lu tr v x l trong my tnh). Sau nh c
bin i nng cao cht lng nh nhm thu c nhiu thng tin hn, c thquan st bng mt.- Giai on nhn dng mu (Patten Recognition): h thng s x l
a ra cc c trng ca nh hay cc i tng trong nh. Sau h thng snh gi ni dung nh hoc nhn bit cc mu trong nh.
3. Mt s khi nim lin quan3.1. Phn t nh
- nh trong t nhin l nhng tn hiu lin tc v khng gian v gi tr sng. c th lu tr v biu din nh bng my tnh, con ngi
phi tin hnh bin i cc tn hiu lin tc thnh mt s hu hncc tn hiu ri rc thng qu qu trnh lng t ha v ly mu thnh
phn gi tr sng.- Mt phn t nh (Picture Element) l mt gi tr biu din cho mc
xm hay cng nh ti mt v tr sau khi bin i nh thnh mts hu hn cc tn hiu ri rc.
3.2. Mc xm- L kt qu ca s bin i tng ng gi tr sng ca mt im nh vimt gi tr s nguyn dng. Ty thuc vo s gi tr biu din mc xm mmi im nh s c biu din trn 1, 4, 8, 24 hay 32 bit. S lng bit biu
din mc xm cng ln th cht lng nh cng cao nhng s tn dung lngb nh nhiu hn lu tr v cn mt h thng mnh hn x l.3.3. nh
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
1
8/3/2019 Nhan Dang Va Xu Li Anh
2/17
Bi ging mn hc Nhn Dng v X L nh
- L mt tp hp hu hn cc im nh k nhau. nh thng c biu dinbng mt ma trn hai chiu, mi phn t ca ma trn tng ng vi mt imnh.- nh nh phn (en trng): l nh c gi tr mc xm ca cc im nh c
biu din bng 1 bit (gi tr 0 hoc 1).V d v biu din nh nh phn:
0 1 1 0
1 1 1 0
0 0 1 1
0 1 1 1
- nh xm: gi tr mc xm ca cc im nh c biu din bng 8 bit (gi
tr t 0 n 255).V d v biu din nh xm:
0 5 12 0
15 94 21 0
0 0 156
9
0 11 245
12
- nh mu: thng thng, nh mu c to nn t 3 nh xm i vi munn (RED), xanh l cy (GREEN), xanh lam (BLUE). Tt c cc mutrong t nhiu u c th c tng hp t 3 thnh phn mu trn theo cc tl khc nhau.V d v biu din nh mu:Ma trn biu din mc xm ca thnh phn RED:
0 7 11 0
115 94 20 0
0 0 15 16
0 11 225
12
Ma trn biu din mc xm ca thnh phn GREEN:
0 1 121
0
14 9 21 0
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
2
8/3/2019 Nhan Dang Va Xu Li Anh
3/17
Bi ging mn hc Nhn Dng v X L nh
0
0 0 115
16
0 11 22 2Ma trn biu din mc xm ca thnh phn BLUE:
0 17 21
0
135
93 50
0
0 0 15
67
0 11 25
19
4. Mt s nh dng nh hin nay4.1. nh BMP (Bitmap)
- L nh c m t bi mt ma trn cc gi tr s xc nh mu vbng mu ca cc im nh tng ng khi hin th. u im ca nh Bitmapl tc v v tc x l nhanh. Nhc im ca n l kch thc rt ln.
4.2. nh JPEG (Joint Photographic Experts Group)- y l mt nh dng nh c h tr bi nhiu trnh duyt web. nh
JPEG c pht trin nn dung lng v lu tr nh chp, v c sdng tt nht cho ha c nhiu mu sc, v d nh l nh chp c scan.File nh JPEG l nh Bitmap c nn li.4.3. nh GIF (Graphics Interchange Format)
- nh GIF c pht trin dnh cho nhng nh c tnh cht thay i.N c s dng tt nht cho ha c t mu, v d nh l nh hot hnh
hoc l nhng bc v vi nhiu ng thng. File nh GIF l nhng nhBitmap c nn li.- C hai s khc nhau c bn gia nh GIF v nh JPEG:
+ nh GIF nn li theo cch gi nguyn ton b d liu nh trong khinh JPEG nn li nhng lm mt mt s d liu trong nh.+ nh GIF b gii hn bi s mu nhiu nht l 256 trong khi nhJPEG khng gii hn s mu m chng s dng.
4.4. nh WMF (Windows Metafiles)- L mt tp hp cc lnh GDI dng m t nh v ni dung nh. C
hai u im khi s dng nh WMF: kch thc file WMF nh v t ph thucvo thit b hin th hn so vi nh Bitmap.
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
3
8/3/2019 Nhan Dang Va Xu Li Anh
4/17
Bi ging mn hc Nhn Dng v X L nh
BI 2X L NH NH PHN
1. L thuyt v nh nh phn1.1. Khi nim
- Mt nh c xem l nh nh phn (nh en trng) nu cc im nhca n ch nhn gi tr l 0 hoc 1 (tng ng vi mu en hoc trng).Do mi gi tr im nh c biu din bng 1 bit nn kch thc filenh rt nh.- Ta k hiu: J l tp cc im nh c gi tr bng 1
J l tp hp cc im nh c gi tr 0 (im nn).1.2. K thut phn ngng
- Dng chuyn i nh a cp xm sang nh nh phn- Vi mt gi tr cho trc, gi tr ca im nh s c gn bng 1nu mc xm ca n >= , gn bng 0 nu mc xm < .- K thut ny lm cho tnh cht mu lin tc ca nh b gin onnhng c hiu qu trong vic th hin cc loi nh c ng nt nhvn bn, vn tay- Ci t:
+ D liu vo: ma trn I kch thc mxn biu din mc xm ca
cc im nh. Gi tr ngng .+ D liu ra: ma trn I c bin i mc xm.+ M t thut ton:
for x=1 to mfor y=1 to nif I(x,y)>= then I(x,y)=1else I(x,y)=0
- V d:
nh gc =9 nh u ra
0 8 5 0 0 0
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
4
8/3/2019 Nhan Dang Va Xu Li Anh
5/17
Bi ging mn hc Nhn Dng v X L nh
9 2 30
1 0 1
8 12
40
0 1 1
1.3. K thut Dithering- S dng mt ma trn cng kch thc cho trc bin i nh.- Nu gi tr mc xm ca im nh gc ln hn gi tr ca phn ttng ng trong ma trn Dithering th mc xm u ra s c gn
bng 1 v ngc li.- Ci t:
+ D liu vo: ma trn I kch thc [mxn] biu din mc xmca cc im nh. Ma trn Dithering kch thc [mxn].
+ D liu ra: ma trn I c bin i mc xm.+ M t thut ton:for x=1 to mfor y=1 to nif I(x,y)> Dithering(x,y) then I(x,y)=1else I(x,y)=0
- V d
nh gc Ma trn D nh u ra
1 7 9 0 8 5 1 0 1
6 12
45
9 2 30
0 1 1
14
18
13
8 12
40
1 1 0
2. im k - tp im lin thng i tng nh2.1. im k
Cho trc mt im nh I(x,y), khi :- Cc im nh I(x-1,y), I(x+1,y), I(x,y-1), I(x,y+1) c gi l cc
im k 4 ca I(x,y).- Cc im nh I(x-1,y-1), I(x+1,y-1), I(x-1,y+1), I(x+1,y+1) v cc
im k 4 c gi l cc im k 8 ca I(x,y).- Tng ng vi cc im k 8, ta c mt n 8 hng xc nh cc
im k 8 :3 2 1
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
5
8/3/2019 Nhan Dang Va Xu Li Anh
6/17
Bi ging mn hc Nhn Dng v X L nh
4 P 0
5 6 7
Tng ng vi cc hng nh sau:
2.2. Tp im lin thng- Hai im nh P1 v P2 J c gi l lin thng 4(hoc 8) trong J nu tn
ti tp cc im {(x0,y0), (x1,y1), , (xn,yn)} sao cho:+ P1 = (x0,y0)+ P2 = (xn,yn)+ V(xk,yk) v (xk+1,yk+1) J th (xk+1,yk+1) l k 4(hoc 8) ca (xk,yk)vi k= [0..n-1]
(tp cc im {(x0,y0), (x1,y1), , (xn,yn)} c gi l ng i).
- Mt tp im c gi l lin thng nu vi hai im bt k trong tp hp u lin thng (4 hoc 8).
2.3. i tng nh- L mt tp hp cc im nh lin thng.- Quan h K lin thng trong J l mt quan h c tnh cht phn x, i xng,
bc cu, v vy, n l mt quan h tng ng2.4. im binim nh P trong nh nh phn c gi l im bin nu c tn ti t nht
mt im k 4 c mc xm khc vi P. Tp cc im bin ca mt i tng s tothnh bin ca i tng nh .2.5. Chu tuynChu tuyn ca mt i tng nh l tp hp cc im bin: {P1, P2, Pn}
ca i tng nh sao cho hai im Pi v Pi+1 l cc im k 8 ca nhau (i=1..n-1)v P1 l k 8 ca Pn.
K hiu chu tuyn l C=
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
6
3 2
0
1
4
5
67
8/3/2019 Nhan Dang Va Xu Li Anh
7/17
Bi ging mn hc Nhn Dng v X L nh
Hnh v: chu tuyn ca mt i tng nh* Chu tuyn i ngu:Hai chu tuyn C= v CT = c gi l i ngu ca
nhau khi v ch khi mi i (i=1..n) u tn ti duy nht j (j=1..m) sao cho:
- Pi v Qj l cc im k 4 ca nhau- Mc xm ca Pi khc Qj
* Chu tuyn ngoi:Chu tuyn C= c gi l chu tuyn ngoi nn s im bin ca
C nh hn chu tuyn i ngu CT* Chu tuyn trong:Chu tuyn C= c gi l chu tuyn ngoi nn s im bin ca
C ln hn chu tuyn i ngu CT
Hnh v: chu tuyn trong chu tuyn ngoi
3. Mt s k thut d bin trong nh nh phn3.1. D bin hnh thc ha- Nu cc k hiu (b,g) l mt cp im vi b l im nh v g l im nn.- Dy cc cp im (b1,g1), (b2,g2), , (bn,gn) l cc im k 8 ca nhau v
(b1,g1) (bn,gn),- Gi T l thut ton tm bin, p dng thut ton T cho cp im (b i,gi) ta s
tm c cp im tip theo: (bi+1,gi+1) = T(bi,gi)
- Khi p dng thut ton T, qu trnh d bin c thc hin theo th t ttrn xung di v t tri sang phi cho ton b nh.
3.2. Thut ton d bin FreemanXut pht t mt im nh P, qu trnh d bin s i theo cc hng: 0, 2, 4,
6 trong mt n 8 hng. Nu gp im nh th sang tri, im nn th sang phi. Qutrnh trn c lp li cho n khi quay li ng v tr xut pht P. Khi nim sangtri, sang phi ph thuc vo hng n ca im ang xt thay i hng i caim n im tip theo nh trong bng di y.
im nh sang tri im nn sang phiHng n Hng i n Hng n Hng i n
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
7
8/3/2019 Nhan Dang Va Xu Li Anh
8/17
Bi ging mn hc Nhn Dng v X L nh
im tip theo im tip theo
0 2 0 6
2 4 2 0
4 6 4 26 0 6 4
Thut ton Freeman b hn ch kh nng phi xt n nhng im khng cn quantm trong qu trnh d bin. V d di y s th hin iu .nh nh phn c kch thc 8x8 vi im bin xut pht P c ta (2,4)
Nhng im khng cn quan tm: (0,3), (4,7), (7,3), (4,0)
3.3. Thut ton Freeman ci tinXut pht t mt im nh P, qu trnh d bin s i theo cc hng: 0, 2, 4,6 trong mt n 8 hng. Nu gp im nh th sang tri, im nn th quay ngctr li. Qu trnh trn c lp li cho n khi quay li ng v tr xut pht P. Khinim sang tri, quay li ph thuc vo hng n ca im ang xt thay ihng i ca im n im tip theo nh trong bng di y.
im nh sang tri im nn li li
Hng n Hng i nim tip theo
Hng n Hng i nim tip theo
0 2 0 4
2 4 2 6
4 6 4 0
6 0 6 2
Gii thut ci tin s khc phc c hn ch ca gii thut Freeman. V d diy s th hin iu :nh nh phn c kch thc 8x8 vi im bin xut pht P c ta (2,4)
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
8
8/3/2019 Nhan Dang Va Xu Li Anh
9/17
Bi ging mn hc Nhn Dng v X L nh
BI 3CC PHP TON HNH THI TRN NH NH PHN
1. Php ton hnh thi (Morphology)- Hnh thi l thut ng ch cu trc ca mt i tng nh trong c phm
vi v mi quan h gia cc phn ca i tng.- Vi nh nh phn IMxN, im nh ti v tr (x,y) l I(x,y) c xc nh:
= 0 nu l im nn= 1 nu l im nhGi A l tp hp cc im nh, ta k hiu: A={(xi,yi) | I(xi,yi) = 1}Ac l tp hp cc im nn:
V d:
0 0 1 1 0
1 0 0 1 00 1 0 0 0
A = {(0,2), (0,3), (1,0), (1,3), (2,1)}
2. Cc khi nim c bn* Php dch:
Cho mt vector x v tp hp cc im A, php dch A + x c xc nh bi:
* Cc php ton tp hp Minkowski:
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
9
8/3/2019 Nhan Dang Va Xu Li Anh
10/17
Bi ging mn hc Nhn Dng v X L nh
Cho A, B l cc tp hp im:Php cng Minkowski:
Php tr Minkowski:
3. Php gin nh v co nhT hai php ton Minkowski, ta c php ton hnh thi c bn l php gin nh vco nh :
Php gin nh (Dilation)
Php co nh (Erosion)
Trong :
* Mt s tnh cht:
Giao hon:
Khng giao hon :
Kt hp:
Dch chuyn bt bin:
* V d minh ha:
(a) Gin nh D(A,B) (b) Co nh E(A,B)
A v B c th c xem l cc i tng nh v B c gi l phn t cu trc.
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
10
8/3/2019 Nhan Dang Va Xu Li Anh
11/17
Bi ging mn hc Nhn Dng v X L nh
Thng thng, php gin nh lm tng kch thc i tng nh trong khi php conh lm gim kch thc. iu ny ty thuc vo vic chn phn t cu trc. C hai
phn t cu trc ph bin thng c dng l tp hp k-4 v tp hp k-8 trongh ta cc:
(a) N4 (b) N8
ngha:- Php gin nh bin i gi tr ca cc im nn k-4 (hoc k-8) vi im nh thnhcc im nh, do vy, n lm tng kch thc cc im nh.- Php co nh bin i gi tr ca cc im nh k-4 (hoc k-8) vi im nn thnhcc im nn, do vy, n lm gim kch thc cc im nh.V d:
(a) B = N4 (b) B= N8Cc im nh gc l cc im mu xm, cc im thm vo l cc im c mu en.
4. Php m v ng nhChng ta c th kt hp php gin nh v co nh to nn hai ton t quan trnghn:
M nh:
ng nh:* Mt s tnh cht:
- i ngu:
- Dch chuyn:
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
11
8/3/2019 Nhan Dang Va Xu Li Anh
12/17
Bi ging mn hc Nhn Dng v X L nh
ngha:- Php m nh s m rng nhng khong trng gia cc phn tip xc trongi tng nh, lm cho nh bt gai hn.
- Php ng nh s lm mt i nhng khong trng nh trong nh, lm mt inhiu trong nh.
5. Mt s kt quCc ton t cu trc thng c p dng:
(a) (b) (c)
a) nh A b)Gin nh vi 2B c)Co nh vi 2B
d)M nh vi 2B e) ng nh vi 2B f)it-and-Miss viB1 v B2
V d vi cc ton t hnh thi
6. Php ton HitAndMiss
Cho mt nh A v hai phn t cu trc B1 v B2, ta c:
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
12
8/3/2019 Nhan Dang Va Xu Li Anh
13/17
Bi ging mn hc Nhn Dng v X L nh
vi B1 v B2 l gii hn v ri rc nhau (B1 B2 = )
(php ton ny cn c gi l xc nh vin mu, mu B1 cho i tng nhv mu B2 cho nn nh)
* ng vin cc im k 4:
* ng vin cc im k 8:
Mt cch bin din khc:
Biu din phn t cu trc di dng ma trn (gm B1 v B2)
* Cch thc hin: dch chuyn im gc ca phn t cu trc ln lt trn cc imnh theo th t t trn xung di, t tri qua phi, nu cc im nn v im nhca phn t cu trc khp vi trn nh th ta gi li im nh , nu khng ta t
thnh im nn.
4 phn t cu trc c s dng tm gc ca nh trong php ton HitAndMiss(thc cht l mt phn t quay theo 4 hng khc nhau)
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
13
8/3/2019 Nhan Dang Va Xu Li Anh
14/17
Bi ging mn hc Nhn Dng v X L nh
Sau khi tm c gc theo cc phn t cu trc trn, ta kt hp chng li c ktqu l cc gc li ca nh.
S dng php ton HitAndMiss tm gc li ca mt nh7. Xng nh
Khi nim: Xng nh l tp hp cc ng dy l 1, i qua phn gia cai tng nh v bo ton c tnh cht hnh hc ca i tng nh.
Tuy nhin, khng d dng nhn ra xng nh:
V d:
(a) (b)
Trong v d (a), ta khng th tm c ng thng c dy 1 i qua gia itng m phn nh c tnh cht n gin ca i tng. Trong v d (b), ta khngth b i mt im trong i tng k 8 m gi c tnh cht hnh hc ca itng.
Cng thc c bn:
- Cc tp hp con ca xng nh Sk(A):
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
14
8/3/2019 Nhan Dang Va Xu Li Anh
15/17
Bi ging mn hc Nhn Dng v X L nh
vi K l gi tr ln nht ca k trc khi Sk(A) tr thnh rng
(ta c )
Xng nh l hp ca cc tp con xng nh:
Nh vy, i tng nh ban u c th c ti to li t cc tp con xngnh, phn t cu trc B v gi tr K:
Tuy nhin, cng thc ny khng phi lc no cng bo ton c tnh chthnh hc ca nh.
* Php ton lm gy nh:
Cng thc:
Ty thuc vo cch chn B1, B2 m ta c cc thut ton lm gy nh khcnhau.
Mt cch biu din khc:
Phn t cu trc c dng tm xng nh (im gc tm ca phn t cu trc).
Ti mi bc lp, nh s c lm gy bi phn t cu trc bn tri, sau n phnt cu trc bn phi, tip theo vi php quay 90o hai phn t cu trc trn. Qu trnh
c lp i lp li cho n khi php ton lm gy khng dn n s thay i no na.
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
15
8/3/2019 Nhan Dang Va Xu Li Anh
16/17
Bi ging mn hc Nhn Dng v X L nh
Xng nh c tm bng php ton lm gy vi hai phn t cu trc trn
V d v mt s xng nh:
L B Dng Khoa Cng ngh Thng tin - Trng i Hc Hng Hi Vit Nam
16
http://homepages.inf.ed.ac.uk/rbf/HIPR2/images/wdg2skl1.gifhttp://homepages.inf.ed.ac.uk/rbf/HIPR2/images/wdg2thr3.gifhttp://homepages.inf.ed.ac.uk/rbf/HIPR2/images/art7skl1.gifhttp://homepages.inf.ed.ac.uk/rbf/HIPR2/images/art7.gifhttp://homepages.inf.ed.ac.uk/rbf/HIPR2/images/art6skl1.gifhttp://homepages.inf.ed.ac.uk/rbf/HIPR2/images/art6.gif8/3/2019 Nhan Dang Va Xu Li Anh
17/17
Bi ging mn hc Nhn Dng v X L nh
8. Ti to lp y nh
17
http://homepages.inf.ed.ac.uk/rbf/HIPR2/images/phn1ske1.gifhttp://homepages.inf.ed.ac.uk/rbf/HIPR2/images/phn1thr1.gifRecommended