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7/30/2019 Ch02 - Thu Nhan Anh
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Thu nhnnh
11/01/2013Phm Vit Hng Nhp mn x l nh 1
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11/01/2013 Phm Vit Hng Nhp mn x l nh 2
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Ghi li thng qua cc thitb thu nhnnh
Raster
Camera
Scanner
Vector
Bn s ha
Sensor
Qun trnh thu nhnnh
Cmbin: bininnglng quang hchocnnglng khcthnh nnglngin (lymu)
Tnghpnnglngin thnh nh (lngt ha)
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Sdngcmbinhoc scanner
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nhcbiudinbi hm f(x,y)
dx v dy l chu k lymu theo trc x v y (khong
cch tithiugia 2 imcs ha)
fx=1/dx, fy=1/dy l tnslymu theo trc x, y
nhgc c th ti toc th fx2fxmax v
fy2fymax (vi fxmax v fymax l tns cao nhtcatn hiu vo)
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nh sau lymus c dng f(m,n) (vi m,n l cc
s nguyn). Tuy nhin f(m,n) vn l gi trvt l lin
tc, s ha th gi tr ny cnclngt
ha.
Lngt ha l nh xbin lin tc u vo binri
rc u* thuctphuhn [u1,u2uL]
nhacp xm (gray scale) th L=256, f(m,n) = g [0,255]
nh 24 bit th L=224, f(m,n) = g [0, 224-1]
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M hnh Raster
Ma trn
M hnh Vector
Vector
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Ma trnim (imnh)
Phbinnht
Thunli
khi inn
(my in theoim
)
nginv khi nim tuy nhin kch thc khng
nh (phthuc vo kch c)
Pht trinnht trn m hnh ny l cc phngphp nn nh(BMP, TIF, GIF, PCX)
11/01/2013 Phm Vit Hng Nhp mn x l nh 8
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Bao gm cc itng hnh hc
Phbin trong phnmm m hang (2D v
cbit m hnh 3D)
Kch thc file (khng phthuc vo kch c)
Zoom ty (khng bv)
Thunli trong lutr v thitk SVG (Scalable Vector Graphics)
11/01/2013 Phm Vit Hng Nhp mn x l nh 9
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nh l tphp cc imnh, thng tin catngimnhsquytnhloinh
C 3 loinhs
nhentrng nhnh phn
nhmc xm
N mc, t 8 n 256 hocnhiuhn
nhmu Bao gm 3 trngmu, xanh da tri v xanh l
Mitrng c th dng 8,16 hoc 24 bit m ha
11/01/2013 Phm Vit Hng Nhp mn x l nh 10
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Mt con ngi c khnng phn bitkhong 10
triumu.
Tuy nhin no b con ngichc thcmnhn
cs khc bitca vi chc ngn mu.
Cc m hnh mucsdng ti hinli
mtphntphp cc mu nhn thycnhng
khng phi l ttc
11/01/2013 Phm Vit Hng Nhp mn x l nh 11
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11/01/2013 Phm Vit Hng Nhp mn x l nh 12
Chpnm 1911 bng ba tmlc, xanh l cy v xanh da tri.hinthli ba hnh chiuphiclng ln nhau trong phng ti
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11/01/2013 Phm Vit Hng Nhp mn x l nh 13
Red
Green
Blue
Da vo l thuyt 3 mu
Young-Helmholtz uth
k 19
Da vo phng php
phimucng.
Sdng trong hinth
trn mn hnh.
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Cmbinchcmnhncng sng Cn c lplc xc nhmu
Lplc Bayercsdngnhiu trong my nh
c y thng tin cho mtimnh, mtsthut
ton ni suy csdng
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tng nt v gimnhiu do cc thut ton ni
suy 3 sensor cho ba mu c thc dng ring bit
Sdngchyu trong my quay chuyn nghip
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11/01/2013 Phm Vit Hng Nhp mn x l nh 16
Quy trnh in 3 mu, 1902
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Ba mu ny l phn b tngngca ba mu
gc RGB.
Hmu ny sdngphng php phi mu tr
thay v phi mu cng.
Sdngchyu trong in n.
11/01/2013 Phm Vit Hng Nhp mn x l nh 17
B
G
R
Y
M
C
1
1
1
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M hnh mu ny munspxplihmu RGB hayCMY theo mt cch d hnhdung hn.
Trong Hue l tng mu,Saturation l sc
Value l gi trcng
sng hoc Lightness l sng (tennmuntrng).
11/01/2013 Phm Vit Hng Nhp mn x l nh 19
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Khi biudinmu trong h HSV v HSL th l hnh tr
tuy nhin do lngmu trng qu nhiu nn thng
thngngi ta hinth dng hnh nn(HSV) hoc
hnh nn i(HSL) v chiu bn knh gi l Chroma
11/01/2013 Phm Vit Hng Nhp mn x l nh 20
HSL HSV
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M=max(R,G,B), m=min(R,G,B)
C=M-m
H =
H = 60x H
11/01/2013 Phm Vit Hng Nhp mn x l nh 21
khng tnti nu C=0
nu M=R
nu M=G
nu M=B
mod6C
BG
2C
RB
4C
GR
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V = M
L =
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m)(M2
1
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0C,V
C
0C0,
SHSV
0C,
1-2L-1
C
0C0,
SHSL
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void RGBtoHSV( float r, float g,
float b, float *h, float *s,
float *v )
{float min, max, delta;
min = MIN( r, g, b );
max = MAX( r, g, b );
*v = max; // v
delta = max - min;
if( max != 0 )
*s = delta / max; // s
else {
// r = g = b = 0
// s = 0, v is undefined
*s = 0;
*h = -1;
return;
}
11/01/2013 Phm Vit Hng Nhp mn x l nh 24
if( r == max ){
*h = ( g - b ) / delta;
// between yellow & magenta
}else if( g == max ){
*h = 2 + ( b - r ) / delta;
// between cyan & yellow}else{
*h = 4 + ( r - g ) / delta;
// between magenta & cyan
}
*h *= 60; // degrees
if( *h < 0 )
*h += 360;
}
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void HSVtoRGB( float *r, float *g,
float *b, float h, float s, float
v )
{
int i;
float f, p, q, t;
if( s == 0 ) {
// achromatic (grey)
*r = *g = *b = v;return;
}
h /= 60; // sector 0 to 5
i = floor( h );
f = h - i; // factorial part of h
p = v * ( 1 - s );
q = v * ( 1 - s * f );
t = v * ( 1 - s * ( 1 - f ) );
11/01/2013 Phm Vit Hng Nhp mn x l nh 25
switch( i ) {
case 0:
*r = v;
*g = t;
*b = p;
break;case 1:
*r = q;
*g = v;
*b = p;
break;
case 2:
*r = p;
*g = v;
*b = t;break;
case 3:
*r = p;
*g = q;
*b = v;
break;
case 4:
*r = t;
*g = p;*b = v;
break;
default: // case 5:
*r = v;
*g = p;
*b = q;
break;
}
}
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Trong sch bo, tp ch, kthutnacng
(half tone) csdng
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Grayscale CMYK separation
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phn giiim trong kthutnacng
c tnh bnglpi (lines per inch)
Bo thng dng 85 lpi
Tpchin nt hnvi 135 n 150 lpi
c chtlngnhchun th nhgcphi c phn
giigp 1.5 lnnhnacng, numunnhcht
lng cao th con s ny l 2.
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L mtdngnacng.
Sdngchuynnhmu lin tc sang dng
nacngvnchuyn v in n.
u tin c pht trinbi Richard Howland
Ranger cho hthngginh qua inthoi v
in bo.
11/01/2013 Phm Vit Hng Nhp mn x l nh 29
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Cch nginnhtchuynnhmu lin tc sang
nh halftone (vich2 knh tnhacp xm):
Qut nhlnlttng dng v tngimnhmt.
So snh vi gi tr xm trung bnh.
Nu gi tr xm lnhn th thay bngimnhtrng.
Nu gi tr xm nhhn th thay bngimnhen.
V imnhhocenhoctrng nn gi trb lm trn, phn
tha ny cchuyn sang imtip theo.
Qu trnh tiptcclpli.
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Khuch tn limtchiuthnglinhng
ngthngdc khng mong mun.
Khuch tn li hai chiu gip gimlictrng
ny.
Phndsckhuch tn mtphncxung
dng di
11/01/2013 Phm Vit Hng Nhp mn x l nh 31
11
2#
4
1
# l imnhangcx l
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Ma trnkhuch tn c thc tinh chnhhn
na:
Ma trnca Floyd v Steinberg:
Ma trnca J F Jarvis, C N Judice v W H Ninke t Bell
Labs:
11/01/2013 Phm Vit Hng Nhp mn x l nh 32
1537#
161 - v # l nhngimnh
v angcx l
13531
35753
57#
48
1 - v # l nhngimnh v angcx l
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Trong nhmu: Thut ton nh trn c thcsdng cho tng knh
mu khc nhau
Tuy nhin nn chuyn qua hmu HSV hoc HSL trc V s khc bit trong sng dc pht hinbimt
ngihn.
V hthng nn khuch tn lida vo sng hn l sc
hay nht.
Phn chnh trong qu trnh chuynmucng nn c tnh
ton v chuyn sang imnhtip theo.
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Vinhiu knh xm hn:
Khi sdngvithitbu ra (my in, mn hnh) c
nhiuhn hai mc sng.
Thay v sdngmtngng th nhiungngscsdng, gi trsc lm trn tingnggnnht.
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BMP (BITMAP)
Chun raster dng trong MS-Windows
GIF (Graphics Interchange Format)
Nhgn v dng trn web
nhc m ha theo 4 bc
Khi cgii m tngbcschinth.
iu ny gip victinhhiuquhn v ngi dung c thdngvictinhnuthynh khng thch hp.
IMG
nhentrng
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JPEG (Joint Photographic Experts Group)
Nn tianh (tl nn t 5:1 n 15:1) :
Tiu ha cch lutrdliu.
Xc nh v loibtiadliutha.
V l nn khng bo ton nn chtlngnhcngbnhhng
khi tl nn cao.
TIFF (Tagged-Image File Format
6 kiu m ha (khng nn, Huffman, Pack Bits, LZW, FaxGroup 3, Fax Group 4)
3 kiumu (entrng, acp xm, mu)
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PNG (Portable Network Graphic)
L phin bn m ngunm thay th cho GIF
Nn c bo ton nn ph hpvinh c nhiumngngmuln.
Ph hpvi web v c khnnghinthtngbc
C thm knh alpha thhin trong.
RAW
Xuthin trn mts my nh tuy nhin c th khng cngchun
C th c nn c bo ton
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SVG (Scalable Vector Graphics)
W3C (World Wide Web Consortium)
Khng c nn tuy nhin v cutobi XML, SVG c th
c nn bi gzip
AI (Adobe Illustrator)
CDR (CorelDRAW)