Ch02 - Thu Nhan Anh

7/30/2019 Ch02 - Thu Nhan Anh

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Thu nhnnh

11/01/2013Phm Vit Hng Nhp mn x l nh 1


2/38

11/01/2013 Phm Vit Hng Nhp mn x l nh 2


3/38

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)



4/38

Sdngcmbinhoc scanner



5/38

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)



6/38

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]



7/38

M hnh Raster

Ma trn

M hnh Vector

Vector



8/38

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)



9/38

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)



10/38

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



11/38

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



12/38


Chpnm 1911 bng ba tmlc, xanh l cy v xanh da tri.hinthli ba hnh chiuphiclng ln nhau trong phng ti


13/38


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.


14/38

Cmbinchcmnhncng sng Cn c lplc xc nhmu

Lplc Bayercsdngnhiu trong my nh

c y thng tin cho mtimnh, mtsthut

ton ni suy csdng



15/38

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



16/38


Quy trnh in 3 mu, 1902


17/38

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.


B

G

R

Y

M

C

1

1

1


18/38



19/38

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).



20/38

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


HSL HSV


21/38

M=max(R,G,B), m=min(R,G,B)

C=M-m

H =

H = 60x H


khng tnti nu C=0

nu M=R

nu M=G

nu M=B

mod6C

BG

2C

RB

4C

GR


22/38

V = M

L =


m)(M2

1


23/38


0C,V

C

0C0,

SHSV

0C,

1-2L-1

C

0C0,

SHSL


24/38

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;

}


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;

}


25/38

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 ) );


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;

}

}


26/38

Trong sch bo, tp ch, kthutnacng

(half tone) csdng


Grayscale CMYK separation


27/38



28/38

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.



29/38

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.



30/38

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.



31/38

Khuch tn limtchiuthnglinhng

ngthngdc khng mong mun.

Khuch tn li hai chiu gip gimlictrng

ny.

Phndsckhuch tn mtphncxung

dng di


11

2#

4

1

# l imnhangcx l


32/38

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:


1537#

161 - v # l nhngimnh

v angcx l

13531

35753

57#

48

1 - v # l nhngimnh v angcx l


33/38

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.



34/38

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.



35/38

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



36/38

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)



37/38

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



38/38

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)

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Ch02 - Thu Nhan Anh