Method and apparatus for rendering image signal

US007697012B2

(12) United States Patent

(10) Patent N0.2

Lee et a]. (54)

US 7,697,012 B2

(45) Date of Patent:

METHOD ANDAPPARATUS FOR

5,341,153 A *

*Apr. 13, 2010

8/1994 Benzschawelet a1. .... .. 345/694

RENDERING IMAGE SIGNAL

(75) Inventors: Seong-deok Lee, Kyungki-do (KR); Chang-yeong Kim, Kyungki-do (KR);

(Continued)

Won-hee Choe, Gyeongsangbuk-do

FOREIGN PATENT DOCUMENTS

(KR) EP

(73) Assignee: Samsung Electronics Co., Ltd., SuWon-Si (KR) (*)

Notice:

0346621

Subject to any disclaimer, the term of this patent is extended or adjusted under 35

(Continued)

U.S.C. 154(b) by 1280 days.

OTHER PUBLICATIONS

This patent is subject to a terminal dis claimer.

(Continued)

Aug. 8, 2003

(65)

Primary Examinerilavid A Amini (74) Attorney, Agent, or FirmiStaas & Halsey LLP

Prior Publication Data US 2004/0234163 A1

(30)

Foley et al, Computer Graphics: Principles and Practice, Second Edition in C, The Systems Programing Series, Addison Wesley

Publishers (2nd edition, 1996).

(21) Appl.No.: 10/636,689 (22) Filed:

5/1989

Nov. 25, 2004

(57)

ABSTRACT

Foreign Application Priority Data

Aug. 10, 2002

(KR)

.................... .. 10-2002-0047358

Mar. 14,2003

(KR)

.................... .. 10-2003-0016016

(51)

Int. Cl. G09G 5/02

(52) (58)

US. Cl. ..................................... .. 345/613; 349/108 Field of Classi?cation Search ............... .. 382/298;

(2006.01)

345/613; 349/108 See application ?le for complete search history. (56)

References Cited U.S. PATENT DOCUMENTS 4,800,375

A

1/1989

Silverstein et a1.

4 991 122 A 5,122,783 A *

21991 Sanders 6/1992 Bassetti Jr‘ ________________ __ 345/88

5,225,823

7/1993

A

*

5,339,092 A *

Kanaly

. ... ... .. ..

. . . . ..

Provided is a method for rendering image signals, Which represent a predetermined number of colors, in an apparatus used for rendering an image signal that has a plurality of pixels composed of three different sub-pixels among four or more different sub-pixels. The method for rendering image

signals comprises (a) selecting three-color signals out of the four or more color signals to be outputted according to a type

of sub-pixel, Which forms a predetermined pixel, (b) obtain ing values of the selected three-color signals in peripheral pixels of the pixels, (0) calculating brightness values of each sub-pixel of the pixel by using the values of the selected three-color signals and corresponding color signal values of the_ peripheral pixels, and (d) driving a display, Which controls _ _ _ _ brightness of an image that 1s represented 1n the display according to the calculated brightness values of sub-pixels.

345/89

8/1994 Johnson et al. ........... .. 345/611

41 Claims, 16 Drawing Sheets

420

I" --------------------- "-Z-""|

II

430

Il

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I

I P2

440

I

SECOND

T

SUB-PIXEL

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I I

:

—;—-—- Q2 :

I

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I

/46O SIGNAL

P4

SELECTION PART I

450 THIRD

I

i |

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US 7,697,012 B2 Page 2 2003/0095134 A1*

U.S. PATENT DOCUMENTS

5,416,890 5,485,293 5,668,940 5,781,257 5,929,843 5,936,694 5,982,470 6,188,385 6,348,929 6,384,839 6,388,644 6,407,793 6,681,053 7,113,231 7,184,066 7,268,757 7,268,792 2002/0008812 2002/0191009 2003/0011613 2003/0016318

5/1995 1/1996 9/1997 7/1998 7/1999 8/1999 11/1999 2/2001 2/2002 5/2002 5/2002 6/2002 1/2004 9/2006 2/2007 9/2007 9/2007 1/2002 12/2002 1/2003 1/2003

Beretta

345/88 345/592 349/57 345/600

Suzuki et al. .. Nakahara et al. ..

349/151 349/153

Hill et al. ........ ..

345/614

Acharya et al. Paul

Liang et al. Zhu

EP

EP EP EP JP

JP WO

......................... .. 345/613

De Zwart et al. ..

. 349/139

Conner et a1. ................ ..

349/5

............... .. 345/694

Ben-David et al. .......... .. 345/88 Lee et a1. ........ ..

345/694

Conner et a1. ............. .. 349/106

Liang et al. ............... .. 345/694 Booth, Jr.

0367848 A1 *

0 778 696 0 778 696 A2 0 778 696 A3 09251160

5/1990

6/1997 6/1997 7/1997 *

2002-191055 01/37251 A1

9/1997

7/2002 5/2001

OTHER PUBLICATIONS

345/60

......................... .. 382/258

Elliot et a1.

Tuomiet al. .............. .. 345/611

FOREIGN PATENT DOCUMENTS

..................... .. 345/590

Robinder Steiner et al. Gal et al. Tanioka

5/2003

European Search Report dated Jun. 20, 2005. Korean Of?ce Action dated Nov. 17, 2004 (With English translation), which Was ?led in an Information Disclosure Statement on Feb. 17,

2005 in US. Appl. No. 10/429,713. European Search Report dated Jan. 10, 2006 Which Was ?led in an Information Disclosure Statement on Feb. 21, 2006 in US. Appl. No. 10/429,713 .

European Of?ce Action dated Sep. 16, 2009, issued in corresponding European Patent Application No. 032548471

................. .. 345/589

Liang et al. ............... .. 349/106

* cited by examiner

US. Patent

Apr. 13, 2010

Sheet 3 0f 16

US 7,697,012 B2

FIG. 3B col-2

Row-2 ____.______T__.

I

l I I I i

FIG. 4A

R G

L410 SIGNAL CONVERSION UNIT

P1 P2 P3 P4

f 420

SIGNAL RENDERING UNIT

Q1 Q2 03

/ 470

DISPLAY DRIVER

US. Patent

Apr. 13, 2010

Sheet 4 0f 16

US 7,697,012 B2

FIG. 4B 420

F __________________ "'4'"? P1 1 FIRST ——+- SUB-PIXEL I RENDING PART I

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FIG. 5A

Apr. 13, 2010

Sheet 6 0f 16

US 7,697,012 B2

( START ) INPUT THREE PRIMARY OOLOR IMAGE SIGNALS -—S2OO

CONVERT THREE PRiMARY OOLOR IMAGE

_?_ S

SIGNALS INTO EOUR COLOR SIGNALS

220

CALCULATES BRIGHTNESS vALuES FOR EACH SUB-PiXEL WITH RESPECT TO THREE P5240 OOLOR SIGNALS

ORIvE DISPLAY

-—-S26O

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FIG. 5B

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( START ) cALGuLATE FIRST SUB-PIXEL VALUE

} -~ S242

CALCULATE SECOND SUB-PIXEL VALUE —~S24Ar SELECT SIGNALS CORRESPONDING TO SUB-PIXELS

*5

cALcuLATE THIRO SUB-PIXEL VALUE

-~ S248

END

245

US. Patent

FIG. 50

Apr. 13, 2010

Sheet 7 0f 16

US 7,697,012 B2

G 1

CALCULATE REPRESENTATIVE VALUE

___ S

FOR EACH MASK SUB-CELL

5'0

CALCULATE DIFFERENCE VALUE FOR EACH MASK SUB-CELL

___S52

D

CALCULATE INCREASE/DECREASE AMOUNT FOR EACH MASK SUB-CELL

E“ 5530

CALCULATE LEVEL VALUES OF SUB-PIXELS END

MULTIPLY BRIGHTNESS VALUE OF PIXEL DISPOSED iN MASK SUB-CELL BY WEIGHT OF AREA OCCUPlED BY THE PIXEL

EXTRACT REPRESENTATIVE VALUE OF MASK SUB-CELL

ARE ALL OF MASK

SUB-CELLS PROCESSED?

( TO S520 )

854-0

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Apr. 13, 2010

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Sheet 9 0f 16

US 7,697,012 B2

FIG. 5F (

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MULTIPLY REPRESENTATIVE VALUE OF MASK SUB-CELL BY DIFFERENCE VALUE OF CORRESPONDTNG MASK SUB-CELL

MULTTPLY MULTIPLIED VALUE BY PREDETERMENEO

WEIGHT AND EXTRACT INCREASE/DECREASE AMOUNT FOR EACH MASK SUB-CELL

ARE ALL OF MASK

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TO S540 )

US. Patent

Apr. 13, 2010

Sheet 10 0f 16

US 7,697,012 B2

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Apr. 13, 2010

Sheet 11 0f 16

US 7,697,012 B2

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Sheet 12 0f 16

US 7,697,012 B2

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Apr. 13, 2010

Sheet 13 0f 16

US 7,697,012 B2

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Apr. 13, 2010

Sheet 14 0f 16

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US. Patent

Apr. 13, 2010

Sheet 15 0f 16

US 7,697,012 B2

FIG. 1 1A

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Apr. 13, 2010

Sheet 16 0f 16

US 7,697,012 B2

FIG. 12

@ INPUT THREE PRIMARY COLOR IMAGE SIGNALS -—sI2o0

CONVERT THREE PRIMARY COLOR IMAGE SIGNALS INTO FOUR COLOR SIGNALS

#51220

CALCULATE BRIGHTNESS VALUES OF FOUR SUB-PIXELS

____S1 40 2

DRIVE DISPLAY

—--S1 260

1

END

US 7,697,012 B2 1

2

METHOD AND APPARATUS FOR RENDERING IMAGE SIGNAL

not disclose processing, i.e., scaling required in a case Where the image resolution is different from the display resolution.

BACKGROUND OF THE INVENTION

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for rendering an image signal in Which the apparent resolution of a display is increased by using different arrangement of sub pixels When the spatial resolution of a display is loWer than

This application claims the priority of Korean Patent Application Nos. 2002-47358, ?led on Aug. 10, 2002 and 2003-16016, ?led on Mar. 14, 2003, in the Korean Intellectual Property O?ice, the disclosure of Which is incorporated herein in its entirety by reference.

that of an inputted image signal, and more particularly, a

method and apparatus for rendering an image signal in Which the apparent spatial resolution of a four-primary color dis play, With restricted spatial resolution, is increased by per

1. Field of the Invention The present invention relates to a method and apparatus for rendering an image signal, and more particularly, to a method

forming color matching for each sub-pixel position using a different arrangement of sub-pixels.

for rendering an inputted image While minimiZing degrada

According to an aspect of the present invention, there is provided a method for rendering image signals in an appara tus for rendering an image signal comprising pixels Which are

tion of image quality When the resolution of an inputted image signal is higher than the resolution of a display, and an appa

ratus for rendering an image signal using the method. 2. Description of the Related Art

20

respectively, the method comprising (a) selecting three-color

When the number of actual pixels of a display is smaller than the number of pixels of an inputted image signal, or When

the spatial resolution of the inputted signal is higher than that of the display, the image signal has to be doWn-sampled so

signals out of the four or more color signals to be outputted according to a type of sub-pixel, Which forms a predeter

mined pixel; (b) obtaining values of the selected three-color 25

30

degraded quality of the image presented on the display. As a conventional method for solving the above problem, an anti-aliasing method performed on a per-pixel basis has

been introduced in “Computer Graphics: Principles and Prac

35

tice” by Foley et al., Addison Wesley Publishers (2” edition, 1996). In the method, an image signal is loW-pass ?ltered, 40

In the method, due to the reduction of the difference in bright

are composed of three different sub-pixels among four or more different sub-pixels representing four or more signals

signal out of the four or more color signals excluding prede termined tWo-color signals according to a type of sub-pixel, Which forms a predetermined pixel; (b) obtaining a value of the selected one-color signal and representing the level values

in peripheral pixels of the pixels; (c) calculating brightness

ness values betWeen pixels, caused by loW-pass ?ltering, blurring that the contrast effect of an image is reduced and the

resolution of the image is greatly loWered, occurs. A method for controlling a boundary betWeen an object

values of the selected three-color signals and corresponding color signal values of the peripheral pixels; and (d) driving a display, Which controls brightness of an image that is repre sented in the display according to the calculated brightness values of sub-pixels. According to another aspect of the present invention, there is provided a method for rendering image signals in an appa ratus for rendering an image signal comprising pixels Which

respectively, the method comprising: (a) selecting one-color

smoothened, and is then sampled to reduce the difference in

brightness values betWeen neighboring pixels, and to prevent rough image rendering phenomena, such as a jagged pattern.

signals in peripheral pixels of the pixels; (c) calculating brightness values of each sub-pixel of the pixel by using the

that the entire area of the inputted signal can be presented on

the display. HoWever, due to doWn-sampling of the image signal, a jagged pattern occurs in the portions (for example, text, line, and edge, etc.) of an image With a high spatial frequency (hereinafter, referred to as aliasing), resulting in

composed of three different sub-pixels among four or more different sub-pixels representing four or more color signals

45

and a character on a per-sub-pixel (RGB component) basis is

values of each sub-pixel of the pixel by using the value of the selected one-color signal and corresponding color signal val ues of the peripheral pixels; and (d) driving a display, Which controls brightness of an image that is represented in the display according to the calculated brightness values of three

sub-pixels.

disclosed in Us. Pat. No. 6,384,839 by Agfa Monotype Cor poration. When processing for each sub-pixel, a sudden color

Preferably, step (c) comprises (c1) generating a represen

transition at a boundary betWeen objects can cause a color 50 tative value, Which is the value of a predetermined color

signal and to represent color signals of the sub-pixels con tained in the pixels among inputted color signals in each mask sub-cell, With respect to each mask sub-cell; (c2) generating

fringe error. In the method, the color fringe error is reduced by

boundary processing for each sub-pixel, improving the reso lution of an image and reducing the difference in brightness

deviation information on a representative value betWeen a

betWeen adjacent pixels. In the method, in order to obtain a

Weight for reducing the brightness difference betWeen adja

55

generating output color signal values, Which are represented

cent pixels at a boundary betWeen objects, an image is dis criminated from a foreground and a background, the fore

ground and the background are binariZed, and the image binariZed to a 5-pixel Wide WindoW is loW-pass ?ltered, thereby obtaining a Weight for the an entire area of the image. HoWever, the method uses only a horizontal loW-pass ?lter

by sub-pixels contained in the center mask sub-cell to repre sent a predetermined color signal among the inputted color signals in an entire mask, according to the representative 60

for an RGB-striped structure in a horizontal direction, and performs one-to-one conversion for each pixel, thus the same

channel (sub-pixel having the same primary color) must be arranged in a vertical direction. Accordingly, the method is not suitable for adoption in a four-channel display and does

center mask sub-cell and an adjacent mask sub-cell; and (c3)

65

value and the deviation information. The mask includes a

predetermined number of sub-cells having a siZe smaller than that of a pixel, and the sub -pixels that represent the predeter mined color signal are contained in the center mask sub-cell. According to another aspect of the present invention, there is provided an apparatus for rendering an image signal com prising pixels Which are composed of three different sub pixels among four or more different sub-pixels representing

US 7,697,012 B2 3

4

four or more colors respectively, the apparatus comprising: a

ratus With a plurality of pixels composed of a plurality of

signal selection unit that selects three-color signals With

sub-pixels, the method comprising: (a) selecting a second

respect to each pixel out of the four or more color signals according to a type of sub-pixel, Which forms a predeter

predetermined number of color signals out of a ?rst predeter mined number of color signals to be represented in the appa ratus according to the type of a sub-pixel of the apparatus; (b) setting a mask having a predetermined number of sub-cells

mined pixel; a color signal extracting unit that obtains values of the selected three-color signals to be represented in periph eral pixels of the pixels; a sub-pixel rendering unit that cal culates brightness values to be represented in sub-pixels con tained in the pixel by using the level values of the selected three-color signals and color signal values of the peripheral pixels; and a display driver that controls brightness of an image that is represented in the display according to the

smaller than the pixel so that a center mask sub-cell includes

sub-pixels that represent predetermined color signals among the second predetermined number of color signals; (c) gen erating a representative value, Which is a color signal value, to be outputted to represent the predetermined color signal in the sub-pixel corresponding to each mask sub-cell, With respect to each mask sub-cell; (d) generating deviation information

calculated brightness values of sub-pixels. According to another aspect of the present invention, there

on a representative value betWeen a center mask sub-cell and

an adjacent mask sub-cell; (e) generating output color signal

is provided an apparatus for rendering an image signal com prising pixels Which are composed of three different sub pixels among four or more different sub-pixels representing four or more colors respectively, the apparatus comprising: a signal selection unit that selects an one-color signal out of the four or more color signals excluding predetermined tWo

values Which are represented by sub-pixel contained in the center mask sub-cell to represent the predetermined color signal among the second predetermined number of color sig nals in an entire mask area according to the representative 20

value and the deviation information; and (f) performing (b) through (e) With respect to all of the second predetermined number of color signals. According to another aspect of the present invention, there is provided an apparatus With a plurality of pixels composed

25

of a plurality of sub-pixels, the apparatus comprising: a rep resentative value generation unit that generates a representa tive value, Which is a color signal value to be outputted to

color signals according to a type of sub-pixel, Which forms a

predetermined pixel; a color signal extracting unit that obtains a value of the selected one-color signal to be repre

sented in peripheral pixels of the pixels; a sub-pixel rendering unit that calculates brightness values to be represented in

sub-pixels contained in the pixels by using the value of the selected one-color signal and values of color signals of the peripheral pixels; and a display driver that controls brightness of an image that is represented in the display according to the calculated brightness values of three sub-pixels. Preferably, the sub-pixel rendering unit comprises: a rep

represent predetermined color signals in the sub-cells of the 30

resentative value calculation part that generates a representa tive value, Which is a color signal value, to be outputted to represent color signals of the sub-pixels contained in the

pixels among inputted color signals in each mask sub-cell,

ates deviation information on a representative value between a center mask sub-cell and an adjacent mask sub-cell; a sub 35

pixel value generation unit that generates output color signal values, Which are represented by sub-pixels contained in the center mask sub-cell to represent the predetermined color signal among the inputted color signals in an entire mask according to the representative value and the deviation infor mation; and a display driver to control brightness of an image

With respect to each mask sub-cell; a difference value calcu lation part that generates deviation information on a repre sentative value betWeen a center mask sub-cell and an adja

cent mask sub-cell; and a sub-pixel value generation part that

generates values of output color signals to be represented by

mask having a predetermined number of sub-cells having a siZe smaller than that of the pixels, With respect to each mask sub-cell; a deviation information generation unit that gener

40

that is represented in the display according to the output color

sub-pixel contained in the center mask sub-cell to represent a

signal values generated by the sub-pixel value generation

predetermined color signal among the inputted color signals

unit.

in an entire mask according to the representative value and the deviation information. The mask includes a predetermined number of sub-cells having a siZe smaller than that of a pixel,

BRIEF DESCRIPTION OF THE DRAWINGS 45

The above and other aspects and advantages of the present invention Will become more apparent by describing in detail preferred embodiments thereof With reference to the attached

and the sub-pixels that represent the predetermined color signal are contained in the center mask sub-cell.

According to antoher aspect of the present invention, there is provided a method for rendering image signals Which rep resent a predetermined number of colors in an apparatus With

draWings in Which: 50

a plurality of pixels composed of a plurality of sub-pixels, the method comprising: (a) setting a mask having a predeter mined number of sub-cells smaller than the pixel so that a center mask sub-cell includes sub-pixels that represent a pre

determined color signal; (b) generating a representative

FIG. 1 shoWs an example of the ?lter arrangement of an RGB-striped structure in a display; FIGS. 2A and 2B shoW examples of the color ?lter struc ture of an LCD display, in Which another primary color sub

pixel (White) is added to sub-pixels of RGB colors; 55

value, Which is a color signal value, to be outputted to repre

FIGS. 3A and 3B shoW other examples of the color ?lter structure of the LCD display, in Which another primary color

sent the predetermined color signals among inputted color signals With respect to each mask sub-cell; (c) generating

sub-pixel (White) is added to sub-pixels of RGB colors;

deviation information on a representative value betWeen a

apparatus for rendering an image signal according to an embodiment of the present invention;

center mask sub-cell and an adjacent mask sub-cell; and (d)

FIG. 4A is a block diagram illustrating the structure of an 60

FIG. 4B is a block diagram illustrating the structure of a

generating output color signal values to be represented by sub-pixel contained in the center mask sub-cell and to repre sent a predetermined color signal among the inputted color signals in an entire mask according to the representative value and the deviation information.

According to another aspect of the present invention, there is provided a method for rendering image signals in an appa

signal rendering unit 420 shoWn in FIG. 4A; FIG. 4C is a block diagram illustrating the structure of a

sub-pixel rendering part 430 shoWn in FIG. 4B; 65

FIG. 5A is a ?owchart illustrating a method for rendering

an image signal performed in the apparatus shoWn in FIG. 4A, according to an embodiment of the present invention;