EP0439714B1 - Méthode anti-aliasing pour un dispositif d'affichage graphique - Google Patents

Méthode anti-aliasing pour un dispositif d'affichage graphique Download PDF

Info

Publication number
EP0439714B1
EP0439714B1 EP19900122594 EP90122594A EP0439714B1 EP 0439714 B1 EP0439714 B1 EP 0439714B1 EP 19900122594 EP19900122594 EP 19900122594 EP 90122594 A EP90122594 A EP 90122594A EP 0439714 B1 EP0439714 B1 EP 0439714B1
Authority
EP
European Patent Office
Prior art keywords
pixels
image
triangular regions
color
original
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19900122594
Other languages
German (de)
English (en)
Other versions
EP0439714A2 (fr
EP0439714A3 (en
Inventor
Willie Williamson, Jr.
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
International Business Machines Corp
Original Assignee
International Business Machines Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by International Business Machines Corp filed Critical International Business Machines Corp
Publication of EP0439714A2 publication Critical patent/EP0439714A2/fr
Publication of EP0439714A3 publication Critical patent/EP0439714A3/en
Application granted granted Critical
Publication of EP0439714B1 publication Critical patent/EP0439714B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
    • G09G5/20—Function-generator circuits, e.g. circle generators line or curve smoothing circuits
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G1/00—Control arrangements or circuits, of interest only in connection with cathode-ray tube indicators; General aspects or details, e.g. selection emphasis on particular characters, dashed line or dotted line generation; Preprocessing of data
    • G09G1/28—Control arrangements or circuits, of interest only in connection with cathode-ray tube indicators; General aspects or details, e.g. selection emphasis on particular characters, dashed line or dotted line generation; Preprocessing of data using colour tubes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
    • G09G5/36—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the display of a graphic pattern, e.g. using an all-points-addressable [APA] memory
    • G09G5/39—Control of the bit-mapped memory
    • G09G5/391—Resolution modifying circuits, e.g. variable screen formats

Definitions

  • the present invention relates to the generating images in a computer system by selective assignment of a color to each of a pluralities of pixels on a display surface of a display device, and more specifically to a method for anti-aliasing raster images resulting from a computer translation of an original raster image to a resulting raster image having a greater number of pixels than the original raster image.
  • Raster images are typically displayed using a raster image.
  • the raster image is a rectangular array of rectangular picture elements known as pixels.
  • Raster images can be displayed on CRT monitors in monochrome or various colors. Raster images are also used to display text and graphics on printers, plotters, and other display devices.
  • Aliasing is the jagged, stair-step appearance when lines and edges are displayed which are neither vertical nor horizontal. This problem is more noticeable when a small number of large pixels are used for a given area. Increasing the resolution of the display device, thereby increasing the number of pixels per unit area, improves the appearance of the raster image.
  • One of the more successful anti-aliasing algorithms involves edge blur. Along the edge of the diagonal or curved line, where stair-steps occur, there is ordinarily a sharp transition between the pixels that are drawn in the different colors of the two regions. The staircase appearance occurs because pixels of one color lay immediately adjacent to those of another color, making the jagged transition between them noticeable.
  • edge blur algorithm With an edge blur algorithm, however, it is possible to average the color values of the two regions along the edge and then display missing pixels in the staircase using this in-between color. The result is a blurring or softening of the edge, smoothing over the transition between the colors of the different regions.
  • One disadvantage of this approach is that the display device must be able to display colors which are intermediate between the colors of the two different regions.
  • the larger display or printout usually has more pixels for displaying the image than the original image.
  • a simple method to enlarge the original raster image is to simply enlarge the original pixels, mapping them to the pixels of the enlarged image. If, for example, the zoom factor is 8, each pixel of the original image becomes an 8x8 square of pixels in the resulting image. If the pixels are simply enlarged in this manner, each of the 64 pixels in a square corresponding to an original pixel is simply given the same color value as the original pixel. This gives the same appearance as using very large pixels in the resulting image, and the stair-step phenomena is generally more noticeable than in the original image. Use of intermediate colors for these large pixels does not completely solve the problem.
  • a known process for converting a raster image of a given pixel density to a corresponding magnified raster image of an increased pixel density includes a first step dealing with the original image and a second step dealing with the converted image (EP-A-0336776).
  • a region defined by four adjacent pixel centers is divided into four sections corresponding to that adjacent pixel centers.
  • Such sections may consist of eight triangular sections four of which forming an inner rectangular region centered within a surrounding rectangular region defined by the center points of the adjacent pixels.
  • the area of a converted pixel of the magnified image which lies within the defined region of the original image when both images are superimposed is projected onto that region.
  • the concentration of the converted pixels is calculated and the result is quantized to a binary value which is made one to designate the color black when the calculated concentration is greater or equal to 0,5 and is made zero to designate white when the calculated value is smaller than 0,5.
  • the calculation may be performed by logic operations which within a predetermined short range of one of the four adjacent original pixel centers derive the concentration values to be calculated from the concentration value of the nearest original pixel regardless of the concentrations in the other three pixels.
  • a method for determining the values of pixels in a resulting image having a greater number of pixels than an original image describes a technique for calculating the values of the new pixels in the resulting image.
  • a rectangular region centered on a junction of four pixels in the original image is used as the basis for calculation. This rectangular region contains one-fourth of the adjacent original pixels, and is divided into 8 triangular regions. All of the pixels of the resulting image within a triangular region are given the same color, and the color assigned to the pixels in each such triangular region is a function of the colors of the four adjacent pixels in the original image.
  • Figure 1 shows a portion of a raster image 10 formed from a plurality of pixels.
  • the pixels of Figure 1 are divided into four rows R1, R2, R3 and R4, and four columns C1, C2, C3 and C4. Pixels can be referred to by their coordinates, so that pixel 12 is identified by the location (R2, C4) and pixel 14 is identified by the location (R4, C2).
  • FIG 2 shows the four adjacent pixels in the upper left hand corner of Figure 1. Shading of the pixels is omitted in Figure 2 for clarity.
  • a method for calculating the pixel colors in the resulting image utilizes rectangular region 16. Rectangular region 16 has the same shape as each of the pixels, which is square as shown in Figures 1 and 2. Rectangular region 16 is centered on the intersection point 18 of the four pixels. In Figure 2, the four pixels illustrated are shown as being slightly spaced apart both for clarity and because adjacent pixels are actually separated by a small space in some types of displays. Rectangular region 16 is considered to include the nearest one-fourth of each adjacent pixel.
  • Figure 3 illustrates logical regions 1-8 into which rectangular region 16 is divided. Regions 1 and 5 correspond to the lower right hand corner of pixel (R1, C1) of Figure 2. Regions 2 and 6 correspond to the lower left hand corner of pixel (R1, C2). The remaining regions likewise correspond to the remaining pixels adjacent to intersection point 18. The numbered regions will be used in connection with the detailed description of the preferred method for assigning pixel colors as described in connection with Figure 4.
  • Figure 4 is a flowchart of the calculations necessary to assign colors to all of the pixels within one rectangular region 16. In order to determine the colors of all of the pixels in the resulting array, the calculation outlined in Figure 4 is performed for a rectangular region 16 for the intersection point 18 between every set of four adjacent pixels in the array. The calculation of Figure 4 is therefore performed a number of times equal to (N-1)*(M-1) for an N X M array of pixels.
  • the first step 30 is to assign colors to the pixels located in regions 1, 2, 3, 4.
  • the pixels in these regions are assigned the same color as the color of the original pixel of which each region is a part. Therefore, for example, considering rectangular region 16 of Figure 2, regions 1, 3, and 4 are assigned the shaded color, while region 2 is assigned the unshaded color.
  • the next step is to perform the conjunctive logical comparisons of step 32. If the color of region 1 is equal to the color of region 2, region 3, and region 4, the YES branch is taken. When this condition occurs, all four of the original pixels have the same color, and the entire area of rectangular region 16 is assigned this color. Therefore, regions 5, 6, 7, and 8 are assigned the same color as region 1 is step 34.
  • step 36 the test shown in step 36 is performed. This is a comparison to see whether the color of region 1 is the same as the color of 4, and the color or region 2 is the same as that of region 3. If this is the case, the four original pixels formed a checkerboard pattern using two colors, and no changes will be made within the area encompassed by rectangular region 16. Thus, if the result of test 36 is true, control skips ahead to step 38 which assigns interior triangular regions 5, 6, 7, and 8 to have the same color as their adjacent exterior triangular regions 1, 2, 3, 4. After step 38, processing is complete.
  • step 40 the color of region 1 is compared to the color of region 4. If they are the same color, control passes to step 42. If this point is reached in the flowchart, it is known that the upper left and lower right pixels have the same color, while the lower left and upper right pixels are of differing colors. This means that a line is formed by the upper left and lower right pixels, and all of the interior regions 5, 6, 7, 8 are given the same color as region 1.
  • step 42 the test of step 42 is performed. This test is analogous to that performed in step 40, except that a check is made to see whether the same colors are found in regions 2 and 3. If so, control passes to step 46. If this point in the flowchart is reached, it is known that regions 2 and 3 have the same color, while regions 1 and 4 have dissimilar colors. Therefore, all of the interior triangular regions 5, 6, 7, 8 are assigned the same color as region 2.
  • step 38 assigns each of the interior triangular regions the same color as their adjacent exterior triangular region. If step 38 is reached, it is known that one of three situations has occurred with respect to the four adjacent pixels. If control passes from step 44 to step 38, either each of the adjacent pixels is a different color from all of the others, or any adjacent pixels of the same color are vertically or horizontally adjacent. If control has reached step 38 from step 36, the two color checkerboard pattern described above occurs. In either event, the four corners of the rectangular region 16 are given the same value as the original pixels from which they are derived.
  • Figure 5 illustrates the effect of the method of Figure 4 on a portion of the raster image of Figure 1.
  • the four original pixels (R2, C2), (R2, C3), (R3, C2), and (R3, C3) are shown.
  • the zoom, or magnification, factor is 8, meaning that each original pixel is translated to an 8x8 region of pixels in the resulting image. If the pixels of Figure 1 were translated unchanged into Figure 5, a large stair-step would be evident.
  • Applying the method of Figure 4 to the various intersection points of Figure 1 gives the result of Figure 5, wherein the upper right hand corners of the (R2, C2) and (R3, C3) regions are set to the non-shaded color, and the lower left triangular region of (R2, C3) is shaded.
  • the method described above can be used when a raster image is converted to be shown on a CRT display having a greater number of pixels than that of the original display. It is also suitable for use when a raster image is to be greatly enlarged so that it can be printed on a printer or plotter. This allows, for example, an image suitable for viewing on a CRT display to be enlarged and printed on a large chart suitable for showing to an auditorium.
  • the detailed embodiment described above can be generalized to include more than eight triangular regions if desired. For example, if diagonal lines are drawn between the corners of rectangular region 16 in Figure 3, 16 triangular regions would result. These can be assigned colors as a function of the four adjacent pixels. It is also possible to center such a 16-piece region on a pixel instead of an intersection, and color the triangular regions as a function of the eight surrounding pixels. Dividing the rectangular region 16 into a large number of triangular regions is not preferred because it is computationally expensive. Also, the information content of the original pixels is much lower than that of the resulting image, and performing complex interpolations usually does not improve the resulting image to a degree which justifies the extra computation. It is usually more fruitful to simply recreate the original image at a higher resolution if possible.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Image Processing (AREA)
  • Image Generation (AREA)
  • Editing Of Facsimile Originals (AREA)

Claims (7)

  1. Procédé pour l'anti-crénelage d'images à trame récurrente résultant d'un transcodage par ordinateur d'une image à trame récurrente d'origine en une image à trame récurrente résultante ayant un nombre plus grand de pixels que l'image à trame récurrente d'origine,
    ledit procédé comportant les étapes consistant à
    a) définir dans l'image d'origine des groupes de pixels de quatre pixels se rencontrant aux intersections,
    b) définir une région rectangulaire par les points centraux desdits quatre pixels de l'image d'origine, ladite région rectangulaire étant divisée en huit régions triangulaires, quatre desdites régions triangulaires formant une région rectangulaire interne centrée à l'intérieur de ladite région rectangulaire définie et quatre desdites régions triangulaires formant des régions triangulaires extérieures contiguës auxdites régions triangulaires de ladite région rectangulaire interne,
    caractérisé par les étapes suivantes consistant à :
    c) affecter à chacune des quatre régions triangulaires extérieures de l'image à trame récurrente d'origine une couleur qui est la même que la couleur du groupe contigu dudit groupe de quatre pixels dans l'image d'origine,
    d) si exactement une paire de régions diagonalement opposées desdites régions triangulaires extérieures présentent la même couleur, alors affecter cette couleur à la totalité desdites régions triangulaires de ladite région rectangulaire interne sinon affecter à chaque région triangulaire de ladite région rectangulaire interne la même couleur que présente la région triangulaire extérieure adjacente,
    e) faire correspondre chacune desdites régions triangulaires de l'image à trame récurrente d'origine avec des pixels sélectionnés de ladite image résultante et affecter les couleur affectées par l'étape d) aux régions triangulaires de l'image à trame récurrente d'origine aux pixels correspondants desdits pixels sélectionnés de ladite image à trame récurrente résultante.
  2. Procédé selon la revendication 1, dans lequel la totalité des régions triangulaires ont la même dimension.
  3. Procédé selon la revendication 1, caractérisé en ce qu'avant d'effectuer l'étape d), on affecte à chacune des quatre régions triangulaires extérieures de ladite image à trame récurrente d'origine la couleur dudit groupe des quatre pixels si la totalité desdits quatre pixels ont la même couleur.
  4. Procédé selon la revendication 1, caractérisé par l'étape consistant à comparer dans une étape les couleurs de deux paires de régions diagonalement opposées desdites régions triangulaires extérieures de l'image à trame récurrente d'origine et si les couleurs comparées sont les mêmes affecter la couleur de chacune desdites paires des régions diagonalement opposées desdites régions triangulaires extérieures aux régions contiguës desdites régions triangulaires de ladite région rectangulaire interne.
  5. Procédé selon l'une quelconque des revendications 1 à 4, comprenant de plus l'étape consistant à visualiser l'image résultante sur un dispositif d'affichage.
  6. Procédé selon la revendication 5, dans lequel le dispositif d'affichage est un écran vidéo.
  7. Procédé selon la revendication 5, dans lequel le dispositif d'affichage est une imprimante.
EP19900122594 1990-01-05 1990-11-27 Méthode anti-aliasing pour un dispositif d'affichage graphique Expired - Lifetime EP0439714B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US46134290A 1990-01-05 1990-01-05
US461342 1990-01-05

Publications (3)

Publication Number Publication Date
EP0439714A2 EP0439714A2 (fr) 1991-08-07
EP0439714A3 EP0439714A3 (en) 1992-04-01
EP0439714B1 true EP0439714B1 (fr) 1995-05-24

Family

ID=23832183

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900122594 Expired - Lifetime EP0439714B1 (fr) 1990-01-05 1990-11-27 Méthode anti-aliasing pour un dispositif d'affichage graphique

Country Status (3)

Country Link
EP (1) EP0439714B1 (fr)
JP (1) JPH03252778A (fr)
DE (1) DE69019723T2 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19954029C1 (de) * 1999-11-11 2001-04-05 Grundig Ag Vorrichtung zur Verbesserung der Bilddarstellung auf einem Display
US7205992B2 (en) 2000-04-13 2007-04-17 Nokia Corporation Method of mapping into triangles an area of wireless lan and portable device thereof

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3273937D1 (en) * 1981-03-20 1986-11-27 Indep Broadcasting Authority Decoder for digital information in a t.v. signal
JPS58204668A (ja) * 1982-05-24 1983-11-29 Dainippon Screen Mfg Co Ltd 画像走査記録方法
JPS5966261A (ja) * 1982-10-08 1984-04-14 Hitachi Ltd ２値画像の密度変換装置
JPS61264482A (ja) * 1985-05-18 1986-11-22 Nippon Telegr & Teleph Corp <Ntt> 画面変換処理方式
JPS62229428A (ja) * 1986-03-31 1987-10-08 Toshiba Corp ハ−ドコピ−制御装置
CA1335794C (fr) * 1988-04-07 1995-06-06 Yoshiyuki Okada Methode et dispositif d'agrandissement d'images

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19954029C1 (de) * 1999-11-11 2001-04-05 Grundig Ag Vorrichtung zur Verbesserung der Bilddarstellung auf einem Display
US7205992B2 (en) 2000-04-13 2007-04-17 Nokia Corporation Method of mapping into triangles an area of wireless lan and portable device thereof

Also Published As

Publication number Publication date
JPH03252778A (ja) 1991-11-12
DE69019723D1 (de) 1995-06-29
DE69019723T2 (de) 1996-01-25
EP0439714A2 (fr) 1991-08-07
EP0439714A3 (en) 1992-04-01

Similar Documents

Publication Publication Date Title
US5282057A (en) Bit-map image resolution converter
US4570233A (en) Modular digital image generator
US5301038A (en) Image processor and method for processing pixel data
US4992955A (en) Apparatus for representing continuous tone and high contrast images on a bilevel display
JPH04192671A (ja) ピンホール消去方法
EP0592770B1 (fr) Procédé de remplissage des pixels intérieurs dans un polygone
JPS6380375A (ja) テクスチヤマツピング装置
US5491769A (en) Method and apparatus for variable minification of an image
JP3174342B2 (ja) 多値レベルから２値レベルへのラスタ形状コンバータ
US5719598A (en) Graphics processor for parallel processing a plurality of fields of view for multiple video displays
WO1993005499A1 (fr) Appareil et procede permettant de generer un halo d&#39;image d&#39;affichage anti-replie
EP0477904B1 (fr) Méthode et appareil pour la génération d&#39;images réduites
US5418894A (en) Coloring of designated image area and pinhole elimination by image scaling
EP0439714B1 (fr) Méthode anti-aliasing pour un dispositif d&#39;affichage graphique
EP0574245A2 (fr) Procédé et appareil d&#39;élargissement et réduction variable d&#39;une image
Schmandt Soft Typography.
US5333250A (en) Method and apparatus for drawing antialiased lines on a raster display
EP0127249B1 (fr) Dispositif pour le traitement de données de modèle
EP0855682B1 (fr) Rendu de convolutions en lignes de balayage
EP0268038B1 (fr) Système de traitement de données graphiques
JPH0668271A (ja) 画像処理装置
JPH04127775A (ja) 画像データ処理方法
EP0418895B1 (fr) Méthode et appareil de traitement d&#39;une image ayant plusieurs zones
KR100227282B1 (ko) 이미지 보간방법
JPH07254979A (ja) 画像処理方法

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): DE FR GB IT

17P Request for examination filed

Effective date: 19911112

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): DE FR GB IT

17Q First examination report despatched

Effective date: 19931126

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR GB IT

ITF It: translation for a ep patent filed

Owner name: IBM - DR. ING. FABRIZIO LETTIERI

REF Corresponds to:

Ref document number: 69019723

Country of ref document: DE

Date of ref document: 19950629

ET Fr: translation filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19951024

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19951107

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19951123

Year of fee payment: 6

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19961127

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19961127

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19970731

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19970801

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20051127