JPH02292959A - Color picture encoding system - Google Patents
Color picture encoding systemInfo
- Publication number
- JPH02292959A JPH02292959A JP1113243A JP11324389A JPH02292959A JP H02292959 A JPH02292959 A JP H02292959A JP 1113243 A JP1113243 A JP 1113243A JP 11324389 A JP11324389 A JP 11324389A JP H02292959 A JPH02292959 A JP H02292959A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- area
- character
- color
- halftone
- 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.)
- Pending
Links
- 238000000034 method Methods 0.000 claims description 7
- 239000000872 buffer Substances 0.000 abstract description 8
- 238000000926 separation method Methods 0.000 abstract description 6
- 230000006835 compression Effects 0.000 abstract description 5
- 238000007906 compression Methods 0.000 abstract description 5
- 238000006243 chemical reaction Methods 0.000 abstract description 4
- 238000010586 diagram Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 1
Abstract
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、カラー画像の符号化方式に関する。[Detailed description of the invention] [Industrial application field] The present invention relates to a color image encoding method.
(従来の技術〕
カラ一画像はモノクローム画像の3倍の画像情報量を持
っているため、その伝送やファイリングに多くの時間や
記憶容量が必要とされる。そこで、カラー画像の伝送や
ファイリングの際に、カラー画像を符号化し情+!量を
圧縮する必要がある。(Prior art) Since a color image has three times the amount of image information as a monochrome image, much time and storage capacity are required for its transmission and filing. In some cases, it is necessary to encode color images and compress the amount of information.
従来、このようなカラー画像の符号化に関して、カラー
画像を色分解した原色信号R,G,Bを輝度信号Yと色
度信号I,Qに変換し、I,Q信号によって色彩部と無
彩部を判別し、色彩部についてはY信号とI,Q信号を
共に符号化し、無彩部についてはY信号だけを符号化す
る(I,Q信号は捨てる)方式が知られている(特開昭
62−1373号)。Conventionally, regarding the encoding of such a color image, the primary color signals R, G, and B obtained by color-separating the color image are converted into a luminance signal Y and chromaticity signals I, Q, and the I and Q signals are used to distinguish between colored parts and achromatic parts. There is a known method (Japanese Patent Application Laid-Open No. 2003-130000) in which the Y signal and I and Q signals are encoded together for the colored portion, and only the Y signal is encoded for the achromatic portion (the I and Q signals are discarded). (Sho 62-1373).
この符号化方式は、白黒方式とカラー写真が混在するよ
うな画像に適用すれば、カラー画像全体についてY信号
と■,Q信号をすべて符号化する方式に比べ高い圧縮効
率が得られる。If this encoding method is applied to an image containing a mixture of black-and-white and color photographs, higher compression efficiency can be obtained than a method that encodes all of the Y signal, ■, and Q signal for the entire color image.
しかし、カラーの文字とカラー写真が混在したような画
像に適用した場合、文字部の色情報が失われてしまい、
画像の再現性が悪いという問題がある。However, if this is applied to an image containing a mixture of color text and color photos, the color information of the text will be lost.
There is a problem of poor image reproducibility.
よって本発明の目的は、カラーの文字部が含まれたカラ
ー画像に対しても,必要な色情報を保存しつつ高い圧縮
率を達成できるカラー符号化方式を提供することである
。SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a color encoding method that can achieve a high compression rate while preserving necessary color information even for color images containing color text.
本発明によれば、カラー画像の輝度信号より文字領域と
中間領域を分離し、中間調領域において従来と同様にカ
ラー画像の輝度信号および色度信号を共に符号化するが
、文字領域においては従来と違って、カラー画像の輝度
信号が所定レベルを越える部分ではカラー画像の輝度信
号および色度信号を共に符号化し、それ以外の部分では
カラー画像の輝度信号のみを符号化する。According to the present invention, a character area and an intermediate area are separated from the luminance signal of a color image, and in the intermediate area, the luminance signal and chromaticity signal of the color image are encoded together in the same way as before. In contrast, in parts where the brightness signal of the color image exceeds a predetermined level, both the brightness signal and the chromaticity signal of the color image are encoded, and in other parts, only the brightness signal of the color image is encoded.
(作 用〕
輝度信号に基づいて文字領域と中間調領域を分離するの
で、文字領域が彩色されていても、その分離を正しく行
うことができる。(Function) Since the character area and the halftone area are separated based on the luminance signal, even if the character area is colored, the separation can be performed correctly.
そして、文字領域の輝度信号レベルが小さい部分では色
度信号が捨てられることになるが、このような部分は背
景の白地部分であるため、情報の欠落が問題とならない
。Although the chromaticity signal is discarded in portions of the character area where the luminance signal level is low, since such portions are white portions of the background, missing information does not pose a problem.
したがって、カラーの文字部とカラー写真部等が混在し
たカラー画像についても、再現性を損なわずに高い圧縮
率を実現できる。Therefore, a high compression rate can be achieved without impairing reproducibility even for color images in which color text parts, color photograph parts, etc. coexist.
第1図は本発明の一実施例を示すブロック図である。第
1図において、色空間変換部1は、外部より入力するカ
ラー画像の原色信号R,G,Bを輝度信号と色度信号に
変換する。輝度信号および色度信号は、例えば次式で示
されるようなY信号(輝度信号)とI,Q信号(色度信
号)である。FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, a color space conversion unit 1 converts primary color signals R, G, and B of a color image inputted from the outside into a luminance signal and a chromaticity signal. The luminance signal and chromaticity signal are, for example, a Y signal (luminance signal) and I,Q signals (chromaticity signal) as shown in the following equation.
Y=0.299R+0.5870+O.ll4BI=0
.596 R−0.275 G−0.321 BQ=0
.212 R−0.523 G−0.311 B文字・
中間調分離部2はY信号より入力カラー画像の文字領域
と中間調領域を分離し、文字領域では文字領域信号をオ
ンし、また中間調領域では中間調領域信号をオンする。Y=0.299R+0.5870+O. ll4BI=0
.. 596 R-0.275 G-0.321 BQ=0
.. 212 R-0.523 G-0.311 B letter
The halftone separation unit 2 separates the input color image into a character area and a halftone area based on the Y signal, turning on the character area signal for the character area, and turning on the halftone area signal for the halftone area.
この領域分離は、例えば特開昭6 3 − 1 9 9
,8 6 9号公報に述べられているような濃度勾配
による方法に行うことができる。このようにY信号(輝
度信号)に基づいて領域分離を行うので、文字領域がカ
ラーであっても、その分離が可能である.
中間調領域符号化部3は,文字・中間調分離部2からの
中間調領域信号をオンしたときに有効となり、Y.I,
Q信号をすべて符号化する.この符号化は例えばコサイ
ン変換符号化等である。This area separation is described, for example, in Japanese Patent Application Laid-open No. 63-199.
A method using a concentration gradient as described in Japanese Patent Publication No. 8,699, may be used. Since region separation is performed based on the Y signal (luminance signal) in this way, even if the character region is in color, it can be separated. The halftone area encoder 3 becomes effective when the halftone area signal from the character/halftone separator 2 is turned on, and the Y. I,
Encode all Q signals. This encoding is, for example, cosine transform encoding.
文字領域符号化部4は、文字領域信号がオンすると有効
となり、文字領域についての選択的符号化を行う部分で
あり、その構成が第2図に、その処理アルゴリズムが第
3図に、それぞれ示されている。The character area encoding unit 4 is activated when the character area signal is turned on, and is a part that selectively encodes the character area. Its configuration is shown in FIG. 2, and its processing algorithm is shown in FIG. 3. has been done.
この文字領域符号化部3において、Y信号符号化回路5
はY信号を無条件に符号化(例えばコサイン変換符号化
)する。Y信号判定回路6はY信号のレベルを閾値TH
と比較し、Y≧THの部分では工信号をI信号バツファ
7に,Q償号をQ信号バッファ8にそれぞれ蓄積させる
が、Y>THの部分ではI,Q信号を蓄積させない。ど
れにより、Y信号レベルが閾値TH以上の部分のI,Q
信号の一次元情報列がI,Q信号バッファ7,8に得ら
れる。I.Q信号符号化回路9,10は、Y信号の.符
号化後に、I,Q信号バッファ7.8に蓄積されたI,
Q信号をそれぞれ符号化する。In this character area encoding section 3, a Y signal encoding circuit 5
encodes the Y signal unconditionally (eg, cosine transform encoding). The Y signal determination circuit 6 sets the level of the Y signal to a threshold value TH.
In comparison, in the portion where Y≧TH, the engineering signal is stored in the I signal buffer 7 and the Q compensation signal is stored in the Q signal buffer 8, but in the portion where Y>TH, the I and Q signals are not stored. Which determines the I and Q portions where the Y signal level is higher than the threshold TH?
A one-dimensional information sequence of the signal is obtained in the I and Q signal buffers 7 and 8. I. The Q signal encoding circuits 9 and 10 encode the Y signal. After encoding, the I, Q signals stored in the I, Q signal buffer 7.8
Each Q signal is encoded.
この符号化は例えばDPCM符号化である。This encoding is, for example, DPCM encoding.
以上説明した如く、本発明によれば、カラー画像の文字
領域において、色情報保存の必要性が低い背景に当たる
部分では輝度信号のみを符号化し、輝度信号レベルが高
く色情報の欠落が問題となる部分では輝度信号および色
度信号を符号化するため、彩色された文字部が混在した
ようなカラー画像の場合でも、必要な色情報を保存して
良好な再現性を維持しつつ高い圧縮率を得ることができ
る。As explained above, according to the present invention, in the character area of a color image, only the luminance signal is encoded in the background portion where there is little need to preserve color information, and the luminance signal level is high and loss of color information becomes a problem. Since the luminance signal and chromaticity signal are encoded in the part, even in the case of a color image containing a mixture of colored characters, the necessary color information can be preserved and a high compression rate can be achieved while maintaining good reproducibility. Obtainable.
第1図は本発明の一実施例を示すブロック図、第2図は
文字領域符号化部の詳細ブロック図、第3図は文字領域
符号化部の処理アルゴリズムを示すフローチャートであ
る。
1・・・色空間変換部、 2・・・文字・中間調分離部
,3・・・中間調領域符号化部、
4・・・文字領域符号化部、
5・・・Y信号符号化回路、
7・・・I信号バッファ、
9・・・工信号符号化回路、
1o・・・Q信号符号化回路。
6・・・Y信号判定回路,
8・・・Q信号バッファ、
第1
第2図FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a detailed block diagram of a character area encoding section, and FIG. 3 is a flowchart showing a processing algorithm of the character area encoding section. DESCRIPTION OF SYMBOLS 1... Color space conversion unit, 2... Character/halftone separation unit, 3... Halftone area encoding unit, 4... Character area encoding unit, 5... Y signal encoding circuit , 7... I signal buffer, 9... Engineering signal encoding circuit, 1o... Q signal encoding circuit. 6...Y signal judgment circuit, 8...Q signal buffer, 1st 2nd figure
Claims (1)
を分離する分離手段、該分離手段により分離された中間
調領域において前記カラー画像の輝度信号および色度信
号を共に符号化する手段、前記分離手段により分離され
た文字領域において、前記カラー画像の輝度信号が所定
レベルを越える部分は前記カラー画像の輝度信号および
色度信号を共に符号化し、それ以外の部分は前記カラー
画像の輝度信号のみを符号化する手段を有することを特
徴とするカラー画像符号化方式。(1) Separating means for separating a character area and halftone area from a luminance signal of a color image; means for encoding both the luminance signal and chromaticity signal of the color image in the halftone area separated by the separating means; In the character area separated by the separating means, the luminance signal and chromaticity signal of the color image are encoded together in a portion where the luminance signal of the color image exceeds a predetermined level, and only the luminance signal of the color image is encoded in the other portions. A color image encoding method characterized by having means for encoding.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1113243A JPH02292959A (en) | 1989-05-02 | 1989-05-02 | Color picture encoding system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1113243A JPH02292959A (en) | 1989-05-02 | 1989-05-02 | Color picture encoding system |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH02292959A true JPH02292959A (en) | 1990-12-04 |
Family
ID=14607197
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP1113243A Pending JPH02292959A (en) | 1989-05-02 | 1989-05-02 | Color picture encoding system |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH02292959A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0491556A2 (en) * | 1990-12-19 | 1992-06-24 | Canon Kabushiki Kaisha | Image processing method and apparatus |
EP0685963A3 (en) * | 1994-05-31 | 1996-07-17 | Canon Kk | Image processing apparatus and method. |
KR100477656B1 (en) * | 2002-07-27 | 2005-03-22 | 삼성전자주식회사 | Method and apparatus for improvement of digital image quality |
-
1989
- 1989-05-02 JP JP1113243A patent/JPH02292959A/en active Pending
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0491556A2 (en) * | 1990-12-19 | 1992-06-24 | Canon Kabushiki Kaisha | Image processing method and apparatus |
US5588069A (en) * | 1990-12-19 | 1996-12-24 | Canon Kabushiki Kaisha | Image processing apparatus for advantageously encoding blocks of data having either substantially the same or varied colors |
EP0685963A3 (en) * | 1994-05-31 | 1996-07-17 | Canon Kk | Image processing apparatus and method. |
KR100477656B1 (en) * | 2002-07-27 | 2005-03-22 | 삼성전자주식회사 | Method and apparatus for improvement of digital image quality |
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