JPH065887B2 - Gradation correction method - Google Patents
Gradation correction methodInfo
- Publication number
- JPH065887B2 JPH065887B2 JP60056631A JP5663185A JPH065887B2 JP H065887 B2 JPH065887 B2 JP H065887B2 JP 60056631 A JP60056631 A JP 60056631A JP 5663185 A JP5663185 A JP 5663185A JP H065887 B2 JPH065887 B2 JP H065887B2
- Authority
- JP
- Japan
- Prior art keywords
- gradation
- input image
- image signal
- gradation correction
- correction method
- 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
Links
Landscapes
- Television Signal Processing For Recording (AREA)
- Facsimile Image Signal Circuits (AREA)
Description
【発明の詳細な説明】 〈技術分野〉 本発明は入力画像信号から階調再現範囲が制限された収
納装置用の記録信号を得る階調補正方法に関する。Description: TECHNICAL FIELD The present invention relates to a gradation correction method for obtaining a recording signal for a storage device having a limited gradation reproduction range from an input image signal.
〈従来技術〉 従来、例えばテレビジョン信号の階調範囲は極めて広い
が、このテレビジョン信号をハードコピーする場合、プ
リンタの階調再現範囲はテレビジョン信号の階調範囲に
比べて狭いので階調補正が行なわれていた。例えばこの
階調補正方法としては入力画像信号の階調レベル別にヒ
ストグラムをとり、入力画像信号の最大階調レベルをプ
リンタの最大階調レベルと一致させ、入力画像信号の最
小階調レベルをプリンタの最小階調レベルと一致させて
いた。斯かる方法により常に高コントラストの画像を再
現することが可能であったが、元々コントラストがない
フラットな画像にコントラストがついてしまったり、暗
調の画像部分が暗くつぶれてしまうといった欠点があっ
た。<Prior Art> Conventionally, for example, the gradation range of a television signal is extremely wide, but when a hard copy of this television signal is performed, the gradation reproduction range of the printer is narrower than the gradation range of the television signal, and therefore the gradation range is small. Corrections were being made. For example, this gradation correction method takes a histogram for each gradation level of the input image signal, matches the maximum gradation level of the input image signal with the maximum gradation level of the printer, and sets the minimum gradation level of the input image signal of the printer. It matched the minimum gradation level. Although it is possible to always reproduce a high-contrast image by such a method, there are drawbacks such that a flat image originally having no contrast has contrast, and a dark image portion is crushed darkly.
〈目的〉 本発明は上述の如き従来技術の欠点に鑑み、入力画像信
号の持っている特性に近い画像を再現し得る階調補正方
法の提供を目的としている。<Purpose> In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a gradation correction method capable of reproducing an image having characteristics close to those of an input image signal.
〈実施例〉 以下、本発明を白、黒テレビジョン信号を白黒画像プリ
ンタで記録する場合の実施例について説明する。<Embodiment> An embodiment of the present invention in which a black and white television signal is recorded by a monochrome image printer will be described below.
第１図は本実施例の白黒画像プリンタのブロック図であ
る。図においてＹは入力テレビジョン信号の輝度信号、
１１はアナロク／デジタル変換器、１２はＣＰＵでヒス
トグラム処理及び階調補正処理を実行する。１３はデジ
タル／アナログ変換器、１４は階調性のある画像を記録
できる記録ヘッド、１５はヒストグラムデータ或はＣＰ
Ｕ１２の処理に必要な値を記憶するＲＡＭ、１６はＣＰ
Ｕ１２の処理プログラムを格納したＲＯＭである。FIG. 1 is a block diagram of the monochrome image printer of this embodiment. In the figure, Y is the luminance signal of the input television signal,
Reference numeral 11 is an analog / digital converter, and reference numeral 12 is a CPU that executes histogram processing and gradation correction processing. Reference numeral 13 is a digital / analog converter, 14 is a recording head capable of recording an image having gradation, and 15 is histogram data or CP.
RAM for storing values required for U12 processing, 16 for CP
It is a ROM that stores the U12 processing program.
以下動作について第２図のフローチャートを参照して説
明する。The operation will be described below with reference to the flowchart of FIG.
まずステップＳ１で入力輝度信号Ｙについてヒストグラ
ムをとる。即ち一画面の各画素の輝度レベル別の頻度分
布を求める。Ｓ２でヒストグラムから全頻度の最小輝度
から１％の輝度をダークポイントＹ（１％）とし、９９
％の輝度をハイライトポイントＹ（９９％）とする。ス
テップＳ１、Ｓ２の処理については本出願人が提案した
特願昭５８−１９３１２９号に詳しい。First, in step S1, a histogram is obtained for the input luminance signal Y. That is, the frequency distribution for each brightness level of each pixel on one screen is obtained. In S2, the brightness of 1% from the minimum brightness of all frequencies is set as the dark point Y (1%) from the histogram, and 99
The luminance of% is the highlight point Y (99%). The details of steps S1 and S2 are described in Japanese Patent Application No. 58-193129 proposed by the present applicant.
ステップＳ３ではプリンタの最大再現輝度Ｙｍａｘ（記
録紙の白地）と最小再現輝度Ｙｍｉｎの差から求められ
る再現範囲Ｄｏｕｔと、入力画像信号の階調範囲Ｄｉｎ
＝Ｙ（９９％）−Ｙ（１％）との大きさを比較する。Ｓ
３でＤｏｕｔ＜Ｄｉｎの場合、即ちヒストグラムが第３
図（１）の場合は、プリンタの階調再現範囲が入力画像
信号の階調範囲よりも狭いのでステップＳ４で次式に従
い階調補正を行う。In step S3, the reproduction range Dout obtained from the difference between the maximum reproduction luminance Ymax (white background of recording paper) and the minimum reproduction luminance Ymin of the printer, and the gradation range Din of the input image signal.
= Y (99%)-Y (1%). S
3 and Dout <Din, that is, the histogram is the third
In the case of FIG. 1A, since the gradation reproduction range of the printer is narrower than the gradation range of the input image signal, gradation correction is performed according to the following equation in step S4.
元々コントラストのある入力画像に対して高コントラス
トのまま階調補正を施すことが可能となる。 It is possible to perform gradation correction on an input image that originally has contrast, while maintaining high contrast.
又、Ｓ３でＤｏｕｔ≧Ｄｉｎで、ステップＳ６でＹ（１
％）≧Ｙｍｉｎと判断された場合、即ちヒストグラムが
第３図（２）の場合は入力画像信号のヒストグラムが全
てプリンタの階調再現範囲内に入っているのでステップ
Ｓ７に示す如く階調補正を行なわず入力輝度信号Ｙをそ
のまま出力信号Y′として出力する。Further, in S3, Dout ≧ Din, and in step S6, Y (1
%) ≧ Ymin, that is, when the histogram is as shown in FIG. 3B, all the histograms of the input image signals are within the gradation reproduction range of the printer, so gradation correction is performed as shown in step S7. The input luminance signal Y is output as it is as the output signal Y ′ without being performed.
このようにプリンタの階調制限範囲に含まれる入力画像
信号に対しては階調補正を行っていないので入力画像信
号の特性がそのまま維持されて記録が行なわれる。As described above, since the gradation correction is not performed on the input image signal included in the gradation limitation range of the printer, the characteristic of the input image signal is maintained and recording is performed.
又Ｓ３、Ｓ６でＤｉｎ≧ＤｏｕｔでＹ（１％）＜Ｙｍｉ
ｎの場合、即ちヒストグラムが第３図（３）の様にあら
わされる場合はステップＳ９で次式に従い、入力画像信
号の階調範囲を保存したままで階調補正する。Further, in S3 and S6, Din ≧ Dout and Y (1%) <Ymi
In the case of n, that is, when the histogram is represented as shown in FIG. 3 (3), gradation correction is performed in step S9 according to the following expression while the gradation range of the input image signal is retained.
Ｙ＋（Ｙｍｉｎ−Ｙ（１％））→Y′ かかる構成により暗調の入力画像を同じコントラストで
しかも暗調のまま出力することが可能となる。Y + (Ymin−Y (1%)) → Y ′ With such a configuration, it is possible to output a dark-tone input image with the same contrast and in the dark tone.
尚、第３図においてｉｎは入力画像信号のヒストグラ
ム、ｏｕｔは出力画像信号のヒストグラムを示す。In FIG. 3, in indicates a histogram of the input image signal and out indicates a histogram of the output image signal.
〈他の実施例〉 本実施例においては白黒画像について述べたが、カラー
画像についてはＲＧＢ信号について同様の処理を行なえ
ばよい。又、輝度、色差信号を用いる場合には輝度信号
について処理を行なえばよい。又、出力装置としてプリ
ンタを例に説明したが階調再現範囲が比較的狭いデイス
プレイ装置にも適用可能である。又、ヒストグラムでＹ
（１％）、Ｙ（９９％）を用いたが、Ｙ（０％）、Ｙ
（１００％）を含めて他の％値を用いてもよい。<Other Embodiments> Although a black and white image has been described in this embodiment, a color image may be subjected to similar processing with respect to RGB signals. Further, when the luminance and color difference signals are used, the luminance signal may be processed. Although the printer has been described as an example of the output device, the present invention can be applied to a display device having a relatively narrow gradation reproduction range. Also, in the histogram Y
(1%) and Y (99%) were used, but Y (0%) and Y
Other% values may be used, including (100%).
〈効果〉 以上詳細に説明した如く、本発明に依れば入力画像信号
の特性を生かしたまま出力する事が可能となり極めて自
然な画像再現ができる。<Effect> As described in detail above, according to the present invention, it is possible to output while making the best use of the characteristics of the input image signal, and it is possible to reproduce an extremely natural image.
第１図は本実施例の白黒プリンタのブロック図、第２図
は第１図のＣＰＵ１２の処理フローチャート図、第３図
は入出力ヒストグラムを示す図である。FIG. 1 is a block diagram of the black and white printer of this embodiment, FIG. 2 is a processing flowchart of the CPU 12 of FIG. 1, and FIG. 3 is an input / output histogram.
Claims (1)
画像を出力する為の階調補正方法において、入力画像信
号が前記出力装置の階調再現範囲におさまるか否か判断
し、入力画像信号が前記階調再現範囲におさまらない場
合に前記入力画像信号に対して階調圧縮処理を施すこと
を特徴とする階調補正方法。1. In a gradation correction method for outputting a gradation image with an output device having a limited gradation reproduction range, it is judged whether or not an input image signal falls within the gradation reproduction range of the output device. A gradation correction method, wherein gradation compression processing is performed on the input image signal when the input image signal does not fall within the gradation reproduction range.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60056631A JPH065887B2 (en) | 1985-03-21 | 1985-03-21 | Gradation correction method |
| US06/838,785 US4731662A (en) | 1985-03-21 | 1986-03-12 | Image processing method for processing an image signal differently depending on the range of an image characteristic thereof relative to the range within which an output device can reproduce the image characteristic |
| DE3609049A DE3609049C3 (en) | 1985-03-21 | 1986-03-18 | Image editing process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60056631A JPH065887B2 (en) | 1985-03-21 | 1985-03-21 | Gradation correction method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61214863A JPS61214863A (en) | 1986-09-24 |
| JPH065887B2 true JPH065887B2 (en) | 1994-01-19 |
Family
ID=13032654
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60056631A Expired - Lifetime JPH065887B2 (en) | 1985-03-21 | 1985-03-21 | Gradation correction method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH065887B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0647254U (en) * | 1992-12-01 | 1994-06-28 | 北 雅子 | Equipment for peeling off adhesive tapes |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63184880A (en) * | 1987-01-28 | 1988-07-30 | Fuji Electric Co Ltd | Picture density converter |
| JP2752358B2 (en) * | 1987-06-19 | 1998-05-18 | 富士写真フイルム株式会社 | Image signal processing method |
| JPH06101854B2 (en) * | 1987-11-17 | 1994-12-12 | 三菱電機株式会社 | Color reproduction processing method |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6040225B2 (en) * | 1976-09-22 | 1985-09-10 | 株式会社リコー | inkjet printer |
| JPS56169978A (en) * | 1980-06-02 | 1981-12-26 | Sony Corp | A-d converter for image sensor |
| JPS58186291A (en) * | 1982-04-23 | 1983-10-31 | Sony Corp | Gradation converting method of color video signal |
| JPH0757006B2 (en) * | 1983-08-09 | 1995-06-14 | 富士写真フイルム株式会社 | Automatic setting method of gradation conversion table |
-
1985
- 1985-03-21 JP JP60056631A patent/JPH065887B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0647254U (en) * | 1992-12-01 | 1994-06-28 | 北 雅子 | Equipment for peeling off adhesive tapes |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61214863A (en) | 1986-09-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4731662A (en) | Image processing method for processing an image signal differently depending on the range of an image characteristic thereof relative to the range within which an output device can reproduce the image characteristic | |
| US7570390B2 (en) | Image processing device and method | |
| US7057653B1 (en) | Apparatus capable of image capturing | |
| US6952503B2 (en) | Image processing apparatus and method | |
| US5317427A (en) | Image processing apparatus and method for allowing the dynamic range of digital image data having a wide dynamic range to be compressed while preserving information of the digital image data | |
| JP4466378B2 (en) | History adding device, electronic camera, and image processing program | |
| JP7105737B2 (en) | Image processing device, image processing method, and program | |
| JPH0568147B2 (en) | ||
| EP0442369B1 (en) | Gradation correcting apparatus | |
| US7613338B2 (en) | Image processing method and apparatus, program, and storage medium | |
| CN100411445C (en) | Image processing method and apparatus for correcting image brightness distribution | |
| JP3184309B2 (en) | Gradation correction circuit and imaging device | |
| US20080044099A1 (en) | Image processing device that quickly performs retinex process | |
| JP3757747B2 (en) | Electronic camera, recording medium storing image processing program, and image processing method | |
| US7912308B2 (en) | Image processing device that quickly performs retinex process | |
| EP2246818A1 (en) | Image signal processing device and image signal processing program | |
| JPH065887B2 (en) | Gradation correction method | |
| JP3201049B2 (en) | Gradation correction circuit and imaging device | |
| JP7329932B2 (en) | Image processing device, image processing method, and program | |
| JPH0832060B2 (en) | Color image processing method | |
| US6931161B2 (en) | Method for making an exposure adjustment on a rendered image | |
| JPS6084084A (en) | Picture signal processing unit | |
| JP2543857B2 (en) | Color image processing device | |
| JP2002094810A (en) | Picture processor, picture processing method and memory medium having stored programs for the method | |
| JP4024735B2 (en) | Image processing method, image processing apparatus, image forming apparatus, imaging apparatus, and computer program |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |