JP2004015679A - Gradation correction curve creating method, gradation correction curve creating apparatus, and gradation correction curve creation program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To create a gradation correction curve rightly reflected in a gray direction by correcting dispersion of measuring instruments in a gradation correction curve creating method or the like for creating the gradation correction curve for correcting a gradation of an image. <P>SOLUTION: A chromaticity value is not directly measured but a spectrum is measured and the spectrum 54 is corrected. Then, the chromaticity value is found based upon the corrected spectrum 55, and the gradation correction curve is created by using the chromaticity value thus found. <P>COPYRIGHT: (C)2004,JPO

Description

【００９４】
但し、Ｄ_Ｒは網％に変換しようとしている実測濃度値
Ｄ_Ｖはベタの濃度値
を表わす。
【００９５】
図１２（Ｅ）の横軸（入力）は、標準的な特性のカラープリンタ３０でカラーチャートを出力したときに得られるはずの、あらかじめ分かっている標準的な網％値であり、図１２（Ｅ）の縦軸（出力）は、（１）式に基づいて求めた、網％値である。図１２（Ｅ）は、図１２（Ｂ）と同じく、Ｃ，Ｍ，Ｙの３色を代表させて１色分のグラフのみ示したものである。
【００９６】
また、これも図１２（Ｂ）の場合と同様、図１２（Ｅ）のグラフにおいて、入力と出力の関係は、図１２（Ｅ）に点線で示すようなリニアな関係となることが好ましいが、図１に示す実際のカラープリンタ３０は標準的な特性から多少なりとも外れた特性を有するものであり、入力と出力の関係は、図１２（Ｅ）に実線で示すような、リニアな関係からは外れた関係となる。
【００９７】
そこで、次に図１２（Ｆ）に示すように、図１２（Ｅ）とは逆の関係の曲線を作成する。この図１２（Ｆ）に実線で示す曲線は、前回の階調補正曲線に従って階調補正された後のデータを、さらにこの図１２（Ｆ）の曲線に従って変換した後にカラープリンタ３０に向けて出力したとき、カラープリンタ３０では、図１２（Ｆ）に点線で示すリニアな関係を持った画像が出力される。ただし、この単色の濃度パッチに基づいて階調補正曲線を作成した場合、ＣＭＹ重色のグレーの色味が必ずしも理想的なものとはならない。この図１２（Ｆ）に実線で示す曲線は、本発明にいう第２の補正曲線の一例に相当する。
【００９８】
次に、図５に示す階調補正曲線作成装置４１０の階調補正曲線作成部４１８のうちの補正曲線内分演算部４１８２の処理、すなわち図６に示すフローチャートの階調補正曲線作成過程（ステップ（ｈ））のうちの補正曲線内分過程（ステップ（ｈ２））における処理が行なわれる。
【００９９】
ここでは、オペレータによるキーボード２２あるいはマウス２３（図２参照）の操作に応じて、図５に示す重み設定部４１９から、補正曲線内分演算部４１８２に、内分演算の重みが設定される。
【０１００】
この重みは、図１２（Ｇ）に示すように、図１２（Ｃ）に実線で示す曲線と、図１２（Ｆ）に実線で示す曲線を内分して新たな曲線を生成するときの、それら図１２（Ｃ），図１２（Ｆ）に示す曲線をどの程度の割合で内分するかを指示するものであり、例えば、この重みとして０％が指示されると、図１２（Ｃ）のグレーパッチに基づく曲線は採用されずに図１２（Ｆ）の単色のパッチに基づく曲線のみが採用され、この重みとして５０％が指示されると、図１２（Ｃ），図１２（Ｆ）の曲線を等分に用いて内分演算が行なわれ、この重みとして１００％が指示されると、図１２（Ｆ）の単色のパッチに基づく曲線は採用されずに図１２（Ｃ）のグレーパッチに基づく曲線のみが採用される。この重み設定部４１９からは、Ｃ，Ｍ，Ｙの各単色を区別せず、Ｃ，Ｍ，Ｙのいずれについても同一の重みが設定される。同一の重みで十分であり、かつその方がオペレータによる重み設定の手間が少なくて済むからである。
【０１０１】
この内分演算により求められる曲線が、本発明にいう第３の補正曲線の一例に相当する。
【０１０２】
このような内分演算が行なわれた後、図５の階調補正曲線作成装置４１０の階調補正曲線作成部４１８の、階調補正曲線調整部４１８３による処理（図６のフローチャートの階調補正曲線作成過程（ステップ（ｈ））の、階調補正曲線調整過程（ステップ（ｈ３））の処理）が行なわれる。
【０１０３】
ここでは、図１２（Ｈ）に示すように、図１２（Ｃ）と図１２（Ｆ）の２つの曲線の重み付け内分により求められた曲線を用いて、前回の階調補正曲線が補正される。この補正により得られた階調補正曲線は、図１２に示す処理の流れから判るように、ＣＭＹの単色とグレーとの双方についてバランスのとれた、かつ、図１に示す１台のカラープリンタ３０に適合した階調補正曲線である。
【０１０４】
このようにして求められた階調補正曲線は、図１に示すパーソナルコンピュータ２０において、カラープリンタ３０で実際に画像をプリント出力しようとするときの実際の画像データの階調補正に用いられる。
【０１０５】
尚、Ｋ（黒）の階調補正曲線の作成にあたっては、グレーパッチからの情報は存在しないため、図１２の単色のルート（図１２（Ｄ），（Ｅ），（Ｆ）の流れ）を経由し、図１２（Ｇ）の処理は飛ばして、図１２（Ｈ）においてＫについて前回の階調補正曲線の補正が行なわれる。
【０１０６】
上述の実施形態によれば、ＣＭＹ単色のみでなくグレーについても測色により客観的なデータを得、重み付け内分演算によりグレーの測色データが反映されるため、特別なスキルを必要とせず、短時間かつ容易に階調補正曲線を作成することができる。また、オペレータは重みを設定することができ、その重み設定を通じてそのオペレータの階調補正への考え方あるいは好みが取り入れられ、そのオペレータに応じた高精度の階調補正曲線を作成することができる。
【０１０７】
また、上述の実施形態によれば、グレーパッチの色度値を、補正（変換）されたスペクトルに基づいて求めているため、歪みの少ない補正曲線（図１２（Ｃ））が求められ、グレーを正しく反映させた階調補正曲線が作成される。
【０１０８】
【発明の効果】
以上、説明したように、本発明によればグレーを正しく反映させた階調補正曲線を作成することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態が適用された画像入力−色変換−画像出力システムの全体構成図である。
【図２】図１に１つのブロックで示すパーソナルコンピュータの外観斜視図である。
【図３】パーソナルコンピュータのハードウェア構成図である。
【図４】本発明の階調補正曲線作成プログラムの一実施形態を示した図である。
【図５】本発明の階調補正曲線作成装置の一実施形態の機能ブロック図である。
【図６】図５に示す階調補正曲線作成装置を使って階調補正曲線を作成する方法を示すフローチャートである。
【図７】標準グレーチャートの一例を示す図である。
【図８】カラーチャートの一例を示す図である。
【図９】基準スペクトルと標準パッチスペクトルの一例を示した図である。
【図１０】変換定義の説明図である。
【図１１】実測用パッチスペクトルの変換過程の説明図である。
【図１２】階調補正曲線作成過程における処理の内容を示した模式図である。
【符号の説明】
１０　　カラースキャナ
１１　　原稿画像
２０　　パーソナルコンピュータ
２１　　本体装置
２２　　画像表示装置
２３　　キーボード
２４　　マウス
３０　　カラープリンタ
３１　　プリント画像
５１　　基準スペクトル
５２　　標準パッチスペクトル
５３　　グラフ
５４　　実測用パッチスペクトル
５５　　変換後の実測用パッチスペクトル
３１０　　階調補正曲線作成プログラム
３１１　　第１のスペクトル取得部
３１２　　パッチデータ生成部
３１３　　第２のスペクトル取得部
３１４　　変換定義演算部
３１５　　スペクトル変換部
３１６　　色度値算出部
３１７　　濃度値取得部
３１８　　階調補正曲線作成部
３１８１　　補正曲線作成部
３１８２　　補正曲線内分演算部
３１８３　　階調補正曲線調整部
３１９　　重み設定部
４１０　　階調補正曲線作成装置
４１１　　第１のスペクトル取得部
４１２　　パッチデータ生成部
４１３　　第２のスペクトル取得部
４１４　　変換定義演算部
４１５　　スペクトル変換部
４１６　　色度値算出部
４１７　　濃度値取得部
４１８　　階調補正曲線作成部
４１８１　　補正曲線作成部
４１８２　　補正曲線内分演算部
４１８３　　階調補正曲線調整部
４１９　　重み設定部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gradation correction curve creating method and a gradation correction curve creating apparatus for creating a gradation correction curve for correcting the gradation of an image, and an information processing apparatus that is executed in an information processing apparatus such as a computer. The present invention relates to a tone correction curve creation program that operates as a tone correction curve creation device.
[0002]
[Prior art]
Conventionally, an output device such as a color printer that takes in image data into a personal computer or the like, edits the image on the image data, and outputs the edited image data such as a color printer. The color conversion is performed in accordance with the above characteristics, gradation correction and the like are performed and output to the output device, and a desired image is output from the output device.
[0003]
A personal computer or the like performs various processes as described above. In the gradation correction process, for example, for each single color of C (cyan), M (magenta), Y (yellow), and K (black). In addition, a gradation correction curve is defined in a format such as LUT (look-up table), and processing for converting each image data of CMYK based on each gradation correction curve is performed.
[0004]
Here, in creating the gradation correction curve, image data representing a color chart composed of a plurality of density patches for each of C, M, Y, and K is generated by a personal computer or the like, and the image data is used as a color printer or the like. And output a color chart, and measure the density of each of the density patches of C, M, Y, and K constituting the output color chart. A tone correction curve can be created by associating the density measurement result of the density measurement patch thus obtained with the value of the image data when the density patch is generated.
[0005]
The gradation correction curve can be basically created as described above, but the gradation correction curve created as described above is considered only for the color axis directions of C, M, Y, and K. Therefore, the gray direction composed of the three colors C, M, and Y is not necessarily completely adjusted.
[0006]
On the other hand, in order to create a gradation correction curve that also considers the gray direction, the density of C, M, and Y single-color density patches is measured to obtain the first correction curve, and it is composed of CMY heavy colors. The gray patch is measured and a second correction curve for each CMY single color is obtained from the chromaticity value, and gradation correction is performed using both the first correction curve and the second correction curve thus obtained. Has been proposed (see Japanese Patent Application Laid-Open No. 2001-245171). According to the method proposed in this publication, not only C, M, and Y single-color densities but also gray that has been objectively evaluated by colorimetry is reflected in the gradation correction curve, and can be easily and easily reduced. A highly accurate gradation correction curve can be obtained in time.
[0007]
[Problems to be solved by the invention]
In the method proposed in the above publication, it is necessary to measure the chromaticity value by measuring the gray patch composed of CMY heavy colors as described above, but it depends on the type of measuring instrument and individual differences of each measuring instrument. Even with the same color, the chromaticity values are different, and even if correction processing is performed, an error due to variations in measuring instruments remains, and there is a problem that it is impossible to create a gradation correction curve that is correctly reflected in the gray direction.
[0008]
SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a gradation correction curve creation method and a gradation correction curve creation apparatus that create a gradation correction curve that is correctly reflected in the gray direction by correcting errors due to variations in measuring instruments with high accuracy. And a gradation correction curve creation program.
[0009]
[Means for Solving the Problems]
The gradation correction curve creation method of the present invention that achieves the above object is a gradation correction curve creation method for creating a gradation correction curve for correcting the gradation of an image output by an output device that outputs an image. And
Standards with standard chromaticity values that are the target of each chromaticity value for each of multiple gray patches for measurement with different chromaticity values that are created by overlaying multiple single colors using an output device that is subject to gradation correction A first spectrum acquisition process of acquiring each reference spectrum, which is each spectrum measured using a first measuring instrument as a reference of the gray patch;
A patch output process for outputting a plurality of gray patches for actual measurement using an output device for gradation correction;
Each of the actually measured patch spectra, which is each spectrum measured using a predetermined second measuring instrument, of the plurality of actually measured gray patches output in the patch output process, and the second of the plurality of standard gray patches. A second spectrum acquisition process for acquiring each standard patch spectrum, which is each spectrum measured using a measuring instrument;
A conversion definition calculation process for obtaining each conversion definition for converting each standard patch spectrum acquired in the second spectrum acquisition process to a corresponding reference spectrum acquired in the first spectrum acquisition process;
A spectrum conversion process for obtaining each measured patch spectrum after conversion by converting each measured patch spectrum obtained in the second spectrum acquisition process according to each conversion definition obtained in the conversion definition calculation process;
A chromaticity value calculation process for calculating each chromaticity value of a plurality of actual measurement gray patches output in the patch output process based on each actual measurement patch spectrum after being converted in the spectrum conversion process,
A gradation correction curve creation process for creating a gradation correction curve based on the chromaticity values of a plurality of actual gray patches calculated in the chromaticity value calculation process and the standard chromaticity values of a plurality of standard gray patches. It is characterized by having.
[0010]
The gradation correction curve creation method of the present invention obtains a spectrum (reference spectrum) of a standard gray patch obtained by measuring a standard gray patch that is a target of the chromaticity value with a first measuring instrument as a reference. The spectrum obtained by measuring the standard gray patch with the second measuring instrument (standard patch spectrum) and the gray for actual measurement output from the output device to be corrected. The spectrum obtained by measuring the patch with the same second measuring instrument (actual patch spectrum) is acquired (second spectrum acquisition process), and the standard patch spectrum obtained with the second measuring instrument is the same spectrum as the reference spectrum. A conversion definition for conversion to (conversion definition calculation process), apply this conversion definition to the actual patch spectrum, and convert the actual patch spectrum (spec) Chromaticity value is calculated on the basis of the converted patch spectrum for actual measurement thus obtained (chromaticity value calculation process), and the chromaticity value thus calculated and the standard gray patch The tone correction curve is created based on the standard chromaticity value of the image (gradation correction curve creation process). In summary, the chromaticity value is not measured directly, but the spectrum is measured. Since the spectrum is corrected and a chromaticity value based on the corrected spectrum is obtained, a gradation correction curve that correctly reflects gray is created.
[0011]
Here, in the gradation correction curve creating method of the present invention,
The patch output process is a process of outputting a plurality of actually measured gray patches using an output device to be subjected to gradation correction, and outputting a plurality of actually measured single color patches having different density values for each single color. ,
Furthermore, it has a density value acquisition process for acquiring each density value of each of the plurality of actually measured single color patches output in the patch output process,
The gradation correction curve creation process is based on the chromaticity values of the plurality of actual gray patches calculated in the chromaticity value calculation process and the standard chromaticity values of the plurality of standard gray patches, and further in the density value acquisition process. Preferably, the gradation correction curve is created based on the obtained density values of the plurality of actually measured single color patches.
[0012]
By creating a gradation correction curve based not only on the chromaticity value of gray but also on the density value for each single color, it is possible to create a gradation correction curve with high accuracy that is reflected correctly for gray.
[0013]
Here, when the gradation correction curve is created based on both the gray chromaticity value and the density value for each single color, the gradation correction curve creation process includes:
The gradation for each single color for gradation correction prepared in advance based on the chromaticity values of the plurality of actual gray patches calculated in the chromaticity value calculation process and the standard chromaticity values of the plurality of standard gray patches A first correction curve for correcting the correction curve is obtained for each single color, and a first correction curve for correcting the gradation correction curve based on the density values of a plurality of actually measured single color patches acquired in the density value acquisition process. A correction curve creation process for obtaining two correction curves for each single color;
In the correction curve for obtaining a third correction curve for each single color by internally dividing the first correction curve and the second correction curve obtained in the above correction curve creation process with an adjustable predetermined weight. Minute process,
A gradation correction curve for creating a new gradation correction curve for each single color for gradation correction by adjusting the gradation correction curve based on the third correction curve obtained in the correction curve internal division process It is preferable to have an adjustment process.
[0014]
In this case, the correction curve internal division process internally divides the first correction curve and the second correction curve created in the correction curve creation process for each single color with the same weighting for any single color. Thus, the process of obtaining the third correction curve for each single color may be used.
[0015]
Thus, the first correction curve and the second correction curve for correcting the gradation correction curve are obtained, the weight between them is adjusted, and the two correction curves are assigned the adjusted weight. Then, a third correction curve is obtained by dividing and the above-described gradation correction curve is adjusted based on the third correction curve, whereby a new highly accurate gradation correction for each single color is performed. A curve can be easily obtained.
[0016]
In this case, the same weight is sufficient for any single color, and setting the same weight facilitates the setting of the weight.
[0017]
The gradation correction curve creating apparatus of the present invention that achieves the above object is a gradation correction curve creating apparatus for creating a gradation correction curve for correcting the gradation of an image output by an output device that outputs an image. Because
Standards with standard chromaticity values that are the target of each chromaticity value for each of multiple gray patches for measurement with different chromaticity values that are created by overlaying multiple single colors using an output device that is subject to gradation correction A first spectrum acquisition unit that acquires each reference spectrum, which is each spectrum measured by using a first measuring instrument as a reference, of the gray patch;
A patch data generation unit that generates gray patch data for actual measurement representing a plurality of gray patches for actual measurement;
Based on the actual gray patch data generated by the patch data generation unit, a plurality of actual gray patches output using the output device to be subjected to gradation correction were measured using a predetermined second measuring device. A second spectrum acquisition unit that acquires each actual patch spectrum that is each spectrum and each standard patch spectrum that is each spectrum measured by using the second measuring instrument of a plurality of standard gray patches;
A conversion definition calculation unit for obtaining each conversion definition for converting each standard patch spectrum acquired by the second spectrum acquisition unit to each corresponding reference spectrum acquired by the first spectrum acquisition unit;
A spectrum conversion unit for obtaining each measured patch spectrum after conversion by converting each actual measurement patch spectrum acquired by the second spectrum acquisition unit according to each conversion definition obtained by the conversion definition calculation unit;
A chromaticity value calculation unit that calculates each chromaticity value of a plurality of gray patches for actual measurement based on each patch spectrum for actual measurement after being converted by the spectrum conversion unit,
A gradation correction curve creation unit that creates the gradation correction curve based on the chromaticity values of the plurality of actual gray patches calculated by the chromaticity value calculation unit and the standard chromaticity values of the plurality of standard gray patches; It is provided with.
[0018]
Here, in the gradation correction curve creating apparatus of the present invention,
The patch data generation unit generates gray patch data for actual measurement, and also generates single color patch data for actual measurement representing a plurality of actual measurement single color patches having different density values for each single color,
Furthermore, a density value acquisition unit that acquires each density value of each of a plurality of actual measurement single color patches output by the output device to be subjected to gradation correction based on the actual measurement single color patch data generated by the patch data generation unit,
The gradation correction curve creation unit is based on the chromaticity values of the plurality of actual gray patches calculated by the chromaticity value calculation unit and the standard chromaticity values of the plurality of standard gray patches, and further includes a density value acquisition unit. It is preferable that the gradation correction curve is created based on the density values of the plurality of actually measured single color patches obtained in step (1).
[0019]
In this case, the gradation correction curve creating unit
A gradation for each single color for gradation correction prepared in advance based on the chromaticity values of a plurality of actual gray patches calculated by the chromaticity value calculation unit and the standard chromaticity values of a plurality of standard gray patches A first correction curve for correcting the correction curve is obtained for each single color, and a first correction curve for correcting the gradation correction curve based on the density values of the plurality of actually measured single color patches acquired by the density value acquisition unit. A correction curve creation unit for obtaining two correction curves for each single color;
A third correction curve for each single color is obtained by internally dividing the first correction curve and the second correction curve created by the correction curve creation unit with a weight set according to the operation. A correction curve internal component calculation unit;
A tone for creating a new tone correction curve for each single color for tone correction by adjusting the tone correction curve based on the third correction curve obtained by the correction curve internal division calculation unit It is preferable to include a correction curve adjustment unit.
[0020]
Further, in this case, a common weight that is applied to any single color internal division calculation is operated as the internal weight of the first correction curve and the second correction curve generated by the correction curve generation unit. It is preferable that a weight setting unit that is set according to the above is provided.
[0021]
A gradation correction curve creation program of the present invention that achieves the above object is executed in an information processing apparatus that executes the program, and the information processing apparatus is operated by an output device that outputs an image. A gradation correction curve creation program that operates as a gradation correction curve creation device for creating a gradation correction curve for correcting
The information processing apparatus is
Standards with standard chromaticity values that are the target of each chromaticity value for each of multiple gray patches for measurement with different chromaticity values that are created by overlaying multiple single colors using an output device that is subject to gradation correction A first spectrum acquisition unit that acquires each reference spectrum, which is each spectrum measured by using a first measuring instrument as a reference, of the gray patch;
A patch data generation unit that generates gray patch data for actual measurement representing a plurality of gray patches for actual measurement;
Based on the actual gray patch data generated by the patch data generation unit, a plurality of actual gray patches output using the output device to be subjected to gradation correction were measured using a predetermined second measuring device. A second spectrum acquisition unit that acquires each actual patch spectrum that is each spectrum and each standard patch spectrum that is each spectrum measured by using the second measuring instrument of a plurality of standard gray patches;
A conversion definition calculation unit for obtaining each conversion definition for converting each standard patch spectrum acquired by the second spectrum acquisition unit to each corresponding reference spectrum acquired by the first spectrum acquisition unit;
A spectrum conversion unit for obtaining each measured patch spectrum after conversion by converting each actual measurement patch spectrum acquired by the second spectrum acquisition unit according to each conversion definition obtained by the conversion definition calculation unit;
A chromaticity value calculation unit that calculates each chromaticity value of a plurality of gray patches for actual measurement based on each patch spectrum for actual measurement after being converted by the spectrum conversion unit,
A gradation correction curve creation unit that creates a gradation correction curve based on the chromaticity values of the plurality of actual gray patches calculated by the chromaticity value calculation unit and the standard chromaticity values of the plurality of standard gray patches. It is characterized by operating as a gradation correction curve creation device provided.
[0022]
Here, in the gradation correction curve creation program of the present invention,
The patch data generation unit generates gray patch data for actual measurement, and also generates single color patch data for actual measurement representing a plurality of actual measurement single color patches having different density values for each single color,
Furthermore, a density value acquisition unit that acquires each density value of each of a plurality of actual measurement single color patches output by the output device to be subjected to gradation correction based on the actual measurement single color patch data generated by the patch data generation unit,
The gradation correction curve creation unit is based on the chromaticity values of the plurality of actual gray patches calculated by the chromaticity value calculation unit and the standard chromaticity values of the plurality of standard gray patches, and further includes a density value acquisition unit. It is preferable to create a tone correction curve based on the density values of a plurality of actually measured single color patches acquired in
In this case, the gradation correction curve creation process is as follows.
A gradation for each single color for gradation correction prepared in advance based on the chromaticity values of a plurality of actual gray patches calculated by the chromaticity value calculation unit and the standard chromaticity values of a plurality of standard gray patches A first correction curve for correcting the correction curve is obtained for each single color, and the tone correction curve is corrected based on the density values of a plurality of actually measured single color patches acquired by the density value acquisition unit. A correction curve creation unit for obtaining a second correction curve for each single color;
A third correction curve for each single color is obtained by internally dividing the first correction curve and the second correction curve created by the correction curve creation unit with a weight set according to the operation. A correction curve internal component calculation unit;
A tone for creating a new tone correction curve for each single color for tone correction by adjusting the tone correction curve based on the third correction curve obtained by the correction curve internal division calculation unit It is preferable to include a correction curve adjustment unit,
Further, in this case, as the internal weight of the first correction curve and the second correction curve created by the correction curve creation unit, a common weight applied to any single color internal division calculation is used for the operation. It is preferable to provide a weight setting unit that is set accordingly.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0024]
FIG. 1 is an overall configuration diagram of an image input-color conversion-image output system to which an embodiment of the present invention is applied.
[0025]
Here, a color scanner 10 is shown. The color scanner 10 reads an original image 11 and generates three-color image data composed of C (cyan), M (magenta), and Y (yellow). The The CMY image data is input to the personal computer 20. In the personal computer 20, the image data obtained by the color scanner 10 is converted into image data for image output suitable for a color printer 30 described later. The image data for image output is input to the color printer 30, and the color printer 30 performs print output based on the input image data to form a print image 31.
[0026]
In the system shown in FIG. 1, a color printer 30 is shown as an example of an output device that outputs an image based on image data. However, the color printer 30 may be an electrophotographic color printer or an inkjet color printer. It may be a printer, or it may be a printer that develops the photographic paper by exposing the photographic paper with a modulated laser beam, and it does not matter what the printing method is. The output device is not limited to a printer, and may be a printing machine, or may be an image display device such as a CRT display device or a plasma display device that displays and outputs an image on a display screen. Good.
[0027]
However, here, description will be made on the assumption that a system including the color printer 30 is an example of an output device.
[0028]
Here, the feature of the system shown in FIG. 1 as an embodiment of the present invention resides in the processing contents executed inside the personal computer 20, and the personal computer 20 will be described below.
[0029]
2 is an external perspective view of the personal computer 20 shown as one block in FIG. 1, and FIG. 3 is a hardware configuration diagram of the personal computer 20. As shown in FIG.
[0030]
The personal computer 20 has an appearance configuration, a main body device 21, an image display device 22 that displays an image on a display screen 22a in accordance with an instruction from the main body device 21, and a main body device 21 in accordance with various key operations. A keyboard 23 for inputting information and a mouse 24 for inputting an instruction corresponding to, for example, an icon or the like displayed at that position by designating an arbitrary position on the display screen 22a are provided. The main body device 21 has an FD loading port 21a for loading a flexible disk (FD) and a CD-ROM loading port 21b for loading a CD-ROM.
[0031]
As shown in FIG. 3, the main body device 21 includes a CPU 211 that executes various programs, a main memory 212 that is read out by a program stored in the hard disk device 213 and developed for execution by the CPU 211, and various programs. , A hard disk device 213 storing data and the like, an FD drive 214 loaded with the FD 100 and accessing the loaded FD 100, a CD-ROM 110 loaded, and a CD-ROM drive 215 accessing the loaded CD-ROM 110, An input interface 216 that is connected to the color scanner 10 (see FIG. 1) and receives image data from the color scanner 10 and an output interface 217 that sends image data to the color printer 30 are built-in. Also shown in the image Display device 22, a keyboard 23, a mouse 24 are connected to each other via a bus 25.
[0032]
Here, the CD-ROM 110 stores a tone correction curve creation program for operating the personal computer 20 as a tone correction curve creation device, and the CD-ROM 110 is loaded in the CD-ROM drive 215. The gradation correction curve creating power program stored in the CD-ROM 110 is uploaded to the personal computer 20 and stored in the hard disk device 213.
[0033]
FIG. 4 is a diagram showing an embodiment of the gradation correction curve creation program of the present invention stored in the gradation correction curve creation program storage medium. The gradation correction curve creation program storage medium 300 represents a storage medium such as the CD-ROM 110 and the hard disk in the hard disk device 213 shown in FIG.
[0034]
The gradation correction curve creation program storage medium 300 stores a gradation correction curve creation program 310. The tone correction curve creation program 310 includes a first spectrum acquisition unit 311, a patch data generation unit 312, a second spectrum acquisition unit 313, a conversion definition calculation unit 314, a spectrum conversion unit 315, a chromaticity value calculation unit 316, a density A value acquisition unit 317, a gradation correction curve creation unit 318, and a weight setting unit 319 are included. Among these, the gradation correction curve creation unit 318 includes a correction curve creation unit 3181, a correction curve internal component calculation unit 3182, and a tone correction curve adjustment unit 3183.
[0035]
The operation of each part of the gradation correction curve creation program 310 will be described later.
[0036]
FIG. 5 is a functional block diagram of an embodiment of the gradation correction curve creating apparatus of the present invention.
[0037]
The gradation correction curve creating apparatus 410 shown in FIG. 5 is loaded with the gradation correction curve creating program 310 shown in FIG. 4 on the personal computer 20 shown in FIGS. This is realized by executing the correction curve creation program 310.
[0038]
5 includes a first spectrum acquisition unit 411, a patch data generation unit 412, a second spectrum acquisition unit 413, a conversion definition calculation unit 414, a spectrum conversion unit 415, a chromaticity value. The calculation unit 416, the density value acquisition unit 417, the gradation correction curve creation unit 418, and the weight setting unit 419 include a correction curve creation unit 4181, a correction curve internal component, The calculation unit 4182 and the gradation correction curve adjustment unit 4183 are configured.
[0039]
The first spectrum acquisition unit 411, the patch data generation unit 412, the second spectrum acquisition unit 413, the conversion definition calculation unit 414, the spectrum conversion unit 415, and the chromaticity value calculation in the tone correction curve creation device 410 shown in FIG. The unit 416, the density value acquisition unit 417, the tone correction curve creation unit 418 (the correction curve creation unit 4181, the correction curve internal component calculation unit 4182, and the tone correction curve adjustment unit 4183) and the weight setting unit 419 are respectively The first spectrum acquisition unit 311, the patch data generation unit 312, the second spectrum acquisition unit 313, the conversion definition calculation unit 314, the spectrum conversion unit 315, the chromaticity value calculation unit 316, and the density value as software components shown in FIG. An acquisition unit 317, a tone correction curve creation unit 318 (a correction curve creation unit 3181, a correction curve internal component calculation unit 3182, and a tone correction A curve adjusting unit 3183), and the weight setting unit 319, necessary for realizing the function of each part, and a combination of hardware and operating system (OS) or the like of the personal computer 20.
[0040]
FIG. 6 is a flowchart showing a method of creating a gradation correction curve using the gradation correction curve creating apparatus 410 shown in FIG.
[0041]
6 will be described below with reference to each part of the gradation correction curve creating apparatus 410 shown in FIG. 5 (and thus each part of the gradation correction curve creating program 310 shown in FIG. 4).
[0042]
First, in the first spectrum acquisition process (step (a)) of FIG. 6, the output device is a target for gradation correction in the present embodiment. This first spectrum acquisition process is a target for each chromaticity value of each of a plurality of actually measured gray patches having different chromaticity values that are created by overlapping a plurality of single colors using the color printer 30 shown in FIG. This is a process of acquiring each reference spectrum, which is each spectrum measured using a first measuring instrument as a reference, of a plurality of standard gray patches having each standard chromaticity value.
[0043]
FIG. 8 is a diagram illustrating an example of a standard gray chart.
[0044]
This standard gray chart is a chromaticity value of a plurality (13 in this example) of gray patches when a color chart shown in FIG. 8 to be described later is printed out based on patch data predetermined by the color printer 30. Each standard chromaticity value to be a target is composed of a plurality of standard gray patches (13 in the example shown here), and is created in advance by the provider of the system shown in FIG.
[0045]
The first measuring instrument used for measuring the standard gray patch that constitutes the standard gray chart is a high-precision measuring instrument that serves as a reference. For example, the system provider side may include a plurality of standard gray charts that constitute the standard gray chart. Each spectrum (reference spectrum) of the patch is measured by a high-precision first measuring instrument serving as a reference, and the reference spectrum measured with high accuracy is provided to the user side together with the standard gray chart. For the user, in the first spectrum acquisition process of FIG. 6 ((step a)), the reference spectrum measured with high accuracy is acquired from the system provider side. The acquired reference spectrum is input to the first spectrum acquisition unit 411 of the gradation correction curve creation device 410 of FIG.
[0046]
The first spectrum acquisition unit 411 of the gradation correction curve creation device 410 is a functional part that receives the reference spectrum input to the personal computer 20 as described above.
[0047]
In the present embodiment, the first spectrum acquisition unit 411 includes a storage unit (not shown) that stores a reference spectrum. The storage unit stores a reference spectrum that has been input once. It eliminates the need to enter the spectrum each time. In the present embodiment, for a plurality of standard gray patches constituting the standard gray chart, in addition to each reference spectrum, each chromaticity value (each standard chromaticity value) obtained from each reference spectrum can be obtained. The acquired standard chromaticity value is input to the first spectrum acquisition unit 411 of the gradation correction curve creating apparatus 410 of FIG. 5 together with the reference spectrum, and the first spectrum acquisition is performed. The information is stored together with the reference spectrum in the storage unit of the unit 411. However, this standard chromaticity value does not need to be provided from the system provider side, and the chromaticity value calculation process in step (f) of FIG. 416), the standard chromaticity value may be obtained from the reference spectrum.
[0048]
Next, in the patch output process (step (b)) of FIG. 6, the patch data generation unit 412 of FIG. 5 operates to generate patch data, and a patch based on the patch data is output. That is, in the patch data generation unit 412 of the gradation correction curve creating apparatus 410 shown in FIG. Gray patch data representing the gray density patches are generated. In this embodiment, in addition to C, M, and Y single colors, single-color patch data representing single-color density patches for K (black) is also generated.
[0049]
The generated patch data is sent to the color printer 30 shown in FIG. 1, and the color printer 30 outputs a color chart in which a large number of patches are arranged based on the sent patch data.
[0050]
FIG. 8 is a diagram showing an example of a color chart.
[0051]
Here, a density patch of 21 steps is formed for each single color of C, M, Y, and K, and a density patch of 13 steps is formed for gray as a heavy color of C, M, and Y.
[0052]
Next, in the second spectrum acquisition process of FIG. 6 ((step (c)), the spectrum (measurement patch spectrum) of the 13 gray patches in the color chart shown in FIG. This second measuring device is simpler and less expensive than the standard first measuring device purchased on the user side, and therefore has a considerably larger error than the first measuring device. This measurement itself is an operation performed by the operator away from the gradation correction curve creating apparatus 410 in FIG.
[0053]
Further, in this same second spectrum acquisition process ((step (c)), a plurality of standard gray charts (in this case, which are provided with data of a reference spectrum and standard chromaticity values from the system provider side) The spectrum of the standard gray patch of 13) (standard patch spectrum) is also measured using the same second measuring instrument.
[0054]
Data of the spectrum (measured patch spectrum and standard patch spectrum) measured in this way is input to the second spectrum acquisition unit 413 of the gradation correction curve creating apparatus 410 shown in FIG.
[0055]
The spectrum data is input to the gradation correction curve creating apparatus 410 by, for example, an operator inputting the data from the keyboard 22 of the personal computer 20 shown in FIG. Alternatively, when the measuring instrument used for the measurement has a function of outputting the measurement data as a signal as it is, the measuring data is directly connected to the personal computer 20 shown in FIG. You may input into the personal computer 20 (namely, the gradation correction curve creation apparatus 410 shown in FIG. 5).
[0056]
The second spectrum value acquisition unit 413 of the gradation correction curve creation device 410 of FIG. 5 is a functional part that receives the data of the actual measurement patch spectrum and the standard patch spectrum input to the personal computer 20 as described above. is there.
[0057]
Next, the density value acquisition process in step (g) of FIG. 6 will be described first.
[0058]
In this density value acquisition process (step (g)), the density measurement of each single color patch of C, M, Y, K in the color chart shown in FIG. 8 is performed.
[0059]
The above-mentioned second measuring instrument is a measuring instrument (for example, a colorimeter with a density measuring mode) capable of measuring a density in addition to a spectrum. The density measurement in step (g) is also an operation performed by the operator away from the gradation correction curve creating apparatus 410 in FIG.
[0060]
The density value data obtained by this measurement is input to the density value acquisition unit 417 of the gradation correction curve creating apparatus 410 shown in FIG.
[0061]
Similarly to the case of acquiring the spectrum data in the second spectrum acquisition unit 413 of the gradation correction curve creating apparatus 410 in FIG. 5, the density value data is input to the gradation correction curve creating apparatus 410 by, for example, an operator. This is done by inputting the data from the keyboard 22 of the personal computer 20 shown in FIG. Alternatively, when the measuring instrument used for the measurement has a function of outputting the measurement data as a signal as it is, the measuring data is directly connected to the personal computer 20 shown in FIG. You may input into the personal computer 20 (namely, the gradation correction curve creation apparatus 410 shown in FIG. 5).
[0062]
The density value acquisition unit 417 of the gradation correction curve creating apparatus 410 in FIG. 5 is a functional part that receives the density value data input to the personal computer 20 as described above.
[0063]
Next, the conversion definition creation process in step (d) of FIG. 6 will be described. Here, the conversion definition calculation unit 414 of the gradation correction curve creating apparatus 410 in FIG. 5 operates, and here, the conversion definition is created as follows.
[0064]
FIG. 9 is a diagram illustrating an example of a reference spectrum and a standard patch spectrum.
[0065]
The reference spectrum 51 is acquired by being provided by the system provider in the first spectrum acquisition process (step (a) in FIG. 6) (first spectrum acquisition unit 411 of the gradation correction curve creating apparatus 410 in FIG. 5). The standard patch spectrum was acquired in the second spectrum acquisition process ((step (c)) (second spectrum acquisition unit 413 of the gradation correction curve creation device 410 in FIG. 5). This is a spectrum obtained by measuring a standard gray chart (see FIG. 7) provided with reference spectrum data from the system provider side using the second measuring device on the user side.
[0066]
FIG. 9 shows a reference spectrum and a standard patch spectrum of any one of the plurality of (here, 13 as shown in FIG. 7) standard gray patches.
[0067]
Although the standard patch spectrum 52 measured by using the second measuring device on the user side is a spectrum obtained by measuring the same standard gray patch, the system providing side has a difference depending on the measuring device. This is different from the reference spectrum 51 measured using the first measuring instrument as a reference.
[0068]
Therefore, the conversion definition calculation process (step (d) in FIG. 6) (the conversion definition calculation unit 414 of the gradation correction curve creating apparatus 410 in FIG. 5) converts the standard patch spectrum 52 into a spectrum that matches the reference spectrum 51. A conversion definition is created.
[0069]
FIG. 10 is an explanatory diagram of the conversion definition.
[0070]
When the conversion definition for converting the standard patch spectrum 52 shown in FIG. 9 to match the reference spectrum 51 is expressed as a correction coefficient for each wavelength λ, a graph 53 shown in FIG. 10 is obtained.
[0071]
That is, since the standard patch spectrum 52 in FIG. 9 has a smaller value than the reference spectrum 51 on the shorter wavelength λ side (left side in FIG. 9), the graph 53 in FIG. Since the standard patch spectrum 52 of FIG. 9 has a larger value than the reference spectrum 51 on the longer wavelength λ side (right side of FIGS. 9 and 10), the graph 53 of FIG. The correction coefficient is relatively small so as to suppress the standard patch spectrum 52 to a slightly small value.
[0072]
In the conversion definition calculation process (step (d) in FIG. 6) (the conversion definition calculation unit 414 of the gradation correction curve creating apparatus 410 in FIG. 5), each of the 13 standard gray patches constituting the standard gray chart shown in FIG. A conversion definition as shown by a graph 53 in FIG. 10 is created.
[0073]
In the next spectrum conversion process (step (e) in FIG. 6), the spectrum conversion unit 415 of the gradation correction curve generation device 410 in FIG. 5 operates, and the patch for measurement is measured using the conversion definition generated as described above. The spectrum is converted.
[0074]
FIG. 11 is an explanatory diagram of the conversion process of the actually measured patch spectrum.
[0075]
The actually measured patch spectrum 54 is obtained by measuring the 13 gray patches in the color chart shown in FIG. 8 output by the color printer 30 shown in FIG. 1 with the second measuring device on the user side. FIG. 11 shows one actual measurement patch spectrum corresponding to one standard gray patch whose reference spectrum is shown in FIG. 9 among the actual measurement patch spectra.
[0076]
The conversion definition shown by the graph 53 in FIG. 10 is applied to the actually measured patch spectrum 54 shown in FIG. That is, on the short side of the wavelength λ (the left side of FIGS. 10 and 11), the correction coefficient shown in FIG. 10 is relatively large, and when this correction coefficient (conversion definition) is applied to the actually measured patch spectrum 54, the wavelength λ On the short side (left side of the figure), the value of the spectrum is raised. Similarly, on the longer wavelength λ side (right side in FIGS. 10 and 11), the correction coefficient shown in FIG. 10 is relatively small, and this correction coefficient (conversion definition) is applied to the actual measurement patch spectrum 54. As a result, the value of the spectrum is suppressed on the longer wavelength λ side (the right side in the figure).
[0077]
When such conversion is performed, the actual measurement patch spectrum 54 shown in FIG. 11 is converted into the actual measurement patch spectrum 55 after conversion. The actual measurement patch spectrum 55 after conversion is equivalent to the spectrum obtained when the actual measurement gray patch in the color chart shown in FIG. 8 is measured by a high-precision first measuring instrument on the system provider side. is there.
[0078]
In the chromaticity value calculation process of step (f) in FIG. 6 (the chromaticity value calculation unit 416 of the gradation correction curve creation device 410 in FIG. 5), based on the converted patch spectrum for actual measurement obtained as described above. And the chromaticity value (here L ^* a ^* b ^* Value). The algorithm for obtaining the chromaticity value from the spectrum is originally a colorimeter, which first obtains the spectrum and obtains the chromaticity value based on the obtained spectrum. Description is omitted.
[0079]
Here, in the chromaticity value calculation process (step (f) in FIG. 6 (the chromaticity value calculation unit 416 of the gradation correction curve creating apparatus 410 in FIG. 5)), the process is performed based on the actually measured patch spectrum. The chromaticity value of the gray patch shown in FIG. 8 was obtained, and together with this, the first spectrum acquisition process (step (a) in FIG. 6) (the first spectrum acquisition unit of the gradation correction curve creating apparatus 410 in FIG. 5). 411), the standard chromaticity value that is the chromaticity value of the standard gray patch (see FIG. 7) may be obtained, but in this embodiment, as described above, the color of the standard gray patch The standard chromaticity value, which is a chromaticity value, is also acquired from the system provider side and stored in the storage unit in the first spectrum acquisition unit 411 of the gradation correction curve creating apparatus 410 in FIG. (Step (f) in FIG. 6) In the chromaticity value calculating portion 416 of the gradation correction curve creation apparatus 410) it does not need to again determine the standard chromaticity value.
[0080]
Next, in the gradation correction curve creation process (gradation correction curve creation unit 418 in FIG. 5) in step (h) of FIG. 6, a gradation correction curve is created as follows.
[0081]
The gradation correction curve creation process (step (h)) in FIG. 6 includes a correction curve creation process (step (h1)), a correction curve internal division calculation process (step (h2)), and a gradation correction curve adjustment process (step). (H3)), and the correction curve creation unit 4181 in the gradation correction curve creation unit 418 of the gradation correction curve creation device 410 of FIG. 5 operates in the correction curve creation process (step (h1)) of them. To do.
[0082]
The correction curve creation unit 4181 stores a gradation correction curve for each single color created last time. Here, the previously created gradation correction curve is referred to as “previous gradation correction curve”.
[0083]
Here, the color printers 30 shown in FIG. 1 have slightly different characteristics even if they are in the same model, so that even if the same gradation image is printed out, each color printer 30 is different for each unit. A slightly different tone correction curve is required, but here, the machine difference of each unit is ignored, and a tone correction curve for a standard one of the same model as the color printer 30 is prepared in advance. Each time the gradation correction curve prepared in advance is updated as described below, the “previous gradation correction curve” is currently created. That is, the color chart of FIG. 7 is printed out by the color printer 30 based on the patch data after being corrected based on the “previous gradation correction curve”.
[0084]
The correction curve creation unit 4181 obtains the previous gradation correction curve stored in the correction curve creation unit 4181 based on the density value of each single color patch constituting the color chart of FIG. 8 acquired by the density value acquisition unit 417. The correction curve for correcting (an example of the second correction curve in the present invention) is obtained, and the chromaticity values of the gray patches constituting the color chart shown in FIG. 8 obtained by the chromaticity value calculation unit 416 are obtained. And the standard chromaticity value of the standard gray patch constituting the standard gray chart (see FIG. 7), the correction curve for each single color for correcting the previous gradation correction curve (the first correction according to the present invention). An example of a correction curve) is obtained.
[0085]
FIG. 12 is a schematic diagram showing the contents of processing in the gradation correction curve creation process (step (h) in FIG. 6).
[0086]
In the correction curve creation process (step (h1) in FIG. 6) performed by the correction curve creation unit 4181 of the tone correction curve creation unit 418 of the tone correction curve creation device 410 in FIG. 5, FIG. As shown, the chromaticity value (L of the gray patch obtained in the chromaticity value calculation process (step (f) in FIG. 6)) ^* a ^* b ^* Value) and the standard chromaticity value L of the standard gray patch constituting the standard gray chart shown in FIG. ^* a ^* b ^* The value is converted into each value representing halftone% of C, M, and Y according to the profile of the color printer 30.
[0087]
The horizontal axis (input) in FIG. 12B is the C, M, and Y values obtained from the standard chromaticity values of the standard gray patches constituting the standard gray chart, and the vertical axis in FIG. (Output) is each value of C, M, and Y further obtained from the chromaticity value of the gray patch shown in FIG. 8 obtained in the chromaticity value calculation process (chromaticity value calculation unit). Here, only a graph for one color is shown, representing the three colors C, M, and Y.
[0088]
In the graph of FIG. 12B, the relationship between input and output is preferably a linear relationship as shown by a dotted line in FIG. 12B, but the actual color printer 30 shown in FIG. Therefore, the relationship between the input and the output is deviated from the linear relationship as shown by the solid line in FIG.
[0089]
Therefore, next, as shown in FIG. 12C, a curve having a reverse relationship to that in FIG. 12B is created. When the data after tone correction according to the previous tone correction curve is further converted according to the curve of FIG. 12C and then output to the color printer 30, the color printer 30 receives the data shown in FIG. ), An image having a linear relationship color as shown by a dotted line is output. However, the curve in FIG. 12C is created based only on the gray chromaticity value, and an image having an ideal linear relationship is not always output. Details will be described later.
[0090]
A curve indicated by a solid line in FIG. 12C corresponds to an example of a first correction curve according to the present invention.
[0091]
The above is the processing based on the chromaticity value of the gray patch, but the same processing is performed for the density values of the CMY single color density patches as described below. The handling of the K (black) single color patch will be described later.
[0092]
Here, as shown in FIG. 12 (D), the actually measured density values of C, M, and Y are converted into C, M, and Y values representing the halftone percentages of C, M, and Y, respectively. In order to convert the actually measured density value into C, M, and Y values representing the halftone percentage, the following Male Davis equation is used.
[0093]
[Expression 1]

[0094]
However, D _R Is the measured concentration value to be converted to net%
D _V Is solid density value
Represents.
[0095]
The horizontal axis (input) in FIG. 12E represents a standard halftone value that is known in advance and should be obtained when a color chart is output by the color printer 30 having standard characteristics. The vertical axis | shaft (output) of E) is the net | network% value calculated | required based on (1) Formula. FIG. 12E shows only one color graph representing the three colors C, M, and Y as in FIG. 12B.
[0096]
In addition, as in the case of FIG. 12B, it is preferable that the relationship between the input and the output in the graph of FIG. 12E is a linear relationship as indicated by a dotted line in FIG. The actual color printer 30 shown in FIG. 1 has characteristics slightly deviating from standard characteristics, and the relationship between input and output is a linear relationship as shown by a solid line in FIG. It is a relationship that is out of place.
[0097]
Therefore, as shown in FIG. 12 (F), a curve having a reverse relationship to that in FIG. 12 (E) is created. The curve indicated by the solid line in FIG. 12 (F) is output to the color printer 30 after the data after tone correction according to the previous tone correction curve is further converted according to the curve of FIG. 12 (F). Then, the color printer 30 outputs an image having a linear relationship indicated by a dotted line in FIG. However, when a gradation correction curve is created based on this single-color density patch, the CMY heavy gray color is not necessarily ideal. A curve indicated by a solid line in FIG. 12F corresponds to an example of a second correction curve according to the present invention.
[0098]
Next, the processing of the correction curve internal component calculation unit 4182 in the gradation correction curve generation unit 418 of the gradation correction curve generation device 410 shown in FIG. 5, that is, the gradation correction curve generation process (steps) of the flowchart shown in FIG. (H)) in the correction curve internal division process (step (h2)).
[0099]
Here, in accordance with the operation of the keyboard 22 or the mouse 23 (see FIG. 2) by the operator, the weight for the internal division calculation is set from the weight setting unit 419 shown in FIG.
[0100]
As shown in FIG. 12G, this weight is obtained when a new curve is generated by internally dividing the curve indicated by the solid line in FIG. 12C and the curve indicated by the solid line in FIG. 12C and FIG. 12F is instructed at what ratio to internally divide the curve. For example, when 0% is designated as the weight, the curve shown in FIG. If the curve based on the single color patch of FIG. 12 (F) is adopted without using the curve based on the gray patch of FIG. 12 and 50% is designated as the weight, FIGS. 12 (C) and 12 (F). When an internal division calculation is performed using the curve of FIG. 12B and 100% is designated as the weight, the curve based on the single color patch of FIG. 12F is not adopted and the gray of FIG. Only curves based on patches are employed. From the weight setting unit 419, the C, M, and Y single colors are not distinguished, and the same weight is set for all of C, M, and Y. This is because the same weight is sufficient and the operator does not need to set the weight.
[0101]
The curve obtained by the internal division calculation corresponds to an example of the third correction curve referred to in the present invention.
[0102]
After such internal division calculation is performed, the processing by the tone correction curve adjustment unit 4183 of the tone correction curve creation unit 418 of the tone correction curve creation device 410 in FIG. 5 (the tone correction in the flowchart in FIG. 6). A gradation correction curve adjustment process (step (h3)) in a curve creation process (step (h)) is performed.
[0103]
Here, as shown in FIG. 12 (H), the previous gradation correction curve is corrected using the curve obtained by weighted internal division of the two curves in FIG. 12 (C) and FIG. 12 (F). The As can be seen from the processing flow shown in FIG. 12, the gradation correction curve obtained by this correction is balanced with respect to both CMY monochrome and gray, and one color printer 30 shown in FIG. Is a gradation correction curve suitable for.
[0104]
The gradation correction curve obtained in this way is used for gradation correction of actual image data when an image is actually printed out by the color printer 30 in the personal computer 20 shown in FIG.
[0105]
In creating the K (black) tone correction curve, since there is no information from the gray patch, the monochromatic route (flows of FIGS. 12D, 12E, and 12F) of FIG. Then, the process of FIG. 12G is skipped, and the previous gradation correction curve is corrected for K in FIG.
[0106]
According to the above-described embodiment, objective data is obtained by colorimetry not only for CMY single colors but also for gray, and gray colorimetric data is reflected by weighted internal division calculation, so no special skill is required, A gradation correction curve can be created in a short time and easily. Further, the operator can set a weight, and through the weight setting, the operator's concept or preference for gradation correction is taken in, and a highly accurate gradation correction curve corresponding to the operator can be created.
[0107]
Further, according to the above-described embodiment, since the chromaticity value of the gray patch is obtained based on the corrected (converted) spectrum, a correction curve (FIG. 12C) with less distortion is obtained, and the gray patch A gradation correction curve that correctly reflects is created.
[0108]
【The invention's effect】
As described above, according to the present invention, it is possible to create a gradation correction curve that correctly reflects gray.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an image input-color conversion-image output system to which an embodiment of the present invention is applied.
FIG. 2 is an external perspective view of a personal computer shown by one block in FIG.
FIG. 3 is a hardware configuration diagram of a personal computer.
FIG. 4 is a diagram showing an embodiment of a gradation correction curve creation program of the present invention.
FIG. 5 is a functional block diagram of an embodiment of a gradation correction curve creation device of the present invention.
6 is a flowchart showing a method of creating a gradation correction curve using the gradation correction curve creation apparatus shown in FIG.
FIG. 7 is a diagram illustrating an example of a standard gray chart.
FIG. 8 is a diagram illustrating an example of a color chart.
FIG. 9 is a diagram illustrating an example of a reference spectrum and a standard patch spectrum.
FIG. 10 is an explanatory diagram of a conversion definition.
FIG. 11 is an explanatory diagram of a process of converting an actually measured patch spectrum.
FIG. 12 is a schematic diagram showing the contents of processing in the gradation correction curve creation process.
[Explanation of symbols]
10 Color scanner
11 Document image
20 Personal computer
21 Main unit
22 Image display device
23 Keyboard
24 mice
30 Color printer
31 Print image
51 Reference spectrum
52 standard patch spectrum
53 graph
54 Patch spectrum for actual measurement
55 Patch spectrum for actual measurement after conversion
310 Gradation correction curve creation program
311 First spectrum acquisition unit
312 Patch data generator
313 Second spectrum acquisition unit
314 Conversion Definition Calculation Unit
315 Spectrum converter
316 chromaticity value calculation unit
317 Density value acquisition unit
318 Tone correction curve generator
3181 Correction curve generator
3182 Correction curve division calculation unit
3183 Gradation correction curve adjustment unit
319 Weight setting unit
410 Gradation correction curve creation device
411 1st spectrum acquisition part
412 Patch data generator
413 Second spectrum acquisition unit
414 Conversion definition calculation part
415 Spectrum conversion unit
416 Chromaticity value calculation unit
417 Density value acquisition unit
418 Tone correction curve generator
4181 Correction curve generator
4182 Correction curve internal division calculation unit
4183 Gradation correction curve adjustment unit
419 Weight setting unit

Claims (5)

In a gradation correction curve creating method for creating a gradation correction curve for correcting the gradation of an image output by an output device that outputs an image,
Standards with standard chromaticity values that are the target of each chromaticity value for each of multiple gray patches for measurement with different chromaticity values that are created by overlaying multiple single colors using an output device that is subject to gradation correction A first spectrum acquisition process of acquiring each reference spectrum, which is each spectrum measured using a first measuring instrument as a reference of the gray patch;
A patch output process of outputting the plurality of gray patches for actual measurement using the output device to be subjected to gradation correction;
Of each of the plurality of actually measured gray patches output in the patch output process, each of the actually measured patch spectra that is each spectrum measured using a predetermined second measuring instrument, and each of the plurality of standard gray patches, A second spectrum acquisition process for acquiring each standard patch spectrum, which is each spectrum measured using a second measuring device;
A conversion definition calculation process for obtaining each conversion definition for converting each standard patch spectrum acquired in the second spectrum acquisition process into a corresponding reference spectrum acquired in the first spectrum acquisition process; ,
A spectrum conversion process for obtaining each measured patch spectrum after conversion by converting each measured patch spectrum obtained in the second spectrum acquisition process according to each conversion definition obtained in the conversion definition calculation process;
A chromaticity value calculation process for calculating each chromaticity value of the plurality of actual measurement gray patches output in the patch output process, based on each actual measurement patch spectrum converted in the spectrum conversion process,
A gradation correction curve that creates the gradation correction curve based on chromaticity values of the plurality of actual gray patches calculated in the chromaticity value calculation process and standard chromaticity values of the plurality of standard gray patches A gradation correction curve creating method characterized by comprising: a creating process. The patch output process is a process of outputting the plurality of actually measured gray patches using the output device to be subjected to gradation correction and outputting a plurality of actually measured single color patches having different density values for each single color. There,
Furthermore, it has a density value acquisition process for acquiring each density value of each of the plurality of actually measured single color patches output in the patch output process,
The gradation correction curve creation process is based on the chromaticity values of the plurality of actually measured gray patches calculated in the chromaticity value calculation process and the standard chromaticity values of the plurality of standard gray patches. 2. The gradation correction curve creating method according to claim 1, wherein the gradation correction curve is created based on density values of the plurality of actually measured single color patches obtained in the density value obtaining process. The gradation correction curve creation process includes:
Based on the chromaticity values of the plurality of actually measured gray patches calculated in the chromaticity value calculation process and the standard chromaticity values of the plurality of standard gray patches, for each single color for gradation correction prepared in advance A first correction curve for correcting the tone correction curve is obtained for each single color, and the tone correction curve is based on the density values of the plurality of actually measured single color patches acquired in the density value acquisition process. A correction curve creation process for obtaining a second correction curve for correcting each of the single colors;
Correction for obtaining a third correction curve for each single color by internally dividing the first correction curve and the second correction curve obtained in the correction curve creation process with an adjustable predetermined weight. Curve division process,
A gradation that creates a new gradation correction curve for each single color for gradation correction by adjusting the gradation correction curve based on the third correction curve obtained in the process of dividing the correction curve 3. The gradation correction curve creating method according to claim 2, further comprising a correction curve adjustment process. In a gradation correction curve creating apparatus for creating a gradation correction curve for correcting the gradation of an image output by an output device that outputs an image,
Standards with standard chromaticity values that are the target of each chromaticity value for each of multiple gray patches for measurement with different chromaticity values that are created by overlaying multiple single colors using an output device that is subject to gradation correction A first spectrum acquisition unit that acquires each reference spectrum, which is each spectrum measured by using a first measuring instrument as a reference, of the gray patch;
A patch data generating unit that generates gray patch data for actual measurement representing the plurality of gray patches for actual measurement;
Measurement using a predetermined second measuring device of a plurality of gray patches for actual measurement output using the output device for gradation correction based on the gray patch data for actual measurement generated by the patch data generation unit Second spectrum acquisition for acquiring each measured patch spectrum, which is each spectrum obtained, and each standard patch spectrum, which is each spectrum of the plurality of standard gray patches, measured using the second measuring device And
A conversion definition calculation unit for obtaining each conversion definition for converting each standard patch spectrum acquired by the second spectrum acquisition unit into a corresponding reference spectrum acquired by the first spectrum acquisition unit; ,
A spectrum conversion unit for obtaining each measured patch spectrum after conversion by converting each actual measurement patch spectrum acquired by the second spectrum acquisition unit according to each conversion definition obtained by the conversion definition calculation unit;
A chromaticity value calculation unit that calculates each chromaticity value of the plurality of actual measurement gray patches, based on each actual measurement patch spectrum converted by the spectrum conversion unit;
A gradation correction curve that creates the gradation correction curve based on the chromaticity values of the plurality of actual gray patches calculated by the chromaticity value calculation unit and the standard chromaticity values of the plurality of standard gray patches. A gradation correction curve creating apparatus comprising: a creating unit. A gradation correction curve creating apparatus that executes a gradation correction curve that is executed in an information processing apparatus that executes a program and that corrects the gradation of an image output by an output device that outputs an image. A gradation correction curve creation program to be operated as
The information processing apparatus;
Standards with standard chromaticity values that are the target of each chromaticity value for each of multiple gray patches for measurement with different chromaticity values that are created by overlaying multiple single colors using an output device that is subject to gradation correction A first spectrum acquisition unit that acquires each reference spectrum, which is each spectrum measured by using a first measuring instrument as a reference, of the gray patch;
A patch data generating unit that generates gray patch data for actual measurement representing the plurality of gray patches for actual measurement;
Measurement using a predetermined second measuring device of a plurality of gray patches for actual measurement output using the output device for gradation correction based on the gray patch data for actual measurement generated by the patch data generation unit Second spectrum acquisition for acquiring each measured patch spectrum, which is each spectrum obtained, and each standard patch spectrum, which is each spectrum of the plurality of standard gray patches, measured using the second measuring device And
A conversion definition calculation unit for obtaining each conversion definition for converting each standard patch spectrum acquired by the second spectrum acquisition unit into a corresponding reference spectrum acquired by the first spectrum acquisition unit; ,
A spectrum conversion unit for obtaining each measured patch spectrum after conversion by converting each actual measurement patch spectrum acquired by the second spectrum acquisition unit according to each conversion definition obtained by the conversion definition calculation unit;
A chromaticity value calculation unit that calculates each chromaticity value of the plurality of actual measurement gray patches, based on each actual measurement patch spectrum converted by the spectrum conversion unit;
A gradation correction curve that creates the gradation correction curve based on the chromaticity values of the plurality of actual gray patches calculated by the chromaticity value calculation unit and the standard chromaticity values of the plurality of standard gray patches. A gradation correction curve creation program that is operated as a gradation correction curve creation device including a creation unit.

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