JP3658141B2 - Image processing apparatus and image processing method - Google Patents

Description

【００４６】

次に、（２）発光輝度のガンマ特性を考慮してＲ’，Ｇ’，Ｂ’を次式でＲ，Ｇ，Ｂに変換する。
【００４７】

ここで、Ｒ，Ｇ，Ｂ信号は、何れも８ビットの整数値で表されているものとしている（尚、＾はべき上の演算を表す演算子である）。こうして得られたＲ，Ｇ，Ｂ信号は、（１）〜（３）の特性を持つ仮想的な標準モニタに、（４）で指定した標準環境下で正しい色を表示するためのＲ，Ｇ，Ｂ信号となっている。
【００４８】
次に、実際に使用するモニタの特性について考える。実際に使用するモニタの特性が、前記の仮想モニタの特性（１）〜（３）及び（４）と同じであれば、（５）式で得られたＲ，Ｇ，Ｂ信号をそのまま表示すればよい。しかしながら、通常はモニタ毎に特性が異なっている。
【００４９】
今、使用している実在のモニタの特性が、次の（１’）〜（３’）であり、環境条件が（４’）であったとする。
【００５０】
（１’）３色蛍光体の色度座標（ＣＩＥ−ｘｙ色度座標）
赤：ｘ＝０．６０、ｙ＝０．３０
緑：ｘ＝０．３２、ｙ＝０．５８
青：ｘ＝０．１８、ｙ＝０．０８
（２’）発光輝度のガンマ特性
赤、緑、青とも１．８
（３’）白色点の色温度
６５００Ｋ（Ｄ６５標準光源に相当）
（４’）環境光の色温度
４２００Ｋ（通常のオフィス用白色蛍光灯に相当）
尚、従来の方法では、このような特性のモニタを使用している場合は、ＣＭＳのモニタプロファイルにこれらの条件を設定しておき、上記の（５）式及び（６）式ではなく、次の（５’）式、（６’）式を実行してＸＹＺ信号から直接実在のモニタ用のモニタＲＧＢ信号への補正を行っている。
【００５１】
【数２】

【００５２】

一方、本実施形態では、ＣＭＳ１０９の色空間変換部２（２３）において、色空間変換部１（２１）からのＸＹＺ信号に（５）式、（６）式の演算を行うことにより、仮想的な標準モニタ用のＲ，Ｇ，Ｂ信号が求められている。従って、図１の色空間補正部１１では、（５’）式、（６’）式を実行して得られる実在のモニタ用のモニタＲＧＢ信号を生成するために、色空間変換部２（２３）からの仮想的な標準モニタ用のＲＧＢ信号から、実在のモニタ用のモニタＲＧＢ信号を生成しなければならない。
【００５３】
そのため、本実施形態では、図１のモニタ指定装置１２から（１’）〜（３’）の実在のモニタの特性を指定し、環境光指定装置１３から（４’）の条件を設定する。そして、色空間補正部１１は、モニタ指定装置１２にて設定された実在のモニタ１０８の特性データを参照して適正なパラメータを算出し、そのパラメータを使用して仮想的な標準モニタ用のＲＧＢ信号から実在のモニタ１０８用のモニタＲＧＢ信号に補正する。この色空間補正部１１にて行われる補正について図３を参照して説明する。
【００５４】
図３は、本発明の第１の実施形態としての色空間補正部１１における色変換を説明する図であり、図１の色空間補正部１１の内部の詳細を示している。
【００５５】
同図において、図３の入力は図１のＶＲＡＭからのＲＧＢ信号であり、既に説明したようにＣＭＳ１０９の色空間変換部２（２３）により標準モニタのＲＧＢ信号に補正されている。
【００５６】
図３の逆ガンマ補正部３１では、まず標準モニタ信号Ｒ，Ｇ，Ｂを（６）式の変換の逆変換である、次式の逆ガンマ変換を実行してＲ’，Ｇ’，Ｂ’に変換する。
【００５７】

次に（７）式により得られたＲ’，Ｇ’，Ｂ’を、マトリックス変換器３２で次式のようにＲ”，Ｇ”，Ｂ”に変換する。
【００５８】
【数３】

【００５９】

このマトリックス変換の係数Ｍは、（５）式のマトリックスをＭ１、（５’）式のマトリックスをＭ２、及び環境光の色温度補正マトリックスをＭ３としたとき、
Ｍ＝Ｍ３×Ｍ２×Ｍ１-1
で得られる係数である（但し、Ｍ１(-1)はＭ１の逆行列を表す）。
【００６０】
Ｍ３としては、ここでは次のような値を用いている。
【００６１】
【数４】

【００６２】
これは、周知の色順応補正式（ＶｏｎＫｒｉｅｓの色順応補正式が有名である。）を用いてモニタの色温度６５００Ｋから環境光４２００Ｋの色温度へ部分順応効果を考慮して変換するためのマトリックス係数である。
【００６３】
そして、図３のガンマ補正部３３で次式を実行することにより、使用している実在のモニタ表示用のＲ，Ｇ，Ｂ信号であるＲｍ、Ｇｍ、Ｂｍを得る。
【００６４】

上述した（７）式〜（９）式の変換パラメータの生成は、モニタ指定装置１２に設定されたモニタ特性（１’）〜（３’）及び環境光の条件（４’）を参照して行われ、（９）式により得られた信号Ｒｍ、Ｇｍ、Ｂｍがモニタドライバ１０７に送られる。
【００６５】
図７は、本発明の第１の実施形態としての画像処理を示すフローチャートであり、ＣＰＵ１２０がＯＳ１０５を制御して行う上述した本実施形態の処理の概略を示している。
【００６６】
ステップＳ１１：原稿上の画像をスキャナ１０２により読み取ってＲＧＢ信号（スキャナＲＧＢ信号）を入手する。
【００６７】
ステップＳ１２：スキャナＲＧＢ信号を、スキャナプロファイル２２に予め記憶されたデータに基づいて色空間変換部１（２１）にてＸＹＺ信号に変換する。
【００６８】
ステップＳ１３：ＸＹＺ信号を、標準モニタプロファイル２４に予め記憶されたデータに基づいて色空間変換部２（２３）にて標準モニタＲＧＢ信号に変換する。
【００６９】
ステップＳ１４：標準モニタＲＧＢ信号を、オペレータがモニタ指定装置１２にて指定した実在のモニタの特性と、環境光指定装置１３にて指定した周囲の環境光の特性とに応じて、色空間補正部１１にて実在のモニタ用のモニタＲＧＢ信号に補正する。
【００７０】
ステップＳ１５：実在のモニタ用のモニタＲＧＢ信号をモニタ１０８に表示する。
【００７１】
以上、本実施形態では、ＣＭＳ１０９の色空間変換部１（２１）にて得られたＸＹＺ信号を、色空間変換部２（２３）にて（５）式及び（６）式により変換し、仮想的な標準モニタ用のＲＧＢ信号を生成した。そして、色空間補正部１１にて（７）式〜（９）式の順番で変換することにより実在のモニタ表示用のＲｍ、Ｇｍ、Ｂｍを得ている。従って、（５）式から（９）式の変換は、ＸＹＺ信号に直接（５’）式及び（６’）式の変換を施したのと等価である。
【００７２】
このように、コンピュータ１０１内部で画像データを標準モニタの色空間信号に変換して扱い、色空間補正部１１で実際に使用するモニタの色再現特性に適合させるため、個々のモニタの色再現特性データを予め用意する必要は無く、そのとき現在実際に使用しているモニタ上に正しい色を再現することができる。
【００７３】
［第２の実施形態］
次に、本発明の第２の実施形態を図４を参照して説明する。
【００７４】
図４は、本発明の第２の実施形態としてのＣＭＳを備える画像処理装置のシステム構成図である。
【００７５】
同図は、基本的な構成は図１と同様であるが、更に、モニタ／環境光測定センサ４３を備えており、このモニタ／環境光測定センサ４３からの信号によりモニタ／環境光測定装置４２にて実際に使用するモニタ１０８の色再現特性を検出する。
【００７６】
本実施形態では、モニタ１０８上に所定の色パターンを表示しておき、それを周知のＲ，Ｇ，Ｂフォトセンサ（Ｒ，Ｇ，Ｂ３色のカラーフィルタを受光面に配置したセンサ）を備えるモニタ／環境光測定センサ４３で測定する。そして、その検出信号（実際には３色のフォトセンサから出力される電流値）を、実際に使用するモニタ１０８の色再現特性（１’）〜（３’）に相当する数値にモニタ／環境光測定装置４２にて換算する。
【００７７】
次に、モニタ／環境光測定センサ４３の受光部を環境照明光源に向けて環境光の測定（３色のセンサの電流値）を行い、（４’）環境光の色温度に相当する数値にモニタ／環境光測定装置４２にて換算する。
【００７８】
ここで、Ｒ，Ｇ，Ｂフォトセンサの検出信号を、色再現特性及び環境光の色温度に相当する数値に換算する方法について説明する。
【００７９】
以下の説明により、フォトセンサでモニタを測定した検出信号から、次の（１）３色蛍光体の色度座標、（２）発光輝度のガンマ特性、（３）白色点の色温度、そして（４）環境光の色温度の色再現特性値を得る。
【００８０】
はじめに、フォトセンサのＲ，Ｇ，Ｂ３チャンネルの出力値をＸ，Ｙ，Ｚに換算するための換算式を、以下の手順で予め求めておく。
【００８１】
Ｘ，Ｙ，Ｚ値が既知の光源（＝Ｘｉ，Ｙｉ，Ｚｉ）を使用してフォトセンサを照明し、このときのＲ，Ｇ，Ｂ３チャンネルの出力値が、例えばミリボルト単位で表した際Ｒｉ，Ｇｉ，Ｂｉであったとする。このような光源のＸ，Ｙ，Ｚ値と出力電圧との関係を、複数の異なる光源に対して測定しておき、全ての光源についての測定値で下式が満足されるように最小自乗近似を用いて係数Ａjkを求める。
【００８２】
Ｘｉ＝Ａ11×Ｒｉ＋Ａ12×Ｇｉ＋Ａ13×Ｂｉ
Ｙｉ＝Ａ21×Ｒｉ＋Ａ22×Ｇｉ＋Ａ23×Ｂｉ …（Ａ）
Ｚｉ＝Ａ31×Ｒｉ＋Ａ32×Ｇｉ＋Ａ33×Ｂｉ
次に、モニタ上に赤色の色パターンを表示する。赤色とは、モニタの赤の蛍光体のみが発光している状態であり、モニタ信号を８ビットで表現すれば（Ｒ，Ｇ，Ｂ）＝（２５５，０，０）に対応する。
【００８３】
次に、表示されている色パターンに近接してフォトセンサを配置し、その受光面をモニタに向けて測定を行う。測定されたＲ，Ｇ，Ｂの出力電圧は、（Ａ）式によってＸ，Ｙ，Ｚ値に変換可能であり、得られたＸ，Ｙ，Ｚ値は次式で色度座標ｘ，ｙに変換される。
【００８４】
ｘ＝Ｘ／（Ｘ＋Ｙ＋Ｚ）
ｙ＝Ｙ／（Ｘ＋Ｙ＋Ｚ） …（Ｂ）
同様に緑の色パターン、青の色パターンを表示してフォトセンサで測定し（Ａ）式、（Ｂ）式により色度座標（ｘ，ｙ）を求める。求められた色度座標がモニタの色再現特性（１）の値となる。
【００８５】
（３）についても同様にモニタ上に白色の色パターンを表示してフォトセンサで測定し、ｘ，ｙ値に変換する。白色パターンは、８ビットのモニタ信号として（２５５，２５５，２５５）を表示すればよい。得られたｘ，ｙ値は、色度座標値を相関色温度値に換算する周知の換算表を用いて（３）の白色の色温度とすることができる。
【００８６】
（２）に関しては色パターンとして複数の異なる信号レベルの赤、緑、青のパターンを表示して、それぞれのセンサー測定値に基づいて決定できる。例えば、赤のガンマ特性を得る場合は、８ビットのモニタ信号として
（０，０，０），（３２，０，０），（６４，０，０），（９６，０，０），（１２８，０，０），（１６０，０，０），（１９２，０，０），（２２４，０，０），（２５５，０，０）
の９段階の色パターンを表示し、各色をセンサーで測定して（Ａ）式でＹ値を求める。こうして得られた９個のＹ値が次式を満たすようなガンマ値γを最小自乗近似により求め（２）のガンマ値とする。
【００８７】
Ｙ＝Ｙmax×（Ｓ／２５５）＾γ …（Ｃ）
ここでＹmaxは９個のＹ値のうちの最大値を表し、Ｓは９個のモニタ信号の値（０，３２，６４・・・，２５５）を表す。そして、（Ｃ）式で信号値Ｓのときの測定値Ｙが対応するようにγを求める。
【００８８】
（４）については、白色点の色温度（３）を求めたのと同様の手順を環境光に対して適用すれば求められる。すなわち、環境光をフォトセンサで測定し、測定値を上記と同様の手順でＸＹＺ値→ｘｙ値→相関色温度値に変換すれば環境光の色温度（４）となる。
【００８９】
この換算により得られたデータを色空間補正部１１にて参照し、第１の実施形態と同様に、実在のモニタ表示用のＲｍ、Ｇｍ、Ｂｍを得る。
【００９０】
［第３の実施形態］
次に、本発明の第３の実施形態を図５及び図６を参照して説明する。前述の２つの実施形態では、スキャナ１０２から原稿上の画像を読み込み、モニタ１０８に表示する場合を考えたが、本実施形態ではプリンタへの画像出力を考える。
【００９１】
図５は、本発明の第３の実施形態としてのＣＭＳを備える画像処理装置のシステム構成図である。同図が図１の第１の実施形態と異なるのは、スキャナではなくプリンタ１１６が接続されており、コンピュータ１０１内にはプリンタ１１６を制御するドライバソフトウェア１１５を備えていることである。また、コンピュータ１０１のファイル１１２には、予め仮想的な標準モニタＲＧＢ信号に変換されている画像データが記憶されているものとする。それ以外は第１の実施形態と同様なため、説明を省略する。
【００９２】
図６は、本発明の第３の実施形態としてのＣＭＳによる色変換処理を説明する図である。
【００９３】
図中、色空間変換部１（５１）は、ファイル１１２からの標準モニタＲＧＢ信号の画像データを、標準モニタプロファイル５２に予め記憶されたデータに基づいてＸＹＺ信号に変換する。標準モニタプロファイル５２には、第１の実施形態の（１）〜（３）の特性と同様に仮想的な標準モニタプロファイルが予め記憶されている。また、色空間変換部２（５３）は、色空間変換部１（５１）からのＸＹＺ信号を、プリンタプロファイル５４に予め記憶されたデータに基づいてプリンタ用のＣＭＹＫ信号に変換し、プリンタ用のドライバソフトウェア１１５に出力する。プリンタプロファイル５４には、プリンタ１１６の色再現特性データが予め記憶されている。
【００９４】
即ち、色空間変換部１（５１）における標準モニタＲＧＢ信号からＸＹＺ信号への変換は、第１の実施形態で説明した（５）式、（４）式の逆演算により求めればよい。また、色空間変換部２（５３）におけるＸＹＺ信号からＣＭＹＫ信号への変換は、例えば、公知のマスキング演算や予め演算結果をルックアップテーブルとしてプリンタプロファイル５４に記憶しておき、入力されるＸＹＺ信号値に対してそのルックアップテーブルから演算結果を読み出して出力する方式がある。
【００９５】
図８は、本発明の第３の実施形態としての画像処理を示すフローチャートであり、ＣＰＵ１２０がＯＳ１０５を制御して行う上述した本実施形態の処理の概略を示している。
【００９６】
ステップＳ２１：ファイル１１２に予め格納した標準モニタＲＧＢ信号に変換されている画像データを読み出す。
【００９７】
ステップＳ２２：標準モニタＲＧＢ信号を、標準モニタプロファイル５２に予め記憶されたデータに基づいて色空間変換部１（５１）にてＸＹＺ信号に変換する。
【００９８】
ステップＳ２３：ＸＹＺ信号を、プリンタプロファイル５４に予め記憶されたデータに基づいてプリンタ１１６用のＣＭＹＫ信号に変換する。
【００９９】
ステップＳ２４：プリンタ１１６用のＣＭＹＫ信号に基づいてプリンタ１１６にてプリント出力する。
【０１００】
本実施形態では、第１の実施形態と同様に、実際に使用しているモニタ１０８の特性をモニタ指定装置１２から設定し、その設定に応じて、ファイル１１２からの標準モニタＲＧＢ信号を色空間補正部１１にて補正するため、使用するモニタを変更しても、表示する色とプリントアウトの色とが一致しないという不都合は生じない。
【０１０１】
尚、本実施形態では、標準モニタＲＧＢ信号に変換されている画像データを、予めファイル１１２に記憶させたが、図１のようにスキャナ１０２を接続し、コンピュータ１０１内にドライバソフトウェア１０３及び画像表示ソフトウェア１０４を備え、ＣＭＳ１０９’の前段に図２のＣＭＳ１０９を備えるシステムを構成してもよいことは言うまでもない。
【０１０２】
［その他の実施形態］
色空間変換部において行われる色処理は、上述の実施形態で述べた色処理には限られない。例えば、第１の実施形態の係数Ｍに対して、ユーザの指示に基づく微調整を行うことにより、ユーザの色覚特性に応じた係数Ｍを作成するようにしてもよい。
【０１０３】
即ち、色変換部ではＣＭＳで出力デバイスプロファイル（標準モニタプロファイル）に基づき行われる色処理とは異なる色処理を行なうことができる。したがって、出力デバイスの状況に応じたカラーマッチング処理の設計が容易になり、より高精度のカラーマッチングを提供することが可能となる。すなわち、ＯＳがサポートしているＣＭＳを使用しつつ、かつより高精度のカラーマッチングを実現することが可能となる。
【０１０４】
また、上述した実施形態では、モニタ１０８はＣＲＴとして説明したが、液晶ディスプレイやカラープラズマディスプレイ等においても、その発色特性は（１’）〜（３’）と同様に定義できるので、その値に合わせて（６）式〜（８）式のパラメータを設定すればよい。
【０１０５】
また、上述した各実施形態では、予め定義された標準モニタを仮定し、その標準モニタに原稿上の画像の色を再現したときに正しい色再現が実現されるように所定の関係を持って予め定義されている色空間を用いて説明したが、例えば、ＸＹＺ，Ｌ＊ａ＊ｂ、Ｌ＊ｕ＊ｖ＊等の測色的に定義された色空間信号であれば他の色空間であってもよい。
【０１０６】
尚、本発明は、本実施形態のように複数の機器（例えばホストコンピュータ，インタフェイス機器，スキャナ，プリンタ等）から構成されるシステムに適用しても、一つの機器からなる装置（例えば、複写機，ファクシミリ装置等）のように、原稿画像をスキャンして読み取ったデータや記憶装置上に記憶された画像データを単にモニタに表示するような装置、或はモニタ上に表示された画像データを単にプリントアウトするような装置についても同様に適用できることは言うまでもない。
【０１０７】
また、本発明の目的は、前述した実施形態の機能を実現するソフトウェアのプログラムコードを記録した記憶媒体を、システムあるいは装置に供給し、そのシステムあるいは装置のコンピュータ（またはＣＰＵやＭＰＵ）が記憶媒体に格納されたプログラムコードを読出し実行することによっても、達成されることは言うまでもない。
【０１０８】
この場合、記憶媒体から読み出されたプログラムコード自体が前述した実施形態の機能を実現することになり、そのプログラムコードを記憶した記憶媒体は本発明を構成することになる。
【０１０９】
プログラムコードを供給するための記憶媒体としては、例えば、フロッピディスク，ハードディスク，光ディスク，光磁気ディスク，ＣＤ−ＲＯＭ，ＣＤ−Ｒ，磁気テープ，不揮発性のメモリカード，ＲＯＭ等を用いることができる。
【０１１０】
また、コンピュータが読出したプログラムコードを実行することにより、前述した実施形態の機能が実現されるだけでなく、そのプログラムコードの指示に基づき、コンピュータ上で稼働しているＯＳ（オペレーティングシステム）等が実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【０１１１】
更に、、記憶媒体から読出されたプログラムコードが、コンピュータに挿入された機能拡張ボードやコンピュータに接続された機能拡張ユニットに備わるメモリに書込まれた後、そのプログラムコードの指示に基づき、その機能拡張ボードや機能拡張ユニットに備わるＣＰＵ等が実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【０１１２】
本発明を上記記憶媒体に適用する場合、その記憶媒体には、先に説明したフローチャートに対応するプログラムコードを格納することになるが、簡単に説明すると、少なくとも第１の実施形態では図９、第３の実施形態では図１０のメモリマップ例に示す各モジュールのプログラムコードを記憶媒体に格納すればよい。
【０１１３】
図９は、本発明の第１の実施形態としてのメモリマップの一例を示す図である。同図において、
「画像読み取りプログラム」：原稿上の画像をスキャナ１０２を制御して読み取り、ＲＧＢ信号（スキャナＲＧＢ信号）を入手する。
【０１１４】
「色空間変換プログラム１」：スキャナＲＧＢ信号を、スキャナプロファイル２２に予め記憶されたデータに基づいて色空間変換部１（２１）にてＸＹＺ信号に変換する。
【０１１５】
「色空間変換プログラム２」：ＸＹＺ信号を、標準モニタプロファイル２４に予め記憶されたデータに基づいて色空間変換部２（２３）にて標準モニタＲＧＢ信号に変換する。
【０１１６】
「色空間補正プログラム」：標準モニタＲＧＢ信号を、オペレータがモニタ指定装置１２にて指定した実在のモニタの特性に応じて、色空間補正部１１にて実在のモニタ用のモニタＲＧＢ信号に補正する。
【０１１７】
「モニタ出力プログラム」：実在のモニタ用のモニタＲＧＢ信号をモニタ１０８に表示する。
【０１１８】
図１０は、本発明の第３の実施形態としてのメモリマップの一例を示す図である。同図において、
「画像データ読み出しプログラム」：ファイル１１２に予め格納した標準モニタＲＧＢ信号に変換されている画像データを読み出す。
【０１１９】
「色空間変換プログラム１１」：モニタＲＧＢ信号を、標準モニタプロファイル５２に予め記憶されたデータに基づいて色空間変換部１（５１）にてＸＹＺ信号に変換する。
【０１２０】
「色空間変換プログラム１２」：ＸＹＺ信号を、プリンタプロファイル５４に予め記憶されたデータに基づいてプリンタ１１６用のＣＭＹＫ信号に変換する。
【０１２１】
「プリンタ出力プログラム」：プリンタ１１６用のＣＭＹＫ信号に基づいてプリンタ１１６にてプリント出力する。
【０１２２】
【発明の効果】
以上説明したように、異なる環境光の元であっても、色再現特性の異なるデバイス間で安定した色再現が可能な画像処理装置及び画像処理方法の提供が実現する。
【０１２３】
【図面の簡単な説明】
【図１】本発明の第１の実施形態としてのＣＭＳを備える画像処理装置のシステム構成図である。
【図２】本発明の第１の実施形態としてのＣＭＳによる色変換処理を説明する図である。
【図３】る。本発明の第１の実施形態としての色空間補正部１１における色変換を説明する図である。
【図４】本発明の第２の実施形態としてのＣＭＳを備える画像処理装置のシステム構成図である。
【図５】本発明の第３の実施形態としてのＣＭＳを備える画像処理装置のシステム構成図である。
【図６】本発明の第３の実施形態としてのＣＭＳによる色変換処理を説明する図である。
【図７】本発明の第１の実施形態としての画像処理を示すフローチャートである。
【図８】本発明の第３の実施形態としての画像処理を示すフローチャートである。
【図９】本発明の第１の実施形態としてのメモリマップの一例を示す図である。
【図１０】本発明の第１の実施形態としてのメモリマップの一例を示す図である。
【図１１】従来例としてのＣＭＳを備える画像処理装置のシステム構成の一例を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and an image processing method for converting a color space of input image data, for example.
[0002]
[Prior art]
In recent years, with the spread of personal computers, for example, anyone can easily create a document that lays out a color photograph read by a scanner or the like, or create color graphics and print it out from a printer. It is becoming.
[0003]
In general, an operator's operation on a computer is performed via a software copy display device (hereinafter referred to as a monitor) such as a CRT. Therefore, when performing the above operations, the color photograph, which is the original to be scanned, matches the color of the image displayed on the monitor, or the color of the graphic created on the monitor screen. And the color of the image to be printed out are required to match.
[0004]
However, the color reproduction characteristics of a monitor and a scanner, or a monitor and a printer are greatly different, and it is usually very difficult to match them.
[0005]
For these reasons, there is a color management system (hereinafter referred to as CMS) as a technology that has recently attracted attention. An example is shown in FIG.
[0006]
FIG. 11 is a diagram illustrating an example of a system configuration of an image processing apparatus including a CMS as a conventional example, and illustrates a configuration in a case where image data obtained by reading an image on a document with a scanner is displayed on a monitor. .
[0007]
In the figure, a computer 101 as an image processing apparatus and a scanner 102 are connected via a general-purpose interface such as SCSI (Small Computer System Interface).
[0008]
The CPU 120 of the computer 101 controls the entire color management system according to the following software group. The computer 101 reads an image on an original on the scanner 108 by driver software 103 that controls the scanner 102. In addition, an image read by the scanner 102 is displayed on the monitor 108 by the image display software 104 that displays the image on the monitor 108. At this time, each software operates under an OS (Operating System) 105 controlled by the CPU 120, and the image display software 104 requests the OS 105 to display an image on the monitor 108. The OS 105 writes the image data received from the image display software 104 into a VRAM (Video-RAM) 106 that is a screen storage device for monitor display. The image data written in the VRAM 106 is displayed on the monitor 108 by the monitor driver 107. Here, the monitor driver 107 converts the digital signal on the VRAM 106 into an analog signal to generate a raster signal, and supplies the raster signal to the monitor 108.
[0009]
Further, in the conventional example of FIG. 11, not only the image data received from the image display software 104 is displayed as it is on the monitor 108 as described above, but also the OS 105 uses the CMS 109 to convert the image data received from the image display software 104. It can be converted into monitor display data and displayed.
[0010]
That is, in the CMS 109, a scanner profile 110 that describes the color characteristics of the scanner 102 and a monitor profile 111 that describes the color reproduction characteristics of the monitor 108 are stored in advance. The OS 105 performs color signal conversion on the image data received from the image display software 104 using these profiles and then displays the data on the monitor 108 to display the same color as the color on the document read by the scanner 102. (When the color displayed on the monitor 108 is reproduced on the printer output (not shown), the monitor profile 111 and the printer profile (not shown) are used in the same manner. Conversion of the color signal of the image). That is, color matching between different devices is realized. As such CMS, ColorSync (R) of Apple Inc., ICM (TM) of MicroSoft Inc., etc. are known.
[0011]
[Problems to be solved by the invention]
However, in the above conventional example, the color reproduction characteristics are different for each device, so it is necessary to prepare a profile for each device. In particular, there are many types of monitors for computers, and the color reproduction characteristics are different for each of them. Therefore, it is not practical to prepare profiles for all of them.
[0012]
When a profile for a monitor exists, the image data after conversion by CMS can reproduce the same color as the image on the document only when displayed on the monitor. However, when the image data is displayed on another monitor, correct color reproduction cannot be obtained.
[0013]
Since the data read by the scanner at this time has been converted for display on the monitor, if the image data is saved as a file 112 in a storage device such as a hard disk on a computer, the converted data is saved. become. That is, even if the scanners are the same, if different monitor profiles are used by using different monitors, the data stored in the file 112 will be different from each other.
[0014]
Also, when graphic data such as CG created on a computer is printed out using the monitor profile of the monitor used at that time, the color on the monitor can be reproduced on the recording paper. When the same graphic data is printed using a monitor profile of another monitor, different colors are printed out even though the output devices (printers) are the same. That is, there arises a disadvantage that the print result varies depending on the type of monitor being used.
[0015]
Furthermore, it has been clarified that the color appearance on the monitor changes depending on ambient ambient light when the monitor is observed. Considering the usage environment of a general computer, the scanned document is observed under a light source that illuminates the room (hereinafter referred to as ambient light), while the image on the monitor displays the color that is emitted by itself. Will observe. Therefore, even if the same monitor is used, the color appearance of the document changes according to the characteristics of the ambient light. Also, the color appearance on the monitor changes due to the characteristics of ambient light due to the partial adaptation effect of human vision.
[0016]
The characteristic of ambient light is that its color temperature has a major effect on the color appearance. For example, even if the color appearance on a monitor having a white point with a color temperature of 6500K matches the color appearance on an original under ambient light with a color temperature of 6500K, the color temperature of the ambient light is normally set. If the white fluorescent lamp with a color temperature of 4000K used in the office of the company is replaced with the same color, the color appearance will not be the same even if the color of the monitor is the same. Compared to the above color, it will be observed a lot more bluish.
[0017]
In order to eliminate such inconvenience, it is possible to prepare several characteristics of the ambient light when the observer observes the monitor and the document in advance, and to create a monitor profile for each characteristic. However, in that case, a profile corresponding to the characteristics of the ambient light is added to the profile set for each monitor type, which is realistic considering the memory resources necessary for the preparation and storage of the profile. is not.
[0018]
Accordingly, an object of the present invention is to provide an image processing apparatus and an image processing method capable of performing stable color reproduction between devices having different color reproduction characteristics even under different ambient light sources.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, an image processing apparatus of the present invention is characterized by the following configuration.
[0020]
That is, an image processing apparatus that converts the color space of input image data and outputs the image signal, and the image signal input from the input device depends on the device based on characteristic information of the color space of the input device stored in advance First color space conversion means for converting to an image signal of the color space that is not, and the image signal output from the first color space conversion means, based on the color space characteristic information of the standard display device stored in advance, Second color space conversion means for converting to an image signal in a color space depending on the standard display device, first specification means for specifying color reproduction characteristics of the display device, and color characteristics of ambient ambient light are specified. A second designation means; The image signal of the color space depending on the standard device depends on the color reproduction characteristics of the display device designated by the first designation means and the color characteristics of the ambient ambient light designated by the second designation means. Third color space conversion means for converting into an image signal in the color space; It is characterized by providing.
[0021]
In addition, for example, an image signal in a color space independent of the device is an XYZ signal. And The image signal of the color space depending on the standard output device is the RGB signal of the standard output device. Thus, the image signal converted by the third conversion means is an RGB signal. Good.
[0022]
For example, The third color space conversion means performs reverse gamma correction, matrix conversion, and gamma correction, and the correction conditions for the reverse gamma correction are set based on the gamma characteristics of the standard display device, and the conversion conditions for the matrix conversion are Color reproduction characteristics of the standard display device, color characteristics of ambient light assumed by the standard display device, color reproduction characteristics of the display device designated by the first designation means, and designation by the second designation means The correction condition for the gamma correction is set based on the gamma characteristic of the display device designated by the first designation means. Good.
[0023]
Preferably, the first designating unit includes a first measuring unit that measures a color reproduction characteristic of the output device, and the color reproduction of the output device is performed based on a measurement value from the first measuring unit. It is good to generate characteristics.
[0024]
Preferably, the second designating unit includes a second measuring unit that measures ambient ambient light, and generates a color reproduction characteristic of the output device based on a measurement value from the second measuring unit. Good.
[0025]
Or in order to achieve said objective, the image processing method of this invention is characterized by the following structures.
[0026]
That is, an image processing method for converting a color space of input image data and outputting the image signal, wherein an image signal input from an input device is Pre-stored A first color space conversion step of converting into an image signal of a color space independent of a device based on characteristic information of the color space of the input device; and the first color space conversion step Obtained Image signal Pre-stored A second color space conversion step of converting into an image signal of a color space depending on the standard display device based on the characteristic information of the color space of the standard display device; A first designation step for designating color reproduction characteristics of a display device; a second designation step for designating color characteristics of ambient ambient light; and an image signal in a color space depending on the standard device. A third color space conversion step for converting into an image signal in a color space depending on the color reproduction characteristics of the display device specified in the specifying step and the color characteristics of the surrounding ambient light specified in the second specifying step; It is characterized by providing.
[0027]
For example, In the third color space conversion step, reverse gamma correction, matrix conversion, and gamma correction are performed, and the correction condition of the reverse gamma correction is set based on the gamma characteristic of the standard display device, and the conversion condition of the matrix conversion is Color reproduction characteristics of the standard display device, color characteristics of ambient light assumed by the standard display device, color reproduction characteristics of the display device designated by the first designation means, and designation by the second designation means The correction condition for the gamma correction is set based on the gamma characteristic of the display device designated by the first designation means. Good.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an image processing apparatus according to the present invention will be described below in detail with reference to the drawings.
[0031]
[First embodiment]
FIG. 1 is a system configuration diagram of an image processing apparatus including a CMS as a first embodiment of the present invention.
[0032]
In this figure, the configuration different from that of FIG. 11 described above will be described. The color reproduction characteristics of the color space correction unit 11 that performs color space correction processing on the color signal data stored in the VRAM 106 and the monitor 108 actually used are shown. A monitor designating device 12 for designating and an ambient light designating device 13 for designating characteristics of ambient ambient light (details will be described later).
[0033]
Here, it goes without saying that the color space correction unit 11 may be provided on the video circuit of the computer 101, or may be mounted as an external circuit, a processing circuit inside the monitor 108, or the like. Needless to say, the monitor designating device 12 may be realized by software on the computer 101 or may be an external switch box or the like.
[0034]
In the present embodiment, a “standard monitor profile 24” indicating a color reproduction characteristic of a virtual standard monitor is stored in advance in the monitor profile, not a profile representing the color reproduction characteristic of the monitor 108 being used ( Details will be described later).
[0035]
When the operator designates the color characteristics of the currently used monitor from the monitor designating device 12 and designates the ambient ambient light characteristics from the ambient light designating device 13, the OS 105 performs color space correction according to the inputted designation information. Set the parameters of section 11. Note that the parameters of the color space correction unit 11 may be directly rewritten by the designation of the monitor designation device 12 without using the OS 105.
[0036]
The operation of the image processing apparatus according to this embodiment having the above system configuration will be described below.
[0037]
In general, the color reproduction characteristics of a color monitor represent, for example, the color development characteristics of phosphors of the R, G, B3 primary colors applied to the display tube surface in the case of a CRT, and the linearity between the voltage applied to the electron gun and the emission luminance. It can be described by three basic characteristics: a gamma characteristic and a color temperature of a white point. Since these characteristics differ depending on the manufacturer, type, size, etc. of the monitor, it is necessary to create profile data based on these for each monitor. The ambient light characteristics that affect the color appearance on the monitor can be defined by the color temperature (correlated color temperature) of the illumination light source used in the surrounding environment.
[0038]
FIG. 2 is a diagram illustrating color conversion processing by CMS as the first embodiment of the present invention.
[0039]
In the figure, an RGB signal (scanner RGB signal) of an image on a document obtained by reading with the scanner 102 is first converted into a device-independent color space, for example, a CIE-XYZ signal by the color space conversion unit 1 (21). The The scanner profile 22 stores color separation characteristic data of the scanner 102 in advance, and color space conversion is executed based on this data.
[0040]
Next, the XYZ signal obtained by the conversion to the color space is converted into a standard monitor RGB signal by the color space conversion unit 2 (23). The standard monitor profile 24 stores color reproduction characteristic data of the standard monitor in advance, and conversion is executed based on this data. In the present embodiment, a virtual standard monitor profile is set in the standard monitor profile 24 instead of the monitor profile used by the operator.
[0041]
As an example of a standard monitor and a standard observation environment condition, a virtual monitor having the following characteristics is assumed.
[0042]
(1) Chromaticity coordinates (CIE-xy chromaticity coordinates) of a three-color phosphor
Red: x = 0.64, y = 0.33
Green: x = 0.30, y = 0.60
Blue: x = 0.15, y = 0.06
(2) Gamma characteristics of emission luminance
2.2 for red, green and blue
(3) White point color temperature
6500K (equivalent to D65 standard light source)
(4) Color temperature of ambient light
6500K (equivalent to D65 standard light source)
The above characteristics are determined as the standard for high-definition monitors, and the color temperature of the ambient light is the same as the white point of the monitor, but this is an ideal state and does not necessarily match the characteristics of an actual monitor. It does not represent.
[0043]
Assuming that a monitor having the above characteristics exists, this color reproduction characteristic data is preset in the profile 22, and the XYZ signal from the color space conversion unit 1 (21) is converted into the color space conversion unit 2 (23 ) To monitor RGB signals. Further, in order to convert the RGB signal to be displayed on the virtual monitor having the above characteristics (1) to (3), the following conversion may be performed on the XYZ signal.
[0044]
First, considering (1) the chromaticity coordinates (CIE-xy chromaticity coordinates) of the three-color phosphor, (3) the color temperature of the white point, and (4) the color temperature of the ambient light, the XYZ signal is expressed as (5) Conversion into R ′, G ′, and B ′ by an expression.
[0045]
[Expression 1]

[0046]

Next, (2) R ′, G ′, and B ′ are converted into R, G, and B by the following equations in consideration of the gamma characteristic of the emission luminance.
[0047]

Here, it is assumed that the R, G, and B signals are all represented by 8-bit integer values (where ^ is an operator representing a power-up operation). The R, G, B signals thus obtained are displayed on the virtual standard monitor having the characteristics (1) to (3) for displaying the correct color under the standard environment specified in (4). , B signals.
[0048]
Next, let us consider the characteristics of the monitor actually used. If the characteristics of the monitor actually used are the same as the characteristics (1) to (3) and (4) of the virtual monitor, the R, G and B signals obtained by the expression (5) are displayed as they are. That's fine. However, the characteristics usually differ from monitor to monitor.
[0049]
Assume that the characteristics of the actual monitor that is currently used are the following (1 ′) to (3 ′) and the environmental condition is (4 ′).
[0050]
(1 ′) Chromaticity coordinates of three-color phosphors (CIE-xy chromaticity coordinates)
Red: x = 0.60, y = 0.30
Green: x = 0.32, y = 0.58
Blue: x = 0.18, y = 0.08
(2 ') Gamma characteristic of light emission luminance
1.8 for red, green and blue
(3 ') White point color temperature
6500K (equivalent to D65 standard light source)
(4 ') Color temperature of ambient light
4200K (equivalent to a normal office white fluorescent lamp)
In the conventional method, when a monitor having such characteristics is used, these conditions are set in the monitor profile of the CMS, and instead of the above equations (5) and (6), (5 ′) and (6 ′) are executed to correct the XYZ signal directly to the actual monitor RGB signal for monitoring.
[0051]
[Expression 2]

[0052]

On the other hand, in the present embodiment, in the color space conversion unit 2 (23) of the CMS 109, by performing the calculations of the equations (5) and (6) on the XYZ signal from the color space conversion unit 1 (21), the virtual space conversion unit 2 (23) R, G, B signals for standard monitors are required. Therefore, in the color space correction unit 11 of FIG. 1, in order to generate a monitor RGB signal for an actual monitor obtained by executing the equations (5 ′) and (6 ′), the color space conversion unit 2 (23 The monitor RGB signal for the actual monitor must be generated from the virtual standard monitor RGB signal from
[0053]
For this reason, in the present embodiment, the actual monitor characteristics (1 ′) to (3 ′) are designated from the monitor designation device 12 of FIG. 1, and the condition (4 ′) is set from the ambient light designation device 13. Then, the color space correction unit 11 calculates appropriate parameters with reference to the characteristic data of the actual monitor 108 set by the monitor designating device 12, and uses the parameters to calculate RGB for a virtual standard monitor. The signal is corrected to a monitor RGB signal for the actual monitor 108. The correction performed by the color space correction unit 11 will be described with reference to FIG.
[0054]
FIG. 3 is a diagram for explaining color conversion in the color space correction unit 11 as the first embodiment of the present invention, and shows details of the inside of the color space correction unit 11 in FIG.
[0055]
In FIG. 3, the input of FIG. 3 is the RGB signal from the VRAM of FIG. 1, and is corrected to the RGB signal of the standard monitor by the color space conversion unit 2 (23) of the CMS 109 as already described.
[0056]
In the inverse gamma correction unit 31 of FIG. 3, first, the standard monitor signals R, G, B are subjected to the inverse gamma conversion of the following expression, which is the inverse conversion of the conversion of the expression (6), and R ′, G ′, B ′. Convert to
[0057]

Next, R ′, G ′, B ′ obtained by the equation (7) is converted into R ″, G ″, B ″ by the matrix converter 32 as in the following equation.
[0058]
[Equation 3]

[0059]

The matrix conversion coefficient M is expressed as follows: M1 is the matrix of equation (5), M2 is the matrix of equation (5 ′), and M3 is the color temperature correction matrix of the ambient light.
M = M3 × M2 × M1-1
(Where M1 (-1) represents the inverse matrix of M1).
[0060]
As M3, the following values are used here.
[0061]
[Expression 4]

[0062]
This is a matrix for converting the color temperature of the monitor from 6500K to the color temperature of the ambient light 4200K in consideration of the partial adaptation effect using a well-known chromatic adaptation correction formula (VonKries's color adaptation correction formula is well known). It is a coefficient.
[0063]
Then, the following equations are executed by the gamma correction unit 33 in FIG. 3 to obtain Rm, Gm, and Bm that are the actual monitor display R, G, and B signals that are being used.
[0064]

The generation of the conversion parameters of the above-described equations (7) to (9) is described with reference to the monitor characteristics (1 ′) to (3 ′) set in the monitor designating device 12 and the ambient light condition (4 ′). The signals Rm, Gm, and Bm obtained by the equation (9) are sent to the monitor driver 107.
[0065]
FIG. 7 is a flowchart showing image processing according to the first embodiment of the present invention, and shows an outline of the processing of the above-described embodiment performed by the CPU 120 by controlling the OS 105.
[0066]
Step S11: The image on the original is read by the scanner 102 to obtain RGB signals (scanner RGB signals).
[0067]
Step S12: The scanner RGB signals are converted into XYZ signals by the color space conversion unit 1 (21) based on the data stored in advance in the scanner profile 22.
[0068]
Step S13: The XYZ signal is converted into a standard monitor RGB signal by the color space conversion unit 2 (23) based on data stored in advance in the standard monitor profile 24.
[0069]
Step S14: A color space correction unit for the standard monitor RGB signal according to the actual monitor characteristics designated by the operator using the monitor designating device 12 and the ambient ambient light characteristics designated by the ambient light designating device 13 11, the actual monitor RGB signal is corrected.
[0070]
Step S15: Monitor RGB signals for the actual monitor are displayed on the monitor 108.
[0071]
As described above, in the present embodiment, the XYZ signal obtained by the color space conversion unit 1 (21) of the CMS 109 is converted by the color space conversion unit 2 (23) according to the equations (5) and (6), and the virtual RGB signals for standard monitors were generated. The color space correction unit 11 performs conversion in the order of equations (7) to (9) to obtain Rm, Gm, and Bm for actual monitor display. Therefore, the conversion from the equations (5) to (9) is equivalent to the direct conversion of the equations (5 ′) and (6 ′) to the XYZ signal.
[0072]
In this way, the image data is converted into the color space signal of the standard monitor in the computer 101 and handled, and the color reproduction characteristic of each monitor is adapted to the color reproduction characteristic of the monitor actually used by the color space correction unit 11. There is no need to prepare data in advance, and the correct color can be reproduced on the monitor that is actually used at that time.
[0073]
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
[0074]
FIG. 4 is a system configuration diagram of an image processing apparatus including a CMS as a second embodiment of the present invention.
[0075]
The basic configuration of this figure is the same as that of FIG. 1, but it further includes a monitor / ambient light measurement sensor 43, and a monitor / ambient light measurement device 42 according to a signal from the monitor / ambient light measurement sensor 43. The color reproduction characteristics of the monitor 108 that is actually used are detected.
[0076]
In the present embodiment, a predetermined color pattern is displayed on the monitor 108 and provided with a well-known R, G, B photosensor (a sensor in which R, G, B3 color filters are arranged on the light receiving surface). Measurement is performed by the monitor / environment light measurement sensor 43. Then, the detection signal (actually the current value output from the photosensor of three colors) is changed to a numerical value corresponding to the color reproduction characteristics (1 ′) to (3 ′) of the monitor 108 actually used. Conversion is performed by the light measuring device 42.
[0077]
Next, the ambient light is measured (current values of the three color sensors) with the light receiving portion of the monitor / environment light measurement sensor 43 directed toward the ambient illumination light source, and (4 ′) a numerical value corresponding to the color temperature of the ambient light. Conversion is performed by the monitor / ambient light measuring device 42.
[0078]
Here, a method for converting the detection signals of the R, G, and B photosensors into numerical values corresponding to the color reproduction characteristics and the color temperature of the ambient light will be described.
[0079]
From the following description, from the detection signal measured by the monitor with the photosensor, the following (1) chromaticity coordinates of the three-color phosphor, (2) gamma characteristic of the emission luminance, (3) the color temperature of the white point, and ( 4) Obtain the color reproduction characteristic value of the color temperature of the ambient light.
[0080]
First, a conversion formula for converting the output values of the R, G, and B3 channels of the photosensor into X, Y, and Z is obtained in advance by the following procedure.
[0081]
When a photosensor is illuminated using a light source (= Xi, Yi, Zi) whose X, Y, and Z values are known, when the output values of the R, G, and B3 channels at this time are expressed in millivolt units, for example, Ri , Gi, Bi. The relationship between the X, Y, Z values of the light source and the output voltage is measured for a plurality of different light sources, and the least square approximation is performed so that the following equation is satisfied with the measured values for all the light sources. Is used to find the coefficient Ajk.
[0082]
Xi = A11 × Ri + A12 × Gi + A13 × Bi
Yi = A21 * Ri + A22 * Gi + A23 * Bi (A)
Zi = A31 × Ri + A32 × Gi + A33 × Bi
Next, a red color pattern is displayed on the monitor. Red is a state in which only the red phosphor of the monitor emits light, and if the monitor signal is expressed by 8 bits, it corresponds to (R, G, B) = (255, 0, 0).
[0083]
Next, a photo sensor is arranged in the vicinity of the displayed color pattern, and measurement is performed with its light receiving surface facing the monitor. The measured output voltages of R, G, and B can be converted into X, Y, and Z values by the equation (A), and the obtained X, Y, and Z values are converted into chromaticity coordinates x and y by the following equations. Converted.
[0084]
x = X / (X + Y + Z)
y = Y / (X + Y + Z) (B)
Similarly, a green color pattern and a blue color pattern are displayed and measured by a photosensor, and chromaticity coordinates (x, y) are obtained by equations (A) and (B). The obtained chromaticity coordinate is the value of the color reproduction characteristic (1) of the monitor.
[0085]
Similarly for (3), a white color pattern is displayed on the monitor, measured with a photosensor, and converted into x and y values. The white pattern may display (255, 255, 255) as an 8-bit monitor signal. The obtained x and y values can be set to the white color temperature of (3) using a known conversion table for converting the chromaticity coordinate values into correlated color temperature values.
[0086]
With regard to (2), a plurality of different signal level red, green and blue patterns can be displayed as color patterns and determined based on the respective sensor measurement values. For example, to obtain red gamma characteristics, as an 8-bit monitor signal
(0,0,0), (32,0,0), (64,0,0), (96,0,0), (128,0,0), (160,0,0), (192 , 0,0), (224,0,0), (255,0,0)
The nine color patterns are displayed, each color is measured with a sensor, and the Y value is obtained by equation (A). A gamma value γ such that the nine Y values obtained in this way satisfy the following equation is obtained by least square approximation and is used as the gamma value of (2).
[0087]
Y = Ymax × (S / 255) ^ γ (C)
Here, Ymax represents the maximum value among the nine Y values, and S represents the values (0, 32, 64..., 255) of the nine monitor signals. And (g) is calculated | required so that the measured value Y at the time of the signal value S may correspond by (C) Formula.
[0088]
(4) can be obtained by applying the same procedure as that for obtaining the color temperature (3) of the white point to ambient light. That is, the ambient light color temperature (4) is obtained by measuring ambient light with a photosensor and converting the measured value into XYZ values → xy values → correlated color temperature values in the same procedure as described above.
[0089]
Data obtained by this conversion is referred to by the color space correction unit 11 to obtain Rm, Gm, and Bm for actual monitor display as in the first embodiment.
[0090]
[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS. In the above-described two embodiments, the case where an image on a document is read from the scanner 102 and displayed on the monitor 108 is considered, but in this embodiment, image output to a printer is considered.
[0091]
FIG. 5 is a system configuration diagram of an image processing apparatus including a CMS as a third embodiment of the present invention. 1 is different from the first embodiment of FIG. 1 in that a printer 116 is connected instead of a scanner, and driver software 115 for controlling the printer 116 is provided in the computer 101. In addition, it is assumed that the file 112 of the computer 101 stores image data that has been converted into virtual standard monitor RGB signals in advance. Since other than that is the same as that of 1st Embodiment, description is abbreviate | omitted.
[0092]
FIG. 6 is a diagram for explaining color conversion processing by CMS as a third embodiment of the present invention.
[0093]
In the figure, the color space conversion unit 1 (51) converts standard monitor RGB signal image data from the file 112 into XYZ signals based on data stored in the standard monitor profile 52 in advance. In the standard monitor profile 52, a virtual standard monitor profile is stored in advance as in the characteristics (1) to (3) of the first embodiment. Further, the color space conversion unit 2 (53) converts the XYZ signals from the color space conversion unit 1 (51) into CMYK signals for the printer based on the data stored in the printer profile 54 in advance. Output to the driver software 115. The printer profile 54 stores color reproduction characteristic data of the printer 116 in advance.
[0094]
That is, the conversion from the standard monitor RGB signal to the XYZ signal in the color space conversion unit 1 (51) may be obtained by the inverse operation of the equations (5) and (4) described in the first embodiment. Further, the conversion from the XYZ signal to the CMYK signal in the color space conversion unit 2 (53) is performed by, for example, storing a known masking calculation or a calculation result in advance in the printer profile 54 as a lookup table, and inputting the XYZ signal. There is a method of reading out the operation result from the lookup table for the value and outputting it.
[0095]
FIG. 8 is a flowchart showing image processing according to the third embodiment of the present invention, and shows an outline of the processing of this embodiment described above, which is performed by the CPU 120 controlling the OS 105.
[0096]
Step S21: The image data converted into the standard monitor RGB signal stored in the file 112 in advance is read out.
[0097]
Step S22: The standard monitor RGB signal is converted into an XYZ signal by the color space conversion unit 1 (51) based on the data stored in advance in the standard monitor profile 52.
[0098]
Step S23: The XYZ signal is converted into a CMYK signal for the printer 116 based on data stored in advance in the printer profile 54.
[0099]
Step S24: The printer 116 prints out based on the CMYK signal for the printer 116.
[0100]
In the present embodiment, as in the first embodiment, the characteristics of the monitor 108 that is actually used are set from the monitor designating device 12, and the standard monitor RGB signal from the file 112 is converted into the color space according to the setting. Since correction is performed by the correction unit 11, there is no inconvenience that the displayed color and the printout color do not match even if the monitor to be used is changed.
[0101]
In this embodiment, the image data converted into the standard monitor RGB signal is stored in the file 112 in advance. However, the scanner 102 is connected as shown in FIG. Needless to say, a system including the software 104 and the CMS 109 of FIG.
[0102]
[Other Embodiments]
The color processing performed in the color space conversion unit is not limited to the color processing described in the above embodiment. For example, the coefficient M according to the color vision characteristic of the user may be created by performing fine adjustment based on the user's instruction with respect to the coefficient M of the first embodiment.
[0103]
That is, the color conversion unit can perform color processing different from color processing performed by the CMS based on the output device profile (standard monitor profile). Therefore, it becomes easy to design a color matching process according to the status of the output device, and it is possible to provide more accurate color matching. That is, it is possible to realize color matching with higher accuracy while using CMS supported by the OS.
[0104]
In the above-described embodiment, the monitor 108 has been described as a CRT. However, in a liquid crystal display, a color plasma display, or the like, the color development characteristics can be defined in the same manner as (1 ′) to (3 ′), In addition, the parameters of equations (6) to (8) may be set.
[0105]
Further, in each of the above-described embodiments, a pre-defined standard monitor is assumed, and the standard monitor has a predetermined relationship so that correct color reproduction is realized when the color of the image on the document is reproduced on the standard monitor. Although the description has been made using the defined color space, for example, if the color space signal is defined colorimetrically such as XYZ, L * a * b, L * u * v *, etc. May be.
[0106]
Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a scanner, a printer, etc.) as in this embodiment, an apparatus (for example, a copy) composed of a single device. Such as a machine, a facsimile machine, or the like, which scans and reads the original image data or the image data stored on the storage device, or simply displays the image data displayed on the monitor. Needless to say, the present invention can be similarly applied to an apparatus that simply prints out.
[0107]
Another object of the present invention is to supply a storage medium storing software program codes for implementing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in the.
[0108]
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.
[0109]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0110]
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) or the like running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0111]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted in the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion board or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.
[0112]
When the present invention is applied to the above-described storage medium, the storage medium stores program codes corresponding to the flowcharts described above. To explain briefly, at least in the first embodiment, FIG. In the third embodiment, the program code of each module shown in the memory map example of FIG. 10 may be stored in a storage medium.
[0113]
FIG. 9 is a diagram showing an example of a memory map as the first embodiment of the present invention. In the figure,
“Image reading program”: An image on a document is read by controlling the scanner 102 to obtain an RGB signal (scanner RGB signal).
[0114]
“Color space conversion program 1”: The scanner RGB signals are converted into XYZ signals by the color space conversion unit 1 (21) based on the data stored in the scanner profile 22 in advance.
[0115]
“Color space conversion program 2”: The XYZ signal is converted into a standard monitor RGB signal by the color space conversion unit 2 (23) based on data stored in the standard monitor profile 24 in advance.
[0116]
“Color space correction program”: The standard monitor RGB signal is corrected to a monitor RGB signal for an actual monitor by the color space correction unit 11 in accordance with the characteristics of the actual monitor specified by the operator using the monitor specifying device 12. .
[0117]
“Monitor output program”: Monitor RGB signals for an actual monitor are displayed on the monitor 108.
[0118]
FIG. 10 is a diagram showing an example of a memory map as the third embodiment of the present invention. In the figure,
“Image data read program”: Reads image data converted into standard monitor RGB signals stored in the file 112 in advance.
[0119]
“Color space conversion program 11”: The monitor RGB signal is converted into an XYZ signal by the color space conversion unit 1 (51) based on data stored in advance in the standard monitor profile 52.
[0120]
“Color space conversion program 12”: The XYZ signal is converted into a CMYK signal for the printer 116 based on data stored in the printer profile 54 in advance.
[0121]
“Printer output program”: Print is output by the printer 116 based on the CMYK signal for the printer 116.
[0122]
【The invention's effect】
As described above, it is possible to provide an image processing apparatus and an image processing method capable of stable color reproduction between devices having different color reproduction characteristics even under different ambient light sources.
[0123]
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an image processing apparatus including a CMS as a first embodiment of the present invention.
FIG. 2 is a diagram illustrating color conversion processing by CMS as the first embodiment of the present invention.
FIG. It is a figure explaining the color conversion in the color space correction | amendment part 11 as the 1st Embodiment of this invention.
FIG. 4 is a system configuration diagram of an image processing apparatus including a CMS as a second embodiment of the present invention.
FIG. 5 is a system configuration diagram of an image processing apparatus including a CMS as a third embodiment of the present invention.
FIG. 6 is a diagram illustrating color conversion processing by CMS as a third embodiment of the present invention.
FIG. 7 is a flowchart showing image processing according to the first embodiment of the present invention.
FIG. 8 is a flowchart illustrating image processing according to a third embodiment of the present invention.
FIG. 9 is a diagram showing an example of a memory map as the first embodiment of the present invention.
FIG. 10 is a diagram showing an example of a memory map as the first embodiment of the present invention.
FIG. 11 is a diagram illustrating an example of a system configuration of an image processing apparatus including a CMS as a conventional example.

Claims (10)

An image processing apparatus that converts and outputs a color space of input image data,
First color space conversion means for converting an image signal input from an input device into an image signal of a color space independent of the device based on characteristic information of the color space of the input device stored in advance;
A second image signal that is output from the first color space conversion means and is converted into an image signal in a color space depending on the standard display device, based on characteristic information of the color space of the standard display device stored in advance; Color space conversion means;
First specifying means for specifying the color reproduction characteristics of the display device;
A second specifying means for specifying the color characteristics of ambient ambient light;
The image signal of the color space depending on the standard device depends on the color reproduction characteristics of the display device designated by the first designation means and the color characteristics of the ambient ambient light designated by the second designation means. Third color space conversion means for converting to an image signal in the color space;
An image processing apparatus comprising: Image signal of a color space which does not depend on the device is a XYZ signal, the image signal of a color space depending on the standard output have energy RGB signal der of the standard output device, is converted by the third conversion means The image processing apparatus according to claim 1 , wherein the image signal is an RGB signal . The third color space conversion means performs inverse gamma correction, matrix conversion and gamma correction;
The reverse gamma correction correction conditions are set based on the gamma characteristics of the standard display device,
The conversion conditions for the matrix conversion are: color reproduction characteristics of the standard display device, color characteristics of ambient light assumed by the standard display device, color reproduction characteristics of the display device designated by the first designation means, and Set based on the color characteristics of ambient ambient light specified by the second specifying means,
3. The image processing apparatus according to claim 2 , wherein the correction condition for the gamma correction is set based on a gamma characteristic of a display device designated by the first designation means .   The first specifying unit includes a first measurement unit that measures a color reproduction characteristic of the output device, and generates the color reproduction characteristic of the output device based on a measurement value from the first measurement unit. The image processing apparatus according to claim 1.   The second designating unit includes a second measuring unit that measures ambient ambient light, and generates a color reproduction characteristic of the output device based on a measurement value from the second measuring unit. The image processing apparatus according to claim 1.   2. The image processing apparatus according to claim 1, wherein the color reproduction characteristics of the standard output device are a chromaticity coordinate of a three-color phosphor, a gamma characteristic of light emission luminance, and a color temperature of a white point. And storage means for storing an image signal of a color space depending on the standard display device,
The conversion by the first color space conversion means and the second color space conversion means is performed by a color management system,
2. The image processing according to claim 1, wherein the third color space conversion unit reads an image signal of a color space depending on the standard display device stored in the storage unit and performs the conversion. apparatus. An image processing method for converting and outputting a color space of input image data,
A first color space conversion step of converting an image signal input from the input device into an image signal of a color space independent of the device based on characteristic information of the color space of the input device stored in advance ;
A second image signal obtained by converting the image signal obtained in the first color space conversion step into an image signal in a color space depending on the standard display device, based on characteristic information of the color space of the standard display device stored in advance . A color space conversion process;
A first specifying step for specifying the color reproduction characteristics of the display device;
A second specifying step for specifying the color characteristics of ambient ambient light;
The image signal of the color space depending on the standard device depends on the color reproduction characteristics of the display device designated in the first designation step and the color characteristics of ambient ambient light designated in the second designation step. A third color space conversion step for converting to an image signal in the color space ;
An image processing method comprising: In the third color space conversion step, inverse gamma correction, matrix conversion and gamma correction are performed.
The reverse gamma correction correction conditions are set based on the gamma characteristics of the standard display device,
The conversion conditions for the matrix conversion are: color reproduction characteristics of the standard display device, color characteristics of ambient light assumed by the standard display device, color reproduction characteristics of the display device designated by the first designation means, and Set based on the color characteristics of ambient ambient light specified by the second specifying means,
9. The image processing method according to claim 8, wherein the correction condition for the gamma correction is set based on a gamma characteristic of a display device designated by the first designation means. An image processing program for converting and outputting a color space of input image data,
Executing a first color space conversion step of converting an image signal input from an input device into an image signal of a color space independent of the device based on characteristic information of the color space of the input device stored in advance; Program code,
A second image signal obtained by converting the image signal obtained in the first color space conversion step into an image signal in a color space depending on the standard display device, based on characteristic information of the color space of the standard display device stored in advance. Program code for executing the color space conversion process;
  Program code for executing a first specifying step for specifying the color reproduction characteristics of the display device;
Program code for executing a second specifying step for specifying the color characteristics of ambient ambient light;
The image signal of the color space depending on the standard device depends on the color reproduction characteristics of the display device designated in the first designation step and the color characteristics of ambient ambient light designated in the second designation step. Program code for executing a third color space conversion step of converting into an image signal of a color space;
An image processing program comprising:

Images