JP4041954B2 - Printing control apparatus, printing control method, printing system, and printing control program - Google Patents

Description

なお、上記演算式による演算の結果、Ｙが２５５を超える場合には、修正後の階調を２５５にする。
このように、線形補間演算とすることにより簡易かつ高速な処理にて修正前後の階調データの全階調領域の対応関係を決定することができるが、使用環境に応じて、曲線状とする補間演算を行ってきめ細やかに修正前後の階調データの対応関係を決定してもよい。
【００３１】
本実施形態では、決定した対応関係に基づいて、プリンタ標準機用のＬＵＴから修正されたＬＵＴを生成することにしている。印刷制御手段Ｕ３は、画像データを入力し、複数段階とされた基準階調値に対応したカラー調整ＩＤのそれぞれについて決定された対応関係が反映されたＬＵＴを参照して画像データを印刷データに変換し、プリンタ２０に対して印刷制御を行う。このように、複数のカラー調整ＩＤが反映されたＬＵＴを使用することにより、画像データは修正後の印刷データまで一気に変換されるので、変換処理を高速化させることができる。そして、生成される印刷データは、複数段階の階調データに対応した複数の誤差情報のそれぞれについて決定された対応関係に基づいて修正されたデータとなるため、カラー調整ＩＤをインクの種類別に一つだけ用意していた従来と比べ、プリンタ２０はよりきめ細やかな誤差補償をインク量の誤差に対して行いながら印刷媒体上にインクのドットを形成する。
【００３２】
印刷制御手段Ｕ３は、図示しない解像度変換部、色変換部、ハーフトーン処理、ラスタライズ処理部を備える。
解像度変換部では、画像データを入力し、プリンタ２０の解像度に合わせて同画像データの解像度を変換する。入力する画像データは、画像をドットマトリクス状の多数の画素で階調表現したデータであり、様々な種類がある。例えば、ｓＲＧＢ色空間で定義されるＲＧＢから構成された画像データや、ＹＵＶ表色系における輝度（Ｙ成分）、Ｂの色差（Ｕ成分）、Ｒの色差（Ｖ成分）から構成された画像データ等がある。また、画像データの各成分も様々な階調数とされており、例えば、２５６階調、１０２４階調等がある。そこで、ｓＲＧＢやＹＵＶ表色系等の定義に従って、画像データを広域ＲＧＢ色空間内のＲＧＢ各２５６階調（０〜２５５の整数値）のＲＧＢデータに変換する。
【００３３】
色変換部では、ＲＧＢデータを構成する各画素の階調データを変換対象として順次対象画素を移動させながら、修正されたＬＵＴを参照してＲＧＢデータをＣＭＹＫＬｃＬｍインクのそれぞれの使用量に対応した階調データからなるＣＭＹＫＬｃＬｍデータに色変換する。ＣＭＹＫＬｃＬｍデータもＣＭＹＫＬｃＬｍ各２５６階調（０〜２５５の整数値）のデータとされている。図５に示すように、ＬＵＴはＣＭＹＫＬｃＬｍ別に階調データが格納されてＨＤ１４に記憶されており、補間演算を前提として、例えばＲＧＢ各１７すなわち１７の３乗個の格子点に対応した大量のデータを備えている。図では、わかりやすく説明するためＬＵＴ中にＲＧＢデータを示しているが、実際にはＲＧＢデータを構成する各階調データに対応するアドレスからＣＭＹＫＬｃＬｍ４８ビット分のデータを参照することにより、ＲＧＢデータをＣＭＹＫＬｃＬｍデータに変換するようになっている。なお、入力するＲＧＢデータに一致するＣＭＹＫＬｃＬｍデータがＬＵＴに格納されていない場合には、入力するＲＧＢデータに近い複数のＲＧＢデータに対応するＣＭＹＫＬｃＬｍデータを取得し、体積補間等の補間演算によりＣＭＹＫＬｃＬｍデータを算出する。
【００３４】
ハーフトーン処理部では、誤差拡散法等によるハーフトーン処理を行い、２５６階調のＣＭＹＫＬｃＬｍデータをプリンタ２０の印刷ドットに対応する２階調に変換する。そして、ラスタライズ処理部では、プリンタの印刷ヘッド２５の走査幅に基づいて２階調とされたＣＭＹＫＬｃＬｍデータのビットデータを並べ替えるラスタライズ処理を行い、処理後のＣＭＹＫＬｃＬｍデータをプリンタ２０に対して出力する。ＣＭＹＫＬｃＬｍデータはＣＭＹＫＬｃＬｍのインク使用量のデータであり、プリンタ２０は、印刷データであるＣＭＹＫＬｃＬｍデータを入手して対応するインクをメディア上に吐出させると、印刷データに基づく画像を印刷することができる。このようにして、プリンタ２０に対して印刷制御を行うことができる。そして、印刷制御手段Ｕ３とプリンタ２０とから印刷手段が構成される。
なお、ハーフトーン処理やラスタライズ処理を実行可能なプリンタに対してＣＭＹＫＬｃＬｍデータを出力する際には、これらの処理を行わずにＣＭＹＫＬｃＬｍデータをプリンタに対して出力することができる。
【００３５】
（３）印刷制御装置が行う処理：
図７は、本印刷制御装置が行う修正ＬＵＴ作成処理をフローチャートにより示している。本フローは、プリンタ２０用のプリンタドライバがインストールされるときに行われる。
まず、誤差取得手段により、カラー調整ＩＤの入手要求を作成してプリンタ２０に送信する（ステップＳ１０５。以下、「ステップ」の記載を省略）。すると、プリンタ２０は同入手要求を受信し、ＲＯＭ２２からカラー調整ＩＤのＩＤ１〜３全てを読み出してＰＣ１０に対して送信する。そこで、ＰＣ１０では、同カラー調整ＩＤのＩＤ１〜３を取得し、ＨＤ１４の所定領域に格納する（Ｓ１１０）。このように、カラー調整ＩＤがプリンタと一体となっているので、本印刷システムのユーザはプリンタを変更しても別途カラー調整ＩＤを入力する必要がなく、本印刷制御装置は便利である。
【００３６】
次に、対応関係決定手段により、修正前の階調データとインク量の誤差を補償させる修正後の階調データとの対応関係を、インクの色別、かつ、基準階調値別に決定する（Ｓ１１５）。ここでは、上記演算式（１）を用いて色別の基準階調値の修正前後の対応関係データを決定して、図６の上段で示したような対応関係テーブルＴ１を作成する。
その後、プリンタ標準機用のＬＵＴをＨＤから読み出す（Ｓ１２０）。同ＬＵＴには修正前となるＣＭＹＫＬｃＬｍの階調値が格納されているので、上記対応関係テーブルＴ１を参照し、線形補間演算用の演算式（２）を用いてＣＭＹＫＬｃＬｍの階調値を修正する（Ｓ１２５）。演算式（２）の演算結果が２５５よりも大きいときには、階調値２５５に置き換える。すると、図６の下段で示した対応関係となるように階調データの全階調領域について修正後の階調値を決定することができる。
【００３７】
そして、補間演算により修正した各階調値を図５で示した修正ＬＵＴとしてＨＤの所定領域に記憶させ（Ｓ１３０）、本フローを終了する。ここで、修正ＬＵＴに格納されたＣＭＹＫＬｃＬｍの階調値は複数段階の基準階調値に対応した複数のカラー調整ＩＤが反映されているので、同修正ＬＵＴは、画像を画素別の階調データで構成した画像データと、インク量の誤差をきめ細やかに補償させる修正後の階調データで構成した印刷データとの対応関係を複数の参照点について規定するテーブルとなる。
【００３８】
修正ＬＵＴが作成されると、この修正ＬＵＴを使用してプリンタ２０に印刷させる制御を行うことができる。図８は、印刷制御手段により行われる印刷制御処理をフローチャートにより示している。
ＡＰＬはＡＰＬ用印刷機能を有しており、このＡＰＬ用印刷機能にてディスプレイ１８ａに表示される印刷実行メニューが選択されると、本フローを開始する。まず、印刷させる画像を表現する画像データを入力する（Ｓ２０５）。入力する画像データは、図示しないデジタルカメラやスキャナ等にて取り込まれた画像のデータや、ＦＤ１６ａ等に記録した画像データ等がある。なお、データ全体を一括して読み込む必要はなく、部分的に読み込むようにしてもよいし、データの受け渡しに利用されるバッファ領域を表すポインタの受け渡しだけであってもよい。
【００３９】
入力する画像データには様々な種類があるため、広域ＲＧＢ色空間内の２５６階調のＲＧＢデータに変換するとともに、プリンタ２０の解像度に合わせて画像データの解像度を変換する（Ｓ２１０）。ここで、画像データが印刷解像度よりも低い場合には線形補間により隣接する画像データの間に新たなデータを生成し、画像データが印刷解像度よりも高い場合には、一定の割合でデータを間引く。
その後、作成された修正ＬＵＴを参照して、画像データを構成する各画素のＲＧＢからなる階調データをＣＭＹＫＬｃＬｍからなる階調データに変換する（Ｓ２１５）。上述したように、生成されるＣＭＹＫＬｃＬｍデータは、３段階の基準階調値に対応した複数のカラー調整ＩＤのそれぞれについて決定された対応関係に従って修正された階調値とされる。
【００４０】
そして、ハーフトーン処理により２５６階調のＣＭＹＫＬｃＬｍデータを二値化する（Ｓ２２０）。ハーフトーン処理とは多階調のＣＭＹＫＬｃＬｍデータの階調値をプリンタ２０が各画素毎に表現可能な階調値に減色する（色を表現する階調の数を減らす）ことをいい、本実施形態においては２階調への減色を行う。また、ラスタライズ処理により２階調のＣＭＹＫＬｃＬｍデータを並べ替える（Ｓ２２５）。最後に、ＣＭＹＫＬｃＬｍデータをプリンタ２０に対して出力し（Ｓ２３０）、本フローを終了する。
【００４１】
すると、プリンタ２０は、ＣＭＹＫＬｃＬｍデータを入手し、各階調データに対応したインク量となるように印刷ヘッド２５を駆動してインクを印刷用紙上に吐出し、ＣＭＹＫＬｃＬｍデータに基づいて印刷を行う。ここで、ＣＭＹＫＬｃＬｍデータは３段階の基準階調値に対応したカラー調整ＩＤが反映されているので、プリンタ２０はインク量の誤差に対して階調データに応じたきめ細やかな誤差補償を行いながら印刷用紙上にインクのドットを形成する。従って、従来のように印刷用紙上に印刷された画像のある濃度領域において思い通りの色が十分に再現されないことがなくなり、色精度を向上させて印刷物をさらに高画質化させることが可能となる。また、３段階の基準階調値は大きい値から小さい値の順番にしたときに略２分の１ずつ小さくすることより、２分の１ずつ段階的に小さくなる印刷ヘッドの駆動周波数に応じて適切に誤差量を補償することができ、より正確に色精度を向上させることができる。
【００４２】
（４）第二の実施形態：
本発明の印刷制御プログラムを実行可能な印刷制御装置と周辺装置は、様々な構成が可能である。
例えば、プリンタは、コンピュータと一体化されたものであってもよいし、単色画像のみを印刷する専用品であってもよい。上述したフローについては、ＰＣ内で実行する以外にも、一部または全部をプリンタあるいは専用の画像出力機器で実行するようにしてもよい。
また、上述した実施形態以外にも、様々な構成により複数段階の階調データに対応した複数の誤差情報を取得可能である。図９は、第二の実施形態にかかる印刷制御装置が行う修正ＬＵＴ作成処理をフローチャートにより示している。なお、ハードウェア構成は第一の実施形態と概略同じであるが、プリンタ２０は従来通り所定の一つの基準階調値（例えば、１２７）に対応するカラー調整ＩＤのみを記憶しているものとする。
【００４３】
まず、カラー調整ＩＤの入手要求を作成してプリンタ２０に送信し（Ｓ３０５）、所定の基準階調値のみに対応するカラー調整ＩＤを取得し、ＨＤ１４の所定領域に格納する（Ｓ３１０）。このとき、プリンタ２０では、カラー調整ＩＤの入手要求を受信し、ＲＯＭ２２からカラー調整ＩＤを読み出してＰＣ１０に対して送信している。
次に、別の基準階調値のいずれか（例えば、６３）を中心として異ならせた複数の階調値に対応する複数の濃さのパッチ（基準画像）をプリンタ２０に印刷させるパッチ印刷データを作成する（Ｓ３１５）。その際、個々のパッチを識別するため、階調値の違いすなわちパッチの濃さに対応した番号等の情報を印刷させるデータも作成しておく。そして、パッチ印刷データをプリンタ２０に対して出力する（Ｓ３２０）。すると、プリンタ２０はパッチ印刷データを入手し、印刷ヘッド２５等を駆動して、図１０に示すように、インクの種類別に複数の階調値に対応して印刷用紙にインクのドットを形成することにより、複数のパッチＰＡと番号等の情報を印刷する。
【００４４】
その後、カラー測色器３０にてパッチＰＡを色別かつ濃さ別に測色するように促す旨を表示し、Ｌａｂ空間の各Ｌａｂ値からなる測色結果を色および濃さの情報に対応させながら順次入手する（Ｓ３２５）。従って、ＰＣの操作者は、複数のパッチＰＡに順次測色器３０の色検出部を押し当てる作業を行うことになる。
測色結果を入手すると、同測色結果に基づいて、印刷された複数のパッチＰＡのいずれかに対応する階調値を基準階調値に対応する誤差情報として取得する（Ｓ３３０）。例えば、予めＨＤ１４に基準階調値と目標の各Ｌａｂ値とを対応させたテーブルを記憶させておき、このテーブルを参照して最も目標の各Ｌａｂ値に近い測色結果（Ｌａｂ空間内での色差が最も小さい測色結果）に対応する階調値を取得する。なお、Ｓ３２５〜Ｓ３３０の処理を行う代わりに、色別にパッチの番号の選択入力を受け付け、入力された番号のパッチに対応する階調値を取得するようにしてもよい。
【００４５】
そして、誤差情報を取得する基準とした基準階調値に対応するカラー調整ＩＤの値を算出する（Ｓ３３５）。ここで、本実施形態において、誤差情報を取得する基準とした基準階調値をＸ、基準階調値に対応する誤差情報として取得した階調値をＹとすると、基準階調値に対応するカラー調整ＩＤの値ＩＤを以下の式により算出する。
ＩＤ ＝ ５０ × Ｘ ／ Ｙ ・・・（３）
その後は、図７で示したＳ１１５〜Ｓ１３０と同様の修正ＬＵＴ作成処理を行う。すなわち、修正前の階調データとインク量の誤差を補償させる修正後の階調データとの対応関係を、インクの色別、かつ、基準階調値別に決定する（Ｓ３４０）。次に、プリンタ標準機用のＬＵＴをＨＤから読み出し（Ｓ３４５）、対応関係テーブルＴ１を参照して、線形補間演算用の演算式（２）を用いてＣＭＹＫＬｃＬｍの階調値を修正する（Ｓ３５０）。そして、修正した各階調値を修正ＬＵＴとしてＨＤの所定領域に記憶させ（Ｓ３５５）、本フローを終了する。
【００４６】
このように、プリンタが複数段階の階調データに対応した複数の誤差情報を記憶していなくても、修正前の階調データとインク量の誤差を補償させる修正後の階調データとの対応関係を、インクの種類別、かつ、複数段階とされた基準階調値に対応した複数の誤差情報のそれぞれについて決定することができる。そして、作成された修正ＬＵＴは、画像を画素別の階調データで構成した画像データと、インク量の誤差をきめ細やかに補償させる修正後の階調データで構成した印刷データとの対応関係を複数の参照点について規定するテーブルとなる。
【００４７】
（５）第三の実施形態：
また、画像データを入力して印刷制御を開始するときに、印刷装置からシリアルＮｏ（識別データ）を入手し、印刷装置に変更がないと判断したときにはそのまま印刷制御を続ける一方、印刷装置に変更があると判断したときにプリンタ標準機用のＬＵＴを修正して印刷制御を行うようにしてもよい。
図１１は、第三の実施形態にかかる印刷制御装置が行う印刷制御処理をフローチャートにより示している。なお、ハードウェア構成は第一の実施形態と概略同じであり、プリンタのＲＯＭ２２に記憶されたシリアルＮｏ２２ｂをプリンタ２０から取得して修正ＬＵＴと対応させてＨＤ１４に記憶させているものとする。
【００４８】
まず、印刷制御手段により、印刷させる画像を表現する画像データを入力する（Ｓ４０５）。本実施形態では、この段階で対応関係決定手段により、シリアルＮｏの入手要求を作成してプリンタ２０に送信する（Ｓ４１０）。すると、プリンタ２０は同入手要求を受信し、ＲＯＭ２２からシリアルＮｏ２２ｂを読み出してＰＣ１０に対して送信する。そこで、ＰＣ１０では、同シリアルＮｏ２２ｂを取得し（Ｓ４１５）、ＨＤ１４に記憶しているシリアルＮｏと同じか否かを判断する（Ｓ４２０）。
条件成立の場合、修正ＬＵＴを作成する必要がないので、Ｓ４３５に進む。
【００４９】
条件不成立の場合、図７で示した修正ＬＵＴ作成処理を行う（Ｓ４２５）。すなわち、誤差取得手段により、プリンタ２０からカラー調整ＩＤのＩＤ１〜３を取得する。次に、対応関係決定手段により、修正前の階調データとインク量の誤差を補償させる修正後の階調データとの対応関係を、インクの色別、かつ、基準階調値別に決定する。さらに、プリンタ標準機用のＬＵＴをＨＤから読み出し、対応関係テーブルＴ１を参照して、線形補間演算用の演算式（２）を用いてＣＭＹＫＬｃＬｍの階調値を修正し、修正した各階調値を修正ＬＵＴとしてＨＤの所定領域に記憶させる。
修正ＬＵＴを作成すると、Ｓ４１５で取得したシリアルＮｏ２２ｂを修正ＬＵＴと対応させてＨＤ１４に記憶する（Ｓ４３０）。
【００５０】
その後、印刷制御手段により、図８で示したＳ２１０〜Ｓ２３０と同様の処理を行う。すなわち、画像データの解像度を変換し（Ｓ４３５）、作成された修正ＬＵＴを参照してＲＧＢデータをＣＭＹＫＬｃＬｍデータに色変換する（Ｓ４４０）。そして、ハーフトーン処理により２５６階調のＣＭＹＫＬｃＬｍデータを二値化し（Ｓ４４５）、ラスタライズ処理により二値化したＣＭＹＫＬｃＬｍデータを並べ替え（Ｓ４５０）、ＣＭＹＫＬｃＬｍデータをプリンタ２０に対して出力し（Ｓ４５５）、本フローを終了する。
すなわち、プリンタ２０から取得したシリアルＮｏが記憶したシリアルＮｏと異なるときにのみ修正ＬＵＴが作成されることになり、プリンタ標準機用のＬＵＴから修正ＬＵＴを作成する頻度が少なくなるので、印刷制御の処理を高速化させることができる。
【００５１】
（６）第四の実施形態：
本発明は、インクのドットの大きさを変更可能なプリンタに対して印刷制御を行う装置にも適用可能である。図３を参照して説明すると、このようなプリンタでは、ピエゾ素子ＰＥへの電圧の印加パターンを変えることにより、インク滴Ｉｐの大きさを変更する。これにより、例えば大中小の３種類の大きさのドットを形成する。そして、印刷データをインク量の異なる３種類のドットの形成をまとめて表現する階調データから構成し、印刷データを画素別にドットの種類を表現するドットデータに変換すると、プリンタはドットデータに対応してインク量の異なる３種類のドットを印刷用紙上に形成する。
【００５２】
図１２は、大中小のドットを形成するプリンタに記憶されるカラー調整ＩＤを模式的に示している。複数のカラー調整ＩＤは、インクの色別、ドットの種類別、かつ、印刷データを構成する階調データのとりうる階調領域内で異なる値とされた３段階の基準階調値別に設けられている。図のカラー調整ＩＤは、基準階調値６３，１２７，２５５に対応して小ドット用、中ドット用、大ドット用の順にＩＤsml1，ＩＤmid1，ＩＤlarge1（低階調用）、ＩＤsml2，ＩＤmid2，ＩＤlarge2（中階調用）、ＩＤsml3，ＩＤmid3，ＩＤlarge3（高階調用）から構成されている。同カラー調整ＩＤは、第一の実施形態と同様にして決定され、プリンタのＲＯＭに書き込まれるようになっている。
すなわち、色別かつドット種類別に各基準階調値で実際に使用されるインクの重量を測定し、プリンタ標準機で使用されるインクの重量（仕様値）を５０としたときの相対値をカラー調整ＩＤとする。６色のインクを使用し、大中小３種類のドットを形成する場合、基準階調値として３段階設けているので、６×３×３＝５４のカラー調整ＩＤをＲＯＭに書き込むことになる。そして、カラー調整ＩＤで表されるインクの変動量を色別、ドット種類別かつ各階調段階毎に補償して正確な色再現を行う。
【００５３】
上記プリンタに対して印刷制御を行うとき、図８で示したＳ２２０のハーフトーン処理にて、２５６階調のＣＭＹＫＬｃＬｍデータを「ドット形成せず」（例えば、階調値０）、「小ドット形成」（階調値１）、「中ドット形成」（階調値２）、「大ドット形成」（階調値３）の４階調のドットデータに変換する。その際、図５の括弧内に示すように、修正ドット形成テーブルを参照してドットデータに変換する。ハーフトーン処理を行う前のＳ２１５では、解像度変換されたＲＧＢデータからドットの全種類の形成をまとめて表現する階調データから構成されるＣＭＹＫＬｃＬｍデータに変換している。
図１３は、本実施形態におけるハーフトーン処理の流れをフローチャートにより示している。なお、本フローは、ＣＭＹＫＬｃＬｍ別に行われる。
【００５４】
上記Ｓ２１５の色変換処理により生成されるＣＭＹＫＬｃＬｍデータは、画像をドットマトリクス状の多数の画素で多階調表現されているため、まず、ハーフトーンの対象画素の位置を設定する（Ｓ５０５）。次に、対象画素の階調値を取得し、図１４に示すドット形成テーブルＴ２を参照して大ドットのレベルデータＬＬを読みとる（Ｓ５１０）。図１４の横軸はドットの全種類の形成をまとめて表現するときの入力階調値（０〜２５５）、左側の縦軸はドット記録率（％）、右側の縦軸はレベルデータ（０〜２５５）である。ドット記録率とは、一定の階調値に応じて一様な領域が再現されるときにその領域内の画素のうちでドットが形成される画素の割合を意味する。レベルデータとは、ドット記録率を値０〜２５５の２５６段階に換算したデータをいう。例えば、入力階調値がｇｒであれば、大ドットのレベルデータは大ドット用の曲線を用いてＬＬと求められる。実際には、図左上に示したように、入力階調値と大中小各ドットのレベルデータとを対応させたドット形成テーブルＴ２としてＨＤに格納しておき、このドット形成テーブルＴ２を参照してレベルデータを求める。同ドット形成テーブルＴ２は、ドットの全種類の形成をまとめて表現するＣＭＹＫＬｃＬｍデータとドットデータとの対応関係を大中小のドット別に規定したテーブルとも言える。
【００５５】
その後、大ドットレベルデータＬＬが所定の閾値ＴＬより大きいか否かを判断する（Ｓ５１５）。例えば、ディザ法によるドットのオン・オフ判定を行う場合、閾値ＴＬは１６×１６等のディザマトリックスにより各画素毎に異なる値が設定される。
レベルデータＬＬが閾値ＴＬよりも大きい場合、変換後の階調値を大ドット形成を意味する階調値３とし（Ｓ５２０）、Ｓ５６０に進む。
一方、レベルデータＬＬが閾値ＴＬ以下のとき、取得した対象画素の階調値からドット形成テーブルＴ２を参照して中ドットのレベルデータＬＭを読みとる（Ｓ５２５）。そして、中ドットレベルデータＬＭが所定の閾値ＴＭより大きいか否かを判断する（Ｓ５３０）。閾値ＴＭも、ディザ法によるドットのオン・オフ判定を行う場合、大ドット用とは別のディザマトリックスにより各画素毎に異なる値が設定される。
【００５６】
レベルデータＬＭが閾値ＴＭよりも大きい場合、変換後の階調値を中ドット形成を意味する階調値２とし（Ｓ５３５）、Ｓ５６０に進む。
一方、レベルデータＬＭが閾値ＴＭ以下のとき、取得した対象画素の階調値からドット形成テーブルＴ２を参照して小ドットのレベルデータＬＳを読みとる（Ｓ５４０）。そして、小ドットレベルデータＬＳが所定の閾値ＴＳより大きいか否かを判断する（Ｓ５４５）。閾値ＴＳも、ディザ法によるドットのオン・オフ判定を行う場合、大中ドット用とは別のディザマトリックスにより各画素毎に異なる値が設定される。
【００５７】
レベルデータＬＳが閾値ＴＳよりも大きい場合、変換後の階調値を小ドット形成を意味する階調値１とし（Ｓ５５０）、Ｓ５６０に進む。
一方、レベルデータＬＳが閾値ＴＳ以下のとき、変換後の階調値をドットを形成しない意味の階調値０とし（Ｓ５５５）、Ｓ５６０に進む。
Ｓ５６０では、全画素について処理を終了したか否かを判断する。全画素について処理を終了していない場合には繰り返しＳ５０５〜Ｓ５６０の処理を行い、全画素について処理を終了したときには本フローを終了する。
その後は、図８のＳ２２５〜Ｓ２３０にてラスタライズ処理が行われ、ＣＭＹＫＬｃＬｍデータがプリンタ２０に対して出力されることになる。
【００５８】
本実施形態では、上記ドット形成テーブルＴ２のレベルデータを修正することにより、色別、ドットの種類別かつ基準階調値別にインク量の誤差を補償する。ドット形成テーブルを修正する処理は、図７で示した修正ＬＵＴ作成処理と概略同様にして行うことができるため、図７を参照して説明する。
まず、誤差取得手段により、カラー調整ＩＤの入手要求を作成してプリンタに送信し、図１２で示した全てのカラー調整ＩＤを取得し、ＨＤの所定領域に格納する（Ｓ１０５〜Ｓ１１０に相当）。このとき、プリンタでは、カラー調整ＩＤの入手要求を受信し、ＲＯＭから色別、ドットの種類別かつ基準階調値別のカラー調整ＩＤを読み出してＰＣ１０に対して送信している。
【００５９】
次に、対応関係決定手段により、修正前の階調データとインク量の誤差を補償させる修正後の階調データとの対応関係を、インクの色別、ドットの種類別、かつ、基準階調値別に決定する（Ｓ１１５に相当）。ここでは、上記演算式（１）を用いて色別の基準階調値の修正前後の対応関係データを決定して、図１５の上段で示すような対応関係テーブルＴ３を作成する。対応関係テーブルＴ３は、６色のインクとドットの種類の組み合わせのうちのいずれか（図の例はシアンの大ドット）に相当する基準階調値の修正前後の対応関係のデータを格納したテーブルである。
【００６０】
その後、プリンタ標準機用のドット形成テーブルをＨＤから読み出す（Ｓ１２０に相当）。同ドット形成テーブルには修正前となるＣＭＹＫＬｃＬｍの階調値が格納されているので、上記対応関係テーブルＴ３を参照し、線形補間演算用の演算式（２）を用いてＣＭＹＫＬｃＬｍの階調値を修正する（Ｓ１２５に相当）。演算式（２）の演算結果が２５５よりも大きいときには、階調値２５５に置き換える。すると、図１５の下段に示す対応関係となるように階調データの全階調領域について修正後の階調値を決定することができる。なお、図の下段は、６色のインクとドットの種類の組み合わせのうちのいずれかに相当する階調データの修正前後の対応関係をグラフ形式で示したものである。
【００６１】
その結果、図１６に示すように、ドット形成テーブルは同じ入力階調値に対してレベルデータが修正されたテーブルとされる。図１６の例は、シアンの大ドット用のドット形成テーブルについての修正前後の対応関係が図１５で示したデータとして表されている場合に、同ドット形成テーブルの修正前後のレベルデータＬＬをグラフ形式で示したものである。図１５の例では修正前のレベルデータが基準階調値６３であるとき対応関係テーブルＴ３に格納された修正後のデータは６６であるので、図１６において修正前のレベルデータ６３はレベルデータ６６（点Ｐ１）となるように修正される。点Ｐ２，Ｐ３も同様の対応関係にて修正されたレベルデータの位置を示しており、その他のレベルデータについては線形補間演算により修正されたデータとされる。
【００６２】
そして、修正した各階調値を修正ドット形成テーブルとしてＨＤの所定領域に記憶させ（Ｓ１３０に相当）、本フローを終了する。ここで、修正ドット形成テーブルに格納されたＣＭＹＫＬｃＬｍの階調値は複数段階の基準階調値に対応した複数のカラー調整ＩＤが反映されているので、同修正ドット形成テーブルは、２５６階調のＣＭＹＫＬｃＬｍデータと、インク量の誤差をきめ細やかに補償させる修正後のドットデータとの対応関係を複数種類のドット別に複数の階調値について規定するテーブルとなる。
そして、上述した印刷制御処理を行うと、画像データを入力し、２５６階調のＣＭＹＫＬｃＬｍデータに変換した後、ハーフトーン処理により修正ドット形成テーブルを参照して２５６階調のＣＭＹＫＬｃＬｍデータを色別かつドットの種類別のドットデータに変換する。すなわち、複数段階の階調データに対応したカラー調整ＩＤが反映されたドット形成テーブルを使用することにより、２５６階調のＣＭＹＫＬｃＬｍデータを修正後のドットデータまで一気に変換することができ、変換処理を高速化させることができる。その後、ラスタライズ処理を行って並べ替えを行ったドットデータをプリンタに対して出力する。
【００６３】
すると、プリンタは、ＣＭＹＫＬｃＬｍ別かつドット種類別のドットデータ（４階調のＣＭＹＫＬｃＬｍデータ）を入手し、２５６階調のＣＭＹＫＬｃＬｍデータを基準としたときに各階調データに対応したインク量となるように印刷ヘッドを駆動してインクを印刷用紙上に吐出し、印刷を行う。ここで、ドットデータは３段階の基準階調値に対応したカラー調整ＩＤが反映されているので、プリンタはドットの種類別にインク量の誤差に対して階調データに応じたきめ細やかな誤差補償を行いながら印刷用紙上にインクのドットを形成する。従って、インクのドットの大きさを変更して印刷可能な印刷装置にて印刷される色精度を向上させ、印刷物をさらに高画質化させることが可能となる。
【００６４】
なお、本実施形態では、大中小のドット全てに対応するドット形成テーブルを複数段階の階調データのそれぞれに対応した複数のカラー調整ＩＤを用いて修正するようにしたが、大中小いずれかの種類のドットに対応するドット形成テーブルのみを修正するようにしてもよい。例えば、プリンタ標準機用のドット形成テーブルのうち大ドット用のテーブルにはレベルデータのとりうる階調領域として０〜２５５が格納され、中、小ドット用のドット形成テーブルにはその階調領域よりも狭い範囲の階調値が格納されている場合、処理を簡素化させるために大ドット用のドット形成テーブルのみを修正してもよい。このような場合でも、複数段階の階調データのそれぞれに対応した複数のカラー調整ＩＤを用いることにより、修正を行ったドット形成テーブルに対応するドットの種類についてきめ細やかにインク量の誤差を補償することができ、色精度を向上させることができる。
【００６５】
なお、第一〜第四の実施形態で示したように、複数の誤差情報について決定した修正前後の階調データの対応関係に基づいてＬＵＴを修正したりドット形成テーブルを修正したりする以外の手法により、インク量の誤差を補償する構成としてもよい。例えば、プリンタ標準機用のＬＵＴを参照してＲＧＢデータから２５６階調のＣＭＹＫＬｃＬｍデータに色変換した後、図６で示した対応関係に従って注目画素毎に対応関係テーブルＴ１を参照するとともに必要に応じて線形補間演算を行って同ＣＭＹＫＬｃＬｍデータを修正するようにしてもよい。
本発明によると、種々の態様により、色精度を向上させ、印刷物をより高画質化させることが可能な印刷制御装置、印刷システム、印刷制御プログラムおよびその媒体を提供することができる。また、印刷制御方法としても適用可能である。
【図面の簡単な説明】
【図１】 印刷制御装置と周辺装置とからなる印刷システムの概略構成図である。
【図２】 プリンタのブロック構成をＰＣとともに示すブロック構成図である。
【図３】 ピエゾ素子ＰＥとノズルＮｚとの構造を断面視して示す断面図である。
【図４】 複数のカラー調整ＩＤを模式的に示す図である。
【図５】 印刷制御装置の構成を模式的に示す図である。
【図６】 複数段階の階調データの対応関係と補間演算後の全階調の階調データの対応関係を模式的に示す図である。
【図７】 修正ＬＵＴ作成処理を示すフローチャートである。
【図８】 印刷制御処理を示すフローチャートである。
【図９】 第二の実施形態における修正ＬＵＴ作成処理を示すフローチャートである。
【図１０】 印刷用紙に印刷される複数のパッチを示す図である。
【図１１】 第三の実施形態における印刷制御処理を示すフローチャートである。
【図１２】 第四の実施形態において大中小のドットを形成するプリンタに記憶されるカラー調整ＩＤを模式的に示す図である。
【図１３】 第四の実施形態におけるハーフトーン処理を示すフローチャートである。
【図１４】 ドット形成テーブルにおける入力階調値に対するレベルデータの値をグラフ形式で示す図である。
【図１５】 複数段階の階調データの対応関係と補間演算後の全階調の階調データの対応関係を模式的に示す図である。
【図１６】 入力階調値に対する修正前後のレベルデータの値をグラフ形式で示す図である。
【符号の説明】
１０…パーソナルコンピュータ
１１…ＣＰＵ
１２…ＲＯＭ
１３…ＲＡＭ
１４…ハードディスク
１５…ＣＤ−ＲＯＭドライブ
１７ａ〜ｅ…インターフェイス
１８ａ…ディスプレイ
１８ｂ…キーボード
１８ｃ…マウス
２０…インクジェットプリンタ
２２…ＲＯＭ
２２ａ…カラー調整ＩＤ
２２ｂ…シリアルナンバー
２５…印刷ヘッド
２６…ＡＳＩＣ
２６ａ…ヘッド駆動部
３０…カラー測色器
Ｕ１…誤差取得手段
Ｕ２…対応関係決定手段
Ｕ３…印刷制御手段
Ｔ１，Ｔ３…対応関係テーブル
Ｔ２…ドット形成テーブル
ＰＡ…パッチ[0001]
BACKGROUND OF THE INVENTION
  The present invention constitutes print data.PaintingA printing control apparatus, a printing control method, a printing system, a printing control program, and a printing control program that perform printing control are recorded for a printing apparatus that forms ink dots on a printing medium corresponding to distinct gradation data. It relates to the medium.
[0002]
[Prior art]
  Conventionally, this type of printing control apparatus is used for color printers that eject several colors of ink from a print head onto printing paper., PaintingPrint control is performed by generating print data composed of distinct gradation data. Here, in order to obtain good color accuracy and improve image quality, it has been proposed to compensate for an error in the ink ejection amount due to manufacturing variations of the print head for each print head. At this time, the color adjustment ID, which is error information classified by ink type, is stored in the printer, the same color adjustment ID is received from the printer, and the gradation data is multiplied by a coefficient corresponding to the color adjustment ID. The ink amount error is compensated for each ink color.
[0003]
[Problems to be solved by the invention]
  In the conventional technique described above, it may be felt that the desired color is not sufficiently reproduced in a certain density region of the printed image. Therefore, there was a desire to further improve color accuracy and to perform printing as desired.
  The present invention has been made in view of the above problems, and provides a printing control apparatus, a printing control method, a printing system, a printing control program, and a printing control program capable of improving color accuracy and improving the quality of printed matter. The purpose is to provide a recorded medium.
[0004]
[Means for Solving the Problems]
  In order to achieve the above object, the invention according to claim 1 constitutes print data.PaintingA printing control apparatus that performs printing control on a printing apparatus that forms ink dots on a printing medium in correspondence with distinct gradation data, and that represents an error in the ink weight of the ink and has multiple levels. Error acquisition means for acquiring a plurality of error information corresponding to the tone data, and image data representing an image are input, and the ink weight is calculated from the image data based on the plurality of error information acquired by the error acquisition means. Print control means for generating the print data for compensating for the error and performing the print control.The plurality of error information is information corresponding to a plurality of levels of reference gradation values that are different values within the gradation region that the gradation data can take, and the reference gradation value is large. When the value is changed from the smallest value to the smallest value, the value is reduced by about half.As a configuration.
[0005]
  That is, the plurality of pieces of error information acquired by the error acquisition unit is information corresponding to the gradation data of a plurality of stages while representing an error in the ink weight of the ink. The print data generated by the print control unit is data generated so as to compensate the ink weight error from the image data based on a plurality of error information corresponding to the gradation data of a plurality of stages. As a result, the printing apparatus performs fine error compensation on the ink weight error based on the print data reflecting a plurality of error information corresponding to the gradation data of a plurality of stages, while the ink on the print medium. Form dots.
  Therefore, it is possible to improve the color accuracy appearing on the print medium, and the printed matter has a higher image quality.
  Note that there may be a plurality of ink colors or one ink.
  Further, based on the plurality of error information acquired by the error acquisition means, the correspondence between the gradation data before correction and the gradation data after correction for compensating the error of the ink weight is the same as the plurality of error information. Correspondence determining means for determining each of the plurality of error information is generated, and the print control means generates the print data from the image data based on the correspondence relation for each of the determined plurality of error information, and the print control It is good also as composition which performs. That is, the correspondence determining means determines the correspondence between the gradation data before correction and the gradation data after correction for compensating the ink weight error for each of the plurality of error information based on the plurality of error information. decide. Then, the print data generated by the print control unit is data based on the correspondence determined for each of the plurality of error information corresponding to the plurality of levels of gradation data. As a result, the printing apparatus performs fine error compensation on the ink weight error based on the print data reflecting a plurality of error information corresponding to the gradation data of a plurality of stages, while the ink on the print medium. Form dots.
[0006]
  When the printing apparatus stores a plurality of error information, the error acquisition unit may acquire the plurality of error information from the printing apparatus. Since the error information is integrated with the printing apparatus, even if the user of the printing control apparatus changes the printing apparatus, the error information is acquired from the printing apparatus and does not need to be input separately.
  Also, WrongThe difference acquisition unit causes the printing apparatus to print a plurality of reference images corresponding to a plurality of gradation values that differ from each other with respect to any one of the reference gradation values, and corresponds to any of the plurality of printed reference images. You may acquire as error information corresponding to the reference gradation value centering on the gradation value. That is, the plurality of pieces of error information are gradation values corresponding to any of a plurality of reference images corresponding to a plurality of gradation values that are different from each other with respect to any one of the reference gradation values.
  As described above, various specific examples of the configuration for acquiring the error information are conceivable. In addition to these, for example, the print control apparatus may store the error information, or obtain the error information from another computer. May be.
[0007]
  In addition,versusThe response relationship determining means may determine the correspondence relationship of tone values other than the reference tone value in the tone data before correction by performing linear interpolation operation from the reference tone value and a plurality of error information. . That is, the correspondence between the gradation data before and after the correction is determined by a simple calculation from the reference gradation value and a plurality of error information.
[0008]
  When the print control means converts the same image data into the same print data with reference to the color conversion table, the correspondence determining means may correct the color conversion table based on the correspondence for each of the plurality of error information. Good. By using a color conversion table reflecting a plurality of error information, the image data is converted at once to the corrected print data.
[0009]
  When the printing apparatus stores identification data that can identify the printing apparatus, the correspondence determining unit can acquire the identification data from the printing apparatus and store the identification data in association with the corrected color conversion table. When the acquired identification data is different from the stored identification data, the error acquisition means acquires a plurality of error information, and the correspondence relationship of the gradation data before and after correction is determined based on the acquired plurality of error information. The color conversion table may be modified based on the correspondence relationship for each of the plurality of error information. That is, the color conversion table is corrected only when the identification data acquired from the printing apparatus is different from the stored identification data.
[0010]
  The print data is composed of gradation data that collectively represents the formation of multiple types of dots with different ink weights, and the printing device has multiple types of dots with different ink weights corresponding to the dot data that represents the dot types for each pixel. Can be formed on the print medium, the print control means converts the image data into the print data and refers to a dot formation table that defines the correspondence between the print data and the dot data for a plurality of types of dots. The print data may be converted into the same dot data. In this case, the correspondence determination unit may correct the dot formation table based on the correspondence for each of the plurality of error information. That is, by using a dot formation table in which a plurality of error information is reflected, the print data is converted at once to the corrected dot data.
  As described above, there are various possible configurations for the correspondence determining means. In addition to these configurations, for example, gradation data is divided into bands corresponding to each of a plurality of error information, and the image data is corrected. After conversion to the previous print data, the print data may be converted to the corrected print data by multiplying the correction coefficient for each band based on a plurality of error information for each band.
[0011]
  The plurality of error information is information corresponding to a plurality of stages of reference gradation values that are different values within the gradation region that the gradation data can take, and the reference gradation value is determined from a large value. It is designed to be reduced by about a half when the values are set in order of decreasing values.TheThe drive frequency of the print head decreases stepwise by half as it goes from the high gradation region to the low gradation region, and the error amount of the ink weight tends to be an error amount corresponding to the drive frequency. Therefore, the color accuracy can be further improved by decreasing the reference gradation value in half steps.
[0012]
  By the way, the above-described print control apparatus may be implemented alone, or may be implemented with other methods in a state of being incorporated in a certain device, and includes various aspects as an idea of the invention. However, it can be changed as appropriate.
  In addition, the above-described method for performing print control naturally proceeds according to a predetermined procedure, and it is natural that an invention exists in that procedure. Therefore, the present invention is also applicable as a method,Claim 9In the invention according to this embodiment, the same operation is basically performed.
  Furthermore, the present invention can be applied as a printing system including a printing unit that generates print data and performs printing.Claim 10In the invention according to this embodiment, the same operation is basically performed.
[0013]
  When trying to implement the present invention, the print control apparatus may execute a predetermined program. Furthermore, it is conceivable that a medium on which the program is recorded is distributed and the program is appropriately read from the recording medium into a computer. Therefore, it can also be applied as a computer-readable recording medium that records the program or program,Claim 11In the invention according to this embodiment, the same operation is basically performed.
  Of course, claims 2 to 2Claim 8It goes without saying that the configuration described in (1) can be made to correspond to the method, the printing system, the program, and the medium on which the program is recorded.
  Here, the recording medium may be any recording medium developed in the future in addition to the magnetic recording medium and the magneto-optical recording medium. In addition, even when a part is software and a part is realized by hardware, the idea of the present invention is not completely different, and a part is recorded on a recording medium and is appropriately changed as necessary. It includes a reading form. Furthermore, the duplication stages such as the primary replica and the secondary replica are equivalent without any question.
[0014]
【The invention's effect】
  As described above, claims 1, 2,Claims 9 to 11According to the invention, it is possible to improve the color accuracy and improve the quality of the printed matter.
  According to the third aspect of the invention, a plurality of error information can be acquired with a simple configuration in which information stored in the printing apparatus is acquired as it is, and error information is input separately even if the printing apparatus is changed. There is no need to improve convenience.
  According to the fourth aspect of the present invention, a plurality of error information can be acquired using a plurality of printed reference images.
  According to the fifth aspect of the present invention, it is possible to determine the correspondence relationship between the gradation data before and after the correction with a simple configuration.
[0015]
  According to the sixth aspect of the invention, it is possible to speed up the conversion process from image data to print data.
  According to the seventh aspect of the invention, since the frequency of correcting the color conversion table is reduced, the printing control process can be speeded up.
  According to the eighth aspect of the invention, it is possible to speed up the conversion process from print data to dot data..
[0016]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described in the following order.
(1) Configuration of printing system:
(2) Schematic configuration of the print control device:
(3) Processing performed by the print control apparatus:
(4) Second embodiment:
(5) Third embodiment:
(6) Fourth embodiment:
[0017]
(1) Configuration of printing system:
  FIG. 1 shows a schematic configuration of a printing system including a printing control apparatus and peripheral devices according to the first embodiment of the present invention. The printing system includes a personal computer (PC) 10 serving as a printing control apparatus according to the present invention, an ink jet printer 20 capable of color printing serving as a printing apparatus, and the like.
  The PC 10 includes a CPU 11 that is the center of arithmetic processing, and the CPU 11 controls the entire PC 10 via a system bus 10a. The bus 10a is connected to a ROM 12, a RAM 13, a CD-ROM drive 15, a flexible disk (FD) drive 16, various interfaces (I / F) 17a to 17e, and the like. A hard disk (HD) 14 is also connected via a hard disk drive. Although a desktop PC is employed as the computer of this embodiment, a computer having a general configuration can be employed.
[0018]
  The HD 14 stores an operating system (OS), an application program (APL) that can create image information, and the like as software, and these software are appropriately transferred to the RAM 13 by the CPU 11 during execution. The CPU 11 executes various programs while appropriately accessing the RAM 13 as a temporary work area.
  The USB I / F 17a is connected to a color calorimeter 30, a color scanner (not shown), a digital camera, and the like. The color calorimeter 30 directs the color detection unit 30a to the object to be colorimetrically to measure the colorimetric value based on the Lab color system, that is, the L value representing lightness, the a value representing hue and saturation, and b. The value can be measured. The Lab value measured by the colorimeter 30 can be read via the USB I / F 17a. Of course, other connection modes, such as RS-232C connection, can be adopted for the connection between the colorimeter and the PC 10.
  A display 18a for displaying an image based on color image data is connected to the CRTI / F 17b, and a keyboard 18b and a mouse 18c are connected to the input I / F 17c as operation input devices. Further, the printer 20 is connected to the printer I / F 17e via a parallel I / F cable. Of course, various connection modes such as serial I / F, SCSI, and USB connection can be adopted for connection with the printer 20.
[0019]
  The printer 20 uses C (cyan), M (magenta), Y (yellow), K (black), Lc (light cyan), and Lm (light magenta) inks to print paper (printing medium). The ink is ejected so that the ink amount corresponds to the gradation data constituting the print data, and the image is printed. Of course, a printer that uses ink other than six colors may be employed. In addition, various printing apparatuses such as a bubble type printer that generates bubbles in the ink passage and discharges ink and a laser printer can be employed.
  As shown in FIG. 2, in the printer 20, a CPU 21, a ROM 22, a RAM 23, a communication I / O 24, an ASIC 26, an I / F 27, and the like are connected via a bus 20a.
[0020]
  The communication I / O 24 is connected to the printer I / F 17e of the PC 10, and the printer 20 performs a print job including image data converted to CMYKLcLm and page description language transmitted from the PC 10 via the communication I / O 24. Receive. A CMYKLcLm ink cartridge 25b is mounted on the cartridge holder 25a, and each color ink in the ink cartridge 25b is supplied to the print head 25 for each color. The ASIC 26 outputs applied voltage data based on the CMYKLcLm data to the head drive unit 26a while transmitting / receiving a predetermined signal to / from the CPU 21. The head drive unit 26a generates an applied voltage pattern to the piezo elements built in the print head 25 based on the applied voltage data, and causes the print head 25 to eject six colors of ink in dot units. On the ink ejection surface of the print head 25, six sets of nozzle rows that eject six colors of ink are formed so as to be aligned in the main scanning direction of the print head, and each nozzle row has a plurality of nozzles that are constant in the sub-scanning direction. Are arranged in a straight line at intervals of.
[0021]
  Here, when the CMYKLcLm data is a high gradation region, that is, a region where a large amount of ink is used and dots are formed in almost all pixels, the ASIC 26 applies a high frequency driving frequency (frequency is assumed to be f) to the print head 25. Generate applied voltage data to be supplied. When the CMYKLcLm data is in an intermediate gradation region (the amount of ink used is medium) that is one step lower than the high gradation region, the applied voltage data is such that a drive frequency of f / 2 having a lower frequency is supplied to the print head 25. Is generated. When the CMYKLcLm data is in a low gradation region that is one step lower (the amount of ink used is small), the applied voltage data is generated so that the drive frequency of f / 4 is supplied to the print head 25. Therefore, the head driving unit 26a generates an applied voltage pattern having a driving frequency that decreases step by step as the CMYKLcLm data changes from the high gradation region to the low gradation region.
  The carriage mechanism 27a and the paper feed mechanism 27b connected to the I / F 27 perform the main scanning of the print head 25, and the sub-scan by sequentially feeding the printing paper while appropriately performing the page break operation. And CPU21 controls each part according to the program written in ROM22, using RAM23 as a work area.
[0022]
  For each nozzle provided in the print head 25, a piezoelectric element that is one of electrostrictive elements and has excellent responsiveness is arranged. FIG. 3 shows a cross-sectional view of the structure of the piezo element PE and the nozzle Nz. As shown in the upper part of the figure, the piezo element PE is installed at a position in contact with the ink passage 25c that guides ink to the nozzle Nz. The ink passage 25c is hatched as being filled with ink. The piezo element PE is an element that transforms electro-mechanical energy at an extremely high speed because the crystal structure is distorted by application of a voltage. In the present embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element PE, the piezo element PE expands for the voltage application time as shown in the lower part of the figure, and the ink path One side wall of 25c is deformed. As a result, the volume of the ink passage 25c contracts in accordance with the expansion of the piezo element PE, and the ink corresponding to the contraction becomes an ink droplet Ip and is ejected from the tip of the nozzle Nz at high speed. Printing is performed by the ink droplet Ip soaking into the printing paper.
[0023]
  Here, the size of the ink droplet Ip also varies due to manufacturing errors of the ink passage 25c and individual differences of the piezo elements PE. The fluctuation amount is stored in a predetermined area of the ROM 22 as a plurality of color adjustment IDs 22a which are error information. Of course, a non-volatile memory may be provided in the print head unit having the print head 25, and the color adjustment ID may be stored in the non-volatile memory. As schematically shown in FIG. 4, the plurality of color adjustment IDs 22 a have three levels of reference floors that have different values for each ink color and within the gradation area that the gradation data constituting the print data can take. It is provided for each tone value (multiple levels of gradation data). The color adjustment ID 22a shown in the figure includes ID1 (for low gradation), ID2 (for medium gradation), and ID3 (for high gradation) corresponding to the reference gradation values 63, 127, and 255. The color adjustment ID 22a is determined as follows and written in the ROM 22.
[0024]
  That is, the weight of ink actually used at each reference gradation value for each color is measured, and the relative value when the weight (specification value) of ink used in the standard printer is 50 is used as the color adjustment ID. . The lower part of the figure represents the relative value of the measured ink weight as a bar graph based on the specification value. For example, when the specification value of the ink weight at the reference gradation value 63 is 1890 ng and the actually used ink weight is 2190 ng, the value stored as the color adjustment ID is 2190 ÷ 1890 × 50 = 58 (Rounded to the nearest decimal place). Since the printer 20 uses six colors of ink and has three levels as reference gradation values, 6 × 3 = 18 color adjustment IDs are written in the ROM 22. Then, the ink fluctuation amount represented by the color adjustment ID is compensated for each color and for each gradation step, and accurate color reproduction is performed.
[0025]
  As described above, the drive frequency of the print head 25 decreases in half steps as the CMYKLcLm data changes from the high gradation region to the low gradation region, so that the error amount of the ink amount can be taken by the CMYKLcLm data. There is a tendency to vary stepwise within the gradation region. In view of this, the reference gradation value is decreased by approximately one half of 255, 127, and 63 in order from the largest value to the smallest value, thereby further improving the color accuracy.
  The ROM 22 also stores a serial number (serial number) 22b that is identification data that is different for each printer 20 so that the printers 20 can be individually identified. When the printer 20 receives a request for obtaining a color adjustment ID or serial number from the PC 10 via the communication I / O 24, the printer 20 reads the color adjustment ID or serial number from the ROM 22 and transmits it to the PC 10. Yes.
[0026]
  In the PC 10, the BIOS is executed based on the above hardware, and the OS and APL are executed in the upper layer. Various drivers such as a printer driver for controlling the printer I / F 17e are incorporated in the OS, and the hardware is controlled as a part of the OS. The printer driver can perform two-way communication with the printer 20 via the printer I / F 17e, receives image data from the APL via an OS incorporating a GDI (Graphics Device Interface), etc., and performs a print job. Is sent to the printer 20. The print control program of the present invention is composed of the printer driver. Of course, it is also possible to use APL. The HD 14 is a medium on which the program is recorded. Examples of the medium include a CD-ROM, an FD 16a, a magneto-optical disk, a nonvolatile memory, a punch card, and a print medium on which a code such as a barcode is printed. It may be. Of course, it is also possible to connect a communication I / F 17d such as a modem to the Internet network, access a predetermined server, download the print control program, and execute it.
[0027]
  The HD 14 includes gradation data constituting RGB data (image data) representing an image from three element colors of R (red), G (green), and B (blue) before conversion, and 6 CMYKLcLm after conversion. An LUT (color conversion table) called a look-up table that defines the correspondence between a plurality of reference points and gradation data constituting CMYKLcLm data (print data) composed of element colors is stored. This LUT is a table corresponding to the ink amount of the standard printer. The printer driver refers to the LUT, converts RGB data into print data, and performs print control for the printer 20.
[0028]
(2) Schematic configuration of the print control device:
  FIG. 5 schematically shows the configuration of a print control apparatus constructed by the hardware and the print control program in cooperation. The print control program is composed of a plurality of modules, and this module causes the PC 10 to realize an error acquisition function, a correspondence determination function, and a print control function. And various means U1-U3 are comprised corresponding to these functions.
[0029]
  The error acquisition unit U1 has a simple configuration in which a plurality of color adjustment IDs are acquired from the printer 20 as they are. Correspondence determining means U2 determines the correspondence between the gradation data before correction and the corrected gradation data that compensates for the error in the ink amount based on the obtained plurality of color adjustment IDs, for each ink color, In addition, each color adjustment ID corresponding to a plurality of stages of reference gradation values is determined. In the present embodiment, when the color adjustment ID value is represented by ID, the gradation value before correction is represented by X, and the gradation value after modification is represented by Y, the reference gradation value of the gradation data before modification is as follows. The corrected gradation value is determined by the following equation.
    Y = X × 50 / ID (1)
  An example of the correspondence relationship of the reference gradation values determined in this way is shown in the upper part of FIG. The figure shows a correspondence table T1 in which correspondence data before and after correction of a reference gradation value corresponding to one of six colors of ink (cyan in the figure) is stored. That is, the correspondence table T1 is created for each color of CMYKLcLm.
  Note that the gradation value 0 before correction corresponds to the gradation value 0 after correction.
[0030]
  Further, as shown in the lower part of the figure, the corrected gradation values for gradation values other than the reference gradation value in the gradation data before correction are linearly interpolated from the reference gradation value and the color adjustment ID. To make a decision. The figure shows the correspondence before and after correction of gradation data corresponding to one of the six colors of ink in a graph format. The horizontal axis is the gradation value before correction, and the vertical axis is the corrected value. It is a gradation value. Here, two reference gradation values or gradation value 0 before correction used for the interpolation calculation are set to X1, X2 (X1 <X2), and two gradation values X1 and X2 before correction used for the interpolation calculation are used. If the corresponding corrected gradation value is Y1, Y2 (Y1 <Y2), the corrected gradation value Y corresponding to the uncorrected gradation value X is calculated by the following equation.
[Expression 1]

  If Y exceeds 255 as a result of the calculation using the above equation, the corrected gradation is set to 255.
  As described above, the linear interpolation calculation can determine the correspondence relationship of all the gradation areas of the gradation data before and after the correction by simple and high-speed processing. It is also possible to determine the correspondence between the gradation data before and after the correction by performing the interpolation calculation.
[0031]
  In the present embodiment, a modified LUT is generated from the printer standard machine LUT based on the determined correspondence. The print control unit U3 inputs the image data, and refers to the LUT reflecting the correspondence determined for each of the color adjustment IDs corresponding to the reference gradation values in a plurality of stages, and converts the image data into the print data. After conversion, the printer 20 is controlled to print. In this way, by using the LUT in which a plurality of color adjustment IDs are reflected, the image data is converted at once to the corrected print data, so that the conversion process can be speeded up. The generated print data is data corrected based on the correspondence determined for each of the plurality of error information corresponding to the plurality of levels of gradation data. Therefore, the color adjustment ID is set for each ink type. The printer 20 forms ink dots on the print medium while performing finer error compensation with respect to the ink amount error, compared to the conventional case where only one is prepared.
[0032]
  The print control unit U3 includes a resolution conversion unit, a color conversion unit, a halftone process, and a rasterization process unit (not shown).
  The resolution conversion unit inputs image data and converts the resolution of the image data in accordance with the resolution of the printer 20. The image data to be input is data in which an image is expressed by a large number of pixels in a dot matrix, and there are various types. For example, image data composed of RGB defined in the sRGB color space, image data composed of luminance (Y component), B color difference (U component), and R color difference (V component) in the YUV color system. Etc. Each component of the image data has various gradation numbers, for example, 256 gradations and 1024 gradations. Therefore, the image data is converted into RGB data of 256 gradations (integer values of 0 to 255) for each RGB in the wide-range RGB color space in accordance with definitions such as sRGB and YUV color system.
[0033]
  The color conversion unit refers to the modified LUT while referring to the modified LUT while sequentially moving the target pixel using the gradation data of each pixel constituting the RGB data as the conversion target, and converting the RGB data to the level corresponding to each usage amount of the CMYKLcLm ink. Color conversion to CMYKLcLm data composed of tone data is performed. The CMYKLcLm data is also data of 256 gradations (an integer value of 0 to 255) for each CMYKLcLm. As shown in FIG. 5, the LUT stores gradation data for each CMYKLcLm and is stored in the HD 14, and on the premise of interpolation calculation, a large amount of data corresponding to, for example, 17 each of RGB, that is, 17 3 grid points It has. In the figure, the RGB data is shown in the LUT for easy understanding, but actually, the RGB data is converted to CMYKLcLm by referring to the data for 48 bits of CMYKLcLm from the address corresponding to each gradation data constituting the RGB data. It is designed to convert to data. If CMYKLcLm data matching the input RGB data is not stored in the LUT, CMYKLcLm data corresponding to a plurality of RGB data close to the input RGB data is acquired, and CMYKLcLm data is obtained by interpolation such as volume interpolation. Is calculated.
[0034]
  The halftone processing unit performs halftone processing by an error diffusion method or the like, and converts 256 gradation CMYKLcLm data into 2 gradations corresponding to the printing dots of the printer 20. The rasterization processing unit performs rasterization processing for rearranging the bit data of CMYKLcLm data having two gradations based on the scanning width of the print head 25 of the printer, and outputs the processed CMYKLcLm data to the printer 20. . The CMYKLcLm data is CMYKLcLm ink usage data, and the printer 20 can print an image based on the print data when the CMYKLcLm data, which is print data, is obtained and the corresponding ink is ejected onto the medium. In this way, printing control can be performed on the printer 20. The printing control means U3 and the printer 20 constitute printing means.
  When outputting CMYKLcLm data to a printer capable of executing halftone processing or rasterization processing, CMYKLcLm data can be output to the printer without performing these processes.
[0035]
(3) Processing performed by the print control apparatus:
  FIG. 7 is a flowchart showing a modified LUT creation process performed by the print control apparatus. This flow is performed when the printer driver for the printer 20 is installed.
  First, a request for obtaining a color adjustment ID is created by the error acquisition means and transmitted to the printer 20 (step S105; hereinafter, description of “step” is omitted). Then, the printer 20 receives the acquisition request, reads all the IDs 1 to 3 of the color adjustment ID from the ROM 22 and transmits them to the PC 10. Therefore, the PC 10 acquires IDs 1 to 3 of the color adjustment ID and stores them in a predetermined area of the HD 14 (S110). As described above, since the color adjustment ID is integrated with the printer, the user of the printing system does not need to input the color adjustment ID separately even if the printer is changed, and the printing control apparatus is convenient.
[0036]
  Next, the correspondence relationship determining means determines the correspondence relationship between the gradation data before correction and the gradation data after correction for compensating the ink amount error, for each ink color and each reference gradation value ( S115). Here, the correspondence data before and after the correction of the reference gradation value for each color is determined using the arithmetic expression (1), and the correspondence table T1 as shown in the upper part of FIG. 6 is created.
  Thereafter, the LUT for the standard printer is read from the HD (S120). Since the CMYKLcLm gradation value before correction is stored in the LUT, the CMYKLcLm gradation value is corrected using the arithmetic expression (2) for linear interpolation with reference to the correspondence table T1. (S125). When the calculation result of the calculation formula (2) is larger than 255, it is replaced with the gradation value 255. Then, the corrected gradation value can be determined for all gradation areas of the gradation data so as to have the correspondence shown in the lower part of FIG.
[0037]
  Then, each gradation value corrected by the interpolation calculation is stored in a predetermined area of HD as a correction LUT shown in FIG. 5 (S130), and this flow is finished. Here, since the CMYKLcLm gradation values stored in the correction LUT reflect a plurality of color adjustment IDs corresponding to a plurality of stages of reference gradation values, the correction LUT uses the gradation data for each pixel. The table defines a correspondence relationship between the image data configured in (1) and the print data composed of corrected gradation data that finely compensates for an ink amount error for a plurality of reference points.
[0038]
  When the modified LUT is created, the printer 20 can be controlled to print using the modified LUT. FIG. 8 is a flowchart showing print control processing performed by the print control means.
  The APL has an APL printing function, and when the print execution menu displayed on the display 18a is selected by the APL printing function, this flow is started. First, image data representing an image to be printed is input (S205). The input image data includes image data captured by a digital camera or a scanner (not shown), image data recorded on the FD 16a, and the like. Note that it is not necessary to read the entire data all at once, and it may be partially read or only a pointer indicating a buffer area used for data transfer may be transferred.
[0039]
  Since there are various types of image data to be input, the image data is converted into 256 gradation RGB data in a wide RGB color space, and the resolution of the image data is converted in accordance with the resolution of the printer 20 (S210). Here, when the image data is lower than the print resolution, new data is generated between the adjacent image data by linear interpolation, and when the image data is higher than the print resolution, the data is thinned out at a certain rate. .
  Thereafter, with reference to the created correction LUT, the gradation data composed of RGB of each pixel constituting the image data is converted into gradation data composed of CMYKLcLm (S215). As described above, the generated CMYKLcLm data has gradation values corrected according to the correspondence determined for each of the plurality of color adjustment IDs corresponding to the three-stage reference gradation values.
[0040]
  Then, the CMYKLcLm data of 256 gradations is binarized by halftone processing (S220). Halftoning means that the gradation value of multi-tone CMYKLcLm data is reduced to a gradation value that the printer 20 can express for each pixel (reducing the number of gradations expressing a color). In the embodiment, the color is reduced to two gradations. Further, the two-tone CMYKLcLm data is rearranged by rasterization processing (S225). Finally, CMYKLcLm data is output to the printer 20 (S230), and this flow ends.
[0041]
  Then, the printer 20 obtains CMYKLcLm data, drives the print head 25 so that the ink amount corresponds to each gradation data, ejects ink onto the printing paper, and performs printing based on the CMYKLcLm data. Here, since the CMYKLcLm data reflects the color adjustment IDs corresponding to the three-step reference gradation values, the printer 20 performs fine error compensation according to the gradation data for the ink amount error. Ink dots are formed on the printing paper. Accordingly, the desired color is not sufficiently reproduced in a certain density region of the image printed on the printing paper as in the prior art, and it is possible to improve the color accuracy and further improve the image quality of the printed matter. Further, the three-stage reference gradation values are reduced by about a half when the order is changed from a large value to a small value, so that the three-step reference gradation values are reduced in steps of 1/2 according to the print head driving frequency. The error amount can be appropriately compensated, and the color accuracy can be improved more accurately.
[0042]
(4) Second embodiment:
  The print control device and the peripheral device that can execute the print control program of the present invention can have various configurations.
  For example, the printer may be integrated with a computer or may be a dedicated product that prints only a single color image. The flow described above may be partially or entirely executed by a printer or a dedicated image output device in addition to being executed in the PC.
  In addition to the above-described embodiment, a plurality of error information corresponding to a plurality of levels of gradation data can be acquired with various configurations. FIG. 9 is a flowchart showing a modified LUT creation process performed by the print control apparatus according to the second embodiment. Although the hardware configuration is substantially the same as that of the first embodiment, the printer 20 stores only the color adjustment ID corresponding to one predetermined reference gradation value (for example, 127) as usual. To do.
[0043]
  First, a request for obtaining a color adjustment ID is created and transmitted to the printer 20 (S305), and a color adjustment ID corresponding only to a predetermined reference gradation value is acquired and stored in a predetermined area of the HD 14 (S310). At this time, the printer 20 receives the color adjustment ID acquisition request, reads the color adjustment ID from the ROM 22, and transmits it to the PC 10.
  Next, patch print data for causing the printer 20 to print a plurality of darkness patches (reference images) corresponding to a plurality of gradation values that differ from each other (for example, 63) as another center. Is created (S315). At this time, in order to identify individual patches, data for printing information such as numbers corresponding to differences in gradation values, that is, the darkness of the patches is also created. Then, the patch print data is output to the printer 20 (S320). Then, the printer 20 obtains the patch print data, drives the print head 25, etc., and forms ink dots on the printing paper corresponding to a plurality of gradation values for each ink type, as shown in FIG. As a result, information such as a plurality of patches PA and numbers is printed.
[0044]
  After that, the color calorimeter 30 displays a message that the patch PA is urged to measure colors by color and density, and the colorimetric result comprising each Lab value in the Lab space is made to correspond to the color and density information. (S325). Accordingly, the operator of the PC performs an operation of sequentially pressing the color detection unit of the colorimeter 30 against the plurality of patches PA.
  When the color measurement result is obtained, based on the color measurement result, a gradation value corresponding to one of the plurality of printed patches PA is acquired as error information corresponding to the reference gradation value (S330). For example, a table in which the reference gradation value and each target Lab value are associated with each other in advance is stored in the HD 14, and the colorimetric result closest to each target Lab value is referenced with reference to this table (in Lab space). A gradation value corresponding to the color measurement result having the smallest color difference is acquired. Instead of performing the processes of S325 to S330, it is also possible to accept selection input of patch numbers for each color and acquire gradation values corresponding to the input patch number.
[0045]
  Then, the value of the color adjustment ID corresponding to the reference gradation value used as a reference for obtaining the error information is calculated (S335). Here, in this embodiment, if the reference gradation value used as a reference for acquiring error information is X and the gradation value acquired as error information corresponding to the reference gradation value is Y, it corresponds to the reference gradation value. The value ID of the color adjustment ID is calculated by the following formula.
    ID = 50 × X / Y (3)
  Thereafter, the modified LUT creation process similar to S115 to S130 shown in FIG. 7 is performed. That is, the correspondence between the gradation data before correction and the gradation data after correction for compensating for the ink amount error is determined for each ink color and for each reference gradation value (S340). Next, the printer standard machine LUT is read from the HD (S345), and the gradation value of CMYKLcLm is corrected using the calculation formula (2) for linear interpolation with reference to the correspondence table T1 (S350). . Then, each corrected gradation value is stored as a modified LUT in a predetermined area of HD (S355), and this flow is finished.
[0046]
  In this way, even if the printer does not store multiple pieces of error information corresponding to multiple levels of gradation data, the correspondence between the gradation data before correction and the corrected gradation data that compensates for ink amount errors The relationship can be determined for each of a plurality of error information corresponding to the reference gradation value made up of a plurality of stages by ink type. The created modified LUT shows the correspondence between the image data composed of the gradation data for each pixel of the image and the print data composed of the modified gradation data for finely compensating for the ink amount error. This table defines a plurality of reference points.
[0047]
(5) Third embodiment:
  When image data is input and printing control is started, a serial number (identification data) is obtained from the printing apparatus, and if it is determined that the printing apparatus is not changed, the printing control is continued and the printing apparatus is changed. When it is determined that there is a print, the printer standard machine LUT may be modified to perform print control.
  FIG. 11 is a flowchart illustrating print control processing performed by the print control apparatus according to the third embodiment. The hardware configuration is substantially the same as that of the first embodiment, and it is assumed that the serial No 22b stored in the printer ROM 22 is acquired from the printer 20 and stored in the HD 14 in association with the correction LUT.
[0048]
  First, image data representing an image to be printed is input by the print control means (S405). In the present embodiment, at this stage, the correspondence determination means creates a serial number acquisition request and transmits it to the printer 20 (S410). Then, the printer 20 receives the acquisition request, reads the serial number 22b from the ROM 22, and transmits it to the PC 10. Therefore, the PC 10 acquires the serial number 22b (S415), and determines whether or not it is the same as the serial number stored in the HD 14 (S420).
  If the condition is met, there is no need to create a modified LUT, so the process proceeds to S435.
[0049]
  If the condition is not satisfied, the modified LUT creation process shown in FIG. 7 is performed (S425). That is, the color acquisition IDs 1 to 3 are acquired from the printer 20 by the error acquisition means. Next, the correspondence determining means determines the correspondence between the gradation data before correction and the gradation data after correction that compensates for the ink amount error, for each ink color and each reference gradation value. Further, the LUT for the printer standard machine is read from the HD, the CMYKLcLm gradation value is corrected using the equation (2) for linear interpolation with reference to the correspondence table T1, and each corrected gradation value is The correction LUT is stored in a predetermined area of the HD.
  When the modified LUT is created, the serial number 22b acquired in S415 is stored in the HD 14 in association with the modified LUT (S430).
[0050]
  Thereafter, the print control means performs the same processing as S210 to S230 shown in FIG. That is, the resolution of the image data is converted (S435), and the RGB data is color-converted into CMYKLcLm data with reference to the created correction LUT (S440). Then, the CMYKLcLm data of 256 gradations is binarized by halftone processing (S445), the CMYKLcLm data binarized by rasterization processing is rearranged (S450), and the CMYKLcLm data is output to the printer 20 (S455). This flow ends.
  That is, the correction LUT is created only when the serial No acquired from the printer 20 is different from the stored serial No, and the frequency of creating the correction LUT from the LUT for the standard printer is reduced. Processing can be speeded up.
[0051]
(6) Fourth embodiment:
  The present invention is also applicable to an apparatus that performs print control on a printer that can change the size of ink dots. Referring to FIG. 3, in such a printer, the size of the ink droplet Ip is changed by changing the voltage application pattern to the piezo element PE. As a result, for example, three types of large, medium, and small dots are formed. When the print data is composed of gradation data that collectively represents the formation of three types of dots with different ink amounts, and the print data is converted into dot data that represents the dot type for each pixel, the printer supports the dot data. Thus, three types of dots having different ink amounts are formed on the printing paper.
[0052]
  FIG. 12 schematically shows color adjustment IDs stored in a printer that forms large, medium, and small dots. A plurality of color adjustment IDs are provided for each ink color, for each dot type, and for each of the three reference gradation values that have different values within the gradation area that the gradation data constituting the print data can take. ing. The color adjustment IDs in the figure correspond to the reference gradation values 63, 127, and 255 in the order of small dots, medium dots, and large dots in the order of IDsml1, IDmid1, IDlarge1 (for low gradation), IDsml2, IDmid2, and IDlarge2 ( Medium gradation), IDsml3, IDmid3, and IDlarge3 (for high gradation). The color adjustment ID is determined in the same manner as in the first embodiment, and is written in the ROM of the printer.
  That is, the weight of ink actually used at each reference gradation value for each color and dot type is measured, and the relative value when the weight (specification value) of ink used in the standard printer is 50 is color. It is set as an adjustment ID. When three types of large, medium, and small dots are formed using six colors of ink, since three levels are provided as reference gradation values, a color adjustment ID of 6 × 3 × 3 = 54 is written in the ROM. Then, the amount of ink variation represented by the color adjustment ID is compensated for each color, each dot type, and each gradation step, and accurate color reproduction is performed.
[0053]
  When print control is performed on the printer, the CMYKLcLm data of 256 gradations is “not formed” (for example, gradation value 0) and “small dot formation” is performed in the halftone process of S220 shown in FIG. "(Gradation value 1)," medium dot formation "(gradation value 2), and" large dot formation "(gradation value 3). At this time, as shown in parentheses in FIG. 5, the correction dot formation table is referred to and converted into dot data. In S215 before halftone processing is performed, the resolution-converted RGB data is converted into CMYKLcLm data composed of gradation data that collectively represents the formation of all types of dots.
  FIG. 13 is a flowchart showing the flow of halftone processing in this embodiment. This flow is performed for each CMYKLcLm.
[0054]
  Since the CMYKLcLm data generated by the color conversion processing in S215 is expressed in multiple gradations by a number of pixels in a dot matrix, first, the position of the target pixel of the halftone is set (S505). Next, the gradation value of the target pixel is acquired, and the large dot level data LL is read with reference to the dot formation table T2 shown in FIG. 14 (S510). The horizontal axis in FIG. 14 is the input gradation value (0 to 255) when all types of dots are expressed together, the left vertical axis is the dot recording rate (%), and the right vertical axis is the level data (0). ~ 255). The dot recording rate means the proportion of pixels in which dots are formed among the pixels in the region when a uniform region is reproduced according to a certain gradation value. Level data refers to data obtained by converting the dot recording rate into 256 levels from 0 to 255. For example, if the input gradation value is gr, the large dot level data is obtained as LL using the large dot curve. Actually, as shown in the upper left of the figure, the input tone value and the level data of each large, medium, and small dot are stored in the HD as a dot formation table T2, and the dot formation table T2 is referred to. Obtain level data. The dot formation table T2 can also be said to be a table that prescribes the correspondence between CMYKLcLm data and dot data that collectively represent the formation of all types of dots for large, medium, and small dots.
[0055]
  Thereafter, it is determined whether or not the large dot level data LL is greater than a predetermined threshold TL (S515). For example, when performing dot on / off determination by the dither method, the threshold TL is set to a different value for each pixel by a dither matrix such as 16 × 16.
  When the level data LL is larger than the threshold value TL, the converted gradation value is set to gradation value 3 meaning large dot formation (S520), and the process proceeds to S560.
  On the other hand, when the level data LL is equal to or smaller than the threshold value TL, the medium dot level data LM is read with reference to the dot formation table T2 from the acquired gradation value of the target pixel (S525). Then, it is determined whether the medium dot level data LM is greater than a predetermined threshold value TM (S530). The threshold value TM is also set to a different value for each pixel by a dither matrix different from that for large dots when performing dot on / off determination by the dither method.
[0056]
  If the level data LM is larger than the threshold value TM, the converted gradation value is set to gradation value 2 meaning medium dot formation (S535), and the process proceeds to S560.
  On the other hand, when the level data LM is equal to or lower than the threshold value TM, the small dot level data LS is read with reference to the dot formation table T2 from the acquired gradation value of the target pixel (S540). Then, it is determined whether or not the small dot level data LS is larger than a predetermined threshold value TS (S545). The threshold value TS is also set to a different value for each pixel by a dither matrix different from that for large and medium dots when performing dot on / off determination by the dither method.
[0057]
  If the level data LS is larger than the threshold value TS, the converted gradation value is set to gradation value 1 meaning small dot formation (S550), and the process proceeds to S560.
  On the other hand, when the level data LS is equal to or smaller than the threshold value TS, the converted gradation value is set to gradation value 0 meaning that no dot is formed (S555), and the process proceeds to S560.
  In S560, it is determined whether or not processing has been completed for all pixels. If the process has not been completed for all pixels, the processes of S505 to S560 are repeated, and this process is terminated when the process has been completed for all pixels.
  Thereafter, rasterization processing is performed in S225 to S230 in FIG. 8, and CMYKLcLm data is output to the printer 20.
[0058]
  In the present embodiment, by correcting the level data in the dot formation table T2, the ink amount error is compensated for each color, each dot type, and each reference gradation value. The process of correcting the dot formation table can be performed in the same manner as the correction LUT creation process shown in FIG. 7, and will be described with reference to FIG.
  First, a request for obtaining a color adjustment ID is generated by the error acquisition means and transmitted to the printer, and all the color adjustment IDs shown in FIG. 12 are acquired and stored in a predetermined area of HD (corresponding to S105 to S110). . At this time, the printer receives a request for obtaining a color adjustment ID, reads out the color adjustment ID for each color, each dot type, and each reference gradation value from the ROM, and transmits it to the PC 10.
[0059]
  Next, the correspondence between the gradation data before correction and the gradation data after correction that compensates for the error in the ink amount is determined by the correspondence determination means, according to ink color, dot type, and reference gradation. Determined by value (corresponding to S115). Here, correspondence data before and after the correction of the reference gradation value for each color is determined using the arithmetic expression (1), and a correspondence table T3 as shown in the upper part of FIG. 15 is created. The correspondence table T3 stores correspondence data before and after the correction of the reference gradation value corresponding to one of the combinations of the six color inks and the dot types (the example in the figure is a large cyan dot). It is.
[0060]
  Thereafter, a dot formation table for a standard printer is read from the HD (corresponding to S120). Since the CMYKLcLm gradation value before correction is stored in the dot formation table, the gradation value of CMYKLcLm is calculated using the equation (2) for linear interpolation with reference to the correspondence table T3. Correct (corresponding to S125). When the calculation result of the calculation formula (2) is larger than 255, it is replaced with the gradation value 255. Then, the corrected gradation values can be determined for all gradation areas of the gradation data so as to have the correspondence shown in the lower part of FIG. In the lower part of the figure, the correspondence before and after the correction of the gradation data corresponding to one of the combinations of the six color inks and the dots is shown in a graph format.
[0061]
  As a result, as shown in FIG. 16, the dot formation table is a table in which the level data is corrected for the same input gradation value. The example of FIG. 16 is a graph showing level data LL before and after correction of the dot formation table when the correspondence relationship before and after correction for the dot formation table for cyan large dots is expressed as the data shown in FIG. It is shown in the form. In the example of FIG. 15, when the level data before correction is the reference gradation value 63, the corrected data stored in the correspondence table T3 is 66. Therefore, the level data 63 before correction is the level data 66 in FIG. It is corrected to be (point P1). Points P2 and P3 also indicate the positions of the level data corrected in the same correspondence relationship, and the other level data are data corrected by the linear interpolation calculation.
[0062]
  Then, the corrected gradation values are stored in a predetermined area of HD as a corrected dot formation table (corresponding to S130), and this flow is finished. Here, since the CMYKLcLm gradation values stored in the correction dot formation table reflect a plurality of color adjustment IDs corresponding to a plurality of stages of reference gradation values, the correction dot formation table has 256 gradations. This table defines the correspondence between CMYKLcLm data and corrected dot data that finely compensates for ink amount errors for a plurality of gradation values for a plurality of types of dots.
  When the print control process described above is performed, the image data is input and converted into 256-tone CMYKLcLm data, and then the 256-tone CMYKLcLm data is classified by color with reference to the correction dot formation table by halftone processing. Convert to dot data by dot type. In other words, by using a dot formation table that reflects color adjustment IDs corresponding to multiple levels of gradation data, CMYKLcLm data of 256 gradations can be converted at once to the corrected dot data, and conversion processing can be performed. The speed can be increased. Thereafter, the rasterized processing is performed and the rearranged dot data is output to the printer.
[0063]
  Then, the printer obtains dot data for each CMYKLcLm and each dot type (4-level CMYKLcLm data), and the ink amount corresponding to each gradation data is obtained with reference to 256-level CMYKLcLm data. Printing is performed by driving the print head to eject ink onto the printing paper. Here, since the dot data reflects the color adjustment ID corresponding to the three-step reference gradation value, the printer performs fine error compensation according to the gradation data for the ink amount error for each dot type. Ink dots are formed on the printing paper. Accordingly, it is possible to improve the color accuracy of printing with a printing apparatus that can print by changing the size of the ink dots, and to further improve the quality of the printed matter.
[0064]
  In the present embodiment, the dot formation table corresponding to all large, medium, and small dots is corrected using a plurality of color adjustment IDs corresponding to each of a plurality of levels of gradation data. Only the dot formation table corresponding to the type of dot may be corrected. For example, among the dot formation tables for standard printers, 0 to 255 are stored in the large dot table as the gradation area that can be taken by the level data, and the gradation area is stored in the dot formation table for medium and small dots. In the case where gradation values in a narrower range are stored, only the dot formation table for large dots may be corrected in order to simplify the processing. Even in such a case, by using a plurality of color adjustment IDs corresponding to each of the gradation data of a plurality of stages, the ink amount error can be compensated finely for the dot type corresponding to the corrected dot formation table. Color accuracy can be improved.
[0065]
  In addition, as shown in the first to fourth embodiments, other than correcting the LUT or correcting the dot formation table based on the correspondence between the gradation data before and after correction determined for a plurality of error information. A configuration may be adopted in which an error in the ink amount is compensated by a technique. For example, after color conversion from RGB data to CMYKLcLm data of 256 gradations with reference to the printer standard machine LUT, the correspondence table T1 is referenced for each pixel of interest according to the correspondence shown in FIG. The CMYKLcLm data may be corrected by performing linear interpolation calculation.
  According to the present invention, according to various aspects, it is possible to provide a print control device, a print system, a print control program, and a medium thereof that can improve color accuracy and improve the quality of printed matter. It can also be applied as a printing control method.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a printing system including a printing control device and peripheral devices.
FIG. 2 is a block configuration diagram showing a block configuration of a printer together with a PC.
FIG. 3 is a cross-sectional view showing the structure of a piezo element PE and a nozzle Nz in cross-section.
FIG. 4 is a diagram schematically illustrating a plurality of color adjustment IDs.
FIG. 5 is a diagram schematically illustrating a configuration of a print control apparatus.
FIG. 6 is a diagram schematically showing the correspondence between gradation data of a plurality of stages and the gradation data of all gradations after interpolation calculation.
FIG. 7 is a flowchart showing a modified LUT creation process.
FIG. 8 is a flowchart illustrating print control processing.
FIG. 9 is a flowchart showing a modified LUT creation process in the second embodiment.
FIG. 10 is a diagram illustrating a plurality of patches printed on a printing paper.
FIG. 11 is a flowchart illustrating print control processing according to the third embodiment.
FIG. 12 is a diagram schematically illustrating color adjustment IDs stored in a printer that forms large, medium, and small dots in the fourth embodiment.
FIG. 13 is a flowchart showing halftone processing in the fourth embodiment.
FIG. 14 is a diagram showing a level data value for an input tone value in a dot formation table in a graph format.
FIG. 15 is a diagram schematically illustrating a correspondence relationship between gradation data of a plurality of levels and a gradation data of all gradations after interpolation calculation.
FIG. 16 is a graph showing level data values before and after correction with respect to an input gradation value.
[Explanation of symbols]
10 ... Personal computer
11 ... CPU
12 ... ROM
13 ... RAM
14 ... Hard disk
15 ... CD-ROM drive
17a-e ... Interface
18a ... Display
18b ... Keyboard
18c ... Mouse
20 ... Inkjet printer
22 ... ROM
22a ... Color adjustment ID
22b Serial number
25 ... Print head
26 ... ASIC
26a ... Head drive unit
30 ... Color measuring device
U1 ... Error acquisition means
U2 ... Correspondence determination means
U3: Print control means
T1, T3 ... correspondence table
T2 ... Dot formation table
PA ... Patch

Claims (11)

To the printing apparatus for forming ink dots on a printing medium corresponding to the grayscale data having the image Motobetsu that make up the print data, a print control apparatus that performs printing control,
An error acquisition means for expressing an error in the ink weight of the ink and acquiring a plurality of error information corresponding to gradation data of a plurality of stages;
Input image data representing an image, generate the print data for compensating the ink weight error from the image data based on a plurality of error information acquired by the error acquisition means, and perform the print control Printing control means ,
The plurality of error information is information corresponding to a plurality of levels of reference gradation values that are different in a gradation region that can be taken by the gradation data, and the reference gradation value is determined from a large value. A printing control apparatus, wherein the printing control apparatus is configured to decrease by approximately one half when the values are arranged in the order of small values . Based on the plurality of error information acquired by the error acquisition means, the correspondence between the gradation data before correction and the gradation data after correction for compensating the ink weight error is shown in each of the plurality of error information. Correspondence determination means for determining
2. The print control unit according to claim 1, wherein the print control unit generates the print data from the image data based on a correspondence relationship for each of the determined plurality of error information, and performs the print control. Print control device. The plurality of error information is stored in the printing apparatus,
The print control apparatus according to claim 2, wherein the error acquisition unit acquires the plurality of error information from the printing apparatus. Upper Symbol error acquisition unit, a plurality of reference images corresponding to a plurality of gradation values having different around any of the reference grayscale value is printed on the printing device, any of the printed plurality of reference images crab corresponding print control apparatus according to claim 2 or claim 3, characterized in that to obtain the error information the gradation value corresponding to the reference grayscale value was set to the center. Upper Symbol correspondence relationship determining means performs a linear interpolation from the corresponding relationship the reference grayscale value and the plurality of error information about the tone values other than the reference grayscale value of the grayscale data before the modification The printing control apparatus according to claim 4, wherein the printing control apparatus is determined by The print control means refers to the color conversion table that defines the correspondence between the print data and the image data in which the image is composed of gradation data for each pixel for a plurality of reference points. Converted to
6. The print control apparatus according to claim 2, wherein the correspondence relationship determining unit corrects the color conversion table based on a correspondence relationship for each of the plurality of error information. The printing apparatus stores identification data that can identify the printing apparatus,
The correspondence determining means can acquire the identification data from the printing apparatus and store it in correspondence with the corrected color conversion table, and the acquired identification data is different from the stored identification data. , Causing the error acquisition means to acquire the plurality of error information, determining the correspondence relationship based on the plurality of error information acquired, and determining the color conversion table based on the correspondence relationship for each of the plurality of error information. The print control apparatus according to claim 6, wherein the print control apparatus corrects the error. The print data is composed of gradation data that collectively represents the formation of a plurality of types of dots with different ink weights,
The printing apparatus is capable of forming a plurality of types of dots having different ink weights on the print medium in correspondence with dot data representing the types of dots for each pixel,
The print control means converts the image data from the image data to the print data and refers to the dot formation table that defines the correspondence between the print data and the dot data for each of the plurality of types of dots. Convert to dot data,
8. The print control apparatus according to claim 2, wherein the correspondence relationship determination unit corrects the dot formation table based on a correspondence relationship for each of the plurality of error information. To the printing apparatus for forming ink dots on a printing medium corresponding to the grayscale data having the image Motobetsu that make up the print data, a print control method for printing control,
An error acquisition step that represents an error in the ink weight of the ink and acquires a plurality of error information corresponding to the gradation data of a plurality of stages;
Input image data representing an image, generate the print data for compensating the ink weight error from the image data based on a plurality of error information acquired in the error acquisition step, and perform the print control A printing control process ,
The plurality of error information is information corresponding to a plurality of stages of reference gradation values that are different values within the gradation region that the gradation data can take, and the reference gradation value is determined from a large value. A printing control method, wherein the printing control method is configured to decrease by approximately one half when the values are arranged in the order of small values . A printing system for printing by forming ink dots on a printing medium corresponding to the grayscale data having the image Motobetsu that make up the print data,
An error acquisition means for expressing an error in ink weight of the ink and acquiring a plurality of error information corresponding to gradation data of a plurality of stages;
Printing means that inputs image data representing an image, generates the print data for compensating the ink weight error from the image data based on a plurality of error information acquired by the error acquisition means, and performs printing provided with a door,
The plurality of error information is information corresponding to a plurality of levels of reference gradation values that are different in a gradation region that can be taken by the gradation data, and the reference gradation value is determined from a large value. printing system characterized in that it is the smaller one of about 2 minutes when the order of smaller value. To the printing apparatus for forming ink dots on a printing medium corresponding to the grayscale data having the image Motobetsu that make up the print data, a print control program for realizing a function of performing printing control on a computer,
An error acquisition function that represents an error in the ink weight of the ink and acquires a plurality of error information corresponding to the gradation data of a plurality of stages,
Inputs image data representing an image, generates the print data for compensating the ink weight error from the image data based on a plurality of error information acquired by the error acquisition function, and performs the print control. Realize the print control function ,
The plurality of error information is information corresponding to a plurality of levels of reference gradation values that are different in a gradation region that can be taken by the gradation data, and the reference gradation value is determined from a large value. A printing control program characterized in that the printing control program is designed to be reduced by about a half when the values are arranged in the order of small values .

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