JP4044254B2 - Color conversion definition creation method, color conversion definition creation device, and color conversion definition creation program storage medium - Google Patents

Description

【００７２】
ここで、例えばＲ_SRGBを８ビットで表現したものをＲ_8bitで表記すると、
Ｒ_8bit＝２５５×１２．９２Ｒ_SRGB （０＜Ｒ_SRGB＜０．００３０４）
Ｒ_8bit＝２５５×１．０５５Ｒ_SRGB ^(1.0/2.4) −０．０５５（０．００３０４≦Ｒ_SRGB≦１）
となる。Ｇ_SRGB，Ｂ_SRGBを８ビットで表現したＧ_8bit，Ｂ_8bitも同様に、それぞれＧ_SRGB，Ｂ_SRGBから変換することができる。
【００７３】
もしくは、リバーサルフィルムのｃｍｙ濃度で定義される色空間を共通色空間として採用してもよい。共通色空間を定めると、その共通色空間における色表現領域が明確に定義される。
【００７４】
次に、図１〜図３に示すコンピュータシステム２０内で実行される色変換定義作成プログラムによる色変換定義作成方法について説明する。
【００７５】
図８は、コンピュータシステム２０内で実行される色変換定義作成プログラムによる色変換定義作成方法を示したフローチャートである。
【００７６】
ここでは、第１の座標変換過程（ステップａ１）、第２の座標変換（ステップａ２）、および第３の座標変換過程（ステップａ３）を経て色変換定義が作成される。第２の座標変換（ステップａ２）では、基本的には第１過程（ステップａ２２）が実行されるが、本実施形態では、一層高精度な色変換定義が作成されるよう、その第１過程の前段に第２過程（ステップａ２１）が置かれている。
【００７７】
以下、これらの各過程について順次説明する。
【００７８】
先ず図８のステップａ１では、図４を参照して説明したような、カラースキャナ１０用の入力プロファイルが参照され、カラースキャナに依存したＲＧＢ空間内の各座標点（ここではディスクリートに設定された各格子上の座標点）がデバイス非依存の共通色空間（例えばＬ^*ａ^*ｂ^*空間）にそれぞれ写像される。
【００７９】
図９は、図８のステップａ２１で実行される第２の座標変換過程における第２過程の説明図であり、Ｌ^*ａ^*ｂ^*空間におけるカラースキャナ１０の色表現領域およびカラープリンタ３０の色表現領域を示している。
【００８０】
ここでは、コンクリース変換（Ｖｏｎ Ｋｒｉｅｓ変換）を応用した順応変換が行なわれる。すなわち、ここでは、カラースキャナ１０で画像データに変換される前の原稿画像１１（図１参照）で表現される白（原稿画像１１の用紙の色）に相当する座標点Ｗ₁と、原稿画像１１として表現することのできる黒（例えば原稿画像１１がＲ，Ｇ，Ｂ３色それぞれに発色するリバーサルフィルムのとき、Ｒ，Ｇ，Ｂそれぞれが最も高濃度に発色した状態）に相当する座標点Ｂ₁が、それぞれカラープリンタ３０で出力されるプリント画像３１の白（そのプリント画像の用紙の色）相当する座標点Ｗ₃とそのカラープリンタ３０で出力することのできる黒（例えばそのカラープリンタ３１がＲ，Ｇ，Ｂ３色のインクで画像出力を行なうプリンタの場合、Ｒ，Ｇ，Ｂの各色のインクを最大量使って印刷した状態）に相当する座標点Ｂ₃に一致するように座標変換が行なわれる。
【００８１】
図９は、この座標変換過程を図示したものであり、先ず、図９（Ａ）に示す、カラースキャナの色表現領域１０２ａとカラープリンタの色表現領域３０２ａを、図９（Ｂ）に示すように、各黒点Ｂ₁，Ｂ₃が原点０（理論上の黒点）に一致するように平行移動する。これにより、先ず、カラースキャナの色表現領域１０２ｂの黒点とカラープリンタの色表現領域３０２ｂの黒点とが一致する。
【００８２】
次に、この平行移動後の、カラースキャナの色表現領域１０２ｂの白点Ｗ₁が、平行移動後の、カラープリンタの色表現領域３０２ｂの白点Ｗ₃に一致するように、すなわち図９（Ｂ）の直線Ｌ₁が直線Ｌ₃に一致するように、カラースキャナの色表現領域１０２ｂ全体について回転及び伸縮を伴う座標変換が行なわれる。
【００８３】
図９（Ｃ）は、この回転及び伸縮を伴う座標変換を行なった後の状態を示しており、カラースキャナの色表現領域は、図９（Ｂ）に示す色表現領域１０２ｂから図９（Ｃ）に示す色表現領域１０２ｃのように変換される。このとき、カラースキャナの色表現領域の白点Ｗ₁は、カラープリンタの色表現領域の白点Ｗ₃に一致する。
【００８４】
その後、図９（Ｄ）に示すように、図９（Ｃ）に示すように白点，黒点がそれぞれ一致した、カラースキャナの色表現領域１０２ｃを、カラープリンタのもともとの色表現領域、すなわち図９（Ａ）に示す、カラープリンタの色表現領域３０２ａの白点Ｗ₃，黒点Ｂ₃に一致する位置まで平行移動する。
【００８５】
こうすることにより、白点Ｗ₁，黒点Ｂ₁がカラープリンタの白点Ｗ₃，黒点Ｂ₃にそれぞれ一致した、カラースキャナの色表現領域１０２ｄを得ることができる。
【００８６】
以上の操作を式で示すと、以下のようになる。図９は、Ｌ^*ａ^*ｂ^*空間における色表現領域を示したが、コンクリース変換やそのコンクリース変換を応用した上記の順応変換はＸＹＺ空間で実行されることが多く、ここではＸＹＺ空間を想定して説明する。このＸＹＺ空間の各座標点はＬ^*ａ^*ｂ^*空間の各座標点とも対して対応する共通色空間の１つである。
【００８７】
図９（Ａ）に示すカラースキャナの色表現領域１０２ａの白点Ｗ₁，黒点Ｂ₁のＸＹＺ座標をそれぞれ（ＬＸＷ₁，ＬＹＷ₁，ＬＺＷ₁），（ＬＸＢ₁，ＬＹＢ₁，ＬＺＢ₁）とし、図９（Ａ）に示すカラープリンタの色表現領域３０２ａの白点Ｗ₃，黒点Ｂ₃のＸＹＺ座標をそれぞれ（ＬＸＷ₃，ＬＹＷ₃，ＬＺＷ₃），（ＬＸＢ₃，ＬＹＢ₃，ＬＺＢ₃）としたとき、図９（Ｂ）に示す各白点Ｗ₁，Ｗ₃に相当するＸＹＺ座標（ＬＸＷ₁’，ＬＹＷ₁’，ＬＺＷ₁’），（ＬＸＷ₃’，ＬＹＷ₃’，ＬＺＷ₃’）を、各式
ＬＸＷ₁’＝ＬＸＷ₁−ＬＸＢ₁
ＬＹＷ₁’＝ＬＹＷ₁−ＬＹＢ₁
ＬＺＷ₁’＝ＬＺＷ₁−ＬＺＢ₁ ……（１）
ＬＸＷ₃’＝ＬＸＷ₃−ＬＸＢ₃
ＬＹＷ₃’＝ＬＹＷ₃−ＬＹＢ₃
ＬＺＷ₃’＝ＬＺＷ₃−ＬＺＢ₃ ……（２）
により求め、白点Ｗ₁（ＬＸＷ₁’，ＬＹＷ₁’，ＬＺＷ₁’）が白点Ｗ₃（ＬＸＷ₃’，ＬＹＷ₃’，ＬＺＷ₃’）に一致するように回転及び伸縮するためのコンクリース（Ｖｏｎ Ｋｒｉｅｓ）マトリックスを作成する。
【００８８】
ここでは、このコンクリースマトリックスを、
ＶＫ＝［ＭＴＸ_VK］ ……（３）
と表記する。このコンクリースマトリックスは３行×３列のマトリックスとなる。
【００８９】
次に、図８のステップａ１でカラースキャナに依存したＲＧＢ空間内の座標点がＬ^*ａ^*ｂ^*空間に写像され、さらにＸＹＺ空間に変換された（あるいは、カラースキャナに依存したＲＧＢ空間から直接にＸＹＺ空間に写像された）多数の座標点を代表させて（Ｘ，Ｙ，Ｚ）で表わすと、
この（Ｘ，Ｙ，Ｚ）が
Ｘ１＝Ｘ−ＬＸＢ₁
Ｙ１＝Ｙ−ＬＹＢ₁
Ｚ１＝Ｚ−ＬＺＢ₁ ……（４）
により黒点補正（図９（Ｂ）参照）がなされ、次に
【００９０】
【数２】

【００９１】
によりコンクリース変換が行なわれ（図９（Ｃ）参照）、次に
Ｘ’＝Ｘ２−ＬＸＢ₃
Ｙ’＝Ｙ２−ＬＹＢ₃
Ｚ’＝Ｚ２−ＬＺＢ₃ ……（６）
により、黒点をカラープリンタの黒点に一致させるための補正（図９（Ｄ）参照）が行なわれる。
【００９２】
以上の演算を全ての座標点について行なうことにより、Ｌ^*ａ^*ｂ^*空間で表わしたときの図９（Ａ）に示すカラースキャナの色表現領域１０２ａが、白点、黒点がカラープリンタの色表現領域３０２ａの白点、黒点にそれぞれ一致した、図９（Ｄ）に示す色表現領域１０２ｄに変換される。
【００９３】
上記の順応変換をＸＹＺ空間で行なうと、順応変換前の黒点（図９（Ａ）の黒点Ｂ₁，Ｂ₃）の座標（Ｘ，Ｙ，Ｚ）がほぼ（０，０，０）に近く、したがって黒点の補正は数値を僅かに変化させるだけであって、（１）式，（２）式に従って白点の座標を移動させてもその移動量は僅かで済み、ＸＹＺ空間内の広い領域を使って順応変化を行なうことができる点で有利であるが、この順応変化は、必ずしもＸＹＺ空間で行なわなければならない訳でなく、Ｌ^*ａ^*ｂ^*空間で行なってもよく、あるいはその他の共通色空間で行なってもよい。
【００９４】
また、ここでは、白点と黒点との双方をそれぞれ一致させる順応変換について説明したが、色変換の精度は多少落ちるものの、簡単的には、黒点は考慮せずに白点のみ一致させるように順応変換を行なってもよい。
【００９５】
この白点のみ一致させる順応変換は、図９を参照して説明すると、図９（Ａ）に示す直線Ｌ₁’が直線Ｌ₃’に一致するとともに白点Ｗ₁が白点Ｗ₃に一致するような座標変換をいい、数式的には、（１）式，（２）式のように黒点の座標を引き算することなく、白点Ｗ₁（ＬＸＷ₁，ＬＹＷ₁，ＬＺＷ₁）が白点Ｗ₃（ＬＸＷ₃，ＬＹＷ₃，ＬＺＷ₃）に一致するように回転及び伸縮するためのコンクリースマトリックスを求め、（４）式のように、黒点の座標を引き算することなく、そのコンクリースマトリックスを使って（Ｘ，Ｙ，Ｚ）をそのまま変換することを意味する。
【００９６】
さらに、この順応変換は、例えばＣＲＴディスプレイ表示画面上の‘白’はかなり青みかかった白であり、そのＣＲＴディスプレイ表示画面に表示された画像をプリント出力する必要があるときのような、測色的にかなり離れた白を持つデバイス間での色変換の場合に必要となるが、例えば白い用紙上に記録された画像を図１に示す原稿画像１１としてカラースキャナ１０で画像データを得、カラープリンタ３０でも白い用紙上に画像を出力する場合のような、双方の‘白’がほぼ一致している場合、この順応変換、すなわち、図８の第２の座標変換過程の第２過程（ステップａ２１）は省略してもかまわない。
【００９７】
次に、図８に示すフローチャートの第２の座標変換過程中の第１過程（ステップａ２２）について、いくつかの例を説明する。
【００９８】
図１０は、その第１過程における座標変換の第１例の説明図、図１１は、その第１例のフローチャートである。図１０には、Ｌ^*ａ^*ｂ^*空間内のうちのＬ^*−ａ^*平面について明示されているが、これは図示の便宜上のものであって、実際には、Ｌ^*ａ^*ｂ^*空間内で３次元的な座標変換が行なわれる。図１０のみでなく、その後に説明する各種の例についても同様である。
【００９９】
ここでは、先ず、座標変換の基準となる座標変換基準座標点ｃが設定される。この座標変換基準座標点ｃは、経験的にあるいは所定の設定基準に従ってある程度任意に設定されるが、Ｌ^*ａ^*ｂ^*空間に写像されたカラースキャナの色変換領域１０２とカラープリンタの色表現領域３０２との共通領域内に設定される。さらに、座標変換基準座標点ｃは、その共通領域内であって、さらに本実施形態ではＬ^*軸（グレー軸）上に設定される。そうすることにより、以下の説明からわかるように、この座標変換基準座標点ｃは他の座標点にはマッピングされず、したがってグレーバランスを保ちやすいからである。ここでは例えば（Ｌ^*，ａ^*，ｂ^*）＝（５０，０，０）の点が座標変換基準座標点ｃとして設定される。
【０１００】
尚、図８のフローチャートの第２の座標変換過程（ステップａ２）に図９を参照して説明したような順応変換（ステップａ２１）を含むときは、Ｌ^*ａ^*ｂ^*空間に写像されたカラースキャナの色表現領域１０２は、その順応変換後の色表現領域を指すものとする。
【０１０１】
ここでは、マッピングを行なう対象となるＬ^*ａ^*ｂ^*空間上のカラースキャナの色表現領域１０２内の座標点を第１の座標点ｔとする。
【０１０２】
ここで、座標変換基準座標点ｃと第１の座標点ｔとを結ぶ直線を考え、その直線と、カラースキャナの色表現領域１０２の境界との交点を求める（図１１ステップｂ１）。ここではこの交点を第１の基準座標点ａと呼ぶ。
【０１０３】
図１１に示すフローチャートは、このようにして求めた第１の基準座標点ａが、図１０に示すように、Ｌ^*ａ^*ｂ^*空間に写像したカラープリンタの色表現領域３０２から外れている場合のフローチャートであり、この条件を満たすとき、さらに以下のように処理が進められる。
【０１０４】
上記のようにして求めた第１の基準座標点ａについて、Ｌ^*ａ^*ｂ^*空間からカラープリンタ３０に依存した出力ＲＧＢ空間に写像する（図１１ステップｂ２）。この出力ＲＧＢ空間に写像された第１の基準座標点をＰ₁とする。
【０１０５】
次に、出力ＲＧＢ空間において、その第１の基準座標点Ｐ₁の座標値をクリップすることにより、その出力ＲＧＢ空間のカラープリンタ３０の色表現領域の境界上にマッピングする（ステップｂ３）。このマッピングによりカラープリンタ３０の色表現領域の境界上に得られた点Ｐ₂を、今度はその出力ＲＧＢ空間からＬ^*ａ^*ｂ^*空間に写像する（ステップｂ４）。このＬ^*ａ^*ｂ^*空間内に写像された座標点を第２の基準座標点ｂとする（図１０参照）。
【０１０６】
次に、図１０に示す第１の基準座標点ａと第２の基準座標点ｂとの差分を表わす、第１の基準座標点ａを始点とし、第２の基準座標点を終点とする基本差分ベクトルｖを求め（ステップｂ５）、マッピングを行なおうとしている第１の座標点ｔを、その基本差分ベクトルｖの方向と同一方向に、座標変換基準座標点ｃと第２の基準座標点ｂとを結ぶ直線上まで移動させ、その点を、第１の座標点ｔがマッピングされた第２の座標点ｓとする（ステップｂ６）。
【０１０７】
このような座標変換が、Ｌ^*ａ^*ｂ^*空間に写像されたカラースキャナ１０の色表現領域１０２に含まれる座標点のうちの、ステップｂ１により求められた第１の基準座標点ａがカラープリンタの色表現領域３０２の外にある全ての座標点について行なわれる（ステップ７）。
【０１０８】
このように、図１０，図１１を参照して説明した座標変換は、その座標変換の方向を決めるにあたっては、すなわち基本差分ベクトルｖを求めるあたっては、出力ＲＧＢ空間を使って、カラースキャナの色表現領域の境界上の第１の基準座標点ａに対応する、カラープリンタの色表現領域の境界上の第２の基準座標点ｂを定めることにより行なわれ、実際のマッピングは、Ｌ^*ａ^*ｂ^*空間で行なわれる。
【０１０９】
すなわち、出力ＲＧＢ空間（デバイス依存の色空間）という人間の色の感覚に合致した色空間で座標変換（マッピング）の方向が定められるため、調子の不連続性や不自然な画像となってしまう恐れが極めて小さく抑えられ、かつ、実際の座標変換は、Ｌ^*ａ^*ｂ^*空間（共通色空間）で行なわれるため、色彩上高精度の座標変換（マッピング）が行なわれる。
【０１１０】
尚、図１０は、図示の都合上、２次元平面上で座標変換（マッピング）が行なわれるように描かれているが、実際には３次元的なマッピングが行なわれることは前述したとおりである。
【０１１１】
図１２は、図１０，図１１を参照して説明した座標変換の変形例を示す図である。
【０１１２】
ここでは、座標変換基準座標点ｃを取り巻く領域Ｄが設定され、座標変換基準座標点ｃと第１の基準座標点ａを結ぶ直線とその領域Ｄの境界との交点ｄを求め、第１の座標点ｔのマッピングにあたっては、その交点ｄと第２の基準座標点ｂとを結ぶ直線上の座標点ｓにマッピングされる。
【０１１３】
こうすることにより、領域Ｄという、座標が移動しない領域を設定することができる。前述したように、グレーバランスを保つためにはＬ^*軸（グレー軸）については座標を移動させないことが好ましい旨説明したが、この図１２に示すように領域Ｄを設定することにより座標を移動しない領域を任意に設定することができる。
【０１１４】
図１３は、図８に示すフローチャートの第１過程における座標変換の第２例の説明図、図１４は、その第２例のフローチャートである。
【０１１５】
ここでは、図１０，図１１を参照して説明した第１例と同様に、Ｌ^*軸（グレー軸）上に座標変換の基準となる座標変換基準座標点ｃが設定される。
【０１１６】
この座標変換基準座標点ｃと、座標変換の対象としている第１の座標点ｔとを結ぶ直線を考え、その直線と、Ｌ^*ａ^*ｂ^*空間に写像したカラースキャナ１０の色表現領域１０２の境界との交点を求める。その交点を第１の基準座標点と呼ぶ。ここで、このＬ^*ａ^*ｂ^*空間に写像したカラースキャナの色表現領域１０２は、図８のフローチャートの第２過程（ステップａ２）における順応変換が行なわれるときは、その順応変換後の色表現領域を指すものであることは前述したとおりである。
【０１１７】
図１３に示すフローチャートは、図１１に示すフローチャートとは異なり、このようにして求めた第１の基準座標点ａが、図１３に示すように、Ｌ^*ａ^*ｂ^*空間に写像したカラープリンタの色表現領域３０２の内部に存在する場合のフローチャートであり、この条件を満たすときさらに以下のように処理が進められる。
【０１１８】
上記のようにして求めた、カラースキャナの色表現領域の境界上の第１の基準座標点ａに対応する、カラープリンタの色表現領域の境界上の第２の基準座標点ｂを求める（ステップｃ２）。この第２の基準座標点ｂを求めるにあたっては、ここでは、図１３に示すように、第１の基準座標点ａがカラープリンタの色表現領域３０２の内部に存在するため、図１０，図１１を参照して説明した手法を使うことはできない。すなわち、第１の基準座標点ａがカラープリンタの色表現領域３０２の外に存在する場合と同様にして、その第１の基準座標点ａを出力ＲＧＢ空間に写像しても、その写像された第１の基準座標点は出力ＲＧＢ空間におけるカラープリンタの色表現領域の内部に位置することになり、前述したクリップの手法を使うことができないこととなってしまう。そこで、ここでは、以下のようにして、第２の基準座標点ｂが求められる。
【０１１９】
先ず、出力ＲＧＢ空間におけるカラープリンタの色表現領域（ガマット）の境界上の全ての点（点Ｐ₁で代表させる）について、出力ＲＧＢ空間からＬ^*ａ^*ｂ^*空間に写像し（ステップｃ２１）、さらにそのＬ^*ａ^*ｂ^*空間に写像された全ての点Ｐ₂を入力ＲＧＢ空間に写像する（ステップｃ２２）。次いで、その出力ＲＧＢ空間に写像された点Ｐ₃のうちの、入力ＲＧＢ空間上のカラースキャナの色表現領域から外れた点を、前述のように、例えばＲ，Ｇ，Ｂそれぞれについてマイナスの値を０に、２５５を越える値を２５５にクリップすることにより、そのカラースキャナの色表現領域の境界上にマッピングする（ステップｃ２３）。
【０１２０】
このようにして得られた、入力ＲＧＢ空間に写像され、さらにクリップされた全ての点Ｐ₄を、入力ＲＧＢ空間からＬ^*ａ^*ｂ^*空間に写像する（ステップｃ２４）。このようにしてＬ^*ａ^*ｂ^*空間に写像された点Ｐ₅のうち、第１の基準座標点ａに一致した、あるいは一致はしなくても最も近接した点Ｐ₅’を見つけ、出力ＲＧＢ空間の、カラープリンタの色表現領域の境界上の全ての点Ｐ₁のうち、その点Ｐ₅’を得る基になった点Ｐ₁’を見つけ、その点Ｐ₁’を第２の基準座標点ｂとする（ステップｃ２５）。
【０１２１】
このような手順を踏むことにより、図１３に示す基準座標点ａに対応する第２の基準座標点ｂを求めることができる。
【０１２２】
尚、図１４に示すフローチャートの場合、出力ＲＧＢ空間におけるカラープリンタの色表現領域の境界上の全ての点Ｐ₁について一律に入力ＲＧＢ空間に写像したが、図１３に示す、Ｌ^*ａ^*ｂ^*空間に写像したカラープリンタの色表現領域３０２の境界上の座標点のうち、Ｌ^*ａ^*ｂ^*空間に写像したカラースキャナの色表現領域１０２の色表現領域から食み出した部分の座標点のみ、入力ＲＧＢ空間に写像すればよく、あるいはその食み出した部分のうち、推測等により第２の基準座標点ｂの座標位置をさらに絞り込むことができるときは、その絞り込まれた領域内の座標点のみ入力ＲＧＢ空間に写像してクリップしてもよい。
【０１２３】
図１４に示すステップｃ２において、第２の基準座標点ｂが検出されると、図１１のフローチャートの場合と同様、図１３に示すように、第１の基準座標点ａから第２の基準座標点ｂに向かう基本差分ベクトルｖが求められ（ステップｃ３）、さらに図１０，図１１の第１例の場合と同様にして、第１の座標点に対応する第２の座標点が求められる（ステップｃ４）。
【０１２４】
このような座標変換が、Ｌ^*ａ^*ｂ^*空間に写像したカラースキャナの色表現領域１０２内の各座標点のうちの、ステップｃ１により求められた第１の基準座標点ａがカラープリンタの色表現領域３０２の内部に存在する全ての座標点について行なわれる（ステップｃ５）。
【０１２５】
図１５は、図１３，図１４を参照して説明した座標変換の第２例の変形例を示す図である。
【０１２６】
ここには、図１２と同様、座標変換基準座標点ｃを取り巻く領域Ｄが設定され、座標変換基準座標点ｃと第１の基準座標点ａとを結ぶ直線とその領域Ｄの境界との交点ｄが求められ、第１の座標点ｔは、その交点ｄと第２の基準座標点ｂとを結ぶ直線上の座標点ｓにマッピングされる。こうすることにより、座標を移動させない領域Ｄを設定することができる。
【０１２７】
図１６は、図１０，図１１を参照して説明した‘圧縮’と図１３，図１４を参照して説明した‘伸長’とを組み合わせて行なったマッピングの効果説明図である。
【０１２８】
Ｌ^*ａ^*ｂ^*空間上のカラースキャナの色表現領域１０２よりもＬ^*ａ^*ｂ^*空間上のカラープリンタの色表現領域３０２の方が広いラインＬＮ１上の座標点は，カラープリンタの色表現領域３０２を最大限使うように伸長され、カラースキャナの色表現領域１０２の方が広いラインＬＮ２上の各座標点は、カラープリンタ３０２の色表現領域３０２を最大限使うレベルまで圧縮される。これらの伸長、圧縮の方向は、デバイスに依存したＲＧＢ空間を利用して求めたものであるため、マッピングそのものはＬ^*ａ^*ｂ^*空間上で行なっても、調子の不連続や不自然な画像の発生が防止され、かつマッピングそのものはＬ^*ａ^*ｂ^*空間を行なうことから高精度のマッピングが行なわれている。また、カラースキャナの色表現領域１０２とカラープリンタの色表現領域３０２との広さが一致したラインＬＮ３上の各座標点は移動せずにそのままの色が保たれることになる。
【０１２９】
尚、ここで行なわれるマッピングは、図１６では図示の都合上Ｌ^*−ａ^*平面で行なわれるかのように描かれているが、３次元的に行なわれるものであることは前述した通りである。
【０１３０】
図１７は、図８に示すフローチャートの第１過程における座標変換の第３例の説明図、図１８は、その第３例のフローチャートである。ここで説明する第３例は、図１２，図１３を参照して説明した第２例の場合と同様、ステップｄ１で求め、これは第１の基準座標点ａ１が、Ｌ^*ａ^*ｂ^*空間に写像したカラープリンタの色表現領域３０２の内部に存在する場合の一例である。
【０１３１】
ここでも、前述の第１例および第２例と同様に、Ｌ^*軸（グレー軸）上に座標変換の基準となる座標変換基準座標点ｃを設定し、その座標変換基準座標点ｃと座標変換の対象としている第１の座標点ｔとを結ぶ直線を考え、その直線と、Ｌ^*ａ^*ｂ^*空間に写像したカラースキャナの色表現領域１０２の境界との交点を求め、その交点を第１の基準座標点ａ１とし、さらに、その直線と、Ｌ^*ａ^*ｂ^*空間に写像したカラープリンタの色表現領域３０２の境界との交点を求め、その交点を第３の基準座標点ａ２とする（ステップｄ１）。このＬ^*ａ^*ｂ^*空間に写像したカラースキャナの色表現領域１０２は、図８のフローチャートの第２過程（ステップａ２１）における順応変換が行なわれるときは、その順応変換後の色表現領域を指すものであることは、これまでの第１例、第２例の場合と同様である。
【０１３２】
次に、上記のようにして求めた第３の基準座標点ａ２をＬ^*ａ^*ｂ^*空間からスキャナに依存した入力ＲＧＢ空間に写像し（ステップｄ２）、その入力ＲＧＢ空間に写像した点Ｐ₁をその入力ＲＧＢ空間でクリップすることによりカラースキャナの色表現領域の境界上にマッピングし（ステップｄ３）、そのマッピングにより得られた点Ｐ₂をＬ^*ａ^*ｂ^*空間にマッピングする（ステップｄ４）。このようにして得られたＬ^*ａ^*ｂ^*空間の、カラースキャナの色表現領域１０２の境界上の点を第４の基準座標点ｂ２と呼ぶ。
【０１３３】
次に、第３の基準座標点ａ２から第４の基準座標点ｂ２に向かう差分ベクトルｖ１を求め（ステップｄ５）、第１の基準座標点ａ１を通りその差分ベクトルｖ１と平行な直線を考えて、その直線と、Ｌ^*ａ^*ｂ^*空間上のカラープリンタの色表現領域３０２の境界との交点を第２の基準座標点ｂ１とし、第１の基準座標点ａ１から第２の基準座標点ｂ１に向かう基本差分ベクトルｖを求める（ステップｄ６）。その後はこれまで説明した第１例、第２例と同様にして、第１の座標点ｔが、その第１の座標点ｔを基本差分ベクトルｖと平行に移動し、座標変換基準座標点ｃと第２の基準座標点ｂ１とを結んだ直線にぶつかった座標点（第２の座標点ｓ）にマッピングされる（ステップｄ７）。
【０１３４】
このような座標変換が、Ｌ^*ａ^*ｂ^*空間上のカラースキャナの色表現領域内の座標点のうちの、ステップｄ１において、Ｌ^*ａ^*ｂ^*空間上のカラープリンタの色表現領域３０２の内部に位置する第１の基準座標点ａ１が求められる全ての座標点について行なわれる（ステップｄ８）。
【０１３５】
この図１７，図１８に示す第３例は、Ｌ^*ａ^*ｂ^*空間上のカラースキャナの色表現領域１０２とカラープリンタの色表現領域３０２が大きくずれているとき、すなわち、差分ベクトルｖ１と基本差分ベクトルｖが大きく離れているときは誤差を持つが、それら２つのベクトルｖ１，ｖの距離が近く、それら２つのベクトルｖ１，ｖの間の誤差を無視できるときは、この第３例を採用することができ、図１３，図１４を参照して説明した第２例と比べ高速演算が可能となる。
【０１３６】
図１９は、図１７，図１８を参照して説明した座標変換の第３例の変形例を示す図である。
【０１３７】
ここには、図１２，図１５と同様、座標変換基準座標点ｃを取り巻く領域Ｄが設定され、座標変換基準座標点ｃと第１の基準座標点ａ１とを結ぶ直線と、その領域Ｄの境界との交点ｄが求められ、第１の座標点ｔは、交点ｄと第２の基準座標点ｂ１とを結ぶ直線上にマッピングされる。
【０１３８】
このようにして、座標移動が行なわれない領域Ｄを設定することができる。
【０１３９】
図２０は、図８に示すフローチャートの第１過程における座標変換の第４例の説明図、図２１はその第４例のフローチャートである。
【０１４０】
この第４例は、ステップｅ１で求められる第１の基準座標点ａがＬ^*ａ^*ｂ^*空間に写像したカラープリンタの色表現領域３０２の内部に存在するか、あるいはその色表現領域３０２から外れているかを考慮することなく適用することができる方法である。
【０１４１】
ここでも、前述の第１例〜第３例と同様に、Ｌ^*軸（グレー軸）上に座標変換基準座標点ｃを設定し、その座標変換基準座標点ｃと座標変換の対象としている第１の座標点ｔとを結ぶ直線を考え、その直線と、Ｌ^*ａ^*ｂ^*空間上のカラースキャナの色表現領域１０２の境界との交点を求め、その交点を第１の基準座標点ａとする（ステップｅ１）。
【０１４２】
次に、この第１の基準座標点ａをカラースキャナに依存した色空間である入力ＲＧＢ空間に写像する（ステップｅ２）。
【０１４３】
次に、このようにして入力ＲＧＢ空間に写像された入力ＲＧＢ空間上の点Ｐ₁の座標値に対応した座標値、典型的にはその点Ｐ₁の座標値と同一の座標値を持つ、カラープリンタに依存した色空間である出力ＲＧＢ空間上の座標点Ｐ₂を求める（ステップｅ３）。具体例を示すと、図２０に示す第１の基準座標点ａを入力ＲＧＢ空間に写像した点Ｐ₁の座標値を（Ｒ，Ｇ，Ｂ）＝（０，２５５，０）としたとき、同一の座標値（Ｒ，Ｇ，Ｂ）＝（０，２５５，０）を持つ出力ＲＧＢ空間上の点を点Ｐ₂とする。
【０１４４】
次にその出力ＲＧＢ空間上の点Ｐ₂を出力ＲＧＢ空間からＬ^*ａ^*ｂ^*空間に写像し、その写像された点を第２の基準座標点ｂとする（ステップｅ４）。
【０１４５】
第１の基準座標点ａはＬ^*ａ^*ｂ^*空間上のカラースキャナの色表現領域１０２の境界上の点であるため、この第１の基準座標点ａを入力ＲＧＢ空間に写像しても、その入力ＲＧＢ空間におけるカラースキャナの色表現領域の境界上の点（例えば上記の（Ｒ，Ｇ，Ｂ）＝（０，２５５，０））となる。
【０１４６】
これをそのまま、出力ＲＧＢ空間上の点とすると、出力ＲＧＢ空間上では今度はカラープリンタの色表現領域の境界上の点となり、その点をＬ^*ａ^*ｂ^*空間に写像して求めた第２の基準座標点ｂも、そのＬ^*ａ^*ｂ^*空間上のカラープリンタの色表現領域３０２の境界上の点となる。
【０１４７】
このようにして求めた第１の基準座標点ａから第２の基準座標点ｂに向かう基本差分ベクトルｖを求め（ステップｅ５）、第１の座標点ｔを通り、基本差分ベクトルｖと平行に引いた直線と、座標変換基準座標点ｃと第２の基準座標点ｂとを結ぶ直線との交点である第２の座標点ｓを求める（ステップｅ６）。
【０１４８】
上記の座標変換が、Ｌ^*ａ^*ｂ^*空間上のカラースキャナの色表現領域１０２の全域について順次行なわれる。
【０１４９】
図２２は、図２０，図２１を参照して説明した座標変換の第３例の変形例を示す図である。
【０１５０】
ここには、図１２，図１５，図１９の各例と同様、座標変換基準座標点ｃのまわりに領域Ｄが設定され、その領域Ｄ内はマッピングされないようにしている。領域Ｄ内がマッピングされないようにするための手法は、図１２，図１５，図１９の各例の場合と同様であり、説明は省略する。
【０１５１】
図２３は、図８に示すフローチャートの第１過程における座標変換の第５例の途中過程を示す図である。この図２３のみを考えると、これは本発明の実施形態ではなく、それと対比されるべき比較例に相当する。
【０１５２】
ここでは、Ｌ^*軸（グレー軸）上の座標変換基準座標点ｃと、座標変換の対象とされる第１の座標点ｔと結ぶ直線と、Ｌ^*ａ^*ｂ^*空間上のカラースキャナの色表現領域１０２との交点（第１の基準座標点ａ１）およびカラープリンタの色表現領域３０２との交点（第３の基準座標点ａ２）を求め、第１の基準座標点ａ１から第３の基準座標点ａ２に向かう差分ベクトルｖ２を求める。この差分ベクトルｖ２は、デバイス依存の色空間（入力ＲＧＢ空間あるいは出力ＲＧＢ空間）でのクリップ等のマッピングを経ることなく求められる差分ベクトルであり、このままでは本発明とは合致しない。
【０１５３】
この差分ベクトルｖ２を仮に本発明にいう基本差分ベクトルｖと考え、座標変換基準座標点ｃと第１の基準座標点ａ１との間の距離ｃａ１と、座標変換基準座標点ｃと第１の座標点ｔとの間の距離ｃｔとの比率をｃｔ／ｃａ１とし、差分ベクトルｖ２の長さを｜ｖ２｜としたとき、第１の座標点ｔを、差分ベクトルｖ２と同一方向に、（ｃｔ／ｃａ１）×｜ｖ２｜だけ移動させ、その点を座標変換後の第２の座標点ｓとする。こうすることによっても一応マッピングは可能であるが、マッピングの方向（差分ベクトルｖ２の方向）は、人間の色の感覚にあったデバイス依存の色空間上で求めた方向ではなく、このマッピングの手法は、人間の色の感覚が無視されて機械的に定められた方向であり、前述したように調子の不連続が生じたり不自然な画像となる可能性が高い手法である。
【０１５４】
図２４は、図８に示すフローチャートの第１過程における座標変換の第５例の説明図である。
【０１５５】
この図２４において、第１の基準座標点ａ１，第３の基準座標点ａ２，差分ベクトルｖ２は、図２３を参照して説明したものと同様である。また第２の基準座標点ｂは、前述の第１例〜第４例のいずれの手法で求めたものであってもよい。ここでは、第１の基準座標点ａ１から第２の基準座標点ｂに向かうベクトルを差分ベクトルｖ３と称する。
【０１５６】
この図２４に示す例では、このようにして求めた２つの差分ベクトルｖ２，ｖ３が方向に関し重み付け加算され、第１の基準座標点ａ１を通り、その重み付け加算により求められた方向に引いた直線と、Ｌ^*ａ^*ｂ^*空間上のカラープリンタの色表現領域３０２の境界との交点を第５の基準座標点ｅとして求め、第１の基準座標点ａ１から第５の基準座標点ｅに向かう差分ベクトルを基本差分ベクトルｖとする。
【０１５７】
第１の座標点ｔをマッピングするにあたっては、座標変換基準座標点ｃと第５の基準座標点ｅとを結ぶ直線と、第１の座標点ｔを通り基本差分ベクトルｖと平行に引いた直線との交点を、その第１の座標点ｔがマッピングされるべき第２の座標点ｓとする。
【０１５８】
ここで、２つの差分ベクトルｖ２，ｖ３の方向に関する重み付け係数をオペレータにより任意に可変できるようにしておくことで、本発明の手法による座標変換をその重み付け分だけ加味させたマッピングが可能となる。
【０１５９】
次に図８に戻り、第３の座標変換過程（ステップａ３）について説明する。
【０１６０】
この第３の座標変換過程（ステップａ３）では、Ｌ^*ａ^*ｂ^*空間上でカラースキャナの色表現領域１０２からカラープリンタの色表現領域３０２への座標変換（マッピング）が行なわれた後の、カラープリンタの色表現領域３０２内の各座標点が、図５を参照して説明した出力プロファイル（ここではカラープリンタ３０に適合したプロファイル）により、出力ＲＧＢ空間に写像される。
【０１６１】
このようにして、図８のフローチャートに従って、カラースキャナ１０に依存した入力ＲＧＢ空間の各座標点と、カラープリンタ３０に依存した出力ＲＧＢ空間の各座標点との対応関係が定義された、カラースキャナ１０とカラープリンタ３０とを結びつける色変換定義が作成される。
【０１６２】
図２５は、本発明の色変換定義作成装置の一実施形態を含む色変換定義作成／色変換装置の機能ブロック図である。
【０１６３】
この図２５に示す色変換定義作成／色変換装置は、図２，図３に示すパーソナルコンピュータ２０と、そのパーソナルコンピュータで実行されるプログラムとの結合により実現される。
【０１６４】
この図２５に示す色変換定義作成／色変換装置は、データ取得部３１０と、定義作成データ変換部３２０と、データ出力部３３０と、記憶部３４０と、指定部３５０とから構成されている。
【０１６５】
記憶部３４０には、複数種類の入力デバイスそれぞれに対応した複数種類の入力プロファイル３４１ａ，…，３４１ｍと、複数種類の出力デバイスそれぞれに対応した複数種類の出力プロファイル３４２ａ，…，３４２ｎと、複数種類の色変換定義３４３ａ，…，３４３ｐと、さらに、色変換定義作成プログラム３４４が記憶されている。
【０１６６】
入力プロファイル３４１ａ，…，３４１ｍのそれぞれは、各種の入力デバイスについて、基本的には図４を参照した作成方法により作成されたものである。尚、図１には、入力デバイスはカラースキャナ１０の一種類のみ示されているが、図２５の色変換定義作成／色変換装置には、汎用性を持たせるため、複数種類の入力デバイスそれぞれに対応する複数種類の入力プロファイルが用意されている。
【０１６７】
また、記憶部３４０に記憶された出力プロファイル３４２ａ，…，３４２ｎは、各種の出力デバイスについて、基本的には図５を参照して説明した作成方法により作成された出力プロファイルである。
【０１６８】
尚、入力プロファイルの場合と同様、図１には、出力デバイスとして一種類のカラープリンタ３０のみ示されているが、図２５の色変換定義作成／色変換装置は、出力デバイスに関しても汎用性を持たせるため、複数種類の出力デバイスそれぞれに対応する複数種類の出力プロファイルが用意されている。
【０１６９】
また、記憶部３４０に記憶された色変換定義３４３ａ，…，３４３ｐは、記憶部３４０に記憶された色変換定義作成プログラム３４４が定義作成／データ変換部３２０に読み出されて実行されることにより、図８およびその後の各図を参照して説明したようにして作成されたものであり、各色変換定義は、各入力プロファイルと各出力プロファイルとの各組合せに対応している。ここではこれらの色変換定義３４１ａ，…，３４１ｐは、それぞれＬＵＴ（Ｌｏｏｋ Ｕｐ Ｔａｂｌｅ）の形式にまとめられている。
【０１７０】
なお、この記憶部３４０は、ハードウェア上は、図３に示すハードディスク装置２１３の内部に設定されており、この記憶部３４０（図３に示すハードディスク装置）は、本発明の色変換定義作成プログラム記憶媒体の一実施形態にも相当する。
【０１７１】
指定部３５０では、入力デバイス、出力デバイス、および、色変換定義作成モードとデータ変換モードとの区別が指定される。この指定部３５０は、ハードウェア上は、図２，図３に示すキーボード２３あるいはマウス２４がその役割りを担っている。
【０１７２】
指定部３５０で、色変換定義作成モードが指定されるとともに、入力デバイスと出力デバイスが指定されると、記憶部３４０から色変換定義作成プログラム３４４が定義作成／データ変換部３２に読み出されて実行される。この色変換定義作成プログラム３４４は、図８を参照して説明した第１の座標変換過程、第２の座標変換過程（第２過程および第１過程）、および第３の座標変換過程のそれぞれ実行する部分から構成されており、前述したアルゴリズムに基づき、指定された入力デバイス（ここでは、図１に示すカラースキャナ１０とする）に応じた入力プロファイル（ここでは、入力プロファイル３４１ａとする）と、指定された出力デバイス（ここでは図１に示すカラープリンタ３０とする）に応じた出力プロファイル（ここでは出力プロファイル３４２ａとする）が参照されて、それらカラースキャナ１０とカラープリンタ３０との組合せに適合した色変換定義（ここでは色変換定義３４１ａとする）が作成される。この作成された色変換定義３４１ａは記憶部３４０に記憶される。
【０１７３】
このとき、指定部３５０から、色変換定義作成のための各種のパラメータ、例えば、第２の座標変換過程の第２過程を実行するか省略するか、あるいはその第２過程を実行する場合に白点と黒点との双方をそれぞれ一致させるか白点のみを一致させるか、図１０等に示す座標変換基準座標点ｃの座標値、図１２等に示す領域Ｄを設定するか否か、領域Ｄを設定する場合のその領域の指定、第２の座標変換過程の第１過程として各種の例を示したが、それら各種の例のうちのいずれのアルゴリズムを選択するか、図２４を参照して説明した重み付けの手法を採用する場合のその重み付け係数等を指定できるように構成し、様々なバリエーションの色変換定義を作成することができるようにすることが好ましい。
【０１７４】
また、指定部３１０からデータ変換モードが指定され、さらに入力デバイスおよび出力デバイスが指定されると（ここでは入力デバイス、出力デバイスとしてそれぞれ図１に示すカラースキャナ１０、カラープリンタ３０が指定されるものとする）、それら指定されたカラースキャナ１０およびカラープリンタ３０の組合せに適合した色変換定義３４１ａが読み出されて定義作成／データ変換部３２０に入力される。
【０１７５】
データ取得部３１０は、入力デバイスで得られた色データを受け取る役割りを担うものであり、ハードウェア上は、図３に示す入力インタフェース２１６がこれに相当する。
【０１７６】
また、データ出力部３３０は、定義作成データ変換部３２０で色変換された後の色データの出力を担うものであり、ハードウェア上は、図３に示す出力インタフェース２１７がこれに相当する。
【０１７７】
入力デバイス、例えば図１に示すカラースキャナ１０で得られた色データがデータ取得部３１０を経由して定義作成データ変換部３２０に入力されると、定義作成データ変換部３２０では、色変換定義３４３ａによる色データの変換が行なわれる。この変換後の色データはデータ出力部３３０を経由して、出力デバイス、例えば図１に示すカラープリンタ３０に向けて出力される。
【０１７８】
この定義作成データ変換部３２０による色データの変換は、本発明に特有な色変換定義作成方法により作成された色変換定義が参照された変換であり、色調子の優れた出力画像を得ることができる。
【０１７９】
ここで、図２５に示す色変換定義作成色変換装置において、記憶部３４０に記憶された複数の出力プロファイル３４２ａ，…，３４２ｍのうちの１つとして、図２，図３に示す画像表示装置２２に対応する出力プロファイルを用意しておき、定義作成データ変換部３２０で変換された後の色データに基づく画像をその画像表示装置２２の表示画面２２ａ（図２参照）上に表示し、かつ、指定部３５０（キーボード２３やマウス２４）に、データ変換モードにおいても色変換定義を補正する機能を持たせ、表示画面上に表示された画像を見ながら、その画像がより好ましい色調子を持った画像となるように色変換定義を補正できるように構成してもよい。
【０１８０】
図２６は、本発明の色変換定義作成プログラム記憶媒体のもう１つの実施形態を示す図である。
【０１８１】
図２５を参照して、図２５に示す色変換定義作成／色変換装置の記憶部３４０が本発明の色変定義作成プログラム記憶媒体の一実施形態に相当する旨説明したが、この図２６には、本発明の色変換定義作成プログラム記憶媒体のもう１つの例として、図３に示すＣＤ−ＲＯＭ１１０に、色変換定義作成プログラム３４４が記憶された例が示されている。このように、色変換定義作成プログラムを可搬型記憶媒体に記憶させて流通させてもよい。
【０１８２】
このような色変換定義作成プログラムを入手したユーザは、自分のパーソナルコンピュータにその入手した色変換定義作成プログラムをアップロードし、その色変換定義作成プログラムを使って、色調子の優れた色変換を行なうことのできる色変換定義を作成することができる。
【０１８３】
図２７は、ＣＤ−ＲＯＭに本発明の方法により作成された色変換定義が記憶された形態を示す図である。
【０１８４】
このように、本発明の色変換定義作成方法の実施による結果物としての色変換定義の方を可搬型記憶媒体に記憶させて流通させてもよい。
【０１８５】
尚、これまで説明した実施形態は、図１に示すようにカラースキャナ１０等の入力デバイスを用いて画像から画像データを得る系に本発明を適用した例であるが、本発明は、２種類の出力デバイス間における色変換にも適用することができる。
【０１８６】
例えば、ＣＲＴディスプレイ装置（出力デバイスの一例）の表示画面上に画像データに基づく画像を表示し、その表示画像と同じ画像をカラープリンタ（出力デバイスのもう１つの例）でプリント出力しようとするときは、そのＣＲＴディスプレイ装置に対応した色空間の、そのＣＲＴディスプレイ装置の色表現領域内で定義された画像データを、カラープリンタに対応した色空間の、そのカラープリンタの色表現領域内で定義される画像データに変換する必要があるが、このような場面においても本発明を適用することができる。
【０１８７】
【発明の効果】
以上説明したように、本発明によれば、共通色空間でガマットマッピングを行なったときに生じ易い調子の不連続や不自然な画像となってしまうことを避け、かつ色調子の優れた再生画像を得ることのできる色変換定義を作成することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態が適用された画像入力−色変換−画像出力システムの全体構成図である。
【図２】図１に１つのブロックで示すパーソナルコンピュータの外観斜視図である。
【図３】パーソナルコンピュータのハードウェア構成図である。
【図４】入力プロファイルの概念図である。
【図５】出力プロファイルの概念図である。
【図６】入力プロファイルと出力プロファイルとの双方からなる、従来の一例としての色変換定義を示す概念図である。
【図７】カラースキャナとカラープリンタの色表現領域の模式図である。
【図８】コンピュータシステム内で実行される色変換定義作成プログラムによる色変換定義作成方法を示したフローチャートである。
【図９】図８のステップａ２１で実行される第１の座標変換過程の第２過程の説明図である。
【図１０】第１過程における座標変換の第１例の説明図である。
【図１１】その第１例のフローチャートである。
【図１２】座標変換の第１例の変形例を示す図である。
【図１３】第１過程における座標変換の第２例の説明図である。
【図１４】その第２例のフローチャートである。
【図１５】座標変換の第２例の変形例を示す図である。
【図１６】‘圧縮’と‘伸長’とを組み合わせて行なったマッピングの効果説明図である。
【図１７】第１過程における座標変換の第３例の説明図である。
【図１８】その第３例のフローチャートである。
【図１９】座標変換の第３例の変形例を示す図である。
【図２０】第１過程における座標変換の第４例の説明図である。
【図２１】その第４例のフローチャートである。
【図２２】座標変換の第３例の変形例を示す図である。
【図２３】第１過程における座標変換の第５例の途中過程を示す図である。
【図２４】第１過程における座標変換の第５例の説明図である。
【図２５】本発明の色変換定義作成装置の一実施形態を含む色変換定義作成／色変換装置の機能ブロック図である。
【図２６】本発明の色変換定義作成プログラム記憶媒体のもう１つの実施形態を示す図である。
【図２７】ＣＤ−ＲＯＭに本発明の方法により作成された色変換定義が記憶された形態を示す図である。
【符号の説明】
１０ カラースキャナ
１１ 原稿画像
２０ パーソナルコンピュータ
２１ 本体装置
２２ 画像表示装置
２２ａ 表示画面
２３ キーボード
２４ マウス
２５ バス
３０ カラープリンタ
１００ フロッピィディスク
１１０ ＣＤ−ＲＯＭ
２１１ ＣＰＵ
２１２ 主メモリ
２１３ ハードディスク装置
２１４ ＦＤドライバ
２１５ ＣＤ−ＲＯＭドライバ
２１６ 入力インタフェース
２１７ 出力インタフェース
３１０ データ取得部
３２０ 定義作成／データ変換部
３３０ データ出力部
３４０ 定義記憶部
３４１ａ，…，３４１ｍ 入力プロファイル
３４２ａ，…，３４２ｎ 出力プロファイル
３４３，３４３ａ，…，３４３ｐ 色変換定義
３４４ 色変換定義作成プログラム
３５０ 指定部[0001]
BACKGROUND OF THE INVENTION
According to the present invention, for example, when image data obtained by an input device that obtains image data by inputting an image is output by an output device that outputs an image based on the image data, a suitable color tone can be obtained. Color conversion definition creating method, color conversion definition creating apparatus for creating a color conversion definition to be a basis for color conversion, and color conversion definition creating program for creating a color conversion definition for obtaining a suitable color tone The present invention relates to a conversion definition creating program storage medium.
[0002]
[Prior art]
For example, a color scanner that reads recorded images to obtain image data, or a DSC (digital still camera) that obtains image data by forming an image of a subject on a solid-state imaging device and reading the image is input. Various types of input devices for obtaining image data are known. In these input devices, the image data is represented by data in a fixed range such as 0 to 255 for each of the three colors R (red), G (green), and B (blue). There is a limit to the colors that can be expressed by numerical values within the determined range for each of the B3 colors, and even if the original image color has an extremely rich expression, it is once converted into image data using an input device. When converted, the image represented by the image data is limited to colors in a certain color expression area in the R, G, B color space.
[0003]
Also for output devices that output images based on image data, for example, photographic printers, electrophotographic systems, and inkjets that record images on photographic paper by exposing the photographic paper with laser light and developing the photographic paper Image display such as a printer that records images on paper by a method, a printer that rotates a rotary press to create a large amount of printed matter, a CRT display that displays images on the display screen based on image data, a plasma display, etc. Various types of output devices such as devices are known, and these output devices also have a color expression area corresponding to each output device, similar to the above-described input device. That is, the output device can be selected based on, for example, image data expressing three colors of R, G, and B and image data expressing four colors of C (cyan), M (magenta), Y (yellow), and K (black). However, the colors that can be expressed are within a range of 0 to 255 for each of the color expression areas (for example, R, G, and B) in the output device color space (for example, RGB space, CMYK space, etc.). The color expression area is limited to a numerical value). A color expression area in such an input device or output device is called a color gamut.
[0004]
Further, for example, even when there is certain image data (for example, image data representing (R, G, B) = (50, 100, 200)), the color of the image obtained based on the image data is the type of the output device. Varies by This point is the same between the input device and the output device, and the image data of (R, G, B) = (50, 100, 200) obtained by a certain input device is used as it is. In general, the color of the original image input by the input device does not match the color of the image output by the output device. Therefore, when reading an image with a certain input device to obtain image data and trying to reproduce the original image with a certain output device based on that image data, the image data obtained with the input device is directly used as the output device. Instead of sending, it is necessary to convert the image data between them. Here, attention is paid to the color of the image, and the conversion of the image data is referred to as color conversion (Gamut Mapping).
[0005]
As described above, the color expression area differs depending on each device, and even if the image data is numerically the same, the color expressed in each device is different. Therefore, in performing color conversion (gamut mapping), a common color space (Device Independent Data space) that does not depend on a device, for example, L^*a^*b^*Place the color space etc. in the middle, convert the image data on the color space depending on the input device obtained by the input device to the image data on the common color space, perform gamut mapping on the common color space, and the gamut A technique of converting image data after mapping into image data on a color space depending on the output device is employed (for example, Japanese Patent Laid-Open Nos. 60-105376 and 61-288862). JP-A-4-196675).
[0006]
[Problems to be solved by the invention]
As described above, gamut mapping is conventionally performed on a common color space. For example, L^*a^*b^*L in color space^*Axis, a^*Axis, b^*This is a mapping in a three-dimensional space consisting of three axes, and it can be mapped in any way with a large degree of freedom, but on the other hand, the degree of freedom is too large and the adjustment parameter for mapping Setting is difficult, and as a result, there is a high possibility that tone discontinuity (tone jumping or poor tone connection) will occur in the image after mapping, and the image will give an unnatural impression. There are many things.
[0007]
On the other hand, since the finally required image data is image data in a color space (output color space) depending on the output device, it is converted into image data on the output color space, and the output color space (for example, RGB space) In the above, for each of R, G, and B, for example, data that protrudes from the range of 0 to 255 is clipped to 0 for negative data and to 255 for data that exceeds 255, respectively. Have been proposed (Japanese Patent Laid-Open No. 2-214266 (compressed in CMY space), Japanese Patent Laid-Open No. 4-334267 (compressed by density)). Although this is a simple technique, it corresponds to an example of gamut mapping in the output color space.
[0008]
When gamut mapping is performed on this output color space, the output color space is a color space that matches the human color sensation, such as RGB, and therefore, a tone that tends to occur when gamut mapping is performed in the common color space. It is possible to avoid inconveniences such as discontinuity and an unnatural impression.
[0009]
However, the mapping in the output color space has a low degree of freedom because it is basically one-dimensional mapping for each of the three axes R, G, and B that defines the output color space. As described above, for each of R, G, and B, for example, data that protrudes from the range of 0 to 255 is simply clipped to 0 or 255, and the boundary of the color expression area (gamut) (0 for each of R, G, and B). (The surface of the cube with a numerical value of ˜255) is limited to the method of mapping, and in the vicinity of the boundary of the color expression area (color gamut), the accuracy is changed from the color expression area of one device to the color expression area of another device. There is a problem that it is difficult to map well.
[0010]
In view of the above circumstances, the present invention avoids inconveniences such as a discontinuity in tone and an unnatural impression image, and another device from one color expression region to another device in the vicinity of the boundary of the color expression region. Color conversion definition creating method, color conversion definition creating apparatus for creating color conversion definition capable of performing high-precision mapping in color expression area, color conversion definition creating apparatus, and color conversion definition creating program capable of creating such color conversion definition An object of the present invention is to provide a color conversion definition creating program storage medium in which is stored.
[0011]
[Means for Solving the Problems]
The color conversion definition creating method of the present invention that achieves the above object is as follows.
A first device in which a coordinate point in a color representation area of one device in a first color space depending on a first device that mediates between an image and image data is mapped to a common color space that is device-independent A first coordinate conversion process of converting to a coordinate point in the color expression area of
The coordinate point in the color representation area of the first device mapped in the common color space obtained by the first coordinate conversion process is used as the coordinate point in the color representation area of the second device mapped in the common color space. A second color conversion process to convert;
The coordinate point in the color representation area of the second device mapped to the common color space obtained by the second coordinate conversion process is converted to the coordinate point in the color representation area of the second device in the second color space. In the color conversion definition creating method for creating a color conversion definition that defines the correspondence between the coordinate points of the first color space and the coordinate points of the second color space by going through the third coordinate conversion process.
In the second coordinate conversion process, the first coordinate point in the color representation area of the first device mapped in the common color space is converted into the second coordinate in the color representation area of the second device mapped in the common color space. When converting to coordinate points,
Based on the first coordinate point, a first reference coordinate point is obtained in the color representation area of the first device mapped to the common color space;
Based on a first algorithm including coordinate operations in at least one of the first color space and the second color space, the second reference coordinate point corresponding to the first reference coordinate point is shared. Find the color representation area of the second device mapped to the color space,
A first step of obtaining a second coordinate point corresponding to the first coordinate point based on a second algorithm using a basic difference vector representing a difference between the first reference coordinate point and the second reference coordinate point. It is characterized by including.
[0012]
The color conversion definition creating method according to the present invention is based on the above-described first algorithm, that is, based on the algorithm including the coordinate operation in at least one of the first color space and the second color space. A coordinate point is obtained, and a basic difference vector connecting the first reference coordinate point and the second reference coordinate point is determined. That is, according to the color conversion definition creating method of the present invention, the direction of color conversion (gamut mapping) is determined in a device-dependent color space (first color space or second color space). Performed in a common color space.
[0013]
As described above, since the color conversion definition creating method of the present invention determines the direction of mapping in a color space suitable for a human sense depending on the device, it is easy to adjust the mapping characteristics and the present invention. In this color conversion definition creating method, actual mapping is performed in a device-independent common color space, so that high-accuracy mapping including the vicinity of the boundary of the color expression area of the device can be performed.
[0014]
Here, in the color conversion definition creating method of the present invention, the second coordinate conversion process includes
Based on the first coordinate point, the first reference coordinate point is obtained on the boundary of the color representation area of the first device mapped to the common color space,
It is preferable that the second reference coordinate point is obtained on the boundary of the second color expression area mapped to the common color space based on the first algorithm.
[0015]
It is easy to obtain the first reference coordinate point and the second reference coordinate point on each boundary of the color representation area of the first device and the color expression area of the second device, which are mapped to the common color space, respectively. In addition, a basic difference vector that serves as a guide for the direction of color conversion can be obtained.
[0016]
Here, in the color conversion definition creating method of the present invention,
The first process in the second coordinate transformation process is:
A predetermined coordinate transformation reference coordinate point in the common area of the color representation area of the first device mapped to the common color space and the color representation area of the second device mapped to the common color space, and the first coordinate point And the intersection of the first device color expression area mapped to the common color space as the first reference coordinate point,
If the first reference coordinate point is a coordinate point that is out of the color representation area of the second device mapped to the common color space, the first reference coordinate point is mapped to the second color space. Then, mapping on the boundary of the color expression area of the second device in the second color space, and mapping the coordinate points obtained by mapping onto the boundary to the common color space A coordinate point on the boundary of the color representation area of the second device mapped in the common color space obtained on the space is obtained as the second reference coordinate point;
An intersection of a straight line connecting the coordinate conversion reference coordinate point and the second reference coordinate point and a straight line passing through the first coordinate point and parallel to the direction of the basic difference vector is defined as the first coordinate. You may obtain | require as a 2nd coordinate point corresponding to a point.
[0017]
In addition, the first process in the second coordinate conversion process is as follows.
A predetermined coordinate transformation reference coordinate point in the common area of the color representation area of the first device mapped to the common color space and the color representation area of the second device mapped to the common color space, and the first coordinate point And the intersection of the first device color expression area mapped to the common color space as the first reference coordinate point,
When the first reference coordinate point is a coordinate point in the color representation area of the second device mapped in the common color space, the color representation area of the second device mapped in the common color space Of the boundary of the first device mapped to the common color space, the coordinate point of the portion outside the color representation area of the first device is mapped to the first color space, and the first device of the first color space The image is mapped onto the boundary of the color expression area, and the coordinate point obtained by mapping onto the boundary is mapped to the common color space to obtain a coordinate point in the common color space. A coordinate point that coincides with one reference coordinate point or is close to the first reference coordinate point in light of a predetermined criterion, and is mapped to the common color space corresponding to the coordinate point before undergoing the coordinate conversion process. Second device color representation A coordinate point on the boundary is obtained as the second reference coordinate point, a straight line connecting the coordinate conversion reference coordinate point and the second reference coordinate point, and the basic difference vector of the basic difference vector passing through the first coordinate point. An intersection point with a straight line drawn parallel to the direction may be obtained as a second coordinate point corresponding to the first coordinate point.
[0018]
Alternatively, the first process in the second coordinate transformation process is as follows:
A predetermined coordinate transformation reference coordinate point in the common area of the color representation area of the first device mapped to the common color space and the color representation area of the second device mapped to the common color space, and the first coordinate point And the intersection of the line representing the color representation area of the first device mapped to the common color space as a first reference coordinate point,
When the first reference coordinate point is a coordinate point in the color representation area of the second device mapped in the common color space, the straight line and the second device mapped in the common color space An intersection point with the boundary of the color expression area is obtained as a third reference coordinate point, and the third reference coordinate point is mapped to the first color space, and the color expression area of the first device in the first color space is determined. Mapping onto the boundary and mapping the coordinate point obtained by mapping onto the boundary to the common color space results in the fourth on the boundary of the color expression area of the first device mapped to the common color space. The second device mapped to the common color space, and a straight line parallel to the straight line connecting the third reference coordinate point and the fourth reference coordinate point passing through the first reference coordinate point. The intersection point with the boundary of the color expression area is obtained as the second reference coordinate point,
An intersection of a straight line connecting the coordinate conversion reference coordinate point and the second reference coordinate point and a straight line passing through the first coordinate point and parallel to the direction of the basic difference vector is defined as the first coordinate. You may obtain | require as a 2nd coordinate point corresponding to a point.
[0019]
Furthermore, the first process in the second coordinate conversion process is as follows.
A predetermined coordinate transformation reference coordinate point in the common area of the color representation area of the first device mapped to the common color space and the color representation area of the second device mapped to the common color space, and the first coordinate point And the intersection of the line representing the color representation area of the first device mapped to the common color space as a first reference coordinate point,
The first reference coordinate point is mapped to the first color space to obtain a coordinate point on the first color space, and a first coordinate value corresponding to the coordinate value of the coordinate point on the first color space is obtained. By calculating the coordinate point on the second color space and mapping the coordinate point on the second color space to the common color space, the mapping is performed on the common color space obtained on the common color space. A coordinate point on the boundary of the color expression area of the second device is obtained as the second reference coordinate point, a straight line connecting the coordinate conversion reference coordinate point and the second reference coordinate point, and the first coordinate point A point of intersection with a straight line drawn in parallel with the direction of the basic difference vector may be obtained as a second coordinate point corresponding to the first coordinate point.
[0020]
Here, in the various aspects for obtaining the second coordinate point corresponding to the first coordinate point, the first process in the second coordinate conversion process is performed by obtaining the coordinate in obtaining the second coordinate point. Instead of obtaining the intersection of a straight line connecting the conversion reference coordinate point and the second reference coordinate point and a straight line passing through the first coordinate point and parallel to the direction of the basic difference vector, the coordinate conversion reference coordinate point Passing through the intersection of the straight line connecting the first reference coordinate point and the boundary of the predetermined area including the coordinate conversion reference coordinate point and passing through the second reference coordinate point, and passing through the first coordinate point An intersection point with a straight line drawn parallel to the direction of the difference vector may be obtained as a second coordinate point corresponding to the first coordinate point.
[0021]
By doing so, it is possible to secure an area in which the mapped color is stored as it is around the coordinate reference coordinate point for mapping.
[0022]
In the above-described various aspects for obtaining the second coordinate point corresponding to the first coordinate point, the first process in the second coordinate conversion process includes the coordinate conversion reference coordinate point and the first coordinate point. And a third reference coordinate point that is an intersection of the second device color expression area mapped to the common color space, and a first reference coordinate point and a second reference coordinate point Instead of the reference difference vector representing the difference between the first reference coordinate point, the direction of the first difference vector representing the difference between the first reference coordinate point and the second reference coordinate point, and the first difference The straight line drawn in the direction obtained based on the direction of the second difference vector representing the difference between the reference coordinate point and the third reference coordinate point, and the color of the second device mapped to the common color space When the intersection point with the boundary of the conversion area is the fifth reference coordinate point, The vector representing the difference between the reference coordinate point of the coordinate point and the fifth or may be used as a reference difference vector.
[0023]
By doing so, the direction of mapping can be adjusted quite freely.
[0024]
Further, in the above-described various aspects for obtaining the second coordinate point corresponding to the first coordinate point, the first process in the second coordinate conversion process is performed by using a gray color of a common color space as a coordinate conversion reference coordinate point. It is preferable that a point on the axis is selected.
[0025]
The coordinate conversion reference coordinate point is not mapped and the color is stored as it is. Therefore, the gray balance can be preserved by taking the coordinate conversion reference coordinate point on the gray axis.
[0026]
In the color conversion definition creating method of the present invention,
In the second coordinate transformation process, the color of the second device in which the white coordinate point of the color representation area of the first device mapped to the common color space is mapped to the common color space before the first process. Using an adaptation transformation algorithm that transforms to match the white coordinate point of the representation area, the coordinate point in the color representation area of the first device mapped to the common color space is converted into the coordinate point by the adaptation transformation algorithm. Having a second process of converting to transformed coordinate points;
The first device in which the first process in the second coordinate conversion process is a coordinate point obtained by passing through the second process, and the coordinate point to be converted is mapped to a common color space. Preferably, the color expression area is converted by adopting a color expression area obtained by further converting the color expression area using an adaptive conversion algorithm.
[0027]
In this case, the second process in the second coordinate conversion process maps, as an adaptation conversion algorithm, white coordinate points of the color representation area of the first device mapped to the common color space to the common color space. The second device color image is matched with the white coordinate point of the color representation area of the second device, and the black coordinate point of the color expression region of the first device mapped to the common color space is mapped to the common color space. More preferably, it is a process of converting the coordinate points using an adaptive conversion algorithm for converting the color expression area so as to match the black coordinate points.
[0028]
Thus, after the white (or white and black) in the color expression area of the first device is matched with the white (or white and black) in the color expression area of the second device, the first process is executed. As a result, a color conversion definition for performing color conversion with higher accuracy can be created.
[0029]
In addition, the color conversion definition creating apparatus of the present invention that achieves the above-described object,
A first point in which a coordinate point in the color representation area of the first device in the first color space depending on the first device that mediates between the image and the image data is mapped to a common color space independent of the device A first coordinate conversion process for converting to a coordinate point in the color representation area of the device;
The coordinate point in the color representation area of the first device mapped in the common color space obtained by the first coordinate conversion process is used as the coordinate point in the color representation area of the second device mapped in the common color space. A second color conversion process to convert;
The coordinate point in the color representation area of the second device mapped to the common color space obtained by the second coordinate conversion process is converted to the coordinate point in the color representation area of the second device in the second color space. In the color conversion definition creating apparatus for creating a color conversion definition that defines the correspondence between the coordinate points of the first color space and the coordinate points of the second color space by going through the third coordinate conversion process.
In the second coordinate conversion process, the first coordinate point in the color representation area of the first device mapped in the common color space is converted into the second coordinate in the color representation area of the second device mapped in the common color space. When converting to coordinate points,
Based on the first coordinate point, a first reference coordinate point is obtained in the color representation area of the first device mapped to the common color space;
Based on a first algorithm including coordinate operations in at least one of the first color space and the second color space, the second reference coordinate point corresponding to the first reference coordinate point is shared. Find the color representation area of the second device mapped to the color space,
A first step of obtaining a second coordinate point corresponding to the first coordinate point based on a second algorithm using a basic difference vector representing a difference between the first reference coordinate point and the second reference coordinate point. It is characterized by including.
[0030]
Here, in the color conversion definition creating apparatus of the present invention,
In the second coordinate transformation process, the color of the second device in which the white coordinate point of the color representation area of the first device mapped to the common color space is mapped to the common color space before the first process. Using an adaptive transformation algorithm that transforms to match the white coordinate point of the representation area, the coordinate point in the color representation region of the first device mapped to the common color space is represented by the adaptive transformation algorithm. A second step of converting to a coordinate point converted by
The first device in which the first process in the second coordinate conversion process is a coordinate point obtained by passing through the second process, and the coordinate point to be converted is mapped to a common color space. Preferably, the color expression area is converted by adopting a color expression area obtained by further converting the color expression area using an adaptive conversion algorithm.
[0031]
In this case, the second process in the second coordinate conversion process maps, as an adaptation conversion algorithm, white coordinate points of the color representation area of the first device mapped to the common color space to the common color space. The second device color image is matched with the white coordinate point of the color representation area of the second device, and the black coordinate point of the color expression region of the first device mapped to the common color space is mapped to the common color space. More preferably, it is a process of converting the coordinate points using an adaptive conversion algorithm for converting the color expression area so as to match the black coordinate points.
[0032]
Note that the color conversion definition creating apparatus of the present invention includes all the various modes corresponding to all the modes in the above-described color conversion definition creating method of the present invention.
[0033]
Furthermore, the color conversion definition creating program stored in the color conversion definition creating program storage medium of the present invention that achieves the above-described object,
A first point in which a coordinate point in the color representation area of the first device in the first color space depending on the first device that mediates between the image and the image data is mapped to a common color space independent of the device A first coordinate conversion process for converting to a coordinate point in the color representation area of the device;
The coordinate point in the color representation area of the first device mapped in the common color space obtained by the first coordinate conversion process is used as the coordinate point in the color representation area of the second device mapped in the common color space. A second color conversion process to convert;
The coordinate point in the color representation area of the second device mapped to the common color space obtained by the second coordinate conversion process is converted to the coordinate point in the color representation area of the second device in the second color space. A color conversion definition creating program for creating a color conversion definition that defines the correspondence between the coordinate points of the first color space and the coordinate points of the second color space is stored through the third coordinate conversion process. In the color conversion definition creation program storage medium
In the second coordinate conversion process, the first coordinate point in the color representation area of the first device mapped in the common color space is converted into the second coordinate in the color representation area of the second device mapped in the common color space. When converting to coordinate points,
Based on the first coordinate point, a first reference coordinate point is obtained in the color representation area of the first device mapped to the common color space;
Based on a first algorithm including coordinate operations in at least one of the first color space and the second color space, the second reference coordinate point corresponding to the first reference coordinate point is shared. Find the color representation area of the second device mapped to the color space,
A first step of obtaining a second coordinate point corresponding to the first coordinate point based on a second algorithm using a basic difference vector representing a difference between the first reference coordinate point and the second reference coordinate point. It is characterized by including.
[0034]
Here, in the color conversion definition creation program,
In the second coordinate conversion process, the color of the second device in which the white coordinate point of the color representation area of the first device mapped to the common color space is mapped to the common color space before the first process. Using an adaptive transformation algorithm that transforms to match the white coordinate point of the representation area, the coordinate point in the color representation region of the first device mapped to the common color space is converted into the coordinate point by the adaptation transformation algorithm. Having a second process of converting to transformed coordinate points;
The first process in the second coordinate conversion process is the first device in which the coordinate point obtained through the second process is a conversion target, and the conversion target coordinate point is mapped to the common color space. It is preferable that instead of the color expression area, the color expression area is further converted by adopting a color expression area obtained by conversion using an adaptive conversion algorithm.
[0035]
In this case, the second process in the second coordinate conversion process is performed by mapping, as an adaptation conversion algorithm, white coordinate points of the color representation area of the first device mapped to the common color space to the common color space. The second coordinate point is made to coincide with the white coordinate point of the color representation area of the second device and the black coordinate point of the color expression area of the first device mapped to the common color space is mapped to the common color space. It is further preferable that the coordinate point is converted by using an adaptation conversion algorithm that converts the coordinate point to match the black coordinate point of the device color expression area.
[0036]
In the color conversion definition creating program storage medium of the present invention, the color conversion definition creating program stored in the color conversion definition creating program storage medium includes all the aspects of the color conversion definition creating method of the present invention described above. All the corresponding various aspects are included.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0038]
FIG. 1 is an overall configuration diagram of an image input-color conversion-image output system to which an embodiment of the present invention is applied.
[0039]
Here, a color scanner 10 is shown. The color scanner 10 reads an original image 11 and generates RGB three-color image data. The RGB image data is input to the personal computer 20. In the personal computer 20, image data obtained by the color scanner 10 is converted into RGB three-color image data for image output suitable for a color printer 30 described later. The image data for image output is input to the color printer 30, and the color printer 30 performs print output based on the input image data to form a print image 31.
[0040]
Here, the personal computer 20 also serves as an embodiment of the color conversion definition creating apparatus according to the present invention. In the personal computer 20, the color conversion definition is created in advance and the image data obtained by the color scanner 10 is obtained. Is converted to image data for the color printer 30, the created color conversion definition is referred to. This color conversion definition and its creation method will be described later.
[0041]
In the system shown in FIG. 1, a color scanner that reads a document image and generates image data is shown as an example of an input device that inputs an image and obtains image data. In addition, for example, a DSC (digital still camera), a system that records images on a reversal film by taking a photograph using a reversal film, reads the recorded image with a color scanner or the like, and obtains other image data. Any device may be used as long as it can input and obtain image data.
[0042]
In the system shown in FIG. 1, a color printer 30 is shown as an example of an output device that outputs an image based on image data. However, the color printer 30 may be an electrophotographic color printer, and may be an inkjet system. The color printer may be a printer of a type that develops the photographic paper by exposing the photographic paper with modulated laser light, and does not ask what the printing method is. The output device is not limited to a printer, and may be a printing machine, or an image display device such as a CRT display device or a plasma display device that displays an image on a display screen. .
[0043]
However, here, a description will be given on the assumption that a system including the color scanner 10 and the color printer 30 is an example of an input device and an output device.
[0044]
Here, the feature of the system shown in FIG. 1 as an embodiment of the present invention resides in the processing contents executed inside the personal computer 20, and the personal computer 20 will be described below.
[0045]
2 is an external perspective view of the personal computer 20 shown as one block in FIG. 1, and FIG. 3 is a hardware configuration diagram of the personal computer 20. As shown in FIG.
[0046]
The personal computer 20 has an appearance configuration, a main body device 21, an image display device 22 that displays an image on a display screen 22a in accordance with an instruction from the main body device 21, and a main body device 21 in accordance with various key operations. A keyboard 23 for inputting information and a mouse 24 for inputting an instruction corresponding to, for example, an icon or the like displayed at that position by designating an arbitrary position on the display screen 22a are provided. The main body device 21 has a floppy disk loading slot 21a for loading a floppy disk and a CD-ROM loading slot 21b for loading a CD-ROM.
[0047]
As shown in FIG. 3, the main body device 21 includes a CPU 211 that executes various programs, a main memory 212 that is read out by a program stored in the hard disk device 213 and developed for execution by the CPU 211, and various programs. And FD driver 214 for accessing the floppy disk 100 loaded with the floppy disk 100 and the CD-ROM 110 for loading the floppy disk 100 and the CD-ROM for accessing the loaded CD-ROM 110. An output interface that is connected to the ROM driver 215 and the color scanner 10 (see FIG. 1), is connected to an input interface 216 that receives image data from the color scanner 10 and a color printer 30 (see FIG. 1), and sends image data to the color printer 30. Scan 217 is built, and these various elements, the image display device 22 further shown in FIG. 2, a keyboard 23, a mouse 24 are connected to each other via a bus 25.
[0048]
Here, the CD-ROM 110 stores a color conversion definition creation program for operating the personal computer 20 as a color conversion definition creation device, and the CD-ROM 110 is loaded into a CD-ROM driver 215. The color conversion definition creation program stored in the CD-ROM 110 is uploaded to the personal computer 20 and stored in the hard disk device 213.
[0049]
Next, a method for creating a color conversion definition by the color conversion definition creating program uploaded to the computer 20 will be described.
[0050]
FIG. 4 is a conceptual diagram of an input profile necessary for creating a color conversion definition.
[0051]
When the input profile can be obtained from the manufacturer of the color scanner 10 or the like, it is not necessary to create a new input profile. Here, a basic method for creating the input profile will be described.
[0052]
A color patch image made up of a number of color patches is prepared instead of the original image 11 shown in FIG. 1, and the color patch image is read by the color scanner 10, and an RGB space (first color according to the present invention) for each color patch is prepared. An example of a space) The above color data is obtained, and the original image is colorimetrically measured by a colorimeter. For each color patch, for example, L which is an example of a common color space^*a^*b^*Color data representing coordinate points in space is obtained. A detailed description of the common color space will be given later.
[0053]
In this way, coordinate points on the RGB color space and L^*a^*b^*An input profile in which the correspondence with the coordinate points on the color space is defined is obtained. This input profile is a profile depending on the input device, which differs depending on the type of color scanner 10 and, more generally, the type of input device.
[0054]
FIG. 5 is a conceptual diagram of an output profile necessary for creating a color conversion definition.
[0055]
An output profile corresponding to a color printer may be provided by the manufacturer of the color printer. If an output profile corresponding to the color printer to be printed can be obtained, it is not necessary to create an output profile. Here, a basic creation method when the output profile is newly created will be described.
[0056]
From the personal computer 20 shown in FIG. 1, color data in which the values of R, G, and B are sequentially changed is generated as RGB three-color color data, and a color patch image based on the color data thus generated is generated. Print out. Although the print image 31 shown in FIG. 1 is not an image representing a color patch image, it is assumed that a color patch image is printed out instead of the print image 31, and each color patch constituting the color patch image is measured. Measure with a colorimeter. By doing so, the coordinate values on the RGB color space (an example of the second color space in the present invention) and the common color space (here, L^*a^*b^*An output profile representing the correspondence with the coordinate values on the color space) is constructed.
[0057]
This output profile is a profile depending on the output device, which differs depending on the output device.
[0058]
FIG. 6 is a conceptual diagram illustrating a color conversion definition as an example of the related art, which includes both an input profile and an output profile.
[0059]
The input profile and output profile described with reference to FIGS. 4 and 5 are stored in the personal computer 20 shown in FIG. 1, and the RGB image data obtained by the color scanner 10 is as shown in FIG. L depending on the input profile^*a^*b^*Convert to image data in color space^*a^*b^*The image data in the color space is converted into RGB image data by the output profile and transmitted to the color printer. By doing so, the color printer 30 can obtain a print image 31 that reproduces the color expression of the original image 11. However, in this case, as described below, there is a problem that the color expression area (color gamut) of the color scanner 10 and the color expression area (color gamut) of the color printer 30 generally do not match.
[0060]
FIG. 7 is a schematic diagram of color expression areas of the color scanner 10 and the color printer 30.
[0061]
FIG. 7A shows an input RGB space which is a color space on the input side. In FIG. 7A, an RG plane is shown for simplicity of illustration. The same applies to FIG. 7B and FIG. 7C, and FIG.^*a^*b^*L of space^*-A^*FIG. 7C shows the RG plane of the output RGB space, which is the color space on the output side.
[0062]
The color scanner 10 converts the document image 11 into image data representing numerical values ranging from 0 to 255 for each of R, G, and B. In this case, the color expression area of the color scanner 10 is shown in FIG. The rectangular area 101 shown in FIG.
[0063]
Here, using the input profile created with reference to FIG. 4, the color expression area 101 of the color scanner 10 shown in FIG.^*a^*b^*When mapped onto a space, the color expression area of the color scanner 10 is represented as an area 102, and the color expression area 102 is further converted into a color space on the output side using the output profile described with reference to FIG. Is mapped to the output RGB space, the color expression area of the color scanner 10 is represented as shown in an area 103 shown in FIG.
[0064]
On the other hand, the color expression area of the color printer 30 shown in FIG. 1 is a cubic area (R (G, B) in the numerical range of 0 to 255 on the output RGB space shown in FIG. C) is a rectangular region 303) on the RG plane. That is, the original image 11 is read by the color scanner 10 and converted into image data in the input RGB space.^*a^*b^*When converted to image data in the output RGB space via the space, a value exceeding the color that can be expressed by the color printer 30 (range of 0 to 255 for both RGB in the image data), for example, FIG. (R, G) = (110, 290), or (R, G) = (− 100, 260). In this case, since these image data, that is, image data outside the color expression area of the color printer 30 cannot be output by the color printer 30, conventionally, as described above, these image data are used as the color of the color printer 30. It has been proposed to clip the image data to be located at the boundary of the expression area. Specifically, (R, G) = (110,290) is changed to (R, G) = (110,255), and (R, G) = (− 100,260) is changed to (R, G). ) = (0,255).
[0065]
In the case of mapping in such a color space depending on the output device, as described above, the degree of freedom of mapping is small, and the data out of the color expression area of the output device as described above is simply clipped and its color Mapping is performed only by moving to the boundary of the expression area, and particularly when mapping from the color expression area of one device (for example, the color scanner 10) to the color expression area of another device (for example, the color printer 30). In some cases, the accuracy of mapping in the vicinity of the boundary of the color expression area is greatly reduced.
[0066]
On the other hand, the color expression area 303 of the color printer 30 indicated by a rectangular area of 0 to 255 in FIG.^*a^*b^*When mapped to space, it is represented as a region 302 shown in FIG. This L^*a^*b^*Conventionally, in a common color space represented by a space, a number of methods for converting data in the color expression area 102 of the color scanner 10 (input device) into data in the color expression area 302 of the color printer 30 (output device). This has been proposed as described above.
[0067]
L^*a^*b^*In color conversion (mapping) in space, when a color expression area that can be expressed by the color printer 30 is to be widely used, generally, a color scanner as indicated by a dashed arrow in FIG. 'Compression', in which data out of the common area 402 of the ten color expression areas 101 and the color expression area 302 of the color printer 30 is mapped inside the common area 402, is indicated by a solid line arrow in FIG. As described above, the data in the common area 402 is both expanded and expanded outside the common area 402 while maintaining the condition that the data is in the color expression area 302 of the color printer 30.
[0068]
Previously proposed L^*a^*b^*Mapping in a common color space typified by space has a large degree of freedom in mapping, and as described above, there is a high risk that the tone will be discontinuous or an unnatural impression will result.
[0069]
L in FIG. 7 (B)^*a^*b^*When the color expression area 302 of the color printer 30 mapped to the space is further mapped to the input RGB space of FIG. 7A, there is a portion that protrudes from the rectangular area 101 that is the color expression area of the color scanner 10. It is expressed as a “shaped” region 301.
[0070]
Next, the common color space will be described. For this common color space, L^*a^*b^*We explained that color space is one example, but L^*a^*b^*The color space does not need to be a color space, and may be a color space defined so as not to depend on a specific input device or a specific output device. For example, L^*a^*b^*In addition to the color space, it may be an XYZ color space, or a coordinate system clearly defined so that each coordinate point on the color space is associated with the color space on a one-to-one basis. Good. An example of such a coordinate system is a standard RGB signal defined as follows.
[0071]
[Expression 1]

[0072]
Here, for example, R_SRGBIs expressed in 8-bit as R_8bitIs written as
R_8bit= 255 x 12.92R_SRGB    (0 <R_SRGB<0.00304)
R_8bit= 255 x 1.055R_SRGB ^{(1.0 / 2.4)}  −0.055 (0.00304 ≦ R_SRGB≦ 1)
It becomes. G_SRGB, B_SRGBG expressed in 8 bits_8bit, B_8bitSimilarly, each G_SRGB, B_SRGBCan be converted from
[0073]
Alternatively, a color space defined by the cmy density of the reversal film may be adopted as the common color space. When the common color space is defined, the color expression area in the common color space is clearly defined.
[0074]
Next, a color conversion definition creation method by the color conversion definition creation program executed in the computer system 20 shown in FIGS. 1 to 3 will be described.
[0075]
FIG. 8 is a flowchart showing a color conversion definition creation method by a color conversion definition creation program executed in the computer system 20.
[0076]
Here, the color conversion definition is created through the first coordinate conversion process (step a1), the second coordinate conversion process (step a2), and the third coordinate conversion process (step a3). In the second coordinate conversion (step a2), the first process (step a22) is basically executed. In the present embodiment, the first process is performed so that a more accurate color conversion definition is created. The second process (step a21) is placed in the previous stage.
[0077]
Hereinafter, each of these processes will be described sequentially.
[0078]
First, in step a1 of FIG. 8, the input profile for the color scanner 10 as described with reference to FIG. 4 is referred to, and each coordinate point in the RGB space depending on the color scanner (here, set to discrete). The coordinate point on each grid is a device independent common color space (for example, L^*a^*b^*Each space).
[0079]
FIG. 9 is an explanatory diagram of the second process in the second coordinate transformation process executed in step a21 of FIG.^*a^*b^*The color expression area of the color scanner 10 and the color expression area of the color printer 30 in the space are shown.
[0080]
Here, adaptation conversion is performed by applying concretion conversion (Von Kries conversion). That is, here, the coordinate point W corresponding to white (paper color of the document image 11) represented by the document image 11 (see FIG. 1) before being converted into image data by the color scanner 10.₁And black that can be expressed as the original image 11 (for example, when the original image 11 is a reversal film that develops colors of R, G, and B, respectively, R, G, and B are colored at the highest density). Coordinate point B₁Are coordinate points W corresponding to the white of the print image 31 output by the color printer 30 (the color of the paper of the print image)._ThreeAnd black that can be output by the color printer 30 (for example, if the color printer 31 outputs an image with R, G, and B color inks, the maximum amount of ink of each color of R, G, and B is used. Coordinate point B corresponding to (printed state)_ThreeCoordinate conversion is performed so as to match.
[0081]
FIG. 9 illustrates this coordinate conversion process. First, the color expression area 102a of the color scanner and the color expression area 302a of the color printer shown in FIG. 9A are shown in FIG. 9B. In addition, each sunspot B₁, B_ThreeIs translated so as to coincide with the origin 0 (theoretical black point). As a result, first, the black spot in the color expression area 102b of the color scanner matches the black spot in the color expression area 302b of the color printer.
[0082]
Next, the white point W of the color expression area 102b of the color scanner after this parallel movement.₁Is the white point W of the color expression area 302b of the color printer after translation._ThreeIn other words, that is, the straight line L in FIG.₁Is a straight line L_ThreeAre coordinate-transformed with rotation and expansion / contraction for the entire color expression area 102b of the color scanner.
[0083]
FIG. 9C shows a state after the coordinate conversion accompanied with the rotation and expansion / contraction, and the color expression area of the color scanner is changed from the color expression area 102b shown in FIG. 9B to FIG. The color expression area 102c shown in FIG. At this time, the white point W of the color expression area of the color scanner₁Is the white point W of the color expression area of the color printer._ThreeMatches.
[0084]
Thereafter, as shown in FIG. 9D, the color expression area 102c of the color scanner in which the white point and the black point match each other as shown in FIG. The white point W of the color expression area 302a of the color printer shown in FIG._Three, Sunspot B_ThreeTranslate to a position that matches.
[0085]
By doing this, the white spot W₁, Sunspot B₁Is the white point W of the color printer_Three, Sunspot B_ThreeThus, the color expression area 102d of the color scanner can be obtained.
[0086]
The above operation can be expressed as follows. FIG.^*a^*b^*Although the color expression area in the space is shown, the concise transformation and the adaptation transformation using the concree transformation are often executed in the XYZ space, and here, the XYZ space will be described. Each coordinate point of this XYZ space is L^*a^*b^*This is one of the common color spaces corresponding to the coordinate points of the space.
[0087]
The white point W of the color expression area 102a of the color scanner shown in FIG.₁, Sunspot B₁XYZ coordinates of (LXW₁, LYW₁, LZW₁), (LXB₁, LYB₁, LZB₁) And a white point W in the color expression area 302a of the color printer shown in FIG._Three, Sunspot B_ThreeXYZ coordinates of (LXW_Three, LYW_Three, LZW_Three), (LXB_Three, LYB_Three, LZB_Three), Each white point W shown in FIG.₁, W_ThreeXYZ coordinates (LXW₁', LYW₁', LZW₁′), (LXW_Three', LYW_Three', LZW_Three′) For each expression
LXW₁'= LXW₁-LXB₁
LYW₁'= LYW₁-LYB₁
LZW₁'= LZW₁-LZB₁          ...... (1)
LXW_Three'= LXW_Three-LXB_Three
LYW_Three'= LYW_Three-LYB_Three
LZW_Three'= LZW_Three-LZB_Three          (2)
The white spot W₁(LXW₁', LYW₁', LZW₁′) Is white point W_Three(LXW_Three', LYW_Three', LZW_ThreeCreate a Von Kries matrix to rotate and stretch to match ').
[0088]
Here, this concrete matrix is
VK = [MTX_VK] (3)
Is written. This concrete matrix is a matrix of 3 rows × 3 columns.
[0089]
Next, in step a1 in FIG. 8, the coordinate point in the RGB space depending on the color scanner is L.^*a^*b^*When represented by (X, Y, Z), a large number of coordinate points mapped to space and further converted to XYZ space (or mapped directly to XYZ space from RGB space depending on the color scanner) ,
This (X, Y, Z)
X1 = X-LXB₁
Y1 = Y-LYB₁
Z1 = Z-LZB₁          ...... (4)
To correct the black spot (see FIG. 9B).
[0090]
[Expression 2]

[0091]
The concrete conversion is performed by (see FIG. 9C),
X '= X2-LXB_Three
Y '= Y2-LYB_Three
Z '= Z2-LZB_Three          ...... (6)
Thus, correction (see FIG. 9D) for matching the black spot with the black spot of the color printer is performed.
[0092]
By performing the above calculation for all coordinate points, L^*a^*b^*The color expression area 102a of the color scanner shown in FIG. 9A when expressed in space corresponds to the white point and black point of the color expression area 302a of the color printer, respectively, as shown in FIG. 9D. The color expression area 102d shown in FIG.
[0093]
When the above-described adaptation conversion is performed in the XYZ space, the black spot before the adaptation conversion (black spot B in FIG.₁, B_Three) Coordinates (X, Y, Z) are close to (0, 0, 0), so the correction of the black point only changes the numerical value slightly, and the white point according to the equations (1) and (2) Even if the coordinates are moved, the amount of movement is small, and it is advantageous in that the adaptation change can be performed using a wide area in the XYZ space. However, this adaptation change is not necessarily performed in the XYZ space. L does not mean^*a^*b^*It may be performed in a space, or may be performed in another common color space.
[0094]
In addition, here, the adaptation conversion for matching both the white point and the black point has been described. However, although the accuracy of the color conversion is slightly reduced, for simplicity, only the white point is matched without considering the black point. Adaptation conversion may be performed.
[0095]
The adaptation conversion for matching only the white dots will be described with reference to FIG. 9. A straight line L shown in FIG.₁'Is a straight line L_Three'And white point W₁Is white spot W_ThreeIs a coordinate transformation such that the white point W is subtracted without subtracting the black point coordinate as in equations (1) and (2).₁(LXW₁, LYW₁, LZW₁) Is white spot W_Three(LXW_Three, LYW_Three, LZW_Three) To obtain a concretion matrix for rotation and expansion / contraction so as to match It means to convert as it is.
[0096]
Further, this adaptation conversion is performed when, for example, “white” on the CRT display display screen is a bluish white and the image displayed on the CRT display display screen needs to be printed out. This is necessary in the case of color conversion between devices having white that is considerably distant from each other. For example, an image recorded on white paper is used as a document image 11 shown in FIG. In the case where both of the whites are almost identical, as in the case where the printer 30 also outputs an image on white paper, this adaptation conversion, that is, the second process (step 2) of the second coordinate conversion process of FIG. a21) may be omitted.
[0097]
Next, some examples of the first process (step a22) in the second coordinate conversion process of the flowchart shown in FIG. 8 will be described.
[0098]
FIG. 10 is an explanatory diagram of a first example of coordinate transformation in the first process, and FIG. 11 is a flowchart of the first example. In FIG.^*a^*b^*L in space^*-A^*Although the plane is specified, this is for convenience of illustration, and in practice, L^*a^*b^*A three-dimensional coordinate transformation is performed in the space. The same applies not only to FIG. 10 but also to various examples described later.
[0099]
Here, first, a coordinate conversion reference coordinate point c that serves as a reference for coordinate conversion is set. This coordinate conversion reference coordinate point c is set to some extent empirically or according to a predetermined setting criterion.^*a^*b^*The color conversion area 102 of the color scanner mapped in the space and the color expression area 302 of the color printer are set in a common area. Further, the coordinate transformation reference coordinate point c is in the common area, and in this embodiment, L^*Set on the axis (gray axis). By doing so, as will be understood from the following description, this coordinate conversion reference coordinate point c is not mapped to other coordinate points, and therefore it is easy to maintain the gray balance. Here, for example, (L^*, A^*, B^*) = (50, 0, 0) is set as the coordinate conversion reference coordinate point c.
[0100]
If the second coordinate transformation process (step a2) in the flowchart of FIG. 8 includes the adaptation transformation (step a21) as described with reference to FIG.^*a^*b^*The color expression area 102 of the color scanner mapped in the space indicates the color expression area after the adaptation conversion.
[0101]
Here, L to be mapped^*a^*b^*A coordinate point in the color expression area 102 of the color scanner in space is defined as a first coordinate point t.
[0102]
Here, a straight line connecting the coordinate conversion reference coordinate point c and the first coordinate point t is considered, and an intersection of the straight line and the boundary of the color expression area 102 of the color scanner is obtained (step b1 in FIG. 11). Here, this intersection is called a first reference coordinate point a.
[0103]
In the flowchart shown in FIG. 11, the first reference coordinate point a obtained in this way is L, as shown in FIG.^*a^*b^*It is a flowchart in the case where it is out of the color expression area 302 of the color printer mapped in the space. When this condition is satisfied, the processing is further advanced as follows.
[0104]
For the first reference coordinate point a obtained as described above, L^*a^*b^*Mapping is performed from the space to the output RGB space depending on the color printer 30 (step b2 in FIG. 11). The first reference coordinate point mapped to this output RGB space is P₁And
[0105]
Next, in the output RGB space, the first reference coordinate point P₁Is then mapped onto the boundary of the color expression area of the color printer 30 in the output RGB space (step b3). The point P obtained on the boundary of the color expression area of the color printer 30 by this mapping.₂This time, from the output RGB space, L^*a^*b^*Map to space (step b4). This L^*a^*b^*A coordinate point mapped in the space is set as a second reference coordinate point b (see FIG. 10).
[0106]
Next, the first reference coordinate point a representing the difference between the first reference coordinate point a and the second reference coordinate point b shown in FIG. 10 is set as the start point, and the second reference coordinate point is set as the end point. The difference vector v is obtained (step b5), and the first coordinate point t to be mapped is set in the same direction as the direction of the basic difference vector v with the coordinate conversion reference coordinate point c and the second reference coordinate point. The point is moved to a straight line connecting b, and the point is set as a second coordinate point s to which the first coordinate point t is mapped (step b6).
[0107]
  Such coordinate transformation is represented by L^*a^*b^*Of the coordinate points included in the color expression area 102 of the color scanner 10 mapped in the space, the first reference coordinate point a obtained in step b1 is the first reference coordinate point a.Color printer color expression area 302For all coordinate points outside (step 7).
[0108]
As described above, the coordinate conversion described with reference to FIGS. 10 and 11 is performed when determining the direction of the coordinate conversion, that is, when obtaining the basic difference vector v, using the output RGB space. This is done by defining a second reference coordinate point b on the boundary of the color expression area of the color printer corresponding to the first reference coordinate point a on the boundary of the color expression area.^*a^*b^*Done in space.
[0109]
That is, the direction of coordinate transformation (mapping) is determined in a color space that matches the human color sense of the output RGB space (device-dependent color space), resulting in tone discontinuities and unnatural images. The fear is extremely small, and the actual coordinate transformation is L^*a^*b^*Since it is performed in a space (common color space), highly accurate coordinate conversion (mapping) is performed in terms of color.
[0110]
Note that FIG. 10 is drawn so that coordinate transformation (mapping) is performed on a two-dimensional plane for convenience of illustration, but as described above, three-dimensional mapping is actually performed. .
[0111]
FIG. 12 is a diagram illustrating a modification of the coordinate conversion described with reference to FIGS. 10 and 11.
[0112]
Here, a region D surrounding the coordinate conversion reference coordinate point c is set, and an intersection d between the straight line connecting the coordinate conversion reference coordinate point c and the first reference coordinate point a and the boundary of the region D is obtained. In mapping the coordinate point t, the coordinate point t is mapped to a coordinate point s on a straight line connecting the intersection d and the second reference coordinate point b.
[0113]
By doing so, it is possible to set an area D where the coordinates do not move. As described above, in order to maintain gray balance, L^*Although it has been described that it is preferable not to move the coordinates for the axis (gray axis), by setting the area D as shown in FIG. 12, it is possible to arbitrarily set an area where the coordinates are not moved.
[0114]
FIG. 13 is an explanatory diagram of a second example of coordinate transformation in the first step of the flowchart shown in FIG. 8, and FIG. 14 is a flowchart of the second example.
[0115]
Here, as in the first example described with reference to FIGS.^*A coordinate conversion reference coordinate point c that is a reference for coordinate conversion is set on the axis (gray axis).
[0116]
Consider a straight line connecting the coordinate conversion reference coordinate point c and the first coordinate point t to be subjected to the coordinate conversion.^*a^*b^*An intersection point with the boundary of the color expression area 102 of the color scanner 10 mapped to the space is obtained. The intersection is called a first reference coordinate point. Where L^*a^*b^*The color expression area 102 of the color scanner mapped onto the space indicates the color expression area after the adaptive conversion when the adaptive conversion is performed in the second process (step a2) of the flowchart of FIG. Just as you did.
[0117]
The flowchart shown in FIG. 13 is different from the flowchart shown in FIG. 11, and the first reference coordinate point a obtained in this way is L^*a^*b^*It is a flowchart in the case where it exists inside the color expression area 302 of the color printer mapped in the space. When this condition is satisfied, the processing is further advanced as follows.
[0118]
The second reference coordinate point b on the boundary of the color expression area of the color printer, which corresponds to the first reference coordinate point a on the boundary of the color expression area of the color scanner, determined as described above (step) c2). In obtaining the second reference coordinate point b, here, as shown in FIG. 13, the first reference coordinate point a exists inside the color expression area 302 of the color printer. The method described with reference to cannot be used. That is, even if the first reference coordinate point a is mapped to the output RGB space in the same manner as when the first reference coordinate point a exists outside the color expression area 302 of the color printer, the mapping is performed. The first reference coordinate point is located inside the color expression area of the color printer in the output RGB space, and the above-described clip method cannot be used. Therefore, here, the second reference coordinate point b is obtained as follows.
[0119]
First, all points (point P) on the boundary of the color printer color expression area (gamut) in the output RGB space.₁From the output RGB space.^*a^*b^*Map to space (step c21), and then L^*a^*b^*All points P mapped in space₂Is mapped to the input RGB space (step c22). Then, the point P mapped to the output RGB space_ThreeOf these, the points outside the color expression area of the color scanner in the input RGB space are clipped, for example, to a negative value of 0 for each of R, G, and B, and to 255 for a value exceeding 255, as described above. Thus, mapping is performed on the boundary of the color expression area of the color scanner (step c23).
[0120]
All the points P thus mapped and clipped to the input RGB space are obtained._FourL from the input RGB space^*a^*b^*Map to space (step c24). In this way L^*a^*b^*Point P mapped in space_FiveAmong these, the closest point P that coincides with or does not coincide with the first reference coordinate point a_Five'And find all points P on the boundary of the color printer's color representation area in the output RGB space₁Of that point P_FiveThe point P from which ′ was obtained₁Find ', and point P₁'Is the second reference coordinate point b (step c25).
[0121]
By following such a procedure, the second reference coordinate point b corresponding to the reference coordinate point a shown in FIG. 13 can be obtained.
[0122]
In the case of the flowchart shown in FIG. 14, all the points P on the boundary of the color expression area of the color printer in the output RGB space.₁Is uniformly mapped to the input RGB space, L shown in FIG.^*a^*b^*Among the coordinate points on the boundary of the color expression area 302 of the color printer mapped to the space, L^*a^*b^*Only the coordinate points of the portion projected from the color representation area 102 of the color representation area 102 of the color scanner mapped to the space may be mapped to the input RGB space, or the second portion of the projected portion may be estimated by estimation or the like. When the coordinate position of the reference coordinate point b can be further narrowed down, only the coordinate points within the narrowed region may be mapped to the input RGB space and clipped.
[0123]
When the second reference coordinate point b is detected in step c2 shown in FIG. 14, the second reference coordinate point a is changed from the first reference coordinate point a as shown in FIG. 13, as in the flowchart of FIG. A basic difference vector v toward the point b is obtained (step c3), and a second coordinate point corresponding to the first coordinate point is obtained in the same manner as in the first example of FIGS. Step c4).
[0124]
Such coordinate transformation is represented by L^*a^*b^*Of the coordinate points in the color expression area 102 of the color scanner mapped to the space, all the coordinate points where the first reference coordinate point a obtained in step c1 exists in the color expression area 302 of the color printer. (Step c5).
[0125]
FIG. 15 is a diagram illustrating a modification of the second example of coordinate transformation described with reference to FIGS. 13 and 14.
[0126]
Here, similarly to FIG. 12, a region D surrounding the coordinate conversion reference coordinate point c is set, and an intersection of a straight line connecting the coordinate conversion reference coordinate point c and the first reference coordinate point a and the boundary of the region D is set. d is obtained, and the first coordinate point t is mapped to a coordinate point s on a straight line connecting the intersection d and the second reference coordinate point b. By doing so, it is possible to set the region D where the coordinates are not moved.
[0127]
FIG. 16 is an explanatory diagram of the effect of mapping performed by combining the “compression” described with reference to FIGS. 10 and 11 and the “decompression” described with reference to FIGS. 13 and 14.
[0128]
L^*a^*b^*L more than the color expression area 102 of the color scanner in space.^*a^*b^*The coordinate points on the line LN1 that are wider in the color printer color expression area 302 in space are expanded so that the color printer color expression area 302 is maximized, and the color scanner color expression area 102 is wider. Each coordinate point on the LN 2 is compressed to a level that uses the color expression area 302 of the color printer 302 to the maximum extent. These decompression and compression directions are obtained using a device-dependent RGB space, so the mapping itself is L^*a^*b^*Even when performed in space, discontinuity of tone and generation of unnatural images are prevented, and the mapping itself is L^*a^*b^*Since the space is used, high-precision mapping is performed. In addition, each coordinate point on the line LN3 in which the color expression area 102 of the color scanner and the color expression area 302 of the color printer coincide with each other does not move and the color is maintained as it is.
[0129]
The mapping performed here is L for convenience of illustration in FIG.^*-A^*Although it is drawn as if it were performed on a plane, it is as described above that it is performed three-dimensionally.
[0130]
FIG. 17 is an explanatory diagram of a third example of coordinate transformation in the first step of the flowchart shown in FIG. 8, and FIG. 18 is a flowchart of the third example. As in the case of the second example described with reference to FIGS. 12 and 13, the third example described here is obtained in step d1, and this is because the first reference coordinate point a1 is L^*a^*b^*This is an example of a case where the image is present in the color expression area 302 of the color printer mapped to the space.
[0131]
Again, like the first and second examples above, L^*A coordinate conversion reference coordinate point c that is a reference for coordinate conversion is set on the axis (gray axis), and a straight line connecting the coordinate conversion reference coordinate point c and the first coordinate point t that is the target of coordinate conversion is considered. The straight line and L^*a^*b^*An intersection with the boundary of the color expression area 102 of the color scanner mapped in the space is obtained, the intersection is set as the first reference coordinate point a1, and the straight line^*a^*b^*An intersection point with the boundary of the color expression area 302 of the color printer mapped in the space is obtained, and the intersection point is set as a third reference coordinate point a2 (step d1). This L^*a^*b^*The color expression area 102 of the color scanner mapped to the space indicates the color expression area after the adaptive conversion when the adaptive conversion is performed in the second process (step a21) in the flowchart of FIG. This is the same as in the case of the first example and the second example so far.
[0132]
Next, the third reference coordinate point a2 obtained as described above is set to L^*a^*b^*A point P mapped from the space to the input RGB space depending on the scanner (step d2) and mapped to the input RGB space₁Is mapped on the boundary of the color expression area of the color scanner by clipping in the input RGB space (step d3), and the point P obtained by the mapping is mapped.₂L^*a^*b^*Map to space (step d4). L obtained in this way^*a^*b^*A point on the boundary of the color expression area 102 of the color scanner in space is referred to as a fourth reference coordinate point b2.
[0133]
Next, a difference vector v1 from the third reference coordinate point a2 toward the fourth reference coordinate point b2 is obtained (step d5), and a straight line passing through the first reference coordinate point a1 and parallel to the difference vector v1 is considered. , The straight line and L^*a^*b^*The intersection point with the boundary of the color expression area 302 of the color printer in the space is set as the second reference coordinate point b1, and a basic difference vector v from the first reference coordinate point a1 to the second reference coordinate point b1 is obtained (step) d6). Thereafter, similarly to the first and second examples described so far, the first coordinate point t moves the first coordinate point t parallel to the basic difference vector v, and the coordinate conversion reference coordinate point c And the second reference coordinate point b1 are mapped to the coordinate point (second coordinate point s) that hits the straight line (step d7).
[0134]
Such coordinate transformation is represented by L^*a^*b^*Among the coordinate points in the color expression area of the color scanner in space, in step d1, L^*a^*b^*The first reference coordinate point a1 located in the color expression area 302 of the color printer in space is performed for all coordinate points for which the first reference coordinate point a1 is obtained (step d8).
[0135]
The third example shown in FIG. 17 and FIG.^*a^*b^*When the color expression area 102 of the color scanner in the space and the color expression area 302 of the color printer are largely deviated, that is, when the difference vector v1 and the basic difference vector v are greatly separated, there is an error. When the distance between the vectors v1 and v is close and the error between the two vectors v1 and v can be ignored, the third example can be adopted, and the second example described with reference to FIGS. High-speed calculation is possible compared to the example.
[0136]
FIG. 19 is a diagram illustrating a modification of the third example of coordinate transformation described with reference to FIGS. 17 and 18.
[0137]
Here, similarly to FIGS. 12 and 15, a region D surrounding the coordinate conversion reference coordinate point c is set, a straight line connecting the coordinate conversion reference coordinate point c and the first reference coordinate point a 1, and the region D An intersection d with the boundary is obtained, and the first coordinate point t is mapped on a straight line connecting the intersection d and the second reference coordinate point b1.
[0138]
In this way, it is possible to set the region D where no coordinate movement is performed.
[0139]
20 is an explanatory diagram of a fourth example of coordinate transformation in the first step of the flowchart shown in FIG. 8, and FIG. 21 is a flowchart of the fourth example.
[0140]
In the fourth example, the first reference coordinate point a obtained in step e1 is L.^*a^*b^*This is a method that can be applied without considering whether it exists inside the color expression area 302 of the color printer mapped in the space or is out of the color expression area 302.
[0141]
Here, as in the first to third examples, L^*A coordinate conversion reference coordinate point c is set on the axis (gray axis), and a straight line connecting the coordinate conversion reference coordinate point c and the first coordinate point t to be subjected to coordinate conversion is considered.^*a^*b^*An intersection point with the boundary of the color expression area 102 of the color scanner in the space is obtained, and the intersection point is set as a first reference coordinate point a (step e1).
[0142]
Next, the first reference coordinate point a is mapped to the input RGB space which is a color space depending on the color scanner (step e2).
[0143]
Next, the point P on the input RGB space mapped in this way to the input RGB space₁The coordinate value corresponding to the coordinate value of₁Coordinate point P in the output RGB space, which is a color space dependent on the color printer, having the same coordinate value as₂Is obtained (step e3). As a specific example, a point P obtained by mapping the first reference coordinate point a shown in FIG. 20 to the input RGB space.₁When the coordinate value of (R, G, B) = (0, 255, 0) is a point on the output RGB space having the same coordinate value (R, G, B) = (0, 255, 0) Point P₂And
[0144]
Next, the point P in the output RGB space₂L from the output RGB space^*a^*b^*The point mapped to the space is set as the second reference coordinate point b (step e4).
[0145]
The first reference coordinate point a is L^*a^*b^*Since this is a point on the boundary of the color scanner color expression area 102 in space, even if this first reference coordinate point a is mapped to the input RGB space, the boundary of the color scanner color expression area in the input RGB space The upper point (for example, (R, G, B) described above = (0, 255, 0)).
[0146]
If this is used as a point in the output RGB space as it is, it will be a point on the boundary of the color expression area of the color printer in the output RGB space.^*a^*b^*The second reference coordinate point b obtained by mapping to space is also the L^*a^*b^*This is a point on the boundary of the color expression area 302 of the color printer in space.
[0147]
A basic difference vector v from the first reference coordinate point a thus determined to the second reference coordinate point b is obtained (step e5), passes through the first coordinate point t, and is parallel to the basic difference vector v. A second coordinate point s that is an intersection of the drawn straight line and a straight line connecting the coordinate conversion reference coordinate point c and the second reference coordinate point b is obtained (step e6).
[0148]
The above coordinate transformation is L^*a^*b^*This is performed sequentially for the entire color expression area 102 of the color scanner in space.
[0149]
FIG. 22 is a diagram illustrating a modification of the third example of coordinate transformation described with reference to FIGS. 20 and 21.
[0150]
Here, as in the examples of FIGS. 12, 15, and 19, a region D is set around the coordinate transformation reference coordinate point c, and the region D is not mapped. The method for preventing the area D from being mapped is the same as in the examples of FIGS. 12, 15, and 19, and a description thereof will be omitted.
[0151]
FIG. 23 is a diagram illustrating an intermediate process of a fifth example of coordinate transformation in the first process of the flowchart illustrated in FIG. 8. Considering only FIG. 23, this corresponds to a comparative example to be compared with this, not an embodiment of the present invention.
[0152]
Here, L^*A straight line connecting the coordinate conversion reference coordinate point c on the axis (gray axis) and the first coordinate point t to be subjected to coordinate conversion, and L^*a^*b^*An intersection point (first reference coordinate point a1) with the color expression area 102 of the color scanner in space and an intersection point (third reference coordinate point a2) with the color expression area 302 of the color printer are obtained, and the first reference coordinates are obtained. A difference vector v2 from the point a1 toward the third reference coordinate point a2 is obtained. The difference vector v2 is a difference vector that is obtained without mapping of a clip or the like in a device-dependent color space (input RGB space or output RGB space), and does not match the present invention as it is.
[0153]
The difference vector v2 is considered as the basic difference vector v according to the present invention, and the distance ca1 between the coordinate conversion reference coordinate point c and the first reference coordinate point a1, the coordinate conversion reference coordinate point c, and the first coordinate. When the ratio of the distance ct to the point t is ct / ca1 and the length of the difference vector v2 is | v2 |, the first coordinate point t is set in the same direction as the difference vector v2 (ct / ca1) x | v2 | is moved, and the point is set as a second coordinate point s after coordinate transformation. Although mapping is possible by doing this as well, the mapping direction (direction of the difference vector v2) is not the direction obtained in the device-dependent color space that matches the sense of human color, but this mapping method Is a direction that is determined mechanically by ignoring human color sensation, and as described above, there is a high possibility that tone discontinuity will occur or an unnatural image will be produced.
[0154]
FIG. 24 is an explanatory diagram of a fifth example of coordinate transformation in the first step of the flowchart shown in FIG.
[0155]
In FIG. 24, the first reference coordinate point a1, the third reference coordinate point a2, and the difference vector v2 are the same as those described with reference to FIG. The second reference coordinate point b may be obtained by any of the methods of the first to fourth examples described above. Here, a vector from the first reference coordinate point a1 to the second reference coordinate point b is referred to as a difference vector v3.
[0156]
In the example shown in FIG. 24, the two difference vectors v2 and v3 obtained in this way are weighted and added with respect to the direction, pass through the first reference coordinate point a1, and are drawn in the direction obtained by the weighted addition. And L^*a^*b^*An intersection with the boundary of the color expression area 302 of the color printer in the space is obtained as a fifth reference coordinate point e, and a difference vector from the first reference coordinate point a1 to the fifth reference coordinate point e is determined as a basic difference vector v. And
[0157]
In mapping the first coordinate point t, a straight line connecting the coordinate conversion reference coordinate point c and the fifth reference coordinate point e and a straight line passing through the first coordinate point t and parallel to the basic difference vector v are drawn. Is the second coordinate point s to which the first coordinate point t is to be mapped.
[0158]
Here, by allowing the operator to arbitrarily change the weighting coefficients related to the directions of the two difference vectors v2 and v3, it is possible to perform mapping that takes into account the coordinate conversion according to the method of the present invention by the weighting.
[0159]
Next, returning to FIG. 8, the third coordinate conversion process (step a3) will be described.
[0160]
In this third coordinate conversion process (step a3), L^*a^*b^*FIG. 5 shows coordinate points in the color expression area 302 of the color printer after coordinate conversion (mapping) from the color expression area 102 of the color scanner to the color expression area 302 of the color printer in space. The output profile (here, a profile adapted to the color printer 30) is mapped to the output RGB space.
[0161]
In this way, according to the flowchart of FIG. 8, the color scanner in which the correspondence between each coordinate point in the input RGB space depending on the color scanner 10 and each coordinate point in the output RGB space depending on the color printer 30 is defined. A color conversion definition that links 10 and the color printer 30 is created.
[0162]
FIG. 25 is a functional block diagram of a color conversion definition creating / color converting apparatus including an embodiment of the color conversion definition creating apparatus of the present invention.
[0163]
The color conversion definition creation / color conversion apparatus shown in FIG. 25 is realized by combining the personal computer 20 shown in FIGS. 2 and 3 and a program executed on the personal computer.
[0164]
The color conversion definition creation / color conversion apparatus shown in FIG. 25 includes a data acquisition unit 310, a definition creation data conversion unit 320, a data output unit 330, a storage unit 340, and a designation unit 350.
[0165]
The storage unit 340 includes a plurality of types of input profiles 341a,..., 341m corresponding to a plurality of types of input devices, a plurality of types of output profiles 342a,. , 343p, and a color conversion definition creation program 344 are stored.
[0166]
Each of the input profiles 341a,..., 341m is basically created by a creation method referring to FIG. In FIG. 1, only one type of input device is shown as the color scanner 10, but the color conversion definition creation / color conversion device in FIG. 25 has a plurality of types of input devices in order to provide versatility. There are multiple types of input profiles corresponding to.
[0167]
The output profiles 342a,..., 342n stored in the storage unit 340 are basically output profiles created by the creation method described with reference to FIG.
[0168]
As in the case of the input profile, FIG. 1 shows only one type of color printer 30 as an output device. However, the color conversion definition creation / color conversion apparatus in FIG. Therefore, a plurality of types of output profiles corresponding to a plurality of types of output devices are prepared.
[0169]
In addition, the color conversion definitions 343a,..., 343p stored in the storage unit 340 are read out and executed by the color conversion definition generation program 344 stored in the storage unit 340 being read by the definition generation / data conversion unit 320. FIG. 8 and subsequent drawings are created, and each color conversion definition corresponds to each combination of each input profile and each output profile. Here, these color conversion definitions 341a,..., 341p are each grouped in a LUT (Look Up Table) format.
[0170]
The storage unit 340 is set in the hard disk device 213 shown in FIG. 3 in terms of hardware, and the storage unit 340 (hard disk device shown in FIG. 3) is a color conversion definition creation program of the present invention. This also corresponds to an embodiment of the storage medium.
[0171]
The designation unit 350 designates the input device, the output device, and the distinction between the color conversion definition creation mode and the data conversion mode. The designation unit 350 is played by the keyboard 23 or the mouse 24 shown in FIGS. 2 and 3 in hardware.
[0172]
When the color conversion definition creation mode is designated by the designation unit 350 and the input device and the output device are designated, the color conversion definition creation program 344 is read from the storage unit 340 to the definition creation / data conversion unit 32. Executed. The color conversion definition creation program 344 executes each of the first coordinate conversion process, the second coordinate conversion process (second process and first process), and the third coordinate conversion process described with reference to FIG. An input profile (here, referred to as input profile 341a) corresponding to a designated input device (here, referred to as color scanner 10 shown in FIG. 1) based on the algorithm described above, An output profile (here, referred to as output profile 342a) corresponding to a designated output device (here, referred to as color printer 30 shown in FIG. 1) is referred to, and is adapted to the combination of color scanner 10 and color printer 30. The color conversion definition (here, color conversion definition 341a) is created. The created color conversion definition 341a is stored in the storage unit 340.
[0173]
At this time, various parameters for creating the color conversion definition, for example, the second step of the second coordinate conversion process is executed or omitted from the designation unit 350, or when the second process is executed, white Whether both the point and the black point are matched or only the white point is matched, whether the coordinate value of the coordinate conversion reference coordinate point c shown in FIG. 10 or the like, the region D shown in FIG. Various examples have been shown as the first step of the second coordinate transformation process, the designation of the area when setting the value, and which algorithm to select from these various examples will be described with reference to FIG. It is preferable that the weighting coefficient and the like in the case of adopting the described weighting method can be designated so that various variations of color conversion definitions can be created.
[0174]
When the data conversion mode is designated from the designation unit 310 and the input device and the output device are further designated (here, the color scanner 10 and the color printer 30 shown in FIG. 1 are designated as the input device and the output device, respectively). ), The color conversion definition 341a suitable for the designated combination of the color scanner 10 and the color printer 30 is read out and input to the definition creation / data conversion unit 320.
[0175]
The data acquisition unit 310 plays a role of receiving the color data obtained by the input device, and the input interface 216 shown in FIG. 3 corresponds to this in hardware.
[0176]
Further, the data output unit 330 is responsible for outputting the color data after color conversion by the definition creation data conversion unit 320, and the hardware corresponds to the output interface 217 shown in FIG.
[0177]
When color data obtained by an input device, for example, the color scanner 10 shown in FIG. 1 is input to the definition creation data conversion unit 320 via the data acquisition unit 310, the definition creation data conversion unit 320 performs color conversion definition 343a. The color data is converted by. The converted color data is output to an output device such as the color printer 30 shown in FIG.
[0178]
The conversion of the color data by the definition creation data conversion unit 320 is a conversion in which the color conversion definition created by the color conversion definition creation method unique to the present invention is referenced, and an output image with excellent color tone can be obtained. it can.
[0179]
Here, in the color conversion definition creation color conversion apparatus shown in FIG. 25, as one of the plurality of output profiles 342a,..., 342m stored in the storage unit 340, the image display apparatus 22 shown in FIGS. And an image based on the color data converted by the definition creation data conversion unit 320 is displayed on the display screen 22a (see FIG. 2) of the image display device 22, and The designation unit 350 (keyboard 23 and mouse 24) has a function of correcting the color conversion definition even in the data conversion mode, and the image has a more preferable color tone while viewing the image displayed on the display screen. You may comprise so that a color conversion definition can be corrected so that it may become an image.
[0180]
FIG. 26 is a diagram showing another embodiment of the color conversion definition creating program storage medium of the present invention.
[0181]
Referring to FIG. 25, it has been explained that the storage unit 340 of the color conversion definition creating / color converting apparatus shown in FIG. 25 corresponds to an embodiment of the color change definition creating program storage medium of the present invention. As another example of the color conversion definition creating program storage medium of the present invention, an example in which a color conversion definition creating program 344 is stored in the CD-ROM 110 shown in FIG. 3 is shown. Thus, the color conversion definition creation program may be stored in a portable storage medium and distributed.
[0182]
A user who has obtained such a color conversion definition creation program uploads the obtained color conversion definition creation program to his / her personal computer, and performs color conversion with excellent color tone using the color conversion definition creation program. Color conversion definitions that can be created.
[0183]
FIG. 27 is a diagram showing a form in which the color conversion definition created by the method of the present invention is stored in the CD-ROM.
[0184]
As described above, the color conversion definition as a result of the implementation of the color conversion definition creating method of the present invention may be stored in a portable storage medium and distributed.
[0185]
The embodiment described so far is an example in which the present invention is applied to a system for obtaining image data from an image using an input device such as a color scanner 10 as shown in FIG. The present invention can also be applied to color conversion between output devices.
[0186]
For example, when an image based on image data is displayed on a display screen of a CRT display device (an example of an output device), and the same image as the displayed image is to be printed out by a color printer (another example of an output device) The image data defined in the color expression area of the CRT display device in the color space corresponding to the CRT display apparatus is defined in the color expression area of the color printer in the color space corresponding to the color printer. However, the present invention can also be applied to such a situation.
[0187]
【The invention's effect】
As described above, according to the present invention, it is possible to avoid a discontinuity of tone or an unnatural image that is likely to occur when gamut mapping is performed in a common color space, and a reproduced image with excellent color tone. A color conversion definition that can be obtained can be created.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an image input-color conversion-image output system to which an embodiment of the present invention is applied.
FIG. 2 is an external perspective view of a personal computer shown by one block in FIG.
FIG. 3 is a hardware configuration diagram of a personal computer.
FIG. 4 is a conceptual diagram of an input profile.
FIG. 5 is a conceptual diagram of an output profile.
FIG. 6 is a conceptual diagram illustrating a color conversion definition as an example of the related art, which includes both an input profile and an output profile.
FIG. 7 is a schematic diagram of color expression areas of a color scanner and a color printer.
FIG. 8 is a flowchart showing a color conversion definition creation method by a color conversion definition creation program executed in the computer system.
FIG. 9 is an explanatory diagram of a second process of the first coordinate transformation process executed in step a21 of FIG.
FIG. 10 is an explanatory diagram of a first example of coordinate transformation in the first process.
FIG. 11 is a flowchart of the first example.
FIG. 12 is a diagram illustrating a modification of the first example of coordinate transformation.
FIG. 13 is an explanatory diagram of a second example of coordinate transformation in the first process.
FIG. 14 is a flowchart of the second example.
FIG. 15 is a diagram illustrating a modification of the second example of coordinate transformation.
FIG. 16 is an explanatory diagram of the effect of mapping performed by combining 'compression' and 'expansion'.
FIG. 17 is an explanatory diagram of a third example of coordinate transformation in the first process.
FIG. 18 is a flowchart of the third example.
FIG. 19 is a diagram illustrating a modification of the third example of coordinate transformation.
FIG. 20 is an explanatory diagram of a fourth example of coordinate transformation in the first process.
FIG. 21 is a flowchart of the fourth example.
FIG. 22 is a diagram illustrating a modification of the third example of coordinate transformation.
FIG. 23 is a diagram illustrating an intermediate process of a fifth example of coordinate conversion in the first process;
FIG. 24 is an explanatory diagram of a fifth example of coordinate transformation in the first process.
FIG. 25 is a functional block diagram of a color conversion definition creation / color conversion device including an embodiment of a color conversion definition creation device of the present invention.
FIG. 26 is a diagram showing another embodiment of the color conversion definition creating program storage medium of the present invention.
FIG. 27 is a diagram showing a form in which a color conversion definition created by the method of the present invention is stored in a CD-ROM.
[Explanation of symbols]
10 Color scanner
11 Document image
20 Personal computer
21 Main unit
22 Image display device
22a Display screen
23 keyboard
24 mice
25 bus
30 Color printer
100 floppy disks
110 CD-ROM
211 CPU
212 Main memory
213 Hard disk device
214 FD driver
215 CD-ROM driver
216 input interface
217 Output interface
310 Data acquisition unit
320 Definition creation / data conversion section
330 Data output section
340 definition storage unit
341a, ..., 341m Input profile
342a, ..., 342n Output profile
343, 343a, ..., 343p Color conversion definition
344 Color conversion definition creation program
350 Designated part

Claims (17)

The coordinate point in the color representation area of the first device in the first color space depending on the first device that mediates between the image and the image data is mapped to the device independent common color space. A first coordinate conversion process of converting to a coordinate point in the color expression area of one device;
The color expression area of the second device obtained by mapping the coordinate points in the color expression area of the first device mapped to the common color space, obtained by the first coordinate conversion process, to the common color space. A second coordinate conversion process for converting to a coordinate point in
Coordinate points in the color representation area of the second device mapped to the common color space obtained by the second coordinate conversion process are included in the color representation area of the second device in the second color space. A color that creates a color conversion definition that defines the correspondence between the coordinate point of the first color space and the coordinate point of the second color space by passing through a third coordinate conversion process of converting to the coordinate point of In the conversion definition creation method,
In the second coordinate conversion process, the first device coordinate point mapped in the color representation region of the first device mapped to the common color space is mapped to the common color space. When converting to the second coordinate point in
Based on the first coordinate point, a first reference coordinate point is obtained in the color expression area of the first device mapped to the common color space;
A second reference coordinate point corresponding to the first reference coordinate point based on a first algorithm including a coordinate operation in at least one of the first color space and the second color space; For the color representation area of the second device mapped to the common color space,
A second coordinate point corresponding to the first coordinate point is obtained based on a second algorithm using a basic difference vector representing a difference between the first reference coordinate point and the second reference coordinate point. A color conversion definition creating method characterized by including the first step. The second coordinate transformation process includes:
Based on the first coordinate point, the first reference coordinate point is obtained on the boundary of the color representation area of the first device mapped to the common color space,
2. The second reference coordinate point is obtained on a boundary of the second color expression area mapped to the common color space based on the first algorithm. Color conversion definition creation method. The first step in the second coordinate transformation step is:
Predetermined coordinate conversion reference coordinate points in the common area of the color expression area of the first device mapped to the common color space and the color expression area of the second device mapped to the common color space, and the first An intersection of a straight line connecting the coordinate points of the first device and the boundary of the color expression area of the first device mapped to the common color space is determined as the first reference coordinate point;
When the first reference coordinate point is a coordinate point out of the color representation area of the second device mapped to the common color space, the first reference coordinate point is changed to the second color. Mapping onto the boundary of the color representation area of the second device in the second color space and mapping the coordinate points obtained by mapping onto the boundary to the common color space A coordinate point on the boundary of the color expression area of the second device mapped to the common color space obtained on the common color space by the mapping is determined as the second reference coordinate point;
An intersection of a straight line connecting the coordinate conversion reference coordinate point and the second reference coordinate point and a straight line passing through the first coordinate point and parallel to the direction of the basic difference vector is defined as the first coordinate. 3. The color conversion definition creating method according to claim 2, wherein the second coordinate point corresponding to a point is obtained. The first step in the second coordinate transformation step is:
Predetermined coordinate conversion reference coordinate points in the common area of the color expression area of the first device mapped to the common color space and the color expression area of the second device mapped to the common color space, and the first An intersection of a straight line connecting the coordinate points of the first device and the boundary of the color expression area of the first device mapped to the common color space is determined as the first reference coordinate point;
If the first reference coordinate point is a coordinate point in the color representation area of the second device mapped to the common color space, the second device mapped to the common color space The first color space is mapped to the first color space by mapping the coordinate point of the portion of the boundary of the color expression region that is out of the color expression region of the first device mapped to the common color space. A coordinate transformation for obtaining a coordinate point in the common color space by mapping on the boundary of the color representation area of the first device and mapping the coordinate point obtained by the mapping on the boundary to the common color space By passing through the process, the coordinate conversion process corresponding to the coordinate point is obtained by obtaining a coordinate point that matches the first reference coordinate point or is close to the first reference coordinate point in light of a predetermined criterion. Before passing, the mapped to the common color space Coordinate points on the boundary of the color reproduction area of the second device determined as the second reference coordinate point,
An intersection of a straight line connecting the coordinate conversion reference coordinate point and the second reference coordinate point and a straight line passing through the first coordinate point and parallel to the direction of the basic difference vector is defined as the first coordinate. 3. The color conversion definition creating method according to claim 2, wherein the second coordinate point corresponding to a point is obtained. The first step in the second coordinate transformation step is:
Predetermined coordinate conversion reference coordinate points in the common area of the color expression area of the first device mapped to the common color space and the color expression area of the second device mapped to the common color space, and the first An intersection of a straight line connecting the coordinate points of the first device and the boundary of the color expression area of the first device mapped to the common color space is determined as the first reference coordinate point;
When the first reference coordinate point is a coordinate point in the color representation area of the second device mapped to the common color space, the straight line and the second mapped to the common color space An intersection with the boundary of the color expression area of the device is obtained as a third reference coordinate point, the third reference coordinate point is mapped to the first color space, and the first color space has the first reference point. The color of the first device mapped onto the common color space is mapped onto the boundary of the color expression area of the device, and the coordinate point obtained by mapping onto the boundary is mapped onto the common color space. A fourth reference coordinate point on the boundary of the expression area, a straight line passing through the first reference coordinate point and parallel to a straight line connecting the third reference coordinate point and the fourth reference coordinate point; The intersection point with the boundary of the color expression area of the second device mapped to the common color space Determined as the reference coordinate point 2,
An intersection of a straight line connecting the coordinate conversion reference coordinate point and the second reference coordinate point and a straight line passing through the first coordinate point and parallel to the direction of the basic difference vector is defined as the first coordinate. 3. The color conversion definition creating method according to claim 2, wherein the second coordinate point corresponding to a point is obtained. The first step in the second coordinate transformation step is:
Predetermined coordinate conversion reference coordinate points in the common area of the color expression area of the first device mapped to the common color space and the color expression area of the second device mapped to the common color space, and the first An intersection of a straight line connecting the coordinate points of the first device and the boundary of the color expression area of the first device mapped to the common color space is determined as the first reference coordinate point;
The first reference coordinate point is mapped to the first color space to obtain a coordinate point on the first color space, and a coordinate value corresponding to the coordinate value of the coordinate point on the first color space is obtained. The coordinate point on the second color space is obtained, and the coordinate point on the second color space is mapped onto the common color space, thereby obtaining the common point obtained on the common color space by the mapping. Obtaining a coordinate point on the boundary of the color expression area of the second device mapped in the color space as the second reference coordinate point;
A straight line connecting said coordinate conversion reference coordinate point and the second reference coordinate point, said point of intersection between a line drawn parallel to the direction of the first coordinate point as said fundamental difference component vector, the first coordinates 3. The color conversion definition creating method according to claim 2, wherein the second coordinate point corresponding to a point is obtained. When the first process in the second coordinate transformation process obtains the second coordinate point,
Instead of obtaining an intersection of a straight line connecting the coordinate conversion reference coordinate point and the second reference coordinate point and a straight line passing through the first coordinate point and parallel to the direction of the basic difference vector, A straight line passing through the second reference coordinate point while passing through an intersection of a straight line connecting the coordinate conversion reference coordinate point and the first reference coordinate point and a boundary of a predetermined region including the coordinate conversion reference coordinate point; the intersection between a line drawn parallel to the direction of the first coordinate point as the basic difference component vector, claims and characterized in that for obtaining a second coordinate point corresponding to coordinate points of the first Item 7. The color conversion definition creation method according to any one of Items 3 to 6. The first step in the second coordinate transformation step is a boundary between a straight line connecting the coordinate transformation reference coordinate point and the first coordinate point, and a color expression area of the second device mapped to the common color space. A third reference coordinate point that is an intersection of the first reference coordinate point and the first reference coordinate point instead of the reference difference vector representing the difference between the first reference coordinate point and the second reference coordinate point. And the direction of the first difference vector representing the difference between the first reference coordinate point and the second reference coordinate point, and the difference between the first reference coordinate point and the third reference coordinate point. The fifth reference coordinate point is the intersection of the straight line drawn in the direction obtained based on the direction of the second difference vector to be represented and the boundary of the color conversion area of the second device mapped to the common color space. When the first reference coordinate point and the fifth reference coordinate point, Color conversion definition creating method according to any one of claims 3 to 6, wherein the der Turkey which the vector representing the difference between the reference difference vector.   7. The first process in the second coordinate conversion process, wherein a point on the gray axis of the common color space is selected as the coordinate conversion reference coordinate point. The color conversion definition creation method according to any one of the preceding claims. In the second coordinate transformation process, the second coordinate point mapping the white coordinate point of the color representation area of the first device mapped to the common color space to the common color space before the first process. The coordinate point in the color expression area of the first device mapped to the common color space is converted into the coordinate point using an adaptation conversion algorithm that converts the coordinate point to match the white coordinate point of the device color expression area. Has a second process of converting into coordinate points transformed by the adaptive transformation algorithm,
The first process in the second coordinate conversion process uses the coordinate point obtained by passing through the second process as a conversion target, and maps the conversion target coordinate point to the common color space. 2. The color conversion according to claim 1, wherein said color expression area is converted by adopting a color expression area obtained by converting said color expression area using said adaptive conversion algorithm instead of the color expression area of said device. Definition creation method.   The second process in the second coordinate conversion process is performed by mapping, as the adaptation conversion algorithm, white coordinate points of the color expression area of the first device mapped to the common color space to the common color space. The white coordinate point of the second device color expression area is matched with the white coordinate point, and the black coordinate point of the first device color expression area mapped to the common color space is mapped to the common color space. 11. The color conversion definition creating method according to claim 10, wherein the coordinate point is converted using an adaptive conversion algorithm for converting the second device color expression area so as to match the black coordinate point. . The coordinate point in the color representation region of the first device in the first color space depending on the first device that mediates between the image and the image data is mapped to the device independent common color space. A first coordinate conversion process of converting to a coordinate point in the color expression area of one device;
The color representation area of the second device obtained by mapping the coordinate points in the color representation area of the first device mapped in the common color space, obtained in the first coordinate transformation process, in the common color space. A second coordinate conversion process for converting to a coordinate point in
Coordinate points in the color representation area of the second device mapped to the common color space obtained by the second coordinate conversion process are included in the color representation area of the second device in the second color space. A color that creates a color conversion definition that defines the correspondence between the coordinate point of the first color space and the coordinate point of the second color space by passing through a third coordinate conversion process of converting to the coordinate point of In the conversion definition creation device,
In the second coordinate conversion step, the first device coordinate point mapped in the color representation region of the first device mapped to the common color space is mapped to the common color space. When converting to the second coordinate point in
Based on the first coordinate point, a first reference coordinate point is obtained in the color representation area of the first device mapped to the common color space;
A second reference coordinate point corresponding to the first reference coordinate point based on a first algorithm including a coordinate operation in at least one of the first color space and the second color space; For the color representation area of the second device mapped to the common color space,
A second coordinate point corresponding to the first coordinate point is obtained based on a second algorithm using a basic difference vector representing a difference between the first reference coordinate point and the second reference coordinate point. A color conversion definition creating apparatus comprising the first step. In the second coordinate transformation step, the second coordinate point mapping the white coordinate point of the color expression area of the first device mapped to the common color space to the common color space before the first step. The coordinate point in the color expression area of the first device mapped to the common color space is converted to the coordinate point using an adaptation conversion algorithm that converts the coordinate point to match the white coordinate point of the device color expression area. Has a second process of converting into coordinate points transformed by the adaptive transformation algorithm,
The first process in the second coordinate conversion process uses the coordinate point obtained by passing through the second process as a conversion target, and maps the conversion target coordinate point to the common color space. 13. The color conversion definition according to claim 12, wherein the color expression area is converted by adopting a color expression area obtained by converting the color expression area using the adaptation conversion algorithm instead of the color expression area of the device. Creation device.   The second process in the second coordinate conversion process is performed by mapping, as the adaptation conversion algorithm, white coordinate points of the color expression area of the first device mapped to the common color space to the common color space. The white coordinate point of the second device color expression area is matched with the white coordinate point, and the black coordinate point of the first device color expression area mapped to the common color space is mapped to the common color space. 14. The color conversion definition creating apparatus according to claim 13, wherein the coordinate point is converted by using an adaptive conversion algorithm for converting the second device color expression area so as to match the black coordinate point. . The coordinate point in the color representation area of the first device in the first color space depending on the first device that mediates between the image and the image data is mapped to the device independent common color space. A first coordinate conversion process of converting to a coordinate point in the color expression area of one device;
The color expression area of the second device obtained by mapping the coordinate points in the color expression area of the first device mapped to the common color space, obtained by the first coordinate conversion process, to the common color space. A second coordinate conversion process for converting to a coordinate point in
Coordinate points in the color representation area of the second device mapped to the common color space obtained by the second coordinate conversion process are included in the color representation area of the second device in the second color space. A color that creates a color conversion definition that defines the correspondence between the coordinate point of the first color space and the coordinate point of the second color space by passing through a third coordinate conversion process of converting to the coordinate point of In a color conversion definition creating program storage medium storing a conversion definition creating program,
In the second coordinate conversion process, the first device coordinate point mapped in the color representation region of the first device mapped to the common color space is mapped to the common color space. When converting to the second coordinate point in
Based on the first coordinate point, a first reference coordinate point is obtained in the color expression area of the first device mapped to the common color space;
A second reference coordinate point corresponding to the first reference coordinate point based on a first algorithm including a coordinate operation in at least one of the first color space and the second color space; For the color representation area of the second device mapped to the common color space,
A second coordinate point corresponding to the first coordinate point is obtained based on a second algorithm using a basic difference vector representing a difference between the first reference coordinate point and the second reference coordinate point. A color conversion definition creating program storage medium characterized by storing a color conversion definition creating program including the first process. In the second coordinate transformation step, the second coordinate point mapping the white coordinate point of the color expression area of the first device mapped to the common color space to the common color space before the first step. The coordinate point in the color expression area of the first device mapped to the common color space is converted to the coordinate point using an adaptation conversion algorithm that converts the coordinate point to match the white coordinate point of the device color expression area. Has a second process of converting into coordinate points transformed by the adaptive transformation algorithm,
The first process in the second coordinate conversion process uses the coordinate point obtained by passing through the second process as a conversion target, and maps the conversion target coordinate point to the common color space. 16. The color conversion definition according to claim 15, wherein the color expression area is converted by adopting a color expression area obtained by further converting the color expression area using the adaptation conversion algorithm instead of the color expression area of the device. Creation program storage medium.   The second process in the second coordinate conversion process is performed by mapping, as the adaptation conversion algorithm, white coordinate points of the color expression area of the first device mapped to the common color space to the common color space. The white coordinate point of the second device color expression area is matched with the white coordinate point, and the black coordinate point of the first device color expression area mapped to the common color space is mapped to the common color space. The color conversion definition creating program according to claim 16, wherein the coordinate point is converted using an adaptive conversion algorithm for converting the second device color expression area so as to match the black coordinate point. Storage medium.

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