JP3866129B2 - Color conversion definition creation method, color conversion definition creation device, and color conversion definition creation program - Google Patents

Description

【００８６】
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。
【００８７】
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再現領域が明確に定義される。
【００８８】
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。
【００８９】
図９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。
【００９０】
ここでは、色再現領域決定過程（ステップａ１）、座標対応付過程（ステップａ２）、マッピング定義作成過程（ステップａ３）、および色変換定義作成過程（ステップａ４）を経て色変換定義が作成される。マッピング定義作成過程（ステップａ３）では、基本的には第１過程（ステップａ３２）が実行されるが、本実施形態では、一層高精度なマッピング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ａ３１）が置かれている。
【００９１】
以下、これらの各過程について順次説明する。
【００９２】
先ず、図９のステップａ１の色再現領域決定過程について説明する。
【００９３】
このステップａ１では、図１に示すカラーチャート画像１１ａがカラースキャナ１０で読み取られ、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て、そのカラースキャナ１０に依存した入力ＲＧＢ空間（本発明にいう第１の色空間の一例）における、そのカラーチャート画像１１ａの色再現領域（表現される色空間を問わず、そのカラーチャート画像１１ａの色再現領域は、本発明にいう第１の色再現領域の一例に対応する）が、デバイス非依存の共通色空間（例えばＬ^*ａ^*ｂ^*空間）に写像される。
【００９４】
図１０は、入力ＲＧＢ空間における、カラースキャナの色再現領域１０１とカラーチャート画像の色再現領域５０１を示す図である。
【００９５】
この図１０は、図８と同じ内容をＲ，Ｇ，Ｂの３軸からなる立体として表現したものである。
【００９６】
カラーチャート画像の色再現領域５０１の各頂点に付した、Ｗ，Ｋ，Ｒ，Ｇ，Ｂ，Ｃ，Ｍ，Ｙの各符号は、それぞれ、その符号が付された頂点が、そのカラーチャート画像の色再現領域５０１の、白、黒、レッド、グリーン、ブルー、シアン、マゼンタ、イエローの点であることを示している。
【００９７】
また、図１１は、図１０に示す、カラーチャート画像の色再現領域５０１を、カラースキャナ１０の入力プロファイルを参照してＬ^*ａ^*ｂ^*空間に写像したときの、そのＬ^*ａ^*ｂ^*空間におけるカラーチャート画像の色再現領域５０２（本発明にいう第１の色再現領域）と、その色再現領域５０２を内包するとともに、その色再現領域５０２の表面に沿って広がる複数平面で形成された多面体形状（ここでは１２面体形状）の色再現領域６０２（本発明にいう第２の色再現領域の一例に相当する）を示した図である。Ｌ^*ａ^*ｂ^*空間自体は、図１１に示す２つの色再現領域５０２，６０２よりも広く広がっている。
【００９８】
図１０に示すカラーチャート画像の色再現領域５０１をカラースキャナの入力プロファイルに従って図１１に示すようにＬ^*ａ^*ｂ^*空間に写像した後、今度は、そのＬ^*ａ^*ｂ^*空間における、カラーチャート画像の色再現領域５０２が、１２面体で取り囲まれる。
【００９９】
色再現領域５０２を１２面体で取り囲むにあたっては、その色再現領域５０２のＷ，Ｋ，Ｒ，Ｇ，Ｂ，Ｃ，Ｍ，Ｙの各頂点（図１１では色再現領域５０１の各頂点に対する符号は省略）の近傍に、色再現領域５０２を内包するとともにその色再現領域５０２に近似した外形形状を有する１２面体の各頂点Ｗ，Ｋ，Ｒ，Ｇ，Ｂ，Ｃ，Ｍ，Ｙを定め、これにより、図示の１２面体形状の色再現領域６０２を定める。ここで、これらＷ，Ｋ，Ｒ，Ｇ，Ｂ，Ｃ，Ｍ，Ｙを頂点とする多面体が１２面体であることを一例を挙げて説明すると、Ｗ，Ｃ，Ｇ，Ｙの４つの頂点は１つの平面上に位置するとは限らず、一般的には、ＣとＹを結ぶ一点鎖線で示す線分も多面体の１つの辺を形成している。他の部分についても同様である。したがって、これらＷ，Ｋ，Ｒ，Ｇ，Ｂ，Ｃ，Ｍ，Ｙを頂点とする多面体は、一般的には１２面体となる。以下では、このようにして求めた、Ｌ^*ａ^*ｂ^*空間上で１２面体形状をなす色再現領域を、カラーチャート画像の色再現領域を再設定した色再現領域であることに鑑み、色空間の別を問わず、「再設定色再現領域」と称する。
【０１００】
次に、図９のステップａ２の座標対応付過程について説明する。
【０１０１】
上記のようにして、１２面体のチャート内包色再現領域６０２を決定した後、そのチャート内包色再現領域６０２の全域を図１０に破線で示すカラースキャナの色再現領域１０１の全域に対応づける。以下に、この対応付けのアルゴリズムの一例を示す。
【０１０２】
先ず、図１１に示す１２面体の色再現領域６０２の各頂点を、図１０が示す立方体形状のカラーチャートの色再現領域の各頂点に対応づける。
【０１０３】
具体的には、図１１に示す、色再現領域６０２の各頂点Ｗ，Ｂ，Ｒ，Ｇ，Ｂ，Ｃ，Ｍ，Ｙに、それぞれ、
Ｗ＝（２５５，２５５，２５５）
Ｂ＝（０，０，０）
Ｒ＝（２５５，０，０）
Ｇ＝（０，２５５，０）
Ｂ＝（０，０，２５５）
Ｃ＝（０，２５５，２５５）
Ｍ＝（２５５，０，２５５）
Ｙ＝（２５５，２５５，０）
の数値（座標）を割り当てる。
【０１０４】
次に、その１２面体の各辺の上の任意の点について、その辺の両端の頂点の座標から補間演算によりその任意の点の座標を求める。
【０１０５】
次に、その１２面体を形成する各平面内の任意の点について座標を割り付ける。
【０１０６】
図１２は、１２面体を構成する任意の平面上の任意の点への座標の割付け方法の説明図である。
【０１０７】
ここでは、座標を求めようとする点ａは、３つの頂点Ａ，Ｂ，Ｃで規定される平面（平面ＡＢＣ）上にあるものとし、点ａの、Ｌ^*ａ^*ｂ^*空間におけるＬ^*の座標を、Ｌ^*（ａ）とする。
【０１０８】
ここで、先ず、Ｌ^*＝Ｌ^*（ａ）の平面を考え、そのＬ^*＝Ｌ^*（ａ）の平面と、３つの頂点Ａ，Ｂ，Ｃで規定される平面の輪郭をなす辺との交点ｂ，ｃを求める。交点ｂの座標は、頂点Ａの座標と頂点Ｂの座標とを用いた補間演算により求められており、交点Ｃの座標は頂点Ａの座標と頂点Ｃの座標とを用いた補間演算により求められている。
【０１０９】
そこで、ここでは交点ｂの座標と交点ｃの座標とを用いた補間演算により平面ＡＢＣ上の任意の点ａの座標が求められる。
【０１１０】
次に、Ｌ^*ａ^*ｂ^*空間内の任意の点の、図１０のカラースキャナの色再現領域１０１に相当する座標が求められる。
【０１１１】
図１３は、Ｌ^*ａ^*ｂ^*空間内の任意の点の座標の求め方の説明図である。
【０１１２】
この図１３では、１２面体の内側の点ｄ₁あるいは１２面体の外側の点ｄ₂が座標を求めるべき点である。
【０１１３】
ここでは、Ｌ^*軸のＬ^*＝５０の点を原点とし、その原点と座標を求めようとしている点ｄ₁を結んで延長した直線、あるいは原点と座標を求めようとしている点ｄ₂を結んだ直線と、１２面体の表面との交点ａを求める。交点ａの座標は、図１２を参照して説明したようにして既に求められている。そこで、ここでは、原点の座標（Ｌ^*，ａ^*，ｂ^*）＝（５０，０，０）と、点ａの座標とを用いて内挿することにより点ｄ₁の座標が求められ、原点の座標と点ａの座標とを用いて外挿することにより点ｄ₂の座標が求められる。このようにして、図１１の１２面体形状の再設定色再現領域６０２の全域が、図１０に示す、立方体形状のカラースキャナの色再現領域１０１に対応付けられるとともに、図１１の１２面体形状の再設定色再現領域６０２の内側のみでなく、外側についても、図１０の立方体形状の色再現領域１０１の、それぞれ、内側、外側の各点に対応づけられる。
【０１１４】
尚、色再現領域の外部についても座標を割り当てるのは、ガマット変換の演算の際に色再現領域の外側の点の座標も必要となるからである。
【０１１５】
図１１の１２面体形状の再設定色再現領域６０２を図１０の立方体形状の色再現領域１０１に割り当てたときの、図１０の色再現領域１０１を規定する色空間を、本発明では第２の色空間と称している。この第２の色空間における色再現領域１０１は、その第２の色空間における再設定色再現領域である。
【０１１６】
次に、図９のステップａ３のマッピング定義作成過程について説明する。
【０１１７】
以下に説明する、図９のステップａ３のマッピング定義作成過程の説明では、図７（Ａ）、図８、図１０の色再現領域１０１は、本発明にいう第２の色空間の一例としての入力ＲＧＢ空間における再設定色再現領域、すなわち、図９のステップａ２の座標変換過程において図１１の１２面体形状の再設定色再現領域６０１が入力ＲＧＢ空間に写像されたときの、その入力ＲＧＢ空間における再設定色再現領域であるとして説明する。
【０１１８】
図１４は、図９のステップａ３１で実行される、マッピング定義作成過程における第２過程の説明図であり、Ｌ^*ａ^*ｂ^*空間における再設定色再現領域およびカラープリンタ３０の色再現領域を示している。
【０１１９】
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、再設定色再現領域の白（図１１の頂点Ｗ）に相当する座標点Ｗ₁と、再設定色再現領域の黒（図１１の頂点Ｋ）に相当する座標点Ｋ₁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Ｋ₃に一致するように座標変換が行なわれる。
【０１２０】
図１４は、この座標変換過程を図示したものであり、先ず、図１４（Ａ）に示す、再設定色再現領域１０２ａとカラープリンタの色再現領域３０２ａを、図１４（Ｂ）に示すように、各黒点Ｋ₁，Ｋ₃が原点Ｏ（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、再設定色再現領域１０２ｂの黒点とカラープリンタの色再現領域３０２ｂの黒点とが一致する。
【０１２１】
次に、この平行移動後の、再設定色再現領域１０２ｂの白点Ｗ₁が、平行移動後の、カラープリンタの色再現領域３０２ｂの白点Ｗ₃に一致するように、すなわち図１４（Ｂ）の直線Ｌ₁が直線Ｌ₃に一致するように、再設定色再現領域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。
【０１２２】
図１４（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、再設定色再現領域は、図１４（Ｂ）に示す色再現領域１０２ｂから図１４（Ｃ）に示す色再現領域１０２ｃのように変換される。このとき、再設定色再現領域の白点Ｗ₁は、カラープリンタの色再現領域の白点Ｗ₃に一致する。
【０１２３】
その後、図１４（Ｄ）に示すように、図１４（Ｃ）に示すように白点，黒点がそれぞれ一致した、再設定色再現領域１０２ｃを、カラープリンタのもともとの色再現領域、すなわち図１４（Ａ）に示す、カラープリンタの色再現領域３０２ａの白点Ｗ₃，黒点Ｂ₃に一致する位置まで平行移動する。
【０１２４】
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、再設定色再現領域１０２ｄを得ることができる。
【０１２５】
以上の操作を式で示すと、以下のようになる。図１４は、Ｌ^*ａ^*ｂ^*空間における色再現領域を示したが、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^*空間の各座標点に１対１に対応する共通色空間の１つである。
【０１２６】
図１４（Ａ）に示す再設定色再現領域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１４（Ａ）に示すカラープリンタの色再現領域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１４（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。
【０１２７】
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。
【０１２８】
次に、ＸＹＺ空間における順応変換前の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１４（Ｂ）参照）がなされ、次に
【０１２９】
【数２】

【０１３０】
によりコンクリース変換が行なわれ（図１４（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１４（Ｄ）参照）が行なわれる。
【０１３１】
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１４（Ａ）に示す再設定色再現領域１０２ａが、白点、黒点がカラープリンタの色再現領域３０２ａの白点、黒点にそれぞれ一致した、図１４（Ｄ）に示す色再現領域１０２ｄに変換される。
【０１３２】
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１４（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。
【０１３３】
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。
【０１３４】
この白点のみ一致させる順応変換は、図１４を参照して説明すると、図１４（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。
【０１３５】
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、図１に示すカラースキャナ１０で読み取られる画像の白とカラープリンタ３０で出力される画像の白がほぼ一致している場合、この順応変換、すなわち、図９のマッピング定義作成過程の第２過程（ステップａ３１）は省略してもかまわない。
【０１３６】
次に、図９に示すフローチャートのマッピング定義作成過程中の第１過程（ステップａ３２）について、いくつかの例を説明する。
【０１３７】
図１５は、その第１過程における座標変換の第１例の説明図、図１６は、その第１例のフローチャートである。図１５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１５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。
【０１３８】
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^*空間における再設定色変換領域１０２とカラープリンタの色再現領域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。
【０１３９】
尚、図９のフローチャートのマッピング定義作成過程（ステップａ３）に図１４を参照して説明したような順応変換（ステップａ３１）を含むときは、Ｌ^*ａ^*ｂ^*空間における再設定色再現領域１０２は、その順応変換後の色再現領域を指すものとする。
【０１４０】
ここでは、マッピングを行なう対象となるＬ^*ａ^*ｂ^*空間上の再設定色再現領域１０２内の座標点を第１の座標点ｔとする。
【０１４１】
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、再設定色再現領域１０２の境界との交点を求める（図１６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。
【０１４２】
図１６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１５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再現領域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。
【０１４３】
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１６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。
【０１４４】
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の色再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の色再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１５参照）。
【０１４５】
次に、図１５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）。
【０１４６】
このような座標変換が、Ｌ^*ａ^*ｂ^*空間における再設定色再現領域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が再設定色再現領域１０２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）。
【０１４７】
このように、図１５，図１６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、再設定色再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再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。
【０１４８】
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。
【０１４９】
尚、図１５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。
【０１５０】
図１７は、図１５，図１６を参照して説明した座標変換の変形例を示す図である。
【０１５１】
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。
【０１５２】
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１７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。
【０１５３】
図１８は、図９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１９は、その第２例のフローチャートである。
【０１５４】
ここでは、図１５，図１６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。
【０１５５】
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^*空間における再設定色再現領域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^*空間に写像した再設定色再現領域１０２は、図９のフローチャートの第２過程（ステップａ３１）における順応変換が行なわれるときは、その順応変換後の再設定色再現領域を指すものであることは前述したとおりである。
【０１５６】
図１８に示すフローチャートは、図１６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１８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再現領域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。
【０１５７】
上記のようにして求めた、再設定色再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再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１８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再現領域３０２の内部に存在するため、図１５，図１６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再現領域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再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。
【０１５８】
先ず、出力ＲＧＢ空間におけるカラープリンタの色再現領域（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（上述したように、図９のステップａ２の対応付過程で、再設定色再現領域がＲ，Ｇ，Ｂともｂ＝０〜２５５の立方体形状の色再現領域に対応づけられた後の入力ＲＧＢ空間（本発明にいう第２の色空間の一例）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空間上の再設定色再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、その再設定色再現領域の境界上にマッピングする（ステップｃ２３）。
【０１５９】
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再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）。
【０１６０】
このような手順を踏むことにより、図１８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。
【０１６１】
尚、図１９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再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１８に示す、Ｌ^*ａ^*ｂ^*空間に写像したカラープリンタの色再現領域３０２の境界上の座標点のうち、Ｌ^*ａ^*ｂ^*空間に写像した再設定色再現領域１０２の色再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。
【０１６２】
図１９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１６のフローチャートの場合と同様、図１８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１５，図１６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）。
【０１６３】
このような座標変換が、Ｌ^*ａ^*ｂ^*空間における再設定色再現領域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再現領域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）。
【０１６４】
図２０は、図１８，図１９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。
【０１６５】
ここには、図１７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。
【０１６６】
図２１は、図１５，図１６を参照して説明した‘圧縮’と図１８，図１９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。
【０１６７】
Ｌ^*ａ^*ｂ^*空間上の再設定色再現領域１０２よりもＬ^*ａ^*ｂ^*空間上のカラープリンタの色再現領域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再現領域３０２を最大限使うように伸長され、再設定色再現領域１０２の方が広いラインＬＮ２上の各座標点は、カラープリンタ３０の色再現領域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、再設定色再現領域１０２とカラープリンタの色再現領域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。
【０１６８】
尚、ここで行なわれるマッピングは、図２１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。
【０１６９】
図２２は、図９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２３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１７，図１８を参照して説明した第２例の場合と同様、ステップｄ１で求められた第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再現領域３０２の内部に存在する場合の一例である。
【０１７０】
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^*空間における再設定色再現領域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再現領域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^*空間における再設定色再現領域１０２は、図９のフローチャートの第２過程（ステップａ３１）における順応変換が行なわれるときは、その順応変換後の再設定色再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。
【０１７１】
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^*空間から入力ＲＧＢ空間（本発明にいう第２の色空間の一例に相当する入力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再設定色再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、再設定色再現領域１０２の境界上の点を第４の基準座標点ｂ２と呼ぶ。
【０１７２】
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再現領域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）。
【０１７３】
このような座標変換が、Ｌ^*ａ^*ｂ^*空間上の再設定色再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再現領域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）。
【０１７４】
この図２２，図２３に示す第３例は、Ｌ^*ａ^*ｂ^*空間上の再設定色再現領域１０２とカラープリンタの色再現領域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１８，図１９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。
【０１７５】
図２４は、図２２，図２３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。
【０１７６】
ここには、図１７，図２０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。
【０１７７】
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。
【０１７８】
図２５は、図９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２６はその第４例のフローチャートである。
【０１７９】
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再現領域３０２の内部に存在するか、あるいはその色再現領域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。
【０１８０】
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^*空間上の再設定色再現領域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）。
【０１８１】
次に、この第１の基準座標点ａを入力ＲＧＢ空間に写像する（ステップｅ２）。
【０１８２】
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２５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。
【０１８３】
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）。
【０１８４】
第１の基準座標点ａはＬ^*ａ^*ｂ^*空間上の再設定色再現領域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空間における再設定色再現領域の境界上の点（例えば上記の（Ｒ，Ｇ，Ｂ）＝（０，２５５，０））となる。
【０１８５】
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再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再現領域３０２の境界上の点となる。
【０１８６】
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）。
【０１８７】
上記の座標変換が、Ｌ^*ａ^*ｂ^*空間上の再設定色再現領域１０２の全域について順次行なわれる。
【０１８８】
図２７は、図２５，図２６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。
【０１８９】
ここには、図１７，図２０，図２４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１７，図２０，図２４の各例の場合と同様であり、説明は省略する。
【０１９０】
図２８は、図９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２８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。
【０１９１】
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^*空間上の再設定色再現領域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再現領域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。
【０１９２】
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。
【０１９３】
図２９は、図９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。
【０１９４】
この図２９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２８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。
【０１９５】
この図２９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再現領域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。
【０１９６】
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。
【０１９７】
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。
【０１９８】
次に、図９に戻り、色変換定義作成過程（ステップａ４）について説明する。
【０１９９】
この色変換定義作成過程（ステップａ４）では、これまでの各ステップａ１〜ａ３の各過程での処理を踏まえ、図１のカラースキャナ１０に依存した入力ＲＧＢ空間（本発明にいう第１の色空間の一例）から、カラープリンタ３０に依存した出力ＲＧＢ空間（本発明にいう第３の色空間の一例）への色変換を定義した色変換定義が作成される。
【０２００】
ここでは、先ず、図１のカラーチャート画像１１ａをカラースキャナ１０で読み取ったときの、カラースキャナ１０に依存する入力ＲＧＢ空間（本発明にいう第１の色空間の一例）上の任意の座標（これを代表的に第１の座標と称する）を図９の座標対応付過程で対応づけられた座標の対応関係（すなわち、Ｌ^*ａ^*ｂ^*空間上で１２面体形状を成す再設定色再現領域を入力ＲＧＢ空間のＲ，Ｇ，Ｂともに０〜２５５の立方体形状の色再現領域に対応づけるという座標の対応関係）に従って入力ＲＧＢ空間での新たな第２の座標に変換する。このようにして第２の座標に変換された後の入力ＲＧＢ空間は、本発明にいう第２の色空間の一例に相当する。
【０２０１】
次に、この第２の色空間上の第２の座標をＬ^*ａ^*ｂ^*空間上の再設定色再現領域に依存した第３の座標に変換する。さらに、この第３の座標を、図９のマッピング定義作成過程で作成されたマッピング定義に従ってカラープリンタのＬ^*ａ^*ｂ^*空間における色再現領域に依存した、Ｌ^*ａ^*ｂ^*空間上の第４の座標に変換する。さらに、この第４の座標を、カラープリンタのプロファイルに従って出力ＲＧＢ空間上の第５の座標に変換する。
【０２０２】
このような一連の座標変換の出発点となった、カラースキャナ１０に依存する入力ＲＧＢ空間（本発明にいう第１の色空間の一例）の第１の座標と出力ＲＧＢ空間上の第５の座標とを対応づけることにより、図１に示す原稿画像１１をカラースキャナ１０で読み取って得た入力画像データを、カラープリンタ３０に適合した出力画像データに変換するための色変換定義が作成される。
【０２０３】
図３０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。
【０２０４】
この図３０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。
【０２０５】
この図３０に示す色変換定義作成／色変換装置は、データ取得部３１０と、ＬＵＴ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。
【０２０６】
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。
【０２０７】
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、入力デバイスは一種類のカラースキャナ１０のみ示されているが、図３０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。
【０２０８】
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。
【０２０９】
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３０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。
【０２１０】
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ＬＵＴ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９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。
【０２１１】
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いる。
【０２１２】
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。
【０２１３】
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ＬＵＴ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９を参照して説明した色再現領域決定過程（ステップａ１）、座標対応付過程（ステップａ２）、マッピング定義作成過程（ステップａ３）（第２過程（ステップａ３１）および第１過程（ステップａ３２））、および色変換定義作成過程（ステップａ４）のそれぞれに対応する処理を実行する、色再現領域決定部３４４１、座標対応付部３４４２、マッピング定義作成部３４４３（第２過程３４４３ａおよび第１過程３４４３ｂ）、および色変換定義作成部３４４４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）が参照されると共に、カラースキャナ１０で読み取られたカラーチャート画像の画像データが参照されて、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。
【０２１４】
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、マッピング定義作成部の第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１５等に示す座標変換基準座標点ｃの座標値、図１７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、色変換定義作成過程の第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２９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。
【０２１５】
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ＬＵＴ作成／データ変換部３２０に入力される。
【０２１６】
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。
【０２１７】
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。
【０２１８】
入力デバイス、例えば図１に示すカラースキャナ１０で得られた画像データがデータ取得部３１０を経由してＬＵＴ作成／データ変換部３２０に入力されると、ＬＵＴ作成／データ変換部３２０では、色変換定義３４３ａによる画像データの変換が行なわれる。この変換後の画像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。
【０２１９】
このＬＵＴ作成／データ変換部３２０による画像データの変換は、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。
【０２２０】
ここで、図３０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、ＬＵＴ作成／データ変換部３２０で変換された後の画像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。
【０２２１】
図３１は、図３０に示す色変換定義作成／色変換装置のＬＵＴ作成／データ変換部の機能ブロック図である。
【０２２２】
このＬＵＴ作成／データ変換部３２０は、ＬＵＴ作成部３２１とデータ変換部３２２とから構成されている。さらにＬＵＴ作成部３２１は、色再現領域決定部３２１１と、座標対応付部３２１２と、マッピング定義作成部３２１３（第２過程３２１３ａおよび第１過程３２１３ｂ）と、色変換定義作成部３２１４とから構成されている。
【０２２３】
ＬＵＴ作成部３２１は、色変換定義作成モードにおいて動作し、このＬＵＴ作成部３２１には、図３０に示す指定部３５０で指定された入力プロファイルを持つカラースキャナで読み取られたカラーチャート画像を表わす画像データが入力されるとともに、そのＬＵＴ作成部３２１に、図３０に示す色変換定義作成プログラム３４４が設定されて実行される。これにより、そのＬＵＴ作成部３２１の、色再現領域決定部３２１１、座標対応付部３２１２、マッピング定義作成部３２１３（第２過程３２１３ａと第１過程３２１３ｂ）、および色変換定義作成部２１４では、図９に示す色変換定義作成方法の、色再現領域決定過程（ステップａ１）、座標対応付過程（ステップａ２）、マッピング定義作成過程（ステップａ３）（第２過程（ステップａ３１）と第１過程（ステップａ３２））、および色変換定義作成過程（ステップａ４）に対応する各処理が実行され、ＬＵＴ形式の色変換定義が作成される。この作成された色変換定義は、図３０の記憶部３４０に記憶される。
【０２２４】
また、指定部３５０でデータ変換モードが指定されると、データ変換部３２２に、指定部３５０で指定された入力プロファイルと出力プロファイルとの組合せに応じた色変換定義が設定され、入力画像データがその設定された色変換定義に従って出力画像データに変換される。
【０２２５】
図３２は、本発明の色変換定義作成プログラムのもう１つの実施形態を示す図である。
【０２２６】
図３０を参照して、図３０に示す色変換定義作成／色変換装置の記憶部３４０に本発明の一実施形態としての色変定義作成プログラムが記憶されている旨説明したが、この図３２には、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。
【０２２７】
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。
【０２２８】
尚、ここで説明した実施形態はカラーチャート画像の色再現領域をＬ^*ａ^*ｂ^*空間上で１２面体形状の色再現領域で囲う例であるが、１２面体形状の色再現領域で囲うことに代え、図１１に示す一点鎖線が多面体の辺とならないように、Ｗ，Ｋ，Ｒ，Ｇ，Ｂ，Ｃ，Ｍ，Ｙの各点を定めることにより６面体形状の色再現領域で囲ってもよい。また、カラーチャート画像の色再現領域を多面体形状の色再現領域で囲うにあたっては、Ｌ^*ａ^*ｂ^*空間等の共通色空間で囲うことに代え、カラースキャナに依存した入力色空間で多面体形状となるように囲ってもよい。
【０２２９】
【発明の効果】
以上説明したように、本発明によれば、画像記録媒体上に表現することが可能な色の領域の広さや形状にかかわらず、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が避けられた、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色変換アルゴリズム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再現領域の模式図である。
【図８】カラーチャートとカラースキャナの色再現領域の模式図である。
【図９】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１０】入力ＲＧＢ空間における、カラースキャナの色再現領域とカラーチャート画像の色再現領域５０１を示す図である。
【図１１】Ｌ^*ａ^*ｂ^*空間におけるカラーチャート画像の色再現領域（本発明にいう第１の色再現領域）と、その色再現領域を内包する１２面体形状の色再現領域（本発明にいう第２の色再現領域の一例に相当する）を示した図である。
【図１２】１２面体を構成する任意の平面上の任意の点への数値（座標）の割付け方法の説明図である。
【図１３】Ｌ^*ａ^*ｂ^*空間内の任意の点の座標の求め方の説明図である。
【図１４】マッピング定義作成過程の第２過程の説明図である。
【図１５】第１過程における座標変換の第１例の説明図である。
【図１６】その第１例のフローチャートである。
【図１７】座標変換の第１例の変形例を示す図である。
【図１８】第１過程における座標変換の第２例の説明図である。
【図１９】座標変換の第２例のフローチャートである。
【図２０】座標変換の第２例の変形例を示す図である。
【図２１】‘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２２】第１過程における座標変換の第３例の説明図である。
【図２３】座標変換の第３例のフローチャートである。
【図２４】座標変換の第３例の変形例を示す図である。
【図２５】第１過程における座標変換の第４例の説明図である。
【図２６】座標変換の第４例のフローチャートである。
【図２７】座標変換の第３例の変形例を示す図である。
【図２８】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２９】第１過程における座標変換の第５例の説明図である。
【図３０】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３１】図３０に示すＬＵＴ／データ変換部の機能ブロック図である。
【図３２】色変換定義作成プログラムのもう１つの実施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
１１ａ カラーチャート画像
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 フレキシブルディスク
１１０ ＣＤ−ＲＯＭ
２１１ ＣＰＵ
２１２ 主メモリ
２１３ ハードディスク装置
２１４ ＦＤドライブ
２１５ ＣＤ−ＲＯＭドライブ
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 ＬＵＴ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
The present invention provides a color tone so that a suitable color tone can be obtained 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. The present invention relates to a color conversion definition creating method for creating a color conversion definition to be a basis for conversion, a color conversion definition creating apparatus, and a color conversion definition creating program for creating a color conversion definition for obtaining a suitable color tone.
[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). When converted to image data, the image represented by the image data is limited to colors in a color reproduction region depending on the input device in the color space composed of R, G, and B.
[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 apparatuses are known, and these output devices also have color reproduction regions corresponding to the respective output devices as in the case of the input devices described above. 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). The colors that can be expressed are within a range of 0 to 255 for each of the color reproduction regions (for example, R, G, and B) in the output device color space (for example, RGB space, CMYK space, etc.). It is limited to a color reproduction region expressed by a numerical value). A color reproduction region 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 reproduction region varies 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]
As described above, gamut mapping is conventionally performed in a common color space, but gamut mapping in this common color space is, for example, L^*a^*b^*L in color space^*Axis, a^*Axis, b^*It is a mapping in a three-dimensional space consisting of three axes, and has a high degree of freedom and can be mapped in any way, but on the other hand, the degree of freedom is too large, and adjustment parameters for mapping Is difficult to set, 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. It often ends up.
[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 is basically one-dimensional mapping independently 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 (R, G, and B of each color reproduction region (gamut) is set. It is limited to the method of mapping to the surface of a cube having a numerical value of 0 to 255), and in particular, near the boundary of the color reproduction area (color gamut), the color reproduction area of one device is changed to the color reproduction area of another device. There is a problem that it is difficult to accurately map.
[0010]
[Problems to be solved by the invention]
Under such a background, the boundary surface of the color reproduction area of the input device in the input RGB color space depending on the input device and the surface of the color reproduction area of the output device in the output RGB color space depending on the output device The direction of mapping is determined by finding points corresponding to each other, and the actual mapping is device-independent, for example L^*a^*b^*A mapping method of performing in a color space has been proposed (see Japanese Patent Laid-Open No. 2001-103329).
[0011]
According to this mapping method, the mapping direction is determined in a device-dependent color space suitable for human senses, so that the mapping characteristics can be easily adjusted, and the actual mapping is device-independent. Since it is performed in the common color space, high-accuracy mapping can be performed including the vicinity of the boundary of the device color reproduction region.
[0012]
However, the above mapping method can be adopted because the color area that can be expressed on the image read by the input device is a color space that depends on the input device (the input RGB in the above example). The color space is limited to the case where it matches the color reproduction area of the input device (for example, a cubic area having a value of 0 to 255 for any of R, G, and B).
[0013]
On the other hand, for example, a color chart in which a large number of color patches are arranged is formed on a reversal film, and the color chart formed on the reversal film is read by a color scanner, which is disclosed in the above Japanese Patent Laid-Open No. 2001-103329. When mapping is performed according to the mapping method, the color in the color space (for example, input RGB color space) depending on the color scanner when the color chart on the reversal film is read by the color scanner is used. The area occupied by the color represented on the chart is generally the entire color reproduction area of the color scanner, which is the entire cubic area where R, G, and B all take values in the range of 0 to 255. Does not spread and occupies only a part of the cubic region. Moreover, even if the color chart is the same, if the input device that reads the color chart is different, such as the type of the color scanner is different, the color represented on the color chart in the color space that depends on the input device is different. The spread and shape of the occupied area will be different.
[0014]
In this way, the color area that can be expressed on the image read by the input device does not spread over the entire color reproduction area of the input device in the color space depending on the input device, but in a partial area thereof. If the mapping method proposed in Japanese Patent Laid-Open No. 2001-103329 is adopted, the superior performance of the mapping method is not sufficiently exhibited, and the same color chart is used. However, since the area occupied by the color expressed on the color chart differs depending on the type of color scanner, etc., there is a problem that the degree of effect of the mapping method varies depending on the type of color scanner.
[0015]
In view of the above circumstances, the present invention is applicable to the case where the spread of a color area that can be expressed on an image recording medium such as a reversal film is limited to a part of the color reproduction area of the input device, or depending on the input device. Color conversion definition creation method and color conversion definition creation that can create color conversion definitions that perform high-accuracy color conversion that matches the human color sensation even when the area size and shape are different. It is an object of the present invention to provide a color conversion definition creating program capable of operating a device and a computer as such a color conversion definition creating device.
[0016]
[Means for Solving the Problems]
The color conversion definition creating method of the present invention that achieves the above object is adapted to an output device that outputs an image based on image data obtained by reading an image recorded on an image recording medium with an input device. In a color conversion definition creation method for creating a color conversion definition for converting to output image data,
A polyhedral shape formed of a plurality of planes including a first color reproduction area representing a color area that can be expressed on the image recording medium and extending along the surface of the first color reproduction area. A color reproduction region determination process for determining a second color reproduction region;
Each point of the second color reproduction region is assigned to each point of the second color reproduction region so that the entire second color reproduction region is associated with the entire third color reproduction region of the input device in the first color space depending on the input device. A coordinate association process for determining the correspondence between the coordinates of the second color space and the coordinates of the device independent common color space by assigning coordinates to form a second color space;
The coordinates in the second color reproduction area in the common color space are the profiles of the fourth color reproduction area of the output device in the third color space depending on the output device that outputs the image based on the image data. A mapping definition creation process for creating a mapping definition on the common color space for conversion to coordinates in the fourth color reproduction area in the common color space when mapped to the common color space according to
The first coordinate on the first color space is converted to the second coordinate on the second color space, and the second coordinate is converted to the third coordinate on the common color space. Is converted to the fourth coordinate on the common color space in accordance with the mapping definition, and the fourth coordinate is converted to the fifth coordinate on the third color space. And a color conversion definition creating process for creating a color conversion definition between the first coordinate and the fifth coordinate.
[0017]
In the color conversion definition creating method of the present invention, a polyhedral second color reproduction region in which a first color reproduction region representing a color region that can be expressed on an image recording medium such as a reversal film is surrounded by a polyhedron. And a third color reproduction region (for example, R, G, in the input RGB color space) in which the entire second color reproduction region in the first color space depending on the input device is the color reproduction region of the input device. The mapping is performed so as to correspond to the entire area of the cubic color reproduction region (B = 0 to 255). Thereby, the color area that can be expressed on the image recording medium is the third color reproduction area (the color reproduction area of the input device, for example, a cubic area of R, G, B = 0 to 255). It is spread over the whole area.
[0018]
The color conversion definition creating method of the present invention performs such mapping, and thereafter adopts the mapping method proposed in, for example, Japanese Patent Laid-Open No. 2001-103329 to define the mapping definition in the common color space. create. In this way, the color area that can be expressed on the image recording medium is originally spread only in a part of the color reproduction area (third color reproduction area) of the input device, or the area is expanded. Even when the degree and the shape of the spread differ depending on the input device or the like, a highly accurate color conversion definition can always be created stably.
[0019]
Here, in the color conversion definition creating method of the present invention, it is preferable that the color reproduction area determination process is a process of determining a second color reproduction area having a polyhedral shape in the common color space.
[0020]
Enclosing the first color reproduction region with the polyhedron-shaped second color reproduction region may be performed in a first color space depending on the input device, but in that case, an image recording medium (on the image recording medium) Even if the color chart is the same, the first color reproduction region differs depending on the input device, and it may be necessary to newly determine the second color reproduction region every time the input device is different.
[0021]
On the other hand, if the image recording medium (the color chart on the image recording medium) is the same by enclosing the first color reproduction area with the polyhedral-shaped second color reproduction area in the common color space, the input is performed. The second color reproduction region can be determined without being affected by the device.
[0022]
Further, in the color conversion definition creating method of the present invention, the color reproduction region determining process is a dodecahedron shape having each vertex representing white, black, red, green, blue, cyan, magenta, and yellow as vertices. It is preferable that the second color reproduction region be determined.
[0023]
By enclosing with the above dodecahedron, the second color reproduction region having a shape very close to the first color reproduction region can be determined. However, in the present invention, the second color reproduction region does not need to be a dodecahedron, and depending on the shape of the first color reproduction region, the first color reproduction region is surrounded by a hexahedron, The second color reproduction region may be determined.
[0024]
Here, in the color conversion definition creating method according to the present invention, the mapping definition creating step includes a fourth coordinate in the common color space corresponding to the first coordinate point in the second color reproduction region in the common color space. In obtaining the second coordinate point in the color reproduction region,
Based on the first coordinate point, a first reference coordinate point is obtained in the second color reproduction region in 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 second color space and the third color space; For the fourth color reproduction region in the common color space,
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, the second coordinate point corresponding to the first coordinate point is It is preferable that the first process to be obtained is included.
[0025]
In this case, a high-accuracy color conversion definition is created in combination with the fact that the mapping method proposed in Japanese Patent Laid-Open No. 2001-103329 has been eliminated by the above-described coordinate association process. The
[0026]
In the color conversion definition creating method of the present invention, the mapping definition creating process may be configured such that the first reference coordinate point is located on the boundary of the second color reproduction region in the common color space based on the first coordinate point. Is what we want
It is preferable that the second reference coordinate point is obtained on the boundary of the fourth color reproduction area in the common color space based on the first algorithm.
[0027]
By obtaining the first reference coordinate point and the second reference coordinate point on the respective boundaries of the second color reproduction region and the fourth color reproduction region in the common color space, the direction of color conversion can be easily performed. A basic difference vector can be obtained as a guideline for
[0028]
In this case, the first process in the mapping definition creating process is
A straight line connecting a predetermined coordinate transformation reference coordinate point in the common area between the second color reproduction area in the common color space and the fourth color reproduction area in the common color space and the first coordinate point, and the common Obtaining an intersection point with the boundary of the second color reproduction region in the color space as the first reference coordinate point;
If the first reference coordinate point is a coordinate point deviating from the fourth color reproduction area in the common color space, the first reference coordinate point is mapped to the third color space to obtain the third Mapping on the boundary of the fourth color reproduction region in the color space, and mapping the coordinate point obtained by mapping on the boundary to the common color space, was obtained on the common color space by the mapping, Obtaining a coordinate point on the boundary of the fourth color reproduction region in the common color space 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.
[0029]
In addition, the first process in the mapping definition creating process is as follows:
A straight line connecting a predetermined coordinate conversion reference coordinate point in the common area between the second color reproduction area in the common color space and the fourth color reproduction area in the common color space and the first coordinate point; Obtaining an intersection point with the boundary of the second color reproduction region in the common color space as the first reference coordinate point;
If the first reference coordinate point is a coordinate point in the fourth color reproduction area in the common color space, the common color of the boundaries of the fourth color reproduction area in the common color space The coordinate point of the part out of the second color reproduction area in the space is mapped to the second color space, mapped onto the boundary of the second color reproduction area in the second color space, By mapping the coordinate point obtained by the mapping to the common color space, and through a coordinate conversion process for obtaining the coordinate point in the common color space, the first reference coordinate point is coincident or the first judgment point in light of a predetermined criterion. A coordinate point close to one reference coordinate point is obtained, and a coordinate point corresponding to the coordinate point on the boundary of the fourth color reproduction region in the common color space before undergoing the coordinate conversion process is set as a second coordinate point. As a 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.
[0030]
Alternatively, the first step in the mapping definition creation step is
A straight line connecting a predetermined coordinate conversion reference coordinate point in the common area between the second color reproduction area in the common color space and the fourth color reproduction area in the common color space and the first coordinate point; Obtaining an intersection with the boundary of the second color reproduction region in the common color space as a first reference coordinate point;
When the first reference coordinate point is a coordinate point in the fourth color reproduction area in the common color space, an intersection of the straight line and the boundary of the fourth color reproduction area in the common color space is determined. The third reference coordinate point is obtained, and the third reference coordinate point is mapped to the second color space and mapped onto the boundary of the second color reproduction area in the second color space, By mapping the coordinate point obtained by the mapping to the common color space, a fourth reference coordinate point is obtained on the boundary of the second color reproduction region in the common color space, and the first reference coordinate point is obtained. The intersection point between the straight line parallel to the straight line connecting the third reference coordinate point and the fourth reference coordinate point and the boundary of the fourth color reproduction region in the common color space is defined as the second reference coordinate point. Seeking
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.
[0031]
Furthermore, the first process in the mapping definition creating process is as follows:
A straight line connecting a predetermined coordinate transformation reference coordinate point in the common area between the second color reproduction area in the common color space and the fourth color reproduction area in the common color space and the first coordinate point, and the common Obtaining an intersection with the boundary of the second color reproduction region in the color space as a first reference coordinate point;
The first reference coordinate point is mapped to the second color space to obtain a coordinate point on the second color space, and a first coordinate value corresponding to the coordinate value of the coordinate point on the second color space is obtained. The coordinate point on the third color space is obtained, and the coordinate point on the third color space is mapped to the common color space, whereby the fourth color in the common color space obtained on the common color space by the mapping is obtained. A coordinate point on the boundary of the color reproduction region 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 point. May be obtained as a second coordinate point corresponding to.
[0032]
Here, in the above-described various aspects for obtaining the second coordinate point corresponding to the first coordinate point, the first process in the mapping definition creating process determines the coordinate conversion reference when obtaining the second coordinate point. Instead of obtaining an intersection of a straight line connecting the 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 and the first reference coordinate point A basic difference vector 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 in parallel with the direction may be obtained as a second coordinate point corresponding to the first coordinate point.
[0033]
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.
[0034]
Further, in the above-described various aspects for obtaining the second coordinate point corresponding to the first coordinate point, the first step in the mapping definition creating step may include a coordinate conversion reference coordinate point and the first coordinate point. A reference difference representing a difference between the first reference coordinate point and the second reference coordinate point is obtained by obtaining a third reference coordinate point that is an intersection of the connecting straight line and the boundary of the fourth color reproduction region in the common color space. Instead of the vector, it passes through 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, the first reference coordinate point and the first reference coordinate point The intersection of the straight line drawn in the direction obtained based on the direction of the second difference vector representing the difference from the third reference coordinate point and the boundary of the fourth color reproduction region in the common color space is the fifth. The first reference coordinate point and the fifth reference coordinate point Vector representing the difference between the reference points or may be a reference difference vector.
[0035]
By doing so, the direction of mapping can be adjusted quite freely.
[0036]
Furthermore, in the above-described various aspects for obtaining the second coordinate point corresponding to the first coordinate point, the first step in the mapping definition creation step is performed on the gray axis of the common color space as a coordinate conversion reference coordinate point. It is preferable that this point is selected.
[0037]
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.
[0038]
In the color conversion definition creating method of the present invention,
In the mapping definition creation process, before the first process, the white coordinate point of the second color reproduction area in the common color space is matched with the white coordinate point of the fourth color reproduction area in the common color space. A second step of converting coordinate points in the second color reproduction region in the common color space using an adaptive conversion algorithm for converting
In the mapping definition creating process, the first process uses the coordinate point obtained through the second process as a conversion target, and the conversion target coordinate point is used as the second color reproduction area in the common color space. Instead, it is preferable that the second color reproduction area is further converted by adopting a new second color reproduction area obtained by conversion using an adaptive conversion algorithm.
[0039]
In this case, the second step in the mapping definition creation step is an adaptation conversion algorithm in which the white coordinate point of the second color reproduction region in the common color space is replaced with the white coordinate point of the fourth color reproduction region in the common color space. And a conversion algorithm for converting the black coordinate point of the second color reproduction area in the common color space to coincide with the black coordinate point of the fourth color reproduction area in the common color space More preferably, the coordinate point of the second color reproduction region in the common color space is converted using
[0040]
In this way, by executing the first process after matching the white (or white and black) of the second color reproduction area with the white (or white and black) of the fourth color reproduction area, the first process is further performed. It is possible to create a mapping definition on the common color space with high accuracy, and thus to create a color conversion definition between input image data and output image data with higher accuracy.
[0041]
In addition, the color conversion definition creating apparatus of the present invention that achieves the above-described object,
Create a color conversion definition for converting input image data obtained by reading an image recorded on an image recording medium with an input device into output image data suitable for an output device that outputs an image based on the image data In the color conversion definition creation device,
A polyhedron-shaped first formed of a plurality of planes including a first color reproduction area representing a color area that can be expressed on the image recording medium and extending along the surface of the first color reproduction area. A color reproduction region determination unit that determines the color reproduction region of 2;
Each point of the second color reproduction region is assigned to each point of the second color reproduction region so that the entire second color reproduction region is associated with the entire third color reproduction region of the input device in the first color space depending on the input device. A coordinate association unit for determining a correspondence relationship between the coordinates of the second color space and the coordinates of the device-independent common color space by assigning coordinates to form the second color space;
The coordinates in the second color reproduction area in the common color space are the profiles of the fourth color reproduction area of the output device in the third color space depending on the output device that outputs the image based on the image data. A mapping definition creating unit that creates a mapping definition on the common color space for conversion to coordinates in the fourth color reproduction region in the common color space when mapped to the common color space according to
The first coordinate on the first color space is converted to the second coordinate on the second color space, and the second coordinate is converted to the third coordinate on the common color space. Is converted to the fourth coordinate on the common color space in accordance with the mapping definition, and the fourth coordinate is converted to the fifth coordinate on the third color space. And a color conversion definition creating unit for creating a color conversion definition between the first coordinate and the fifth coordinate.
[0042]
Note that the color conversion definition creating apparatus of the present invention includes all the various modes corresponding to all the modes in the color conversion definition creating method of the present invention described above.
[0043]
Furthermore, the color conversion definition creating program of the present invention is executed in a computer, and the computer reads input image data obtained by reading an image recorded on an image recording medium with an input device based on the image data. A color conversion definition creation program that operates as a color conversion definition creation device for creating a color conversion definition for converting to output image data suitable for an output device that outputs
A polyhedron-shaped first formed of a plurality of planes including a first color reproduction area representing a color area that can be represented on the image storage medium and extending along the surface of the first color reproduction area. A color reproduction region determination unit that determines the color reproduction region of 2;
Each point of the second color reproduction region is assigned to each point of the second color reproduction region so that the entire second color reproduction region is associated with the entire third color reproduction region of the input device in the first color space depending on the input device. A coordinate association unit for determining a correspondence relationship between the coordinates of the second color space and the coordinates of the device-independent common color space by assigning coordinates to form the second color space;
The coordinates in the second color reproduction area in the common color space are the profiles of the fourth color reproduction area of the output device in the third color space depending on the output device that outputs the image based on the image data. A mapping definition creating unit that creates a mapping definition on the common color space for conversion to coordinates in the fourth color reproduction region in the common color space when mapped to the common color space according to
The first coordinate on the first color space is converted to the second coordinate on the second color space, and the second coordinate is converted to the third coordinate on the common color space. Is converted to the fourth coordinate on the common color space in accordance with the mapping definition, and the fourth coordinate is converted to the fifth coordinate on the third color space. And a color conversion definition creating unit for creating a color conversion definition between the first coordinate and the fifth coordinate.
[0044]
Note that the color conversion definition creation program of the present invention also includes all the various aspects corresponding to all the aspects of the above-described color conversion definition creation method of the present invention.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0046]
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.
[0047]
Here, a color scanner 10 is shown. The color scanner 10 reads an original image 11 recorded on a color reversal film 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.
[0048]
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. The color conversion definition and its creation method will be described later. In creating the color conversion definition, a color chart 11 a in which a large number of color patches recorded on the color reversal film are arranged is read by the color scanner 10. It is done.
[0049]
In the system shown in FIG. 1, a color printer 30 is shown as an example of an output device that outputs an image based on image data. However, the color printer 30 may be an electrophotographic color printer or an inkjet color printer. It may be a printer, or it may be a printer that develops the photographic paper by exposing the photographic paper with a modulated laser beam, and it does not matter what the printing method is. The output device is not limited to a printer, and may be a printing machine, or an image display device such as a CRT display device or a plasma display device that displays an image on a display screen. .
[0050]
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.
[0051]
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.
[0052]
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 flexible disk loading port 21a for loading a flexible disk and a CD-ROM loading port 21b for loading a CD-ROM.
[0053]
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 a hard disk device 213 storing data and data, a FD drive 214 loaded with the flexible disk 100 and accessing the loaded flexible disk 100, a CD-ROM 110 loaded, and a CD- accessing the loaded CD-ROM 110 Connected to the ROM drive 215 and the color scanner 10 (see FIG. 1) and connected to the input interface 216 for receiving image data from the color scanner 10 and the color printer 30 (see FIG. 1), and an output interface for sending image data to the color printer 30 Esu 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.
[0054]
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. The CD-ROM 110 is loaded in the CD-ROM drive 215, and 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.
[0055]
Next, a method for creating a color conversion definition by a color conversion definition creating program uploaded to the computer 20 will be described. Here, first, a conventional general color conversion method will be described.
[0056]
FIG. 4 is a conceptual diagram of an input profile.
[0057]
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, an outline of a method for creating the input profile will be described.
[0058]
A color patch image 11a 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 11a is read by the color scanner 10 and an input RGB space (first in the present invention) for each color patch. An example of one color space) The above color data is obtained, and the color patch image is measured by the colorimeter 11a. 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.
[0059]
In this way, the coordinate points on the input 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.
[0060]
FIG. 5 is a conceptual diagram of an output profile.
[0061]
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, an outline of a creation method when the output profile is newly created will be described.
[0062]
From the personal computer 20 shown in FIG. 1, image data in which the values of R, G, and B are sequentially changed is generated as RGB three-color image data, and a color patch image based on the generated image data is generated. Print output by the color printer 30. 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 third 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.
[0063]
This output profile is a profile depending on the output device, which differs depending on the output device.
[0064]
FIG. 6 is a conceptual diagram illustrating a color conversion algorithm including both an input profile and an output profile.
[0065]
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.
[0066]
However, in the case of such a simple color conversion algorithm, the color reproduction area (color gamut) of the color scanner 10 and the color reproduction area (color gamut) of the color printer 30 generally match as described below. And the color reproduction area of the color chart 11 a obtained by reading the color chart 11 a shown in FIG. 1 with the color scanner 10 does not match the color reproduction area of the color scanner 10.
[0067]
Hereinafter, these two problems will be described sequentially.
[0068]
First, the problem that the color reproduction area of the color scanner 10 and the color reproduction area of the color printer 30 do not match will be described.
[0069]
FIG. 7 is a schematic diagram of the color reproduction regions of the color scanner 10 and the color printer 30.
[0070]
FIG. 7A shows an input RGB space that 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.
[0071]
The color scanner 10 converts the document image 11 into image data representing values of 0 to 255 for each of R, G, and B. In this case, a rectangular area shown in FIG. The color reproduction area 101 becomes.
[0072]
Here, using the input profile created with reference to FIG. 4, a color reproduction region 101 of the color scanner 10 shown in FIG.^*a^*b^*When mapped onto a space, the color reproduction region of the color scanner 10 is represented as a region 102, and the color reproduction region 102 is further represented by using the output profile described with reference to FIG. Is mapped to the output RGB space, the color reproduction area of the color scanner 10 is represented as shown in an area 103 shown in FIG.
[0073]
On the other hand, the color reproduction region 303 of the color printer 30 shown in FIG. 1 is a cubic region (FIG. 7) in which R, G, and B are shown in the numerical range of 0 to 255 on the output RGB space of FIG. (C) is a rectangular region 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 reproduction region 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 reproduction 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).
[0074]
In the case of mapping in a color space that depends on the output device as described above, the degree of freedom of mapping is small as described above, and data that deviates from the color reproduction area of the output device as described above is simply clipped to the color. Mapping is performed only by moving to the boundary of the reproduction region, and particularly when mapping from the color reproduction region of one device (for example, the color scanner 10) to the color reproduction region 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 reproduction region is greatly reduced.
[0075]
On the other hand, the color reproduction region 303 of the color printer 30 indicated by a rectangular region 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 reproduction region 102 of the color scanner 10 (input device) into data in the color reproduction region 302 of the color printer 30 (output device). This has been proposed as described above.
[0076]
L^*a^*b^*In color conversion (mapping) in space, when a color reproduction region 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 reproduction areas 101 and the color reproduction 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 reproduction area 302 of the color printer 30.
[0077]
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 of discontinuity in tone and an unnatural impression image.
[0078]
L in FIG. 7 (B)^*a^*b^*When the color reproduction region 302 of the color printer 30 mapped to the space is further mapped to the input RGB space of FIG. 7A, a portion protruding from the rectangular region 101 that is the color reproduction region of the color scanner 10 is displayed. It is expressed as a “shaped” region 301.
[0079]
Next, a problem that the color reproduction area of the color chart 11a and the color reproduction area of the color scanner 10 when the color chart 11a shown in FIG.
[0080]
FIG. 8 is a schematic diagram of the color chart and the color reproduction area of the color scanner. As in FIG. 7, the RG plane is also shown here for simplicity of illustration.
[0081]
A rectangular color reproduction region 101 indicated by a broken line in FIG. 8 is the same as the color reproduction region 101 in FIG. 7A, and is a cube indicated by a numerical range of 0 to 255 for each of R, G, and B. This is the color reproduction area of the color scanner 10 in the shape.
[0082]
On the other hand, a color reproduction area 501 indicated by a solid line in FIG. 8 is a color reproduction area of the color chart. The color reproduction area 501 of this color chart occupies only a part of the color reproduction area 101 of the color scanner.
[0083]
In the present embodiment, as described later, in order to perform mapping of both “compression” and “decompression” as shown by a broken-line arrow in FIG. 7B while adapting to the human color sensation. However, if the color chart color reproduction area 501 is significantly different from the color scanner color reproduction area 101 as shown in FIG. It is difficult to create a mapping definition that performs. In order to solve this problem, it is conceivable to extrapolate the color reproduction area 501 of the color chart to extend to the entire area of the color reproduction area 101 of the color scanner. Insertion is difficult, and it is also difficult to create a mapping definition that performs high-precision mapping.
[0084]
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.
[0085]
[Expression 1]

[0086]
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
[0087]
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 reproduction region in the common color space is clearly defined.
[0088]
Next, a color conversion definition creation method by a color conversion definition creation program executed in the computer system 20 shown in FIGS. 1 to 3 will be described.
[0089]
FIG. 9 is a flowchart showing a color conversion definition creation method by a color conversion definition creation program executed in the computer system 20.
[0090]
Here, a color conversion definition is created through a color reproduction region determination process (step a1), a coordinate association process (step a2), a mapping definition creation process (step a3), and a color conversion definition creation process (step a4). . In the mapping definition creation process (step a3), the first process (step a32) is basically executed. However, in the present embodiment, the first stage of the first process is created so that a more accurate mapping definition is created. The second process (step a31) is placed in
[0091]
Hereinafter, each of these processes will be described sequentially.
[0092]
First, the process of determining the color reproduction area at step a1 in FIG. 9 will be described.
[0093]
In step a1, the color chart image 11a shown in FIG. 1 is read by the color scanner 10, and the input profile for the color scanner 10 as described with reference to FIG. In the input RGB space (an example of the first color space referred to in the present invention), the color reproduction area of the color chart image 11a (regardless of the color space to be expressed, the color reproduction area of the color chart image 11a is The first color reproduction region in the invention corresponds to an example of a device-independent common color space (for example, L^*a^*b^*(Space).
[0094]
FIG. 10 is a diagram showing the color reproduction area 101 of the color scanner and the color reproduction area 501 of the color chart image in the input RGB space.
[0095]
FIG. 10 represents the same content as FIG. 8 as a solid composed of three axes of R, G, and B.
[0096]
The W, K, R, G, B, C, M, and Y codes attached to the vertices of the color reproduction area 501 of the color chart image are the vertices to which the codes are attached, respectively. In the color reproduction region 501, the dots are white, black, red, green, blue, cyan, magenta, and yellow.
[0097]
11 shows the color reproduction area 501 of the color chart image shown in FIG. 10 with reference to the input profile of the color scanner 10.^*a^*b^*L when mapped to space^*a^*b^*The color reproduction area 502 of the color chart image in the space (the first color reproduction area referred to in the present invention) and the color reproduction area 502 are formed by a plurality of planes extending along the surface of the color reproduction area 502. FIG. 5 is a diagram showing a polyhedron shape (here, a dodecahedron shape) color reproduction region 602 (corresponding to an example of a second color reproduction region according to the present invention). L^*a^*b^*The space itself is wider than the two color reproduction regions 502 and 602 shown in FIG.
[0098]
As shown in FIG. 11, the color reproduction area 501 of the color chart image shown in FIG.^*a^*b^*After mapping to space, this time, the L^*a^*b^*A color reproduction area 502 of the color chart image in the space is surrounded by a dodecahedron.
[0099]
In enclosing the color reproduction area 502 with a dodecahedron, the vertices of W, K, R, G, B, C, M, and Y of the color reproduction area 502 (in FIG. 11, the reference numerals for the vertices of the color reproduction area 501 are In the vicinity of (omitted), each vertex W, K, R, G, B, C, M, and Y of a dodecahedron that includes the color reproduction area 502 and has an outer shape approximate to the color reproduction area 502 is determined. By doing so, a color reproduction region 602 having a dodecahedron shape shown in FIG. Here, to explain with an example that the polyhedron having W, K, R, G, B, C, M, and Y as vertices is a dodecahedron, the four vertices of W, C, G, and Y are The line segment indicated by the alternate long and short dash line connecting C and Y also forms one side of the polyhedron. The same applies to other parts. Therefore, the polyhedron having W, K, R, G, B, C, M, and Y as vertices is generally a dodecahedron. In the following, L determined in this way^*a^*b^*A color reproduction region having a dodecahedron shape in space is a color reproduction region in which the color reproduction region of the color chart image is reset, and is referred to as a “reset color reproduction region” regardless of the color space. .
[0100]
Next, the process of associating coordinates in step a2 of FIG. 9 will be described.
[0101]
After determining the dodecahedron chart inclusion color reproduction region 602 as described above, the entire chart inclusion color reproduction region 602 is associated with the entire color reproduction region 101 of the color scanner indicated by a broken line in FIG. An example of this association algorithm is shown below.
[0102]
First, each vertex of the dodecahedron color reproduction region 602 shown in FIG. 11 is associated with each vertex of the color reproduction region of the cubic color chart shown in FIG.
[0103]
Specifically, each vertex W, B, R, G, B, C, M, Y of the color reproduction region 602 shown in FIG.
W = (255, 255, 255)
B = (0,0,0)
R = (255, 0, 0)
G = (0,255,0)
B = (0, 0, 255)
C = (0,255,255)
M = (255, 0, 255)
Y = (255, 255, 0)
Assign a numerical value (coordinate).
[0104]
Next, for an arbitrary point on each side of the dodecahedron, the coordinates of the arbitrary point are obtained by interpolation from the coordinates of the vertices at both ends of the side.
[0105]
Next, coordinates are assigned to arbitrary points in each plane forming the dodecahedron.
[0106]
FIG. 12 is an explanatory diagram of a method for assigning coordinates to an arbitrary point on an arbitrary plane constituting the dodecahedron.
[0107]
Here, it is assumed that the point a whose coordinates are to be obtained is on a plane (plane ABC) defined by the three vertices A, B, and C, and that L of the point a is L^*a^*b^*L in space^*The coordinates of L^*(A).
[0108]
Here, first, L^*= L^*Considering the plane of (a), its L^*= L^*Intersection points b and c between the plane of (a) and the side forming the outline of the plane defined by the three vertices A, B and C are obtained. The coordinates of the intersection point b are obtained by an interpolation operation using the coordinates of the vertex A and the coordinates of the vertex B, and the coordinates of the intersection point C are obtained by an interpolation operation using the coordinates of the vertex A and the coordinates of the vertex C. ing.
[0109]
Therefore, here, the coordinates of an arbitrary point a on the plane ABC can be obtained by interpolation using the coordinates of the intersection point b and the coordinates of the intersection point c.
[0110]
Next, L^*a^*b^*The coordinates corresponding to the color reproduction region 101 of the color scanner in FIG. 10 at an arbitrary point in the space are obtained.
[0111]
FIG.^*a^*b^*It is explanatory drawing of how to obtain | require the coordinate of the arbitrary points in space.
[0112]
In FIG. 13, a point d inside the dodecahedron.₁Or a point d outside the dodecahedron₂Is the point where the coordinates should be obtained.
[0113]
Here, L^*Axis L^*= 50, where the point is the origin, and the origin and coordinates of the origin d₁A straight line connecting the two points, or the point d for which the origin and coordinates are to be obtained₂The intersection point a between the straight line connecting the lines and the surface of the dodecahedron is obtained. The coordinates of the intersection point a have already been obtained as described with reference to FIG. Therefore, here, the coordinates of the origin (L^*, A^*, B^*) = (50, 0, 0) and the point d by interpolating using the coordinates of the point a₁Is obtained by extrapolating using the coordinates of the origin and the coordinates of the point a.₂Coordinates are obtained. 11 is associated with the color reproduction region 101 of the cube-shaped color scanner shown in FIG. 10 and the shape of the dodecahedron shape of FIG. Not only the inside of the reset color reproduction area 602 but also the outside is associated with each of the inside and outside points of the cubic color reproduction area 101 of FIG.
[0114]
The reason why the coordinates are also assigned to the outside of the color reproduction area is that the coordinates of the points outside the color reproduction area are also required in the calculation of gamut conversion.
[0115]
The color space that defines the color reproduction region 101 in FIG. 10 when the reset color reproduction region 602 in the dodecahedron shape in FIG. 11 is assigned to the color reproduction region 101 in the cubic shape in FIG. This is called a color space. The color reproduction area 101 in the second color space is a reset color reproduction area in the second color space.
[0116]
Next, the mapping definition creation process in step a3 in FIG. 9 will be described.
[0117]
In the following description of the mapping definition creation process in step a3 in FIG. 9, the color reproduction region 101 in FIGS. 7A, 8 and 10 is an example of the second color space according to the present invention. The reset color reproduction area in the input RGB space, that is, the input RGB space when the reset color reproduction area 601 of the dodecahedron shape in FIG. 11 is mapped to the input RGB space in the coordinate conversion process in step a2 in FIG. It is assumed that this is the reset color reproduction region in FIG.
[0118]
FIG. 14 is an explanatory diagram of the second process in the mapping definition creation process executed in step a31 of FIG.^*a^*b^*The reset color reproduction area in the space and the color reproduction area of the color printer 30 are shown.
[0119]
Here, adaptation conversion is performed by applying concretion conversion (Von Kries conversion). That is, here, the coordinate point W corresponding to white (vertex W in FIG. 11) of the reset color reproduction region.₁And a coordinate point K corresponding to black (vertex K in FIG. 11) of the reset color reproduction region₁Are 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 three colors of R, G, and B, the maximum amount of ink of each color of R, G, and B is used. Coordinate point K corresponding to (printed state)_ThreeCoordinate conversion is performed so as to match.
[0120]
FIG. 14 illustrates this coordinate conversion process. First, as shown in FIG. 14B, the reset color reproduction area 102a and the color reproduction area 302a of the color printer shown in FIG. , Each sunspot K₁, K_ThreeIs translated so as to coincide with the origin O (theoretical black point). As a result, first, the black spot in the reset color reproduction area 102b matches the black spot in the color reproduction area 302b of the color printer.
[0121]
Next, the white point W of the reset color reproduction region 102b after the parallel movement₁Is the white point W of the color reproduction region 302b of the color printer after the parallel movement._Three, That is, the straight line L in FIG.₁Is a straight line L_ThreeIn such a manner, coordinate conversion involving rotation and expansion / contraction is performed on the entire reset color reproduction region 102b.
[0122]
FIG. 14C shows a state after the coordinate conversion accompanied with the rotation and expansion / contraction, and the reset color reproduction region is changed from the color reproduction region 102b shown in FIG. 14B to FIG. 14C. The color reproduction area 102c shown in FIG. At this time, the white point W of the reset color reproduction region₁Is the white point W of the color reproduction area of the color printer._ThreeMatches.
[0123]
Thereafter, as shown in FIG. 14D, the reset color reproduction region 102c in which the white point and the black point coincide with each other as shown in FIG. 14C is replaced with the original color reproduction region of the color printer, that is, FIG. The white point W of the color reproduction area 302a of the color printer shown in FIG._Three, Sunspot B_ThreeTranslate to a position that matches.
[0124]
By doing this, the white spot W₁, Sunspot B₁Is the white point W of the color printer_Three, Sunspot B_ThreeIt is possible to obtain a reset color reproduction region 102d that matches each of the above.
[0125]
The above operation can be expressed as follows. FIG.^*a^*b^*Although the color reproduction 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 that correspond one-to-one to each coordinate point in the space.
[0126]
White point W of the reset color reproduction region 102a shown in FIG.₁, Sunspot B₁XYZ coordinates of (LXW₁, LYW₁, LZW₁), (LXB₁, LYB₁, LZB₁) And a white point W in the color reproduction region 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 ').
[0127]
Here, this concrete matrix is
VK = [MTX_VK] (3)
Is written. This concrete matrix is a matrix of 3 rows × 3 columns.
[0128]
Next, a large number of coordinate points before the adaptive transformation in the XYZ space are represented by (X, Y, Z).
This (X, Y, Z)
X1 = X-LXB₁
Y1 = Y-LYB₁
Z1 = Z-LZB₁          (4)
To correct the black spot (see FIG. 14B).
[0129]
[Expression 2]

[0130]
The concrete conversion is performed by (see FIG. 14C),
X '= X2-LXB_Three
Y '= Y2-LYB_Three
Z '= Z2-LZB_Three          ...... (6)
Thus, correction (see FIG. 14D) for matching the black spot with the black spot of the color printer is performed.
[0131]
By performing the above calculation for all coordinate points, L^*a^*b^*The reset color reproduction area 102a shown in FIG. 14A when expressed in space is shown in FIG. 14D, in which the white point and black point respectively match the white point and black point of the color reproduction area 302a of the color printer. It is converted into a color reproduction area 102d.
[0132]
When the above-described adaptation conversion is performed in the XYZ space, the black spot before the adaptation conversion (the black spot B in FIG. 14A).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.
[0133]
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.
[0134]
The adaptation conversion for matching only the white dots will be described with reference to FIG. 14. 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 that coincides with the white point W without mathematically subtracting the black point coordinate as in the equations (1) and (2).₁(LXW₁, LYW₁, LZW₁) Is white spot W_Three(LXW_Three, LYW_Three, LZW_Three) To obtain a concrete matrix for rotation and expansion / contraction so as to match It means to convert as it is.
[0135]
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 whites that are considerably distant from each other, but the white color of the image read by the color scanner 10 shown in FIG. In this case, this adaptation conversion, that is, the second process (step a31) of the mapping definition creating process of FIG. 9 may be omitted.
[0136]
Next, some examples of the first process (step a32) in the mapping definition creating process of the flowchart shown in FIG. 9 will be described.
[0137]
FIG. 15 is an explanatory diagram of a first example of coordinate transformation in the first process, and FIG. 16 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. 15 but also to various examples described later.
[0138]
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 reset color conversion area 102 in the space and the color reproduction 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.
[0139]
If the mapping definition creation process (step a3) in the flowchart of FIG. 9 includes adaptation conversion (step a31) as described with reference to FIG.^*a^*b^*The reset color reproduction area 102 in the space refers to the color reproduction area after the adaptation conversion.
[0140]
Here, L to be mapped^*a^*b^*A coordinate point in the reset color reproduction area 102 in the space is set as a first coordinate point t.
[0141]
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 reset color reproduction region 102 is obtained (step b1 in FIG. 16). Here, this intersection is called a first reference coordinate point a.
[0142]
The flowchart shown in FIG. 16 shows that the first reference coordinate point a thus obtained is L^*a^*b^*It is a flowchart in the case where it is out of the color reproduction area 302 of the color printer mapped in the space. When this condition is satisfied, the processing is further advanced as follows.
[0143]
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. 16). The first reference coordinate point mapped to this output RGB space is P₁And
[0144]
Next, in the output RGB space, the first reference coordinate point P₁Is then mapped onto the boundary of the color reproduction area of the color printer 30 in the output RGB space (step b3). The point P obtained on the boundary of the color reproduction area of the color printer 30 by this mapping₂This 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. 15).
[0145]
Next, a basic that uses the first reference coordinate point a as the start point and the second reference coordinate point as the end point, which represents the difference between the first reference coordinate point a and the second reference coordinate point b shown in FIG. 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).
[0146]
Such coordinate transformation is represented by L^*a^*b^*Of the coordinate points included in the reset color reproduction area 102 in the space, the first reference coordinate point a obtained in step b1 is performed for all coordinate points outside the reset color reproduction area 102 (step). 7).
[0147]
As described above, the coordinate conversion described with reference to FIGS. 15 and 16 is performed by using the output RGB space when determining the direction of the coordinate conversion, that is, when obtaining the basic difference vector v. This is done by defining a second reference coordinate point b on the boundary of the color reproduction area of the color printer that corresponds to the first reference coordinate point a on the boundary of the reproduction area.^*a^*b^*Done in space.
[0148]
That is, the direction of coordinate transformation (mapping) is determined in a color space that matches the human color sensation of the output RGB space (device-dependent color space), resulting in a discontinuity of tone or an unnatural image. 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.
[0149]
Note that FIG. 15 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. .
[0150]
FIG. 17 is a diagram illustrating a modification of the coordinate conversion described with reference to FIGS. 15 and 16.
[0151]
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.
[0152]
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 coordinate for the axis (gray axis), by setting the region D as shown in FIG. 17, it is possible to arbitrarily set a region where the coordinate is not moved.
[0153]
18 is an explanatory diagram of a second example of coordinate transformation in the first step of the flowchart shown in FIG. 9, and FIG. 19 is a flowchart of the second example.
[0154]
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).
[0155]
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 with the boundary of the reset color reproduction region 102 in the space is obtained. The intersection is called a first reference coordinate point. Where L^*a^*b^*The reset color reproduction region 102 mapped in the space indicates the reset color reproduction region after the adaptive conversion when the adaptive conversion is performed in the second process (step a31) of the flowchart of FIG. As described above.
[0156]
The flowchart shown in FIG. 18 differs from the flowchart shown in FIG. 16 in that 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 reproduction area 302 of the color printer mapped in the space. When this condition is satisfied, the processing is further advanced as follows.
[0157]
The second reference coordinate point b on the boundary of the color reproduction area of the color printer corresponding to the first reference coordinate point a on the boundary of the reset color reproduction area obtained as described above is obtained (step c2). ). In obtaining the second reference coordinate point b, here, as shown in FIG. 18, the first reference coordinate point a exists inside the color reproduction 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 reproduction area 302 of the color printer, the mapping is performed. The first reference coordinate point is located inside the color reproduction 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.
[0158]
First, all the points (points P) on the boundary of the color reproduction area (gamut) of the color printer in the output RGB space₁From the output RGB space.^*a^*b^*Map to space (step c21), and then L^*a^*b^*All points P mapped in space₂The input RGB space (as described above, the reset color reproduction region is associated with the cubic color reproduction region of b = 0 to 255 in R, G, and B in the association process of step a2 in FIG. Mapping to the later input RGB space (an example of the second color space according to the present invention) (step c22) Next, the point P mapped to the output RGB space_ThreeAs described above, a point out of the reset color reproduction region in the input RGB space is clipped to 0 for each of R, G, B, and 255 for values exceeding 255. Thus, mapping is performed on the boundary of the reset color reproduction region (step c23).
[0159]
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 reproduction area of the color printer 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).
[0160]
By following such a procedure, the second reference coordinate point b corresponding to the reference coordinate point a shown in FIG. 18 can be obtained.
[0161]
In the case of the flowchart shown in FIG. 19, all the points P on the boundary of the color reproduction 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 reproduction area 302 of the color printer mapped to the space, L^*a^*b^*Only the coordinate points of the portion projected from the color reproduction region of the reset color reproduction region 102 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 in the narrowed area may be mapped to the input RGB space and clipped.
[0162]
When the second reference coordinate point b is detected in step c2 shown in FIG. 19, the second reference coordinate point a is changed from the first reference coordinate point a as shown in FIG. 18 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).
[0163]
Such coordinate transformation is represented by L^*a^*b^*Of the coordinate points in the reset color reproduction region 102 in the space, the first reference coordinate point a obtained in step c1 is performed for all coordinate points existing in the color reproduction region 302 of the color printer. (Step c5).
[0164]
FIG. 20 is a diagram illustrating a modification of the second example of coordinate transformation described with reference to FIGS. 18 and 19.
[0165]
Here, similarly to FIG. 17, 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.
[0166]
FIG. 21 is an explanatory diagram of the effect of mapping performed by combining the “compression” described with reference to FIGS. 15 and 16 and the “decompression” described with reference to FIGS. 18 and 19.
[0167]
L^*a^*b^*L than the reset color reproduction area 102 in space^*a^*b^*The coordinate points on the line LN1 in the color reproduction area 302 of the color printer in space are expanded so as to use the color reproduction area 302 of the color printer as much as possible, and the line LN2 in the reset color reproduction area 102 is wider. Each upper coordinate point is compressed to a level that uses the color reproduction region 302 of the color printer 30 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 where the widths of the reset color reproduction area 102 and the color reproduction area 302 of the color printer coincide with each other does not move and the color is maintained as it is.
[0168]
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.
[0169]
FIG. 22 is an explanatory diagram of a third example of coordinate transformation in the first step of the flowchart shown in FIG. 9, and FIG. 23 is a flowchart of the third example. In the third example described here, as in the case of the second example described with reference to FIGS. 17 and 18, the first reference coordinate point a1 obtained in step d1 is L^*a^*b^*This is an example of the case where the image is present in the color reproduction area 302 of the color printer mapped in the space.
[0170]
Again, like the first and second examples above, L^*A coordinate conversion reference coordinate point c serving as 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 to be coordinate converted is considered. The straight line and L^*a^*b^*An intersection point with the boundary of the reset color reproduction region 102 in the space is obtained, the intersection point is set as a first reference coordinate point a1, and the straight line and L^*a^*b^*An intersection point with the boundary of the color reproduction region 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 reset color reproduction region 102 in the space indicates the reset color reproduction region after the adaptive conversion when the adaptive conversion is performed in the second process (step a31) in the flowchart of FIG. This is the same as in the first and second examples.
[0171]
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 (input RGB space corresponding to an example of the second color space in the present invention) (step d2).₁Is mapped on the boundary of the reset color reproduction region by clipping in the input RGB space (step d3), and the point P obtained by the mapping is mapped₂L^*a^*b^*Map to space (step d4). L obtained in this way^*a^*b^*A point on the boundary of the reset color reproduction region 102 in the space is referred to as a fourth reference coordinate point b2.
[0172]
Next, a difference vector v1 from the third reference coordinate point a2 to 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^*A point of intersection with the boundary of the color printer color reproduction area 302 in space is defined as a second reference coordinate point b1, and a basic difference vector v from the first reference coordinate point a1 toward 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 a straight line (step d7).
[0173]
Such coordinate transformation is represented by L^*a^*b^*Of the coordinate points in the reset color reproduction area in space, in step d1, L^*a^*b^*The first reference coordinate point a1 located inside the color reproduction area 302 of the color printer in space is performed for all the coordinate points for which the first reference coordinate point a1 is obtained (step d8).
[0174]
The third example shown in FIG. 22 and FIG.^*a^*b^*When the reset color reproduction area 102 in the space and the color reproduction area 302 of the color printer are greatly deviated, that is, when the difference vector v1 and the basic difference vector v are greatly separated, there is an error, but these two vectors When the distance between 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. Compared with, high-speed calculation is possible.
[0175]
FIG. 24 is a diagram illustrating a modification of the third example of coordinate transformation described with reference to FIGS. 22 and 23.
[0176]
Here, similarly to FIGS. 17 and 20, a region D surrounding the coordinate conversion reference coordinate point c is set, and a straight line connecting the coordinate conversion reference coordinate point c and the first reference coordinate point a1 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.
[0177]
In this way, it is possible to set the region D where no coordinate movement is performed.
[0178]
FIG. 25 is an explanatory diagram of a fourth example of coordinate transformation in the first step of the flowchart shown in FIG. 9, and FIG. 26 is a flowchart of the fourth example.
[0179]
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 reproduction region 302 of the color printer mapped in the space or is out of the color reproduction region 302.
[0180]
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 reset color reproduction region 102 in the space is obtained, and the intersection point is set as a first reference coordinate point a (step e1).
[0181]
Next, the first reference coordinate point a is mapped to the input RGB space (step e2).
[0182]
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. 25 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
[0183]
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).
[0184]
The first reference coordinate point a is L^*a^*b^*Since it is a point on the boundary of the reset color reproduction area 102 in space, even if this first reference coordinate point a is mapped to the input RGB space, it is on the boundary of the reset color reproduction area in the input RGB space. The point (for example, (R, G, B) = (0, 255, 0) above) is obtained.
[0185]
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 reproduction 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 reproduction area 302 of the color printer in space.
[0186]
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).
[0187]
The above coordinate transformation is L^*a^*b^*This is sequentially performed for the entire reset color reproduction region 102 in the space.
[0188]
FIG. 27 is a diagram illustrating a modification of the third example of coordinate conversion described with reference to FIGS. 25 and 26.
[0189]
Here, as in the examples of FIGS. 17, 20, and 24, 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 region D from being mapped is the same as in the examples of FIGS. 17, 20, and 24, and a description thereof will be omitted.
[0190]
FIG. 28 is a diagram illustrating an intermediate process of the fifth example of coordinate transformation in the first process of the flowchart illustrated in FIG. 9. Considering only FIG. 28, this is not an embodiment of the present invention, but corresponds to a comparative example to be compared with it.
[0191]
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 reset color reproduction region 102 in space and an intersection point (third reference coordinate point a2) with the color reproduction region 302 of the color printer are obtained, and the first reference coordinate point is obtained. A difference vector v2 from 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.
[0192]
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.
[0193]
FIG. 29 is an explanatory diagram of a fifth example of coordinate transformation in the first step of the flowchart shown in FIG.
[0194]
In FIG. 29, 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.
[0195]
In the example shown in FIG. 29, 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 point with the boundary of the color printer color reproduction area 302 in space is obtained as a fifth reference coordinate point e, and a difference vector from the first reference coordinate point a1 toward the fifth reference coordinate point e is determined as a basic difference vector v. And
[0196]
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.
[0197]
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 transformation according to the method of the present invention by the weighting.
[0198]
Next, returning to FIG. 9, the color conversion definition creation process (step a4) will be described.
[0199]
In this color conversion definition creation process (step a4), the input RGB space (first color referred to in the present invention) depending on the color scanner 10 of FIG. A color conversion definition that defines color conversion from an example space to an output RGB space that depends on the color printer 30 (an example of a third color space according to the present invention) is created.
[0200]
Here, first, when the color chart image 11a of FIG. 1 is read by the color scanner 10, arbitrary coordinates on the input RGB space (an example of the first color space in the present invention) depending on the color scanner 10 ( This is representatively referred to as the first coordinate) and the correspondence relationship of the coordinates associated with the coordinate association process in FIG.^*a^*b^*New coordinates in the input RGB space according to the coordinate relationship that the reset color reproduction area having a dodecahedron shape in space is associated with a cubic color reproduction area of 0 to 255 in R, G, B in the input RGB space) To the second coordinate. The input RGB space after being converted to the second coordinates in this way corresponds to an example of the second color space referred to in the present invention.
[0201]
Next, the second coordinate on the second color space is set to L^*a^*b^*Conversion into the third coordinates depending on the reset color reproduction region in space. Further, the third coordinate is set in accordance with the mapping definition created in the mapping definition creation process of FIG.^*a^*b^*L depending on the color reproduction area in space^*a^*b^*Convert to the fourth coordinate in space. Further, the fourth coordinate is converted into the fifth coordinate on the output RGB space according to the profile of the color printer.
[0202]
The first coordinate in the input RGB space (an example of the first color space referred to in the present invention) that depends on the color scanner 10 and the fifth in the output RGB space, which are the starting points for such a series of coordinate transformations. By associating the coordinates, a color conversion definition for converting input image data obtained by reading the original image 11 shown in FIG. 1 with the color scanner 10 into output image data suitable for the color printer 30 is created. .
[0203]
FIG. 30 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.
[0204]
The color conversion definition creation / color conversion apparatus shown in FIG. 30 is realized by combining the personal computer 20 shown in FIGS. 2 and 3 and a program executed on the personal computer.
[0205]
The color conversion definition creation / color conversion apparatus shown in FIG. 30 includes a data acquisition unit 310, an LUT creation / data conversion unit 320, a data output unit 330, a storage unit 340, and a designation unit 350. .
[0206]
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.
[0207]
Each of the input profiles 341a,..., 341m is basically created by a creation method referring to FIG. Although only one type of color scanner 10 is shown in FIG. 1, the color conversion definition creation / color conversion apparatus in FIG. 30 has a plurality of types of input devices in order to provide versatility. There are multiple types of input profiles corresponding to.
[0208]
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.
[0209]
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.
[0210]
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 LUT generation / data conversion unit 320. FIG. 9 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.
[0211]
The storage unit 340 is set in the hard disk device 213 shown in FIG. 3 in hardware.
[0212]
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.
[0213]
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 LUT creation / data conversion unit 32. Executed. The color conversion definition creation program 344 includes a color reproduction region determination process (step a1), a coordinate association process (step a2), a mapping definition creation process (step a3) (second process (step a1) described with reference to FIG. a color reproduction region determination unit 3441, a coordinate association unit 3442, and a mapping definition creation unit 3443 that execute processing corresponding to each of a31), the first step (step a32)), and the color conversion definition creation step (step a4). (Second process 3443a and first process 3443b), and a color conversion definition creating unit 3444, and based on the algorithm described above, a designated input device (here, color scanner 10 shown in FIG. 1). According to the input profile (here, input profile 341a) and the specified output An output profile (here, referred to as output profile 342a) corresponding to a vise (here, color printer 30 shown in FIG. 1) is referred to, and image data of a color chart image read by the color scanner 10 is referred to. Thus, a color conversion definition (here, color conversion definition 341a) suitable for the combination of the color scanner 10 and the color printer 30 is created. The created color conversion definition 341a is stored in the storage unit 340.
[0214]
At this time, various parameters for creating the color conversion definition are specified from the designation unit 350, for example, the second process of the mapping definition creating unit is executed or omitted, or when the second process is executed, Whether to match both the black point and only the white point, whether to set the coordinate value of the coordinate conversion reference coordinate point c shown in FIG. 15 and the like, the region D shown in FIG. Various examples have been shown as the first process of designating the area and the color conversion definition creating process. Which algorithm is selected from the various examples, the weighting described with reference to FIG. It is preferable that the weighting coefficient and the like in the case of adopting the above method can be designated so that various variations of color conversion definitions can be created.
[0215]
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 specified combination of the color scanner 10 and the color printer 30 is read out and input to the LUT creation / data conversion unit 320.
[0216]
The data acquisition unit 310 plays a role of receiving color data obtained by an input device, and the input interface 216 shown in FIG. 3 corresponds to this in hardware.
[0217]
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.
[0218]
When image data obtained by an input device such as the color scanner 10 shown in FIG. 1 is input to the LUT creation / data conversion unit 320 via the data acquisition unit 310, the LUT creation / data conversion unit 320 performs color conversion. Image data is converted according to the definition 343a. The converted image data is output to an output device such as the color printer 30 shown in FIG.
[0219]
The conversion of the image data by the LUT 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 is obtained. Can do.
[0220]
Here, in the color conversion definition creation / color conversion apparatus shown in FIG. 30, as one of the plurality of output profiles 342a,..., 342m stored in the storage unit 340, the image display apparatus shown in FIGS. 22 is prepared, an image based on the image data converted by the LUT creation / data conversion unit 320 is displayed on the display screen 22a (see FIG. 2) of the image display device 22, In addition, 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 a held image.
[0221]
FIG. 31 is a functional block diagram of the LUT creation / data conversion unit of the color conversion definition creation / color conversion apparatus shown in FIG.
[0222]
The LUT creation / data conversion unit 320 includes an LUT creation unit 321 and a data conversion unit 322. Furthermore, the LUT creation unit 321 includes a color reproduction area determination unit 3211, a coordinate association unit 3212, a mapping definition creation unit 3213 (second process 3213a and first process 3213b), and a color conversion definition creation unit 3214. ing.
[0223]
The LUT creation unit 321 operates in the color conversion definition creation mode, and the LUT creation unit 321 includes an image representing a color chart image read by a color scanner having an input profile designated by the designation unit 350 shown in FIG. Data is input, and a color conversion definition creation program 344 shown in FIG. 30 is set in the LUT creation unit 321 and executed. As a result, the color reproduction region determination unit 3211, the coordinate association unit 3212, the mapping definition creation unit 3213 (second process 3213a and first process 3213b), and the color conversion definition creation unit 214 of the LUT creation unit 321 9, the color reproduction region determination process (step a1), the coordinate correspondence process (step a2), the mapping definition creation process (step a3) (second process (step a31) and the first process (step a1) Each process corresponding to step a32)) and the color conversion definition creation process (step a4) is executed, and a color conversion definition in the LUT format is created. The created color conversion definition is stored in the storage unit 340 of FIG.
[0224]
When the data conversion mode is specified by the specification unit 350, a color conversion definition corresponding to the combination of the input profile and output profile specified by the specification unit 350 is set in the data conversion unit 322, and the input image data is It is converted into output image data in accordance with the set color conversion definition.
[0225]
FIG. 32 is a diagram showing another embodiment of the color conversion definition creating program of the present invention.
[0226]
Referring to FIG. 30, it has been described that the color change definition creating program as one embodiment of the present invention is stored in the storage unit 340 of the color conversion definition creating / color converting apparatus shown in FIG. As another example, an example in which a color conversion definition creating program 344 is stored in the CD-ROM 110 shown in FIG. 3 is shown. In this way, the color conversion definition creation program may be stored in a portable storage medium and distributed.
[0227]
A user who has obtained such a color conversion definition creation program uploads the obtained color conversion definition creation program to his or 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.
[0228]
In the embodiment described here, the color reproduction area of the color chart image is set to L.^*a^*b^*This is an example of enclosing with a dodecahedron-shaped color reproduction region in space, but instead of enclosing with a dodecahedron-shaped color reproduction region, W, K, R so that the alternate long and short dash line shown in FIG. , G, B, C, M, and Y may be defined to enclose a hexahedral color reproduction region. In enclosing the color reproduction area of the color chart image with the polyhedron-shaped color reproduction area, L^*a^*b^*Instead of enclosing in a common color space such as a space, the input color space depending on the color scanner may be enclosed in a polyhedral shape.
[0229]
【The invention's effect】
As described above, according to the present invention, the poor tone that is likely to occur when gamut mapping is performed in the common color space regardless of the size and shape of the color area that can be expressed on the image recording medium. It is possible to create a color conversion definition that can avoid a continuous or unnatural image and can obtain a reproduced image with excellent color tone.
[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 algorithm including both an input profile and an output profile.
FIG. 7 is a schematic diagram of color reproduction regions of a color scanner and a color printer.
FIG. 8 is a schematic diagram of a color reproduction area of a color chart and a color scanner.
FIG. 9 is a flowchart showing a color conversion definition creation method by a color conversion definition creation program executed in the computer system.
FIG. 10 is a diagram showing a color reproduction area of a color scanner and a color reproduction area 501 of a color chart image in an input RGB space.
FIG. 11 L^*a^*b^*Color reproduction region of color chart image in space (first color reproduction region according to the present invention) and dodecahedron shape color reproduction region including the color reproduction region (an example of the second color reproduction region according to the present invention) FIG.
FIG. 12 is an explanatory diagram of a method of assigning numerical values (coordinates) to an arbitrary point on an arbitrary plane constituting a dodecahedron.
FIG. 13 L^*a^*b^*It is explanatory drawing of how to obtain | require the coordinate of the arbitrary points in space.
FIG. 14 is an explanatory diagram of a second process of the mapping definition creating process.
FIG. 15 is an explanatory diagram of a first example of coordinate transformation in the first process.
FIG. 16 is a flowchart of the first example.
FIG. 17 is a diagram illustrating a modification of the first example of coordinate transformation.
FIG. 18 is an explanatory diagram of a second example of coordinate transformation in the first process.
FIG. 19 is a flowchart of a second example of coordinate transformation.
FIG. 20 is a diagram illustrating a modification of the second example of coordinate transformation.
FIG. 21 is an explanatory diagram of the effect of mapping performed by combining 'compression' and 'decompression'.
FIG. 22 is an explanatory diagram of a third example of coordinate transformation in the first process.
FIG. 23 is a flowchart of a third example of coordinate transformation.
FIG. 24 is a diagram illustrating a modification of the third example of coordinate transformation.
FIG. 25 is an explanatory diagram of a fourth example of coordinate transformation in the first process.
FIG. 26 is a flowchart of a fourth example of coordinate transformation.
FIG. 27 is a diagram illustrating a modification of the third example of coordinate transformation.
FIG. 28 is a diagram illustrating an intermediate process of a fifth example of coordinate conversion in the first process;
FIG. 29 is an explanatory diagram of a fifth example of coordinate transformation in the first process.
FIG. 30 is a functional block diagram of a color conversion definition creating / color converting apparatus including an embodiment of a color conversion definition creating apparatus of the present invention.
31 is a functional block diagram of the LUT / data conversion unit shown in FIG. 30. FIG.
FIG. 32 is a diagram showing another embodiment of a color conversion definition creation program.
[Explanation of symbols]
10 Color scanner
11 Document image
11a color chart image
20 Personal computer
21 Main unit
22 Image display device
22a Display screen
23 Keyboard
24 mice
25 bus
30 Color printer
100 flexible disk
110 CD-ROM
211 CPU
212 Main memory
213 Hard disk device
214 FD drive
215 CD-ROM drive
216 input interface
217 Output interface
310 Data acquisition unit
320 LUT creation / data converter
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 (5)

Create a color conversion definition for converting input image data obtained by reading an image recorded on an image recording medium with an input device into output image data suitable for an output device that outputs an image based on the image data In the color conversion definition creation method,
A polyhedral shape formed of a plurality of planes including a first color reproduction area representing a color area that can be expressed on the image recording medium and extending along the surface of the first color reproduction area. A color reproduction region determination process for determining a second color reproduction region;
Each point of the second color reproduction region is set such that the entire second color reproduction region is associated with the entire third color reproduction region of the input device in the first color space depending on the input device. Forming a second color space by assigning each coordinate to a coordinate association process for determining a correspondence relationship between the coordinates of the second color space and the coordinates of the device-independent common color space; ,
A coordinate in the second color reproduction region in the common color space is used as a fourth color reproduction region of the output device in a third color space depending on an output device that outputs an image based on image data. A mapping definition creating process for creating a mapping definition on the common color space for conversion into coordinates in the fourth color reproduction area in the common color space when mapped to the common color space according to the profile of ,
The first coordinate on the first color space is converted to the second coordinate on the second color space, the second coordinate is converted to the third coordinate on the common color space, and the third coordinate Is converted into the fourth coordinate on the common color space according to the mapping definition, and the fourth coordinate is converted into the fifth coordinate on the third color space. , color conversion definition creating how to; and a color conversion definition creating process of creating a color conversion definition between the first coordinates and the fifth coordinates. 2. The color conversion definition creating method according to claim 1, wherein the color reproduction region determining step is a step of determining a second color reproduction region having a polyhedron shape in the common color space. The color reproduction area determining process is a process of determining a dodecahedron-shaped second color reproduction area having each point representing white, black, red, green, blue, cyan, magenta, and yellow as a vertex. The color conversion definition creating method according to claim 1. Create a color conversion definition for converting input image data obtained by reading an image recorded on an image recording medium with an input device into output image data suitable for an output device that outputs an image based on the image data In the color conversion definition creation device,
A polyhedral shape formed of a plurality of planes including a first color reproduction area representing a color area that can be expressed on the image recording medium and extending along the surface of the first color reproduction area. A color reproduction region determination unit for determining a second color reproduction region;
Each point of the second color reproduction region is set such that the entire second color reproduction region is associated with the entire third color reproduction region of the input device in the first color space depending on the input device. A coordinate association unit for determining a correspondence relationship between the coordinates of the second color space and the coordinates of the device-independent common color space ,
A coordinate in the second color reproduction region in the common color space is used as a fourth color reproduction region of the output device in a third color space depending on an output device that outputs an image based on image data. A mapping definition creating unit that creates a mapping definition on the common color space for conversion into coordinates in the fourth color reproduction area in the common color space when mapped to the common color space according to the profile of ,
The first coordinate on the first color space is converted to the second coordinate on the second color space, the second coordinate is converted to the third coordinate on the common color space, and the third coordinate Is converted into the fourth coordinate on the common color space according to the mapping definition, and the fourth coordinate is converted into the fifth coordinate on the third color space. A color conversion definition creating apparatus comprising: a color conversion definition creating unit that creates a color conversion definition between the first coordinate and the fifth coordinate. Input image data that is executed in a computer and obtained by reading the image recorded on the image recording medium by the input device into output image data suitable for an output device that outputs an image based on the image data. A color conversion definition creation program that operates as a color conversion definition creation device for creating a color conversion definition for conversion,
A polyhedral shape formed of a plurality of planes including a first color reproduction area representing a color area that can be expressed on the image recording medium and extending along the surface of the first color reproduction area. A color reproduction region determination unit for determining a second color reproduction region;
Each point of the second color reproduction region is set such that the entire second color reproduction region is associated with the entire third color reproduction region of the input device in the first color space depending on the input device. A coordinate association unit for determining a correspondence relationship between the coordinates of the second color space and the coordinates of the device-independent common color space ,
A coordinate in the second color reproduction region in the common color space is used as a fourth color reproduction region of the output device in a third color space depending on an output device that outputs an image based on image data. A color conversion definition creating unit that creates a mapping definition on the common color space for conversion to coordinates in the fourth color reproduction region in the common color space when mapped to the common color space according to the profile of When,
The first coordinate on the first color space is converted to the second coordinate on the second color space, the second coordinate is converted to the third coordinate on the common color space, and the third coordinate Is converted into the fourth coordinate on the common color space in accordance with the mapping definition, and the fourth coordinate is converted into the fifth coordinate on the third color space. A color conversion definition creating program comprising: a color conversion definition creating unit that creates a color conversion definition between the first coordinate and the fifth coordinate.

Images