JP4526167B2

JP4526167B2 - Hue conversion method

Info

Publication number: JP4526167B2
Application number: JP2000244193A
Authority: JP
Inventors: 信村田; 達彦村田
Original assignee: Rohm Co Ltd
Current assignee: Rohm Co Ltd
Priority date: 2000-08-11
Filing date: 2000-08-11
Publication date: 2010-08-18
Anticipated expiration: 2020-08-11
Also published as: JP2002058042A

Description

【０００１】
【発明の属する技術分野】
本発明は、カラーテレビ受像機、カラー複写機などのカラー画像信号の処理装置における色相変換方法に関する。
【０００２】
【従来の技術】
従来、カラーテレビ受像機、カラー複写機などのカラー画像の色相を調整する場合には、色相を表す色相座標の座標全体を調整したい所定の方向に回転させることにより色相変換を行っていた。
【０００３】
【発明が解決しようとする課題】
この従来の色相変換方法では、色相座標全体を回転させるから全ての色相が変換されてしまうことになり、カラー画像中の所望の色相、例えば人間の肌色付近の色相のみを調整することが出来ないという問題があった。
【０００４】
そこで、本発明は、カラー画像中の調整したい所望の色相を、色相座標上で指示することにより、所望の色相を任意に調整することが出来る色相変換方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本明細書中に開示された第１構成の色相変換方法は、第１の色差信号と第２の色差信号との直交軸によって構成された平面座標系に色信号を表現するようにし、この平面座標系の原点を始点とし任意の方向に向かう複数の軸を設定し、これらの軸は任意に独立に変位を与え得るようにし、前記複数の軸の内の任意の二軸に挟まれる色信号を、前記二軸の少なくとも一方の軸を変位させて変化させることにより、変位された軸の両側の領域の色信号の色相を変換することを特徴とする。
【０００６】
この第１構成の色相変換方法によれば、色信号を表現する色相座標系に、複数の軸を任意の方向に設定し、これらの軸に独立に変位を与えて、その変位した軸の両側の領域の色相を変換するから、所定の色相の調整を任意に行うことが出来る。
【０００７】
また、軸の変位で座標変換をさせるから、階調処理（グラデーション）も滑らかに変更できる。
【０００８】
また、変位された軸の両側の領域が色相変換されるから、色欠けの問題も発生しない。
【０００９】
【発明の実施の形態】
以下、図面を参照して、本発明の色相変換方法の実施の形態について説明する。
【００１０】
図１、図２は、本発明の色相変換を説明するための図である。カラーテレビ受像機、カラー複写機などのカラー画像信号の色相座標は、図１のように、第１の色差信号Ｕと第２の色差信号Ｖとの直交軸によって構成された平面座標系により表現される。ここで、第１の色差信号ＵはＲ−Ｙであり、第２の色差信号ＶはＢ−Ｙである。（なお、Ｒ、Ｂは３原色の赤、青であり、Ｙは輝度信号である。）
【００１１】
図１において、第１の色差信号Ｕと第２の色差信号Ｖとの直交軸によって構成された平面座標系（以下、ＵＶ座標系、という）の任意の点Ｐは、Ｐ（ｕ、ｖ）で表されている。このＵＶ座標系に、点Ｐ（ｕ、ｖ）を挟むように、原点０を通る角度θ１の第１軸Ａと角度θ２の第２軸Ｂを設定する。
【００１２】
この軸Ａ，Ｂで座標系（以下、ＡＢ座標系、という）を構成し、このＡＢ座標系で前記点Ｐ（ｕ、ｖ）を表す。
【００１３】
まず、Ｐ（ｕ、ｖ）を、図１を参照して、ＡＢ座標系の座標α、βで表すと、
【００１４】
【数１】

【００１５】
となるから、
式（１）を変形すると、点Ｐ（α、β）は、
【００１６】
【数２】

【００１７】
と表すことができ、点ＰをＵＶ座標系で表すことができる。
【００１８】
次に、図２のように、角度θ１の第１軸Ａを角度Δθ１だけ変位させ軸Ａ′とし、角度θ２の第２軸Ｂを角度Δθ２だけ変位させ軸Ｂ′とする。この軸Ａ′，Ｂ′で構成されるＡ′Ｂ′座標系で座標（α、β）を表すことにより、点Ｐ（ｕ、ｖ）は、点Ｐ′（ｕ′、ｖ′）に変化する。
【００１９】
この変化後の点Ｐ′（ｕ′、ｖ′）を、Ａ′Ｂ′座標系で表すと、
【００２０】
【数３】

【００２１】
となる。
【００２２】
次に、式（３）のα、βに、式（２）を代入して、整理すると、変化後の点Ｐ′（ｕ′、ｖ′）は、ＵＶ座標系において、
【００２３】
【数４】

【００２４】
のように表される。
【００２５】
式（４）のように、任意の点Ｐの色相変換後の座標Ｐ′（ｕ′、ｖ′）を、変換前の座標Ｐ（ｕ、ｖ）と、角度θ１，θ２，Δθ１、Δθ２で定まる係数とにより、簡単な２次元の行列式で演算して求められる。なお、式（４）でＸ１１〜Ｘ２２は、式整理の結果の係数であり、それぞれ角度θ１，θ２，Δθ１、Δθ２で定まる。
【００２６】
以上の説明では、軸Ａと軸Ｂとに挟まれた領域にある任意の点Ｐについて説明したが、本発明における色相変換の作用は、変位された軸の両側の領域に及ぶ。
【００２７】
すなわち、ＵＶ座標系には複数の軸が設定されているから、この座標系におけるどの点を取っても、２軸に挟まれた領域となる。そして、１つの軸、例えば図１の軸Ｂが変位する場合に、軸Ａと軸Ｂとで挟まれる領域の点が色相変換されるとともに、図２中で破線で例示したように軸Ｃが設けられている場合に軸Ｂと軸Ｃとで挟まれる領域の点も同様に色相変換される。このようにして、変位した軸の両側の領域の色相がそれぞれ対応して変換される。なお、軸数としては最低限２軸あれば良く、この２軸の内の少なくとも１軸を変位させることにより、所定の色相変換を行うことができる。
【００２８】
このように、色信号を表現するＵＶ座標系に、複数の軸（少なくとも２軸Ａ，Ｂ）を設定し、これらの軸Ａ，Ｂに独立に変位を与えて、その変位した軸の両側の領域の色相を変換するから、階調処理（グラデーション）も滑らかに変更できる。また、変位された軸、例えばＡ軸の両側の領域が色相変換されるから、色欠けの問題も発生しない。
【００２９】
図３，図４は、本発明の色相変換方法を、８軸の場合に適用した例を示すものであり、図３はＵＶ座標上での軸Ａ１〜軸Ａ８の設定状況を示しており、図４は色相変換のブロック回路を示している。
【００３０】
図３において、ＵＶ座標系上に、軸Ａ１〜軸Ａ８を、軸Ａ１がｖ軸と一致するように設定し、軸Ａ２以降の各軸はそれぞれ４５度づつ順次ずらした角度で設定されている。この結果、図のように奇数軸である軸Ａ１，軸Ａ３，軸Ａ５，軸Ａ７はそれぞれＵＶ座標の軸と対応し、偶数軸である軸Ａ２，軸Ａ４，軸Ａ６，軸Ａ８はＵＶ座標の軸から４５度の角度にある。
【００３１】
これら軸Ａ１と軸Ａ２とで挟まれた領域▲１▼が形成され、以下同様に軸Ａ２と軸Ａ３で領域▲２▼、軸Ａ３と軸Ａ４で領域▲３▼、軸Ａ４と軸Ａ５で領域▲４▼、軸Ａ５と軸Ａ６で領域▲５▼、軸Ａ６と軸Ａ７で領域▲６▼、軸Ａ７と軸Ａ８で領域▲７▼、軸Ａ８と軸Ａ１で領域▲８▼が、それぞれ形成される。
【００３２】
そして、これらの軸Ａ１〜軸Ａ８は、それぞれ独立して任意の正負の角度だけ変位させることができる。例えば軸Ａ２を軸Ａ３方向に所定角度Δθ２だけ変位させると、この軸Ａ２の変位は、領域▲１▼と領域▲２▼との両方の領域の色相を互いに関連して変更することになる。
【００３３】
図４の色相変換用ブロック回路４０は、ＵＶ座標系で表現されている画像データを入力信号ｕ，ｖとして受けて、所望の色相変換処理を受けた変換後の画像データの出力信号ｕ′，ｖ′を出力するものであり、以下の構成要素を有している。
【００３４】
領域判別及び係数設定装置４１は、入力信号ｕ，ｖが順次入力され、その入力信号が図３の領域▲１▼〜▲８▼のいずれの領域に属するかの判定を行う領域判定機能と、各軸Ａ１〜Ａ８が変位されるかどうか、変位されるとするとどちらの方向にいくら変位するかの色相変更指定Δθ１〜Δθ８が入力され、入力信号ｕ，ｖの領域判定に応じて計算された各係数Ｋ１〜Ｋ４を設定する係数設定機能を有しており、設定された係数Ｋ１〜Ｋ４を出力するものである。
【００３５】
乗算器４２は、入力信号のｕ成分と第１係数Ｋ１を乗算し、同じく乗算器４３は入力信号のｖ成分と第２係数Ｋ２を乗算し、乗算器４４は入力信号のｕ成分と第３係数Ｋ３を乗算し、乗算器４５は入力信号のｖ成分と第４係数Ｋ４を乗算する。
【００３６】
加算器４６は、第１乗算器４２の乗算結果と第２乗算器４３の乗算結果とを加算し、その加算結果ｕ′＝Ｋ１・ｕ＋Ｋ２・ｖを出力し、加算器４７は、第３乗算器４４の乗算結果と第４乗算器４５の乗算結果とを加算し、その加算結果ｖ′＝Ｋ３・ｕ＋Ｋ４・ｖを出力する。この出力された加算結果ｕ′、ｖ′が、色相変換処理を受けた変換後の画像データとなる。
【００３７】
この色相変換ブロック４０における変換式は、前述のように、
ｕ′＝Ｋ１・ｕ＋Ｋ２・ｖ・・・（５）
ｖ′＝Ｋ３・ｕ＋Ｋ４・ｖ・・・（６）
となる。
【００３８】
式（５）、式（６）における各係数Ｋ１〜Ｋ４は次のように定義される。
Ｋ１={cos(a)*sin(b)*cos(Δ1)-sin(a)*sin(b)*sin(Δ1)-sin(a)*cos(b)*cos(Δ2)+sin(a)*sin(b)*sin(Δ2)}/sin(b-a)
=coef1*cos(Δ1)-coef2*sin(Δ1)-coef3*cos(Δ2)+coef2*sin(Δ2) ・・・（７）
Ｋ２={-cos(a)*cos(b)*cos(Δ1)+sin(a)*cos(b)*sin(Δ1)+cos(a)*cos(b)*cos(Δ2)-cos(a)*sin(b)*sin(Δ2)}/sin(b-a)
=-coef4*cos(Δ1)+coef3*sin(Δ1)+coef4*cos(Δ2)-coef1*sin(Δ2) ・・・（８）
Ｋ３={sin(a)*sin(b)*cos(Δ1)+cos(a)*sin(b)*sin(Δ1)-sin(a)*sin(b)*cos(Δ2)-sin(a)*cos(b)*sin(Δ2)}/sin(b-a)
=coef2*cos(Δ1)+coef1*sin(Δ1)-coef2*cos(Δ2)-coef3*sin(Δ2) ・・・（９）
Ｋ４={-sin(a)*cos(b)*cos(Δ1)-cos(a)*cos(b)*sin(Δ1)+cos(a)*sin(b)*cos(Δ2)+cos(a)*cos(b)*sin(Δ2)}/sin(b-a)
=-coef3*cos(Δ1)-coef4*sin(Δ1)+coef1*cos(Δ2)+coef4*sin(Δ2) ・・・（１０）
【００３９】
なお、式（７）〜式（１０）の角度（ａ）、（ｂ）、（Δ1）、（Δ2）は、図１，図２における角度（θ１）、（θ２）、（Δθ１）、（Δθ２）にそれぞれ相当する。
【００４０】
係数Ｋ１〜Ｋ４を表す式（７）〜（１０）において、各変数ｃｏｅｆ１〜ｃｏｅｆ４は、次のように整理される。
coef1=cos(a)*sin(b)/sin(b-a)
coef2=sin(a)*sin(b)/sin(b-a)
coef3=sin(a)*cos(b)/sin(b-a)
coef4=cos(a)*cos(b)/sin(b-a)
【００４１】
また、各変数ｃｏｅｆ１〜ｃｏｅｆ４と領域▲１▼〜▲８▼との関係は、次の表のように整理される。
領域 coef1 coef2 coef3 coef4
▲１▼ １００１
▲２▼ １１００
▲３▼ ０１ −１０
▲４▼ ００ −１１
▲５▼ １００１
▲６▼ １１００
▲７▼ ０１ −１０
▲８▼ ００ −１１
【００４２】
さて、図４の色相変換用ブロック回路４０において、まず、領域判別及び係数設定装置４１に各軸Ａ１〜Ａ８が変位されるかどうか、変位されるとするとどちらの方向にいくら変位するかの色相変更指定Δθ１〜Δθ８が入力される。領域判別及び係数設定装置４１は、色相変更指定Δθ１〜Δθ８により各軸Ａ１〜Ａ８の変更角が設定されるから、この変更角に基づいて各領域▲１▼〜▲８▼での係数Ｋ１〜Ｋ４を式（７）〜式（１０）により計算する。この計算された係数Ｋ１〜Ｋ４は、メモリに記憶しておく。この状態で、ＵＶ座標系で表現されている画像データの入力信号ｕ，ｖが順次入力される。
【００４３】
そして、順次入力される入力信号ｕ，ｖが領域▲１▼〜▲８▼のいずれの領域に属するか判定される。この実施の形態では、８軸をＵＶ座標系上に、軸Ａ１がｖ軸と一致するように設定し、軸Ａ２以降の各軸はそれぞれ４５度づつ順次ずらした角度で設定しているから、入力信号ｕ，ｖのｕ成分とｖ成分との大小及び正負の比較のみで、入力信号ｕ，ｖが領域▲１▼〜▲８▼のどの領域に属するかを判別できるから、領域判別回路を簡単な回路で構成することができる。
【００４４】
この入力信号ｕ，ｖの領域判定結果に基づいて、予め計算され記憶されている係数Ｋ１〜Ｋ４がその領域に応じて、領域判別及び係数設定装置４１から出力される。
【００４５】
そして、入力信号ｕ，ｖのｕ成分とｖ成分及び係数Ｋ１〜Ｋ４とから、乗算器４２〜４５，加算器４６，４７で、それぞれ乗算処理と加算処理が行われて、色相変換された出力信号ｕ′（＝Ｋ１・ｕ＋Ｋ２・ｖ）、ｖ′（＝Ｋ３・ｕ＋Ｋ４・ｖ）が出力される。
【００４６】
この図３，図４の例では、軸数を８軸としているが、この軸数は任意の数とすることができ、また各軸の設定角度も均一に限らず、任意の角度に設定することができる。
【００４７】
【発明の効果】
本明細書中に開示された色相変換方法によれば、色信号を表現する色相座標系に、複数の軸を任意の方向に設定し、これらの軸に独立に変位を与えて、その変位した軸の両側の領域の色相を変換するから、所定の色相の調整を任意に行うことが出来る。
【００４８】
また、軸の変位で座標変換をさせるから、階調処理（グラデーション）も滑らかに変更できる。
【００４９】
また、変位された軸の両側の領域が色相変換されるから、色欠けの問題も発生しない。
【図面の簡単な説明】
【図１】本発明の色相変換を説明するための図。
【図２】本発明の色相変換を説明するための図。
【図３】本発明の色相変換方法を８軸の場合に適用した例を示す図。
【図４】本発明の色相変換方法における色相変換のブロック回路。
【符号の説明】
Ａ１〜Ａ８設定された軸
▲１▼〜▲８▼ 軸により区分される領域
４１領域判別及び係数設定器
４２〜４５乗算器
４６，４７加算器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hue conversion method in a color image signal processing apparatus such as a color television receiver or a color copying machine.
[0002]
[Prior art]
Conventionally, in the case of adjusting the hue of a color image such as a color television receiver or a color copying machine, the hue conversion is performed by rotating the entire coordinates of the hue coordinates representing the hue in a predetermined direction.
[0003]
[Problems to be solved by the invention]
In this conventional hue conversion method, since all the hue coordinates are rotated, all hues are converted, and it is impossible to adjust only a desired hue in a color image, for example, a hue near human skin color. There was a problem.
[0004]
Accordingly, an object of the present invention is to provide a hue conversion method capable of arbitrarily adjusting a desired hue by indicating a desired hue to be adjusted in a color image on hue coordinates.
[0005]
[Means for Solving the Problems]
According to the hue conversion method of the first configuration disclosed in the present specification , a color signal is expressed in a plane coordinate system configured by orthogonal axes of the first color difference signal and the second color difference signal. Set a plurality of axes starting from the origin of the coordinate system and going in any direction, these axes can be arbitrarily displaced, color signal sandwiched between any two of the plurality of axes By changing at least one of the two axes, the hue of the color signal in the area on both sides of the displaced axis is converted.
[0006]
According to the hue conversion method of the first configuration , a plurality of axes are set in an arbitrary direction in the hue coordinate system expressing a color signal, and displacement is independently applied to these axes, and both sides of the displaced axes are set. Since the hue of this area is converted, the predetermined hue can be arbitrarily adjusted.
[0007]
In addition, since the coordinate conversion is performed by the displacement of the axis, the gradation processing (gradation) can be changed smoothly.
[0008]
In addition, since the regions on both sides of the displaced axis are subjected to hue conversion, the problem of lack of color does not occur.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the hue conversion method of the present invention will be described below with reference to the drawings.
[0010]
1 and 2 are diagrams for explaining the hue conversion of the present invention. Hue coordinates of a color image signal of a color television receiver, a color copying machine, etc. are expressed by a plane coordinate system constituted by orthogonal axes of a first color difference signal U and a second color difference signal V as shown in FIG. Is done. Here, the first color difference signal U is RY, and the second color difference signal V is BY. (Note that R and B are the three primary colors red and blue, and Y is a luminance signal.)
[0011]
In FIG. 1, an arbitrary point P in a plane coordinate system (hereinafter referred to as a UV coordinate system) constituted by orthogonal axes of the first color difference signal U and the second color difference signal V is P (u, v). It is represented by In this UV coordinate system, a first axis A having an angle θ1 passing through the origin 0 and a second axis B having an angle θ2 are set so as to sandwich the point P (u, v).
[0012]
A coordinate system (hereinafter referred to as AB coordinate system) is constituted by the axes A and B, and the point P (u, v) is represented by the AB coordinate system.
[0013]
First, P (u, v) is represented by coordinates α and β in the AB coordinate system with reference to FIG.
[0014]
[Expression 1]

[0015]
So,
By transforming equation (1), the point P (α, β) becomes
[0016]
[Expression 2]

[0017]
The point P can be expressed in the UV coordinate system.
[0018]
Next, as shown in FIG. 2, the first axis A at the angle θ1 is displaced by an angle Δθ1 to be an axis A ′, and the second axis B at an angle θ2 is displaced by an angle Δθ2 to be an axis B ′. By expressing the coordinates (α, β) in the A′B ′ coordinate system composed of the axes A ′ and B ′, the point P (u, v) is changed to the point P ′ (u ′, v ′). To do.
[0019]
When the point P ′ (u ′, v ′) after this change is expressed in the A′B ′ coordinate system,
[0020]
[Equation 3]

[0021]
It becomes.
[0022]
Next, when formula (2) is substituted into α and β in formula (3) and rearranged, the point P ′ (u ′, v ′) after the change is expressed in the UV coordinate system as follows:
[0023]
[Expression 4]

[0024]
It is expressed as
[0025]
As shown in the equation (4), the coordinates P ′ (u ′, v ′) after the hue conversion of an arbitrary point P are expressed by the coordinates P (u, v) before the conversion and the angles θ1, θ2, Δθ1, and Δθ2. It is calculated by a simple two-dimensional determinant according to the determined coefficient. In Equation (4), X11 to X22 are coefficients resulting from the rearrangement of equations, and are determined by angles θ1, θ2, Δθ1, and Δθ2, respectively.
[0026]
In the above description, the arbitrary point P in the region sandwiched between the axis A and the axis B has been described. However, the action of hue conversion in the present invention extends to the regions on both sides of the displaced axis.
[0027]
That is, since a plurality of axes are set in the UV coordinate system, any point in this coordinate system is an area sandwiched between two axes. When one axis, for example, the axis B in FIG. 1, is displaced, the point of the region sandwiched between the axis A and the axis B is subjected to hue conversion, and the axis C as illustrated by the broken line in FIG. If provided, the points of the region sandwiched between the axis B and the axis C are similarly subjected to hue conversion. In this way, the hues of the regions on both sides of the displaced axis are converted correspondingly. The number of axes may be at least two, and predetermined hue conversion can be performed by displacing at least one of the two axes.
[0028]
In this way, a plurality of axes (at least two axes A and B) are set in the UV coordinate system that expresses the color signal, and the axes A and B are independently displaced, and both sides of the displaced axes are set. Since the hue of the area is converted, gradation processing (gradation) can be changed smoothly. Further, since the hue of the displaced axis, for example, the area on both sides of the A axis is converted, the problem of lack of color does not occur.
[0029]
3 and 4 show an example in which the hue conversion method of the present invention is applied to the case of 8 axes, and FIG. 3 shows the setting status of the axes A1 to A8 on the UV coordinates. FIG. 4 shows a block circuit for hue conversion.
[0030]
In FIG. 3, on the UV coordinate system, the axes A1 to A8 are set so that the axis A1 coincides with the v-axis, and each axis after the axis A2 is set at an angle that is sequentially shifted by 45 degrees. . As a result, as shown in the figure, the odd-numbered axes A1, A3, A5, and A7 correspond to the UV coordinate axes, and the even-numbered axes A2, A4, A6, and A8 are the UV coordinates. At an angle of 45 degrees from the axis.
[0031]
An area (1) sandwiched between the axes A1 and A2 is formed. Similarly, the area (2) is formed between the axes A2 and A3, the area (3) is formed between the axes A3 and A4, and the areas A3 and A5 are formed. Region (4), Axis A5 and A6 are region (5), Axis A6 and A7 are region (6), Axis A7 and A8 are region (7), Axis A8 and A1 are region (8), Each is formed.
[0032]
These axes A1 to A8 can be independently displaced by any positive and negative angles. For example, when the axis A2 is displaced in the direction of the axis A3 by a predetermined angle Δθ2, the displacement of the axis A2 changes the hues of both the areas (1) and (2) in relation to each other.
[0033]
4 receives the image data expressed in the UV coordinate system as input signals u and v, and outputs output signals u ′ and v ′ of the converted image data subjected to a desired hue conversion process. v 'is output and has the following components.
[0034]
The area determination and coefficient setting device 41 has an area determination function that sequentially receives input signals u and v, and determines which of the areas (1) to (8) in FIG. Hue change designations Δθ1 to Δθ8 indicating whether or not each of the axes A1 to A8 is displaced and in which direction the displacement is assumed are input, and are calculated according to the region determination of the input signals u and v. It has a coefficient setting function for setting the coefficients K1 to K4, and outputs the set coefficients K1 to K4.
[0035]
The multiplier 42 multiplies the u component of the input signal by the first coefficient K1, the multiplier 43 similarly multiplies the v component of the input signal by the second coefficient K2, and the multiplier 44 multiplies the u component of the input signal by the third coefficient K2. Multiplying by the coefficient K3, the multiplier 45 multiplies the v component of the input signal by the fourth coefficient K4.
[0036]
The adder 46 adds the multiplication result of the first multiplier 42 and the multiplication result of the second multiplier 43, and outputs the addition result u ′ = K1 · u + K2 · v. The adder 47 outputs the third multiplication. The multiplication result of the multiplier 44 and the multiplication result of the fourth multiplier 45 are added, and the addition result v ′ = K3 · u + K4 · v is output. The output addition results u ′ and v ′ become the converted image data subjected to the hue conversion process.
[0037]
The conversion formula in the hue conversion block 40 is as described above.
u ′ = K1 · u + K2 · v (5)
v ′ = K3 · u + K4 · v (6)
It becomes.
[0038]
Each coefficient K1-K4 in Formula (5) and Formula (6) is defined as follows.
K1 = {cos (a) * sin (b) * cos (Δ1) -sin (a) * sin (b) * sin (Δ1) -sin (a) * cos (b) * cos (Δ2) + sin ( a) * sin (b) * sin (Δ2)} / sin (ba)
= coef1 * cos (Δ1) -coef2 * sin (Δ1) -coef3 * cos (Δ2) + coef2 * sin (Δ2) (7)
K2 = {-cos (a) * cos (b) * cos (Δ1) + sin (a) * cos (b) * sin (Δ1) + cos (a) * cos (b) * cos (Δ2) -cos (a) * sin (b) * sin (Δ2)} / sin (ba)
= -coef4 * cos (Δ1) + coef3 * sin (Δ1) + coef4 * cos (Δ2) -coef1 * sin (Δ2) (8)
K3 = {sin (a) * sin (b) * cos (Δ1) + cos (a) * sin (b) * sin (Δ1) -sin (a) * sin (b) * cos (Δ2) -sin ( a) * cos (b) * sin (Δ2)} / sin (ba)
= coef2 * cos (Δ1) + coef1 * sin (Δ1) -coef2 * cos (Δ2) -coef3 * sin (Δ2) (9)
K4 = {-sin (a) * cos (b) * cos (Δ1) -cos (a) * cos (b) * sin (Δ1) + cos (a) * sin (b) * cos (Δ2) + cos (a) * cos (b) * sin (Δ2)} / sin (ba)
= -coef3 * cos (Δ1) -coef4 * sin (Δ1) + coef1 * cos (Δ2) + coef4 * sin (Δ2) (10)
[0039]
Note that the angles (a), (b), (Δ1), and (Δ2) in the equations (7) to (10) are the angles (θ1), (θ2), (Δθ1), ( Δθ2) respectively.
[0040]
In the equations (7) to (10) representing the coefficients K1 to K4, the variables coef1 to coef4 are arranged as follows.
coef1 = cos (a) * sin (b) / sin (ba)
coef2 = sin (a) * sin (b) / sin (ba)
coef3 = sin (a) * cos (b) / sin (ba)
coef4 = cos (a) * cos (b) / sin (ba)
[0041]
The relationship between each variable coef1 to coef4 and the areas (1) to (8) is organized as shown in the following table.
Domain coef1 coef2 coef3 coef4
(1) 1 0 0 1
(2) 1 1 0 0
(3) 0 1 -1 0
(4) 0 0 -1 1
(5) 1 0 0 1
(6) 1 1 0 0
(7) 0 1 -1 0
(8) 0 0 -1 1
[0042]
In the hue conversion block circuit 40 shown in FIG. 4, first, whether or not each of the axes A1 to A8 is displaced by the region discrimination and coefficient setting device 41, and if so, how much the hue is displaced. Change designations Δθ1 to Δθ8 are input. In the area determination and coefficient setting device 41, the change angles of the axes A1 to A8 are set by the hue change designations Δθ1 to Δθ8. Based on the change angles, the coefficients K1 to K1 in the areas (1) to (8) are set. K4 is calculated according to equations (7) to (10). The calculated coefficients K1 to K4 are stored in a memory. In this state, input signals u and v of image data expressed in the UV coordinate system are sequentially input.
[0043]
Then, it is determined which of the areas (1) to (8) the input signals u and v that are sequentially input belong. In this embodiment, the eight axes are set on the UV coordinate system so that the axis A1 coincides with the v axis, and each axis after the axis A2 is set at an angle that is sequentially shifted by 45 degrees. Since the input signals u and v can be determined to which of the areas (1) to (8) only by comparing the magnitude and positive / negative of the u component and the v component of the input signals u and v. It can be configured with a simple circuit.
[0044]
Based on the region determination results of the input signals u and v, the coefficients K1 to K4 calculated and stored in advance are output from the region determination and coefficient setting device 41 according to the region.
[0045]
Then, multiplication and addition processing are performed by the multipliers 42 to 45 and the

adders

46 and 47 from the u component and the v component of the input signals u and v, and the coefficients K1 to K4, respectively, and the hue converted output. Signals u ′ (= K1 · u + K2 · v) and v ′ (= K3 · u + K4 · v) are output.
[0046]
In the example of FIGS. 3 and 4, the number of axes is eight. However, the number of axes can be an arbitrary number, and the setting angle of each axis is not limited to be uniform, and is set to an arbitrary angle. be able to.
[0047]
【The invention's effect】
According to the hue conversion method disclosed in the present specification , a plurality of axes are set in an arbitrary direction in the hue coordinate system that expresses a color signal, and the displacement is independently given to these axes. Since the hues of the regions on both sides of the axis are converted, the predetermined hue can be adjusted arbitrarily.
[0048]
In addition, since the coordinate conversion is performed by the displacement of the axis, gradation processing (gradation) can be changed smoothly.
[0049]
In addition, since the regions on both sides of the displaced axis are subjected to hue conversion, the problem of lack of color does not occur.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining hue conversion of the present invention.
FIG. 2 is a diagram for explaining hue conversion according to the present invention.
FIG. 3 is a diagram showing an example in which the hue conversion method of the present invention is applied to the case of eight axes.
FIG. 4 is a block diagram of hue conversion in the hue conversion method of the present invention.
[Explanation of symbols]
A1 to A8 Set axes (1) to (8) Area 41 divided by axes Area discrimination and coefficient setting units 42 to 45

Multipliers

46 and 47 Adders

Claims

The color signal is expressed in a first plane coordinate system configured by orthogonal axes of the first color difference signal and the second color difference signal, and the first plane coordinate system starts in the arbitrary direction starting from the origin of the first plane coordinate system. 1 axis, a second axis adjacent to the first axis, and a third axis adjacent to the second axis,
The first region sandwiched between the first shaft and the second shaft and the second region sandwiched between the second shaft and the third shaft are changed by displacing the second shaft. By letting
Converting the hue of the color signals of the first region and the second region on both sides of the second axis,
The first color signal in the first region represented by the first plane coordinate system is coordinate-transformed into a second plane coordinate system stretched by the first axis and the second axis, and the first Coordinate-transforming the second color signal in the second region represented by a plane coordinate system into a third plane coordinate system stretched by the second axis and the third axis;
Displacing the second axis ;
The second plane coordinate system after the second axis is displaced with respect to the first color signal and the second color signal converted into the second plane coordinate system and the third plane coordinate system before the second axis is displaced. The hue of the first color signal and the second color signal is converted by re-converting to the first plane coordinate system by the coordinate conversion from the third plane coordinate system to the first plane coordinate system. Conversion method.

Adjoin the third axis, and sets a fourth axis outside the second region,
By changing the second region and the third region sandwiched between the third axis and the fourth axis by displacing the third axis,
Converting hues of color signals of the second region and the third region on both sides of the third axis,
The second color signal is coordinate-converted to the third plane coordinate system, and the third color signal in the third region represented by the first plane coordinate system is converted to the third axis and the fourth axis. Coordinate transformation to the fourth plane coordinate system stretched around the axis,
Displacing the third axis;
The third plane coordinate system before displacing the third axis, the second color signal converted to the fourth plane coordinate system, the third color signal, and the third plane coordinate system after displacing the third axis The hue of the second color signal and the third color signal is converted by re-converting to the first plane coordinate system by coordinate conversion from the fourth plane coordinate system to the first plane coordinate system. Item 2. The hue conversion method according to Item 1.

2. The hue conversion method according to claim 1, wherein the first axis and the third axis coincide with one and the other of orthogonal axes of the first planar coordinate system, respectively.

Starting from the origin of the first plane coordinate system, the first color difference signals are sequentially angled from 0 °, 45 °, 90 °, 135 °, 180 °, 225 °, 270 °, and 315 °, respectively. Set the 8 axes to go to
2. The hue conversion method according to claim 1, wherein among the eight axes, any three adjacent axes are the first axis, the second axis, and the third axis.