JP2004096444A - Image processor and method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor and a method thereof that emphasize image data so that saturation will be within a desired color range. <P>SOLUTION: A color range decision part 111 decides whether RGB values of image data outputted from a saturation emphasis part 106 are in a color range based upon color range data in a color range data storage part 12. When all pixels are in the color range, the image data outputted from the saturation emphasis part 106 are outputted as they are to an edge emphasis part 107. When there is a pixel which is not in the color range, a parameter change part 113 is made to obtain a saturation emphasis parameter for weaker saturation emphasis from a saturation emphasis parameter storage part 114 and the obtained saturation emphasis parameter is set to the saturation emphasis part 106. Then the saturation emphasis part 106 is made to perform saturation emphasis processing again. <P>COPYRIGHT: (C)2004,JPO

Description

【００３１】
彩度強調部１０６および色域判定部１１１は、通常撮影モードでは処理を行わず、色補正部１０５から出力される画像データをスルーする。
【００３２】
エッジ強調部１０７は、色域判定部１１１から出力される画像データにフィルタリングを施して、所定方向の輪郭部分をそれぞれ抽出し、抽出した輪郭部分に対して、その方向ごとに最適なエッジ強調フィルタを作用させてエッジ強調を行う。また、輪郭の方向性がなく孤立したノイズ成分に対しては、逆に、ローパス効果のあるフィルタ処理を行う。
【００３３】
ガンマ変換部１０８は、エッジ強調部１０７から出力される画像データのＲＧＢ各チャネルに対して、テーブルを参照して、ディスプレイの電圧−輝度特性（ガンマ特性）に合わせることを主目的とするガンマ変換を施す。
【００３４】
ガンマ変換部１０８から出力される画像データは、画像圧縮部１０９により、所望の画質または圧縮率に応じて圧縮され、記録再生部１１０に出力される。記録再生部１１０は、所定の画像フォーマットに従い、圧縮された画像データおよび撮影時の情報を一つの画像データ（ファイル）として記録媒体２００に記録する。
【００３５】
●彩度強調モード
次に、彩度強調モードの撮影を説明する。なお、色補正部１０５までの処理は通常の撮影モードと同じだから、色補正部１０５の出力以降の動作について説明する。
【００３６】
彩度強調部１０６は、色補正部１０５から出力される画像データに、式（２）に示すマトリクス演算によって彩度強調処理を施す。

【００３７】
色域判定部１１１は、彩度強調部１０６から出力される画像データのＲＧＢ値に対して、色域データ記憶部１１２に記憶されている色域データに基づく、色域内外判定を行う。図３は視覚限界領域を説明する色度図で、図中の馬蹄形の実線（スペクトル軌跡）が視覚限界領域の境界を表す。色域判定部１１１は、入力のＲＧＢ値が図３に示す境界に対して内か外かを判定するもので、図４はその判定アルゴリズムを示すフローチャートである。
【００３８】
まず、ｓｃＲＧＢ色空間の入力画像データから、マトリクス演算により、ＣＩＥ　１９３１　ＸＹＺ系の色座標値（Ｘ，　Ｙ，　Ｚ）を求め、式（３）に従い、色度値ｘ，　ｙを算出する（Ｓ１０１）。
ｘ　＝　Ｘ／（Ｘ　＋　Ｙ　＋　Ｚ）
ｙ　＝　Ｙ／（Ｘ　＋　Ｙ　＋　Ｚ）　　　…（３）
【００３９】
以下、（ｘ，　ｙ，　Ｙ）で示される色が色域の内か外かを、色域データ記憶部１１２に記憶された色域データに基づき判定する。なお、色域データ記憶部１１２には、視覚限界領域のＹの取り得る範囲を表すＹの最大値および最小値、Ｙの範囲を複数の領域に分割した各領域ごとのｘの取り得る範囲を表すｘの最大値および最小値を表す一次元テーブル、（ｘ，　Ｙ）の範囲を複数の領域に分割した各領域ごとのｙの取り得る範囲を表すｙ値の最大値および最小値を表す二次元テーブルが記憶されている。
【００４０】
そして、算出されたＹ値が色域の範囲内か否かを判定する（Ｓ１０２）。Ｙ値が範囲内ならば、次にそのＹ値に対応するｘ値の範囲を取得して（Ｓ１０３）、算出されたｘ値が色域範囲内か否かを判定する（Ｓ１０４）。ｘ値が範囲内ならば、次に（ｘ，　Ｙ）値に対応するｙ値の範囲を取得して（Ｓ１０５）、算出されたｙ値が色域範囲内か否かを判定する（Ｓ１０６）。
【００４１】
そして、ステップＳ１０２、Ｓ１０４およびＳ１０６の判定において、すべて色域範囲内と判定された場合は、画像データが色域範囲内にあることを表すフラグＧｉに‘１’をセットし（Ｓ１０７）、何れかの判定で色域範囲外と判定された場合はフラグＧｉに‘０’をセットする（Ｓ１０８）。なお、この判定は、画像データの全画素について繰り返される。
【００４２】
色域判定部１１１は、画像データの全画素が色域範囲内にある場合（つまりフラグＧｉがすべて‘１’）、彩度強調部１０６から出力された画像データをそのままエッジ強調部１０７に出力する。一方、色域範囲外の画素が存在する場合（つまりフラグＧｉの少なくとも一つが‘０’）、パラメータ変更部１１３に、彩度強調パラメータ記憶部１１４からデフォルトの彩度強調パラメータの次に彩度強調の度合いが弱い彩度強調パラメータを取得させ、取得した彩度強調パラメータを彩度強調部１０６に設定させる。
【００４３】
彩度強調パラメータを再設定した場合、画素補間部１０４の出力画像データの全画素に対して、再度、色補正部１０５による色補正、彩度強調部１０６による彩度強調処理、および、色域判定部１１１による色域内外判定が行われる。彩度強調パラメータ記憶部１１４には複数の彩度強調パラメータが記憶されていて、パラメータ変更部１１３は、彩度強調の度合いが強い彩度強調パラメータから弱い彩度強調パラメータに向かって順次選択する。そして、色域判定部１１１の判定により、全画素が色域範囲内になるまで彩度強調パラメータの選択および設定、並びに、色補正、彩度強調処理および色域内外判定が繰り返される。ただし、パラメータ変更部１１３により、彩度強調の度合いが最も弱い彩度強調パラメータが彩度強調部１１６に設定した場合、色域判定部１１１は、色域判定を行わず、彩度強調部１１６から出力される画像データをそのままエッジ強調部１０７に入力する。
【００４４】
以降のエッジ強調部１０７から記録再生部１１０の処理は、通常の撮影モードと同じだから、その説明を省略する。
【００４５】
このように、本実施形態によれば、彩度強調を施した画像データに対して、色域内外判定を行い、画像データのＲＧＢ値が色域範囲外にある場合は、彩度強調の度合いがより弱い彩度強調パラメータを再設定して、再び彩度強調を行う。従って、撮影時のシーンの色特性を反映し、彩度の高い画像の取得が予想されるシーンに対しても、視覚限界領域内で、できるだけ彩度が強調された画像データを記録することができる。
【００４６】
【第２実施形態】
以下、本発明にかかる第２実施形態の画像処理装置を説明する。なお、第２実施形態において、第１実施形態と略同様の構成については、同一符号を付して、その詳細説明を省略する。
【００４７】
第２実施形態は、第１実施形態と同様、視覚限界領域より広い色空間における画像データの記録を想定し、彩度強調モードにおいて、彩度強調部１０６から出力される画像データが視覚限界領域を逸脱しないように彩度強調処理を行う例を説明する。
【００４８】
図５は第２実施形態の画像処理装置であるディジタルカメラの構成例を示すブロック図である。
【００４９】
撮像部１０１から色補正部１０５までの処理は、第１実施形態と同様であるから、その説明を省略する。
【００５０】
画像解析部１２１は、色補正部１０５から出力される画像データのＲＧＢ値を基に、式（４）を使用して各画素の色差Ｒ−Ｙ、Ｂ−Ｙを計算する。そして、画像データ全体における色差Ｒ−Ｙ、Ｂ−Ｙの最大値をそれぞれ、画像解析結果としてパラメータ選択部１２２に出力する。
Ｒ　−　Ｙ　＝　０．７０×Ｒ　−　０．５９×Ｇ　−　０．１１×Ｂ
Ｂ　−　Ｙ　＝　−０．３０×Ｒ　−　０．５９×Ｇ　＋　０．８９×Ｂ　　　…（４）
【００５１】
彩度強調パラメータ記憶部１１４は、第１実施形態と同様に、彩度強調パラメータを予め複数記憶する。パラメータ選択部１２２は、画像解析部１２１から出力される色差Ｒ−Ｙ、Ｂ−Ｙの最大値と、彩度強調パラメータ記憶部１１４に記憶された各彩度強調パラメータとの関係を示すテーブルを予め記憶する。このテーブルには、色差Ｒ−Ｙおよび色差Ｂ−Ｙそれぞれの値ごとに、視覚限界領域を超えないように彩度強調処理が可能な彩度強調パラメータのうち、彩度の強調の度合いが最も強い彩度強調パラメータのインデックスが記憶されている。
【００５２】
パラメータ選択部１２２は、上記のテーブルから、色差Ｒ−Ｙの最大値に対応する彩度強調パラメータのインデックス、および、色差Ｂ−Ｙの最大値に対応する彩度強調パラメータのインデックスを抽出し、度合いが弱い方の彩度強調パラメータを選択して、彩度強調部１０６に設定する。
【００５３】
彩度強調部１０６は、パラメータ選択部１２２によって設定された彩度強調パラメータを使用して、色補正部１０５から出力される画像データに彩度強調を施す。
【００５４】
以降のエッジ強調部１０７から記録再生部１１０の処理は、第１実施形態と同じだから、その詳細説明を省略する。
【００５５】
このように、パラメータ選択部１２２は、色差Ｒ−Ｙ、Ｂ−Ｙの最大値に応じた彩度強調パラメータを選択し、度合いが弱い方を彩度強調部１０６に設定する。
【００５６】
つまり、色差の最大値が大きい場合は撮影された被写体シーンの彩度が高いものと判断されるが、色差に応じた彩度強調パラメータを使用することで、視覚限界領域を逸脱しないように彩度強調を抑えることができる。また、色差の最大値が小さい場合は撮影された被写体シーンの彩度が低いものと判断されるが、この場も低い彩度に応じた彩度強調パラメータを使用することで、彩度強調したにもかかわらず色褪せた画像にならないように、彩度強調を行うことができる。このような適応的な彩度強調処理によれば、視覚限界領域内で所望する彩度強調効果を得ることができる。
【００５７】
【変形例】
上記では、予め複数記憶した彩度強調パラメータを、画像解析部１２１の出力に応じて選択する例を説明したが、画像解析部１２１の出力に応じて最適な彩度強調パラメータを生成して、彩度強調部１０６に設定するようにしてもよい。例えば、彩度強調パラメータ記憶部１１４に記憶した標準的な彩度強調マトリクスの彩度ゲインを、画像解析部１２１から出力される色差Ｒ−Ｙ、Ｂ−Ｙの最大値に応じて調整して、彩度強調マトリクスとすればよい。
【００５８】
また、上記では、視覚限界範囲より広い色空間における画像データを記録することを想定し、視覚限界範囲に収まるように、彩度強調パラメータを設定し、彩度強調処理を行う例を説明したが、画像データを記録する色空間は、例えばＩＥＣ　６１９６６−２−１に記載されているｓＲＧＢ色空間のような、視覚限界範囲より狭い色空間でもよい。この場合は、画像データを記録する色空間の色域を超えないように、彩度強調パラメータを設定することになる。
【００５９】
例えば、第１実施形態において、色域データ記憶部１１２には、画像データを記録する色空間の色域を記憶させる。また、第２実施形態において、パラメータ選択部１２２のテーブルには、画像データを記録する色空間の色域を超えないような、色差Ｒ−Ｙ、Ｂ−Ｙの最大値と、彩度強調パラメータとの関係を記憶させる。
【００６０】
また、彩度強調された画像データはガンマ変換やエッジ強調などの後、所定のビット数に量子化されて圧縮および記録されるが、画像データを記録する色空間の色域を超えると量子化の際に色再現特性が変ってしまう。これに対して、画像データを記録する色空間の色域に収まるように彩度強調処理を行えば、圧および記録の際に色再現特性が変らず、所望する特性の画像データを出力することができる。
【００６１】
また、画像データを記録媒体に記録する際、画像データを記録する色空間の情報としてＲ、ＧおよびＢ、並びに、白のディジタルデータと色度座標との対応を付帯情報として記録してもよい。こうすれば、記録した画像データをディスプレイに表示したり、プリンタで印刷する際に、画像データ記録時の所望する色再現特性を反映した表示または印刷が可能になる。
【００６２】
また、上記では、彩度強調を行う画像処理装置としてディジタルカメラを取り上げたが、勿論、ディジタルカメラは、画素補間部１０４から出力される画像データを記録媒体２００に記録し、記録媒体２００に記録された画像データを汎用のパーソナルコンピュータに読み込み、色補正部１０５以降の処理をパーソナルコンピュータ上で動作するアプリケーションプログラムで実行する場合にも、上記の彩度強調パラメータの選択・設定、並びに、適応的な彩度強調処理を適応することができる。なお、パーソナルコンピュータ上で、色補正、彩度強調、エッジ強調などの処理を行えば、処理中の画像をディスプレイで確認しながら、処理パラメータの選択や調整が可能になるから、ユーザが所望する画像を容易に得ることができる。また、処理後の画像データの記録や印刷も容易になる。その際、視覚限界領域（または、画像データを記録する色空間の色域）に収まるように彩度強調を行えば、ディスプレイ上における処理中の画像の確認を正確に行うことができる。
【００６３】
【他の実施形態】
なお、本発明は、複数の機器（例えばホストコンピュータ、インタフェイス機器、リーダ、プリンタなど）から構成されるシステムに適用しても、一つの機器からなる装置（例えば、複写機、ファクシミリ装置など）に適用してもよい。
【００６４】
また、本発明の目的は、前述した実施形態の機能を実現するソフトウェアのプログラムコードを記録した記憶媒体（または記録媒体）を、システムあるいは装置に供給し、そのシステムあるいは装置のコンピュータ（またはＣＰＵやＭＰＵ）が記憶媒体に格納されたプログラムコードを読み出し実行することによっても、達成されることは言うまでもない。この場合、記憶媒体から読み出されたプログラムコード自体が前述した実施形態の機能を実現することになり、そのプログラムコードを記憶した記憶媒体は本発明を構成することになる。また、コンピュータが読み出したプログラムコードを実行することにより、前述した実施形態の機能が実現されるだけでなく、そのプログラムコードの指示に基づき、コンピュータ上で稼働しているオペレーティングシステム（ＯＳ）などが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【００６５】
さらに、記憶媒体から読み出されたプログラムコードが、コンピュータに挿入された機能拡張カードやコンピュータに接続された機能拡張ユニットに備わるメモリに書込まれた後、そのプログラムコードの指示に基づき、その機能拡張カードや機能拡張ユニットに備わるＣＰＵなどが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【００６６】
本発明を上記記憶媒体に適用する場合、その記憶媒体には、先に説明したフローチャートに対応するプログラムコードが格納されることになる。
【００６７】
【発明の効果】
以上説明したように、本発明によれば、所望する色域に収まるように、画像データを彩度強調することができる。
【図面の簡単な説明】
【図１】実施形態の画像処理装置であるディジタルカメラの構成例を示すブロック図、
【図２】撮像素子の色フィルタの配列（ベイヤ配列）を示す図、
【図３】視覚限界領域を説明する色度図、
【図４】色域判定部の判定アルゴリズムを示すフローチャート、
【図５】第２実施形態の画像処理装置であるディジタルカメラの構成例を示すブロック図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing apparatus and method, and for example, to image processing for processing an image acquired by an imaging device.
[0002]
[Prior art]
A so-called digital camera is a typical image processing system that processes an image acquired by an image sensor and records image data on a recording medium.
[0003]
A digital camera generates an image having a predetermined color reproduction characteristic by performing predetermined image processing on captured image data. However, since the characteristics of images handled by digital cameras are aimed at creating satisfactory pictures for average scenes and subjects, it is not always necessary to generate an optimal image for creating pictures for a specific subject. is not.
[0004]
For example, when a low-saturation subject is photographed indoors, the entire image has a low-saturation color tone. In order to cope with such a case, the photographing mode of the digital camera includes, in addition to a normal photographing mode for performing an optimal process for an average scene, image processing for increasing the saturation (saturation enhancement processing). ) Is performed (saturation emphasis mode), and a scheme is devised so that the user can select these modes.
[0005]
However, when a scene with high saturation is originally photographed in the saturation enhancement mode, if the saturation enhancement processing is performed on the image data, the range of the surface color that can be viewed (the human visual limit area) or the range of the recordable color can be obtained. And there is a problem that desired color reproduction cannot be performed during recording / reproduction.
[0006]
As a method for visually improving the image beyond the color range at the time of recording and reproduction, a method of correcting the image data so as not to change the hue of the original image data is disclosed in Japanese Patent No. No. 2,601,265. However, the method disclosed in the publication is not an essential solution to the case where the image data is processed and the color range is exceeded. Therefore, for example, as a result of emphasizing the saturation of an image, there is a problem that a color having a high saturation cannot be distinguished.
[0007]
[Problems to be solved by the invention]
In an image processing system such as a digital camera that processes an image acquired by an imaging device and records the image data on a recording medium, the processed image data may have a desired color gamut such as a visual limit area or a recordable color range. It is desirable to perform an optimal saturation emphasis process according to the scene to be photographed so as not to exceed.
[0008]
The present invention is to solve the above-mentioned problems individually or collectively, and has an object to enhance the saturation of image data so as to fall within a desired color gamut.
[0009]
[Means for Solving the Problems]
The present invention has the following configuration as one means for achieving the above object.
[0010]
An image processing apparatus according to the present invention determines an emphasis unit for emphasizing the saturation of image data, and a processing parameter of the emphasis unit such that the image data processed by the emphasis unit falls within a predetermined color gamut. Determining means.
[0011]
An image processing method according to the present invention is characterized in that the saturation of image data is enhanced, and the saturation enhancement processing parameter is determined so that the saturation-enhanced image data falls within a predetermined color gamut. I do.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0013]
[First Embodiment]
[Constitution]
FIG. 1 is a block diagram illustrating a configuration example of a digital camera which is an image processing apparatus according to an embodiment.
[0014]
The imaging unit 101 includes an imaging lens, an imaging device such as a CCD or a CMOS sensor, a gain adjustment circuit that adjusts a gain of an output signal of the imaging device, and an A / D converter that converts an output signal of the imaging device after the gain adjustment into a digital signal. The circuit includes a circuit, a memory for temporarily storing the output digital signal, and the like, and outputs an output signal of the image sensor corresponding to the light input through the imaging lens as digital image data.
[0015]
The exposure adjustment unit 102 determines a shutter speed and an aperture value in accordance with a predetermined program diagram so that image data of appropriate brightness is obtained based on the luminance of a predetermined portion of the image data output from the imaging unit 101. The exposure time of the image sensor of the image pickup unit 101 and the aperture of the photographing lens are controlled.
[0016]
The white balance correction unit 103 adjusts the white balance of the image data output from the imaging unit 101. The pixel interpolation unit 104 outputs image data obtained by interpolating pixel values of three channels of RGB in accordance with the color filter arrangement of the image sensor corresponding to each pixel of the image sensor. The color correction unit 105 corrects the color reproduction characteristics of the image data output from the pixel interpolation unit 104 to desired characteristics.
[0017]
When the saturation enhancement mode is designated as a shooting mode by a switch (not shown), the saturation enhancement unit 106 performs saturation enhancement processing on the image data corrected by the color correction unit 105. The edge emphasizing unit 107 performs a process for emphasizing the outline of the subject on the image data. The gamma conversion unit 108 performs gamma correction with reference to a table for each of the RGB channels of the image data.
[0018]
The image compression unit 109 compresses image data by a predetermined method such as JPEG. The recording / reproducing unit 110 adds predetermined additional information to the compressed image data and records the image data on the recording medium 200 as image data in a predetermined format, or converts the image data recorded on the recording medium 200 into an unillustrated image data. Reproduction of an image to be displayed on a liquid crystal monitor or the like is performed.
[0019]
The color gamut determination unit 111 determines whether or not the image data subjected to the saturation enhancement processing by the saturation enhancement unit 106 exceeds a predetermined color gamut. The color gamut data storage unit 112 is a memory such as a ROM that previously stores color gamut data to be determined by the color gamut determination unit 111. The parameter change unit 113 changes the saturation enhancement parameter of the saturation enhancement unit 106 when the color gamut determination unit 111 determines that the color gamut of the image data exceeds the predetermined color gamut. The saturation enhancement parameter storage unit 114 is a memory such as a ROM that stores a plurality of saturation enhancement parameters processed by the saturation enhancement unit 106 in advance.
[0020]
In FIG. 1, the imaging unit 101 to the saturation enhancement parameter storage unit 114 are components of a digital camera, and the storage medium 200 is a memory such as a memory card that can be attached to and detached from the digital camera, and an optical disk and a hard disk.
[0021]
[Image recording operation]
Hereinafter, an image recording operation at the time of imaging according to the embodiment will be described.
[0022]
This embodiment assumes recording of image data in a color space wider than the visual limit region (for example, scRGB color space described in IEC 61966-2-2) (however, 12-bit non-linear encoding) and performs color gamut determination. An example in which the inside / outside determination of the visual limit region is performed by the unit 111 will be described.
[0023]
● Normal shooting mode First, shooting in the normal shooting mode will be described.
[0024]
When the user presses a shutter button (not shown) to photograph a subject, the exposure adjustment unit 102 controls the exposure time of the image sensor of the imaging unit 101 and the aperture of the imaging lens based on the output of the imaging unit 101, Digital image data is output from the imaging unit 101.
[0025]
The white balance correction unit 103 performs statistical analysis such as calculation of an average value on the image data output from the imaging unit 101, and adjusts the white balance so that the statistic of the image data becomes a target value. Find the coefficient of. At this time, if a plurality of white balance modes of the digital camera can be set in order to correspond to a plurality of light sources, there are target values of statistics according to each mode, and an optimal coefficient for each mode is obtained. Note that these coefficients are obtained for each of the RGB channels.
[0026]
The pixel interpolation unit 104 interpolates RGB three-channel image data from the digital image data output from the imaging unit 101 using the coefficients obtained by the white balance correction unit 103. FIG. 2 is a diagram illustrating an arrangement (Bayer arrangement) of the color filters of the imaging device of the imaging unit 101. As shown in FIG. 2, each pixel of the image sensor outputs only one channel pixel value out of RGB. Therefore, the pixel value of the channel different from the color of the filter needs to be obtained by the following interpolation.
[0027]
When determining the G channel pixel value of the pixel having the G filter color, a value obtained by multiplying the pixel value by a coefficient corresponding to the G channel is set as an output value. When obtaining the pixel value of the R or B channel of the pixel having the G filter color, the coefficient corresponding to each channel is added to the pixel values of two adjacent pixels, and the averaged value is used as the output value.
[0028]
When the pixel value of the channel of the same color as the filter of the pixel of the filter color of R or B is obtained, the value obtained by multiplying the pixel value by the coefficient corresponding to each channel is used as the output value. When calculating the pixel value of a channel of a color different from that of the filter of the pixel of the filter color of R or B, the coefficient corresponding to each channel is added to the pixel values of four adjacent pixels, and the averaged value is output. Value.
[0029]
Note that the above interpolation method is an example. For example, when calculating the pixel value of the R or B channel of a pixel whose filter color is G, the pixel value of the corresponding filter color pixel at a predetermined distance The average value obtained by integrating the coefficients corresponding to the channels and weighting based on the distance may be used as the output value. The image data output from the pixel interpolation unit 104 is temporarily stored in an image memory (not shown) in the pixel interpolation unit 104.
[0030]
The color correction unit 105 performs color correction on the image data output from the pixel interpolation unit 104 by a matrix operation shown in Expression (1), and mainly corrects the hue of the image data.

[0031]
The saturation enhancement unit 106 and the color gamut determination unit 111 do not perform processing in the normal shooting mode, and pass through the image data output from the color correction unit 105.
[0032]
The edge enhancement unit 107 performs filtering on the image data output from the color gamut determination unit 111 to extract outline portions in predetermined directions, and applies an edge enhancement filter optimal for each direction to the extracted outline portions. To perform edge enhancement. Conversely, a filtering process having a low-pass effect is performed on an isolated noise component having no contour directionality.
[0033]
The gamma converter 108 refers to a table for each of the R, G, and B channels of the image data output from the edge emphasizing unit 107, and performs gamma conversion whose main purpose is to match the voltage-luminance characteristics (gamma characteristics) of the display. Is applied.
[0034]
The image data output from the gamma conversion unit 108 is compressed by the image compression unit 109 according to a desired image quality or compression ratio, and output to the recording / reproduction unit 110. The recording / reproducing unit 110 records the compressed image data and the information at the time of shooting as one image data (file) on the recording medium 200 according to a predetermined image format.
[0035]
● Saturation emphasis mode Next, shooting in the saturation emphasis mode will be described. Since the processing up to the color correction unit 105 is the same as in the normal shooting mode, the operation after the output of the color correction unit 105 will be described.
[0036]
The saturation emphasizing unit 106 performs a saturation emphasizing process on the image data output from the color correcting unit 105 by a matrix operation shown in Expression (2).

[0037]
The color gamut determination unit 111 performs a color gamut inside / outside determination on the RGB values of the image data output from the saturation enhancement unit 106 based on the color gamut data stored in the color gamut data storage unit 112. FIG. 3 is a chromaticity diagram for explaining the visual limit region, in which a horseshoe-shaped solid line (spectral locus) represents the boundary of the visual limit region. The color gamut determination unit 111 determines whether the input RGB values are inside or outside the boundary shown in FIG. 3, and FIG. 4 is a flowchart showing the determination algorithm.
[0038]
First, CIE 1931 XYZ color coordinate values (X, Y, Z) are obtained from the input image data in the scRGB color space by a matrix operation, and chromaticity values x, y are calculated according to equation (3) (S101). ).
x = X / (X + Y + Z)
y = Y / (X + Y + Z) (3)
[0039]
Hereinafter, whether the color represented by (x, y, Y) is inside or outside the color gamut is determined based on the color gamut data stored in the color gamut data storage unit 112. The color gamut data storage unit 112 stores the maximum and minimum values of Y representing the range of Y in the visual limit region, and the range of x for each region obtained by dividing the range of Y into a plurality of regions. A one-dimensional table representing the maximum value and the minimum value of x, and a maximum value and a minimum value of the y value representing a possible range of y for each region obtained by dividing the range of (x, Y) into a plurality of regions. A dimension table is stored.
[0040]
Then, it is determined whether the calculated Y value is within the color gamut (S102). If the Y value is within the range, a range of the x value corresponding to the Y value is obtained (S103), and it is determined whether or not the calculated x value is within the color gamut (S104). If the x value is within the range, the y value range corresponding to the (x, Y) value is obtained (S105), and it is determined whether or not the calculated y value is within the color gamut range (S106). .
[0041]
If it is determined in steps S102, S104, and S106 that the image data is all within the color gamut, a flag Gi indicating that the image data is within the color gamut is set to "1" (S107). If it is determined that the value is out of the color gamut, the flag Gi is set to '0' (S108). This determination is repeated for all pixels of the image data.
[0042]
When all the pixels of the image data are within the color gamut range (that is, all the flags Gi are “1”), the color gamut determination unit 111 outputs the image data output from the saturation enhancement unit 106 to the edge enhancement unit 107 as it is. I do. On the other hand, when there is a pixel outside the color gamut (that is, at least one of the flags Gi is “0”), the parameter changing unit 113 stores the saturation next to the default saturation enhancement parameter from the saturation enhancement parameter storage unit 114. A saturation enhancement parameter having a weak degree of enhancement is acquired, and the acquired saturation enhancement parameter is set by the saturation enhancement unit 106.
[0043]
When the saturation enhancement parameter is reset, the color correction by the color correction unit 105, the saturation enhancement by the saturation enhancement unit 106, and the color gamut for all the pixels of the output image data of the pixel interpolation unit 104 are performed again. The color gamut inside / outside determination by the determination unit 111 is performed. A plurality of saturation enhancement parameters are stored in the saturation enhancement parameter storage unit 114, and the parameter change unit 113 sequentially selects the saturation enhancement parameter from the strong saturation enhancement parameter to the weak saturation enhancement parameter. . Then, according to the determination by the color gamut determining unit 111, selection and setting of the saturation enhancement parameter, color correction, saturation enhancement processing, and color gamut inside / outside determination are repeated until all the pixels fall within the color gamut range. However, when the parameter changing unit 113 sets the saturation enhancement parameter having the weakest degree of saturation enhancement to the saturation enhancement unit 116, the color gamut determination unit 111 does not perform the color gamut determination and the saturation enhancement unit 116 Is input to the edge enhancement unit 107 as it is.
[0044]
Subsequent processes from the edge enhancement unit 107 to the recording / reproducing unit 110 are the same as those in the normal shooting mode, and a description thereof will be omitted.
[0045]
As described above, according to the present embodiment, the in-color gamut determination is performed on the image data on which the saturation enhancement has been performed, and when the RGB values of the image data are outside the gamut range, the degree of the saturation enhancement is determined. Resets the weaker saturation enhancement parameter and performs saturation enhancement again. Therefore, it is possible to record image data in which the saturation is enhanced as much as possible within the visual limit area even for a scene in which it is expected to obtain a high-saturation image, reflecting the color characteristics of the scene at the time of shooting. it can.
[0046]
[Second embodiment]
Hereinafter, an image processing apparatus according to a second embodiment of the present invention will be described. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0047]
As in the first embodiment, the second embodiment assumes recording of image data in a color space wider than the visual limit area, and in the saturation enhancement mode, the image data output from the saturation enhancement unit 106 is stored in the visual limit area. An example in which the saturation emphasis processing is performed so as not to deviate from the following will be described.
[0048]
FIG. 5 is a block diagram illustrating a configuration example of a digital camera that is an image processing device according to the second embodiment.
[0049]
The processing from the imaging unit 101 to the color correction unit 105 is the same as in the first embodiment, and a description thereof will be omitted.
[0050]
The image analysis unit 121 calculates the color differences RY and BY of each pixel using Expression (4) based on the RGB values of the image data output from the color correction unit 105. Then, the maximum values of the color differences RY and BY in the entire image data are output to the parameter selection unit 122 as image analysis results.
R−Y = 0.70 × R−0.59 × G−0.11 × B
B−Y = −0.30 × R−0.59 × G + 0.89 × B (4)
[0051]
The saturation enhancement parameter storage unit 114 stores a plurality of saturation enhancement parameters in advance, as in the first embodiment. The parameter selection unit 122 stores a table indicating the relationship between the maximum values of the color differences RY and BY output from the image analysis unit 121 and the saturation enhancement parameters stored in the saturation enhancement parameter storage unit 114. Store in advance. In this table, for each value of the color difference RY and the color difference BY, among the saturation enhancement parameters that can be subjected to the saturation enhancement processing so as not to exceed the visual limit area, the degree of the saturation enhancement is the highest. An index of a strong saturation enhancement parameter is stored.
[0052]
The parameter selection unit 122 extracts, from the table, an index of a saturation enhancement parameter corresponding to the maximum value of the color difference RY and an index of a saturation enhancement parameter corresponding to the maximum value of the color difference BY, The saturation enhancement parameter having the weaker degree is selected and set in the saturation enhancement unit 106.
[0053]
The saturation enhancement unit 106 performs saturation enhancement on the image data output from the color correction unit 105 using the saturation enhancement parameters set by the parameter selection unit 122.
[0054]
Subsequent processes from the edge enhancement unit 107 to the recording / reproducing unit 110 are the same as those in the first embodiment, and a detailed description thereof will be omitted.
[0055]
As described above, the parameter selection unit 122 selects a saturation emphasis parameter corresponding to the maximum value of the color differences RY and BY, and sets the parameter with the weaker degree to the saturation emphasis unit 106.
[0056]
In other words, when the maximum value of the color difference is large, it is determined that the saturation of the photographed subject scene is high. However, by using the saturation enhancement parameter according to the color difference, the saturation of the scene is maintained so as not to deviate from the visual limit region. The degree of emphasis can be suppressed. Also, when the maximum value of the color difference is small, it is determined that the saturation of the captured subject scene is low. In this case, however, the saturation is enhanced by using the saturation enhancement parameter corresponding to the low saturation. Nevertheless, saturation enhancement can be performed so as not to produce a faded image. According to such adaptive saturation enhancement processing, a desired saturation enhancement effect can be obtained within the visual limit region.
[0057]
[Modification]
In the above description, an example is described in which a plurality of saturation enhancement parameters stored in advance are selected in accordance with the output of the image analysis unit 121. However, an optimal saturation enhancement parameter is generated in accordance with the output of the image analysis unit 121, You may make it set to the saturation enhancement part 106. For example, the saturation gain of the standard saturation enhancement matrix stored in the saturation enhancement parameter storage unit 114 is adjusted according to the maximum values of the color differences RY and BY output from the image analysis unit 121. , A saturation emphasis matrix.
[0058]
Further, in the above, an example has been described in which image data in a color space wider than the visual limit range is assumed to be recorded, and a saturation enhancement parameter is set so as to be within the visual limit range, and the saturation enhancement process is performed. The color space for recording image data may be a color space narrower than the visual limit range, such as the sRGB color space described in IEC 61966-2-1. In this case, the saturation enhancement parameter is set so as not to exceed the color gamut of the color space in which the image data is recorded.
[0059]
For example, in the first embodiment, the color gamut data storage unit 112 stores a color gamut of a color space for recording image data. In the second embodiment, the table of the parameter selection unit 122 stores the maximum values of the color differences RY and BY and the saturation enhancement parameter so as not to exceed the color gamut of the color space in which the image data is recorded. Is stored.
[0060]
In addition, after the image data subjected to saturation enhancement is subjected to gamma conversion, edge enhancement, and the like, the data is quantized to a predetermined number of bits and compressed and recorded. In this case, the color reproduction characteristics change. On the other hand, if the saturation enhancement processing is performed so as to be within the color gamut of the color space in which the image data is recorded, the color reproduction characteristics do not change at the time of pressure and recording, and image data having desired characteristics can be output. Can be.
[0061]
When the image data is recorded on the recording medium, R, G, and B as color space information for recording the image data, and correspondence between white digital data and chromaticity coordinates may be recorded as supplementary information. . In this way, when the recorded image data is displayed on a display or printed by a printer, display or printing reflecting desired color reproduction characteristics at the time of recording the image data becomes possible.
[0062]
In the above description, a digital camera has been described as an image processing apparatus that performs saturation enhancement. Of course, the digital camera records image data output from the pixel interpolation unit 104 on the recording medium 200 and records the image data on the recording medium 200. When the image data thus read is read into a general-purpose personal computer, and the processing after the color correction unit 105 is executed by an application program operating on the personal computer, the above-described selection and setting of the saturation emphasis parameter and the adaptive Chroma enhancement processing can be applied. If processing such as color correction, saturation enhancement, and edge enhancement is performed on a personal computer, it is possible to select and adjust processing parameters while checking the image being processed on the display. Images can be easily obtained. Also, recording and printing of the processed image data are facilitated. At this time, if the saturation is enhanced so as to be within the visual limit area (or the color gamut of the color space for recording the image data), the image being processed on the display can be accurately confirmed.
[0063]
[Other embodiments]
The present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but can be applied to a device including one device (for example, a copier, a facsimile machine, etc.). May be applied.
[0064]
Further, an object of the present invention is to supply a storage medium (or a recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or an apparatus, and a computer (or a CPU or a CPU) of the system or the apparatus. Needless to say, the present invention can also be achieved by an MPU) reading and executing a program code stored in a storage medium. In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.
[0065]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is executed based on the instruction of the program code. It goes without saying that the CPU included in the expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.
[0066]
When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.
[0067]
【The invention's effect】
As described above, according to the present invention, saturation of image data can be enhanced so as to be within a desired color gamut.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a digital camera that is an image processing apparatus according to an embodiment;
FIG. 2 is a diagram showing an arrangement (Bayer arrangement) of color filters of an image sensor;
FIG. 3 is a chromaticity diagram illustrating a visual limit region,
FIG. 4 is a flowchart illustrating a determination algorithm of a color gamut determination unit;
FIG. 5 is a block diagram illustrating a configuration example of a digital camera that is an image processing device according to a second embodiment.

Claims (8)

Enhancement means for enhancing the saturation of the image data;
An image processing apparatus comprising: a determination unit configured to determine a processing parameter of the enhancement unit such that the image data processed by the enhancement unit falls within a predetermined color gamut. Further, it is characterized in that it is determined whether or not the image data processed by the enhancing means falls within the predetermined color gamut, and the determining means repeats the determination of the processing parameter until the image data falls within the predetermined color space. The image processing device according to claim 1. The image processing apparatus according to claim 1, wherein the determining unit determines the processing parameter according to a saturation distribution of the image data. The image processing apparatus according to claim 1, wherein the predetermined color gamut is a visual limit area. Further, recording means for converting the image data processed by the emphasizing means into a predetermined data format and recording it on a recording medium,
4. The image processing apparatus according to claim 1, wherein the predetermined color gamut is a color space wider or narrower than a visual limit region. Emphasizes the saturation of image data,
An image processing method comprising: determining a saturation enhancement processing parameter such that saturation-enhanced image data falls within a predetermined color gamut. A program for controlling an image processing apparatus to execute the image processing according to claim 6. A recording medium on which the program according to claim 7 is recorded.

Images