JP4258752B2 - Printer system and white balance control method thereof, and electronic camera and printer - Google Patents

Description

ただし、ａ〜ｉは定数とする。
【００２３】
リニアマトリックス回路２０で処理された信号は、ホワイトバランス調整回路（以下、ＷＢ回路という。）２２及びホワイトバランスゲイン制御部２４へ送られる。なお、本明細書中、必要に応じて「ホワイトバランス」を「ＷＢ」と略記する。ＷＢ回路２２は、ＲＧＢの各色信号のデジタル値を増減するための乗算器から構成されており、各色信号はそれぞれ対応する乗算器に加えられる。各色毎の乗算器には、ＷＢゲイン制御部２４からホワイトバランス補正値（ゲイン値）Ｒｇ、Ｇｇ、Ｂｇの指令が加えられており、各乗算器はその指令に従って色信号のレベルを調節する。ＷＢ回路２２においてホワイトバランス調整されたＲＧＢ信号はガンマ変換回路２６に送られる。ＷＢゲイン制御部２４による制御内容及びその制御に用いられるＷＢ順応率の概念は後述する。
【００２４】
ガンマ変換回路２６は、ホワイトバランス調整されたＲＧＢ信号が所望のガンマ特性となるように入出力特性を変換する。ガンマ変換された信号は、ＲＧＢ→ＹＣr Ｃb 変換回路（以下、ＹＣ変換回路という。）２８に送られ、ＹＣ変換回路２８において、ＲＧＢ信号から輝度信号Ｙと色差信号Ｃｒ、Ｃｂに変換される。
【００２５】
ＹＣ変換回路２８で得られた輝度・色差信号（Ｙ、Ｃr 、Ｃb ）は、Ｃr Ｃb マトリックス回路３０に送られ、色差信号の色補正が行われる。Ｃr Ｃb マトリックス回路３０で処理された画像データは、圧縮／伸張回路３２によってＪＰＥＧその他の所定のフォーマットに従って圧縮された後、メモリカードなどの記録媒体３４に記録される。このとき、ＷＢゲイン制御部２４で制御したＷＢ順応率の情報が画像の付加情報として記録媒体３４に記録される。例えば、画像ファイルのタグ情報にＷＢ順応率が書き込まれる。記録媒体３４は、リムーバブルメディアに限らず、カメラ１０の内部メモリであってもよい。
【００２６】
次に、上記の如く構成されたカメラ１０のホワイトバランス制御方法について説明する。図示せぬシャッターボタンの半押し操作に押下に応動してＡＥ（自動露出調整）制御が行われる。ＡＥ制御では、予め決めた露出値で複数回Ｒ、Ｇ、Ｂ信号を取り込み、これらのＲ、Ｇ、Ｂ信号を積算した積算値に基づいて被写体輝度（撮影ＥＶ値）を求め、この撮影ＥＶ値に基づいて撮影時の絞り値とシャッタースピードを最終的に決定する。そして、シャッターボタンの全押し時に前記決定した絞り値及びシャッタースピードに従って絞りや電子シャッター（電荷蓄積時間）を制御する。
【００２７】
シャッターボタンの全押し操作に応動してＣＣＤ１６より取り込まれた一画面分のＲ、Ｇ、Ｂ信号は、リニアマトリックス回路２０を介してＷＢゲイン制御部２４に送られる。ＷＢゲイン制御部２４は、一画面を複数のエリア（例えば、８×８）に分割し、各分割エリアごとにＲ、Ｇ、Ｂ信号の色別の平均積算値を求め、Ｒ信号の積算値とＧ信号の積算値との比Ｒ／Ｇ、及びＢ信号の積算値とＧ信号の積算値との比Ｂ／Ｇを求める。
【００２８】
各分割エリアごとに求められるＲ／Ｇ、Ｂ／Ｇは、その分割エリアが、図２のグラフ上に表された複数の検出枠のうちのいずれの検出枠内に入るかを判別するために使用される。図２上における日陰検出枠、昼光色検出枠、昼白色検出枠、白色検出枠、タングステン検出枠等の各検出枠は、光源種などの色分布の範囲を規定するものである。検出枠内に入るエリアの個数に基づいて、光源種が自動判別され、光源種に対応したホワイトバランス調整が行われる。
【００２９】
図３は、撮影光源がタングステンの場合のカメラＷＢ順応率の例である。横軸はＢ／Ｇゲイン値を示し、縦軸はＲ／Ｇゲイン値を示す。ただし、デイライト時のＢ／Ｇゲイン値及びＲ／Ｇゲイン値を１に正規化して表示している（Ａ点）。図３中、「タングステン順応率１００％相当ゲイン値」（Ｂ点）、すなわちＲ／Ｇ＝０．５、Ｒ／Ｇ＝２．０での補正を行うと、タングステン光源下のグレイ被写体は、グレイ（Ｒ＝Ｇ＝Ｂ）に撮像される。
【００３０】
一方、「タングステン順応率７０％相当ゲイン値」（Ｃ点）、すなわちＲ／Ｇ＝０．６５、Ｂ／Ｇ＝１．７での補正を行うと、タングステン光源下のグレイ被写体は、光源の雰囲気を残した赤味のあるグレイに撮像される。
【００３１】
このように、順応率は、光源の雰囲気を残す程度を示すものであり、グラフ上、デイライトのゲイン値（Ａ点）と完全補正点（Ｂ点）との距離で定義される。なお、色分布を規定する空間は図３に示した（Ｒ／Ｇ，Ｂ／Ｇ）空間に限らず、ＬＡＢ色空間や他の色度図を用いることもできる。
【００３２】
本例の場合、順応率は１００％（完全補正）〜０％（補正無し）までの間で適宜設定される。順応率１００％は、完全にホワイトバランスを取った場合であり、光源の雰囲気は全く残らない状態である。順応率０％が選択されている場合には、結果的にホワイトバランス補正は行われず、光源の色がそのまま出力される。これはマニュアルホワイトバランスを「デーライト（晴れ）」に設定した状態と同じである。順応率が「０％」に近いほど光源の雰囲気が多く残り、「１００％」に近いほど光源の雰囲気が少なくなることを意味している。
【００３３】
カメラＷＢ順応率は、カメラ１０のオートホワイトバランス（ＡＷＢ）機能によって自動的に決定される場合と、カメラユーザが手動で任意に設定する場合とがある。本実施形態では、ＡＷＢの順応率を撮影者の好みに応じて変更することができる。なお、順応率は段階的に設定できてもよいし、連続的に設定できてもよい。この設定された順応率の情報が画像記録時に付加情報として記録媒体３４に画像とともに記録される。
【００３４】
次に、プリンタについて説明する。図４は、本発明の実施形態に係るプリンタのブロック図である。カメラ１０で撮像された画像及びその付加情報は、着脱可能な記録媒体（リムーバブルメディア）３４を介してカメラ１０からプリンタ４０に受け渡される。画像ファイルがカメラ内部の記録媒体に保存される場合は、無線又は有線のデータ通信手段を用いてカメラ１０からプリンタ４０に画像及びその付加情報が伝送される。
【００３５】
プリンタ４０は、ＪＰＥＧ圧縮画像解凍処理部４２、ＹＣr Ｃb →ＲＧＢ変換回路（以下、ＲＧＢ変換回路という。）４４、ＷＢ補正回路４６、ルックアップテーブル（ＬＵＴ）補正回路４８、ＲＧＢ→ＹＭＣ変換回路（以下、ＹＭＣ変換回路という。）５０、プリントエンジン５２、及びこれらを制御する制御部５４を備えている。
【００３６】
記録媒体３４から読み込まれた画像データは、ＪＰＥＧ圧縮画像解凍処理部４２で伸張処理された後、ＲＧＢ変換回路４４に送られる。ＹＣ信号からＲＧＢ信号に変換された信号はＷＢ補正回路４６に送られ、ここで各色信号のゲイン調整が行われる。制御部５４は、ＪＰＥＧ圧縮画像解凍処理部４２から取り込んだ画像を解析するとともに、その画像の付加情報であるＷＢ順応率の情報に基づいて各色信号のゲイン値を決定し、ＷＢ補正回路４６に対してゲイン制御信号を与える。
【００３７】
ＷＢ補正回路４６で処理されたデータは、ＬＵＴ補正回路４８において補正処理が施された後、ＹＭＣ変換回路５０に送られる。ＹＭＣ変換回路５０では、受入したＲＧＢデータをＹ（イエロー）、マゼンダ（Ｍ）、シアン（Ｃ）の各色信号に変換する。ＹＭＣ信号に変換された画像データはプリントエンジン５２に送られ、画像データが示す画像内容がプリント用紙その他の印刷媒体にプリントされる。こうして、画像内容が印刷されたプリント物５６が得られる。
【００３８】
制御部５４は、画像解析手段と、プリンタAutoSetUp 機能部、及び係数決定部とを備えている。プリンタ４０の制御部５４は、画像の付加情報に含まれるＷＢ順応率情報を読み取り、その順応率の設定を反映したホワイトバランス補正制御を行う。例えば、次の（１）乃至（３）に示すような処理を行う。
【００３９】
（１）ＷＢ順応率の付加情報が無い場合は、通常のＡＷＢ処理を行う。ここで言う「通常のＡＷＢ処理」とは、入力された画像データに対してプリンタ側でホワイトバランスを補正して、赤（Ｒ）、緑（Ｇ）、青（Ｂ）の各色信号レベルが等しくなるグレイ（Ｒ＝Ｇ＝Ｂ）を達成するように各色信号のゲインを調整する処理をいう。
【００４０】
（２）カメラＷＢ順応率１００％未満の場合には、プリンタＡＷＢ処理をオフにする。これにより、カメラ側で設定したホワイトバランスのままプリントが行われ、光源の雰囲気を打ち消すような補正を回避できる。プリンタＡＷＢ処理をオフするか否かの判定基準となるしきい値は、完全補正を示す「１００％」に固定して設定されていてもよいし、ユーザ操作によってしきい値の設定を変更できる構成にしてもよい。例えば、しきい値を８０％に設定した場合、カメラＷＢ順応率８０％未満の場合には、プリンタＡＷＢ処理をオフし、カメラＷＢ順応率が８０％以上の場合にはプリンタＡＷＢ処理を実施するという具合に制御の切り替えを行う。
【００４１】
（３）プリンタ側のＡＷＢ補正量を次式 <２>
【００４２】
【数２】
プリンタＡＷＢ補正量＝通常のＡＷＢ補正量×順応率（％）／１００… <２>
に従って算出し、プリンタ側のＡＷＢ補正にカメラ側の順応率の設定内容を反映させた制御を行う。ここで言う「通常のＡＷＢ補正量」とは、前記通常のＡＷＢ処理によるホワイトバランス補正量を意味している。
【００４３】
図４に示したプリンタ４０において、プリンタ４０側でＷＢ順応率の付加情報を読み取ってもその情報を反映したＡＷＢ制御を実施せずに、通常のプリンタＡＷＢ処理を実行する「カメラ順応率無視モード」を設ける態様も好ましい。
【００４４】
すなわち、プリンタ４０は、カメラ１０側で設定したＷＢ順応率の情報を活用してプリンタ４０のＡＷＢ制御を行う「カメラ順応率活用モード」と、順応率情報を利用しない「カメラ順応率無視モード」とを有し、モード選択手段５８によってユーザが適宜モードを選択できるように構成される。モード選択手段５８の選択情報は制御部５４に入力され、制御部５４は選択されたモードに対応してＡＷＢ制御方式を切り替える。
【００４５】
図５は、上述したカメラ１０とプリンタ４０を組み合わせたシステムの処理手順を示すフローチャートである。まず、カメラ１０は、光源判定用のデータを取得し（ステップＳ１１０）、取得データを基に光源判定を行う（ステップＳ１１２）。次いで、判定した光源に対応した順応率テーブルを読み込み、光源種と順応率によってＲ／Ｇゲイン、Ｂ／Ｇゲインを決定する。なお、ＷＢ順応率は、ステップＳ１１４の如くカメラ側で予め設定されている値を用いてもよいし、ＧＵＩ（グラフィカル・ユーザ・インターフェース）などの手段によって、カメラＷＢ順応率を任意に設定できるように構成してもよい。
【００４６】
次いで、シャッターボタンの押下に連動して撮像された画像データ及びその付加情報（カメラＷＢ順応率を含む）を記録媒体３４に記録する処理を実行する（ステップＳ１１８）。撮影後、カメラ１０から記録媒体３４を取り出し、これをプリンタ１０のメディア挿入口へ装着する。プリンタ４０は、記録媒体３４から画像データ及び付加情報（カメラＷＢ順応率を含む）を読み込む処理を行う（ステップＳ１２０）。読み込んだ画像データ及び付加情報に基づいて、プリンタ側のＡＷＢ処理（上記（１）乃至（３）の何れか一つの処理）を実施して、対象となる画像のプリントを行う（ステップＳ１２２）。
【００４７】
次に、動画記録用のカメラ（ムービーカメラ）への応用例を説明する。
【００４８】
ＷＢ順応率に関する付加情報が無い動画の一シーンをプリントする場合には、プリンタ側で通常のＡＷＢ処理を行う。これに対し、ＷＢ順応率に関する付加情報を有する動画から一シーンを取り出してプリントを行う場合には、上述したカメラ１０（電子スチルカメラ）からのプリントの場合と同様の対応を行う。
【００４９】
動画撮影時のホワイトバランス調整は、光源種や色温度を推定し、推定した光源種や色温度に応じてＷＢの順応率を設定する場合の他に、以下に述べる手法がある。すなわち、画面全体、又は画面の一部分（例えば、中央部の一定領域）についてＲＧＢの積分値、又は色差信号の積分値がグレイになるようにＷＢゲインを設定する。この場合、積分値がグレイになるのに必要なＷＢゲイン値が、ある範囲の場合（予め定めた一定の範囲内の場合）は、意図的にＷＢゲインを弱めに設定する順応率処理が行われる。図６にその例を示す。同図では、符号６２で示したエリアが、順応率１００％に設定する範囲を規定する領域であり、それ以外のエリア（符号６４）は、順応率８０％に設定する範囲を規定するものとして定められている。
【００５０】
例えば、完全なホワイトバランスを取るために必要なＲゲイン、Ｂゲインがそれぞれ１．１、０．９の場合、これは図６において符号６２で示した順応率１００％のエリア内のため、Ｒゲイン＝１．１、Ｂゲイン０．９でＷＢ制御を行う。
【００５１】
また、完全なＷＢを取るのに必要なＲゲイン、Ｂゲインがそれぞれ０．６、２．０の場合、これは符号６４で示した順応率８０％のエリア内なので、各ゲイン値を次式 <３> 、 <４>
【００５２】
【数３】
Ｒゲイン＝１．０−（１．０−０．６）×０．８＝０．６８… <３>
【００５３】
【数４】
Ｂゲイン＝１．０＋（２．０−１．０）×０．８＝１．８ … <４>
に従って算出し、算出されたＲゲイン、ＢゲインでＷＢ制御を行う。
【００５４】
【発明の効果】
以上説明したように本発明によれば、電子カメラで設定したホワイトバランス順応率の情報を画像とともに記録媒体に記録し、プリント時にはプリンタ側で順応率の情報を読み込んでカメラ側における設定に連動したホワイトバランス制御を行うようにしたので、撮影者が意図的に光源の雰囲気（色味）を残して記録した画像について、プリント時にその雰囲気を打ち消す補正がなされてしまうという事態を回避できる。
【図面の簡単な説明】
【図１】本発明の実施形態に係るデジタルカメラのブロック図
【図２】光源種などの色分布の範囲を示す検出枠を示すグラフ
【図３】カメラ側で設定されるホワイトバランス順応率を説明するためのグラフ
【図４】本発明の実施形態に係るプリンタを含むシステムの構成図
【図５】本例のカメラ及びプリンタシステムの処理手順を示すフローチャート
【図６】動画に対するホワイトバランス順応率処理の例を示す図
【符号の説明】
１０…カメラ、１２…撮影レンズ、１６…ＣＣＤ、１８…Ａ／Ｄ変換器、２０…リニアマトリックス回路、２２…ＷＢ回路、２４…ＷＢゲイン制御部、２６…ガンマ変換回路、２８…ＹＣ変換回路、３４…記録媒体、４０…プリンタ、４６…ＷＢ補正回路、４８…ＬＵＴ補正回路、５０…ＹＭＣ変換回路、５２…プリントエンジン、５４…制御部、５８…モード選択手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a white balance control technique for a system including an electronic camera and a printer.
[0002]
[Prior art]
In auto white balance (AWB) of an electronic camera, a light source type is determined from information of an external white balance (WB) sensor for detecting a color temperature or a CCD image sensor, and white balance adjustment suitable for the determined light source is performed. (Japanese Patent Laid-Open No. 2000-224608). The basics of AWB are that a gray subject is imaged in gray under a photographic light source, but depending on the model of the electronic camera, in order to leave the atmosphere of the light source on the spot depending on the light source type determined at that time Some control performs weakening of AWB correction. For example, in order to leave an impression of the scene when shooting under tungsten, a slightly weaker white balance is performed so as to leave a reddish gray.
[0003]
On the other hand, when printing an image captured by an electronic camera, AWB processing is also performed inside the printer. In many cases, the AWB process in the printer is set based on the idea that an electronic camera corrects an image shot with an AWB mistake.
[0004]
[Problems to be solved by the invention]
However, when a print is created by a combination of the above-described “electronic camera having an AWB function that leaves the atmosphere of a light source” and “a printer that performs AWB processing internally”, there are the following drawbacks. That is, the image signal itself obtained by imaging with the electronic camera is subjected to WB processing that leaves the atmosphere of the light source on the spot, but the printer determines that the image is a WB miss. This creates a print that cancels the atmosphere of the light source.
[0005]
The present invention has been made in view of such circumstances, and a printer system capable of reflecting the white balance setting intended on the camera side to the printer side and preventing the creation of a print that cancels the atmosphere of the light source, and It is an object of the present invention to provide a white balance control method and an electronic camera and printer used in the system.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a printer system for printing an image photographed by an electronic camera by a printer, wherein the electronic camera is adapted to an image signal acquired via an imaging means. Leave a shooting light source atmosphere The white balance adaptation rate indicating the degree, depending on the preset white balance adaptation rate, the white balance adaptation rate automatically determined by the auto white balance function, or the white balance adaptation rate set by the user White balance correction means for performing white balance correction processing and the previous Record Recording means for recording data on the weight balance adaptation rate on a recording medium together with a captured image as additional information of the image, and the printer includes an information acquisition means for reading the image recorded on the recording medium and the additional information; Read from the information acquisition means White balance control means for performing white balance correction processing on an image, and when additional information is read together with the image by the information acquisition means, White balance adaptation rate included in additional information The white balance of the scanned image is corrected with the white balance correction amount according to the And white balance control means for controlling white balance processing on the printer side.
[0007]
The electronic camera used in the system of the present invention has a white balance processing function that leaves the atmosphere of the photographing light source, and adaptation rate information indicating the degree of white balance correction is recorded on the recording medium as additional information of the photographed image at the time of photographing. . The adaptation rate on the camera side may be automatically determined by the auto white balance function of the camera, or may be arbitrarily set by the user by operating a predetermined operating means (manually).
[0008]
On the printer side, the adaptation rate information on the camera side is read via the information acquisition means, and white balance processing is controlled according to the information. Thus, by performing the printer white balance control in conjunction with the setting of the white balance adaptation rate in the electronic camera, it is possible to prevent creation of a print that cancels the atmosphere of the light source.
[0009]
The invention described in claim 2 provides a white balance control method applied to the system. That is, this method invention is a white balance control method applied to a printer system that prints an image shot by an electronic camera by a printer, and leaves an atmosphere of a shooting light source when shooting by the electronic camera. The white balance adaptation rate indicating the degree, depending on the preset white balance adaptation rate, the white balance adaptation rate automatically determined by the auto white balance function, or the white balance adaptation rate set by the user Before the white balance correction process and before Record Recording the data relating to the adaptation rate of the light balance on the recording medium together with the photographed image as additional information of the image, capturing the image recorded on the recording medium and the additional information on the printer side, and capturing on the printer side White balance control means for performing white balance correction processing on an image, and when additional information is read together with the image by the information acquisition means, White balance adaptation rate included in additional information The white balance of the scanned image is corrected with the white balance correction amount according to the Printer ~ side And controlling the white balance processing and performing printing by white balance reflecting the setting of the white balance adaptation rate used in the electronic camera.
[0010]
An electronic camera according to a third aspect of the present invention is used in the above-described system, and includes an imaging unit that converts an optical image of a subject into an electrical signal, and an imaging light source for an image signal acquired through the imaging unit. Leave an atmosphere of The white balance adaptation rate indicating the degree, depending on the preset white balance adaptation rate, the white balance adaptation rate automatically determined by the auto white balance function, or the white balance adaptation rate set by the user White balance correction means for performing white balance correction processing and the previous Record And a recording means for recording data relating to the adaptation rate of the weight balance on the recording medium together with the photographed image as additional information of the image.
[0011]
According to a fourth aspect of the present invention, there is provided a printer according to a fourth aspect of the present invention, wherein the printer is used in the above-described system, and an information acquisition unit that reads an image captured by an electronic camera and white balance adaptation rate information indicating a degree of white balance correction for the image; Read from the information acquisition means White balance control means for performing white balance correction processing on an image, wherein the information acquisition means and the image together with the image White balance adaptation rate Is read, the white balance of the read image is corrected with a white balance correction amount corresponding to the white balance adaptation rate. White balance control means for controlling white balance processing at the time of printing, and print that performs white balance printing that reflects the setting of the white balance adaptation rate used in the electronic camera according to white balance control by the white balance control means Means.
[0012]
As one aspect of white balance control on the printer side in conjunction with the white balance adaptation rate setting on the electronic camera side, as shown in claim 5, in the printer of the present invention, white balance correction is performed by white balance correction means inside the printer. The white balance correction processing in the case where the gray (R = G = B) in which the red (R), green (G), and blue (B) color signal levels are equal to each other is achieved is referred to as “normal white balance correction processing”. In other words, the white balance control means performs the normal white balance correction process when the white balance adaptation rate information cannot be acquired.
[0013]
According to an aspect of the present invention, the white balance control unit is configured to execute white balance on the printer side when the white balance adaptation rate read from the information acquisition unit is smaller than a set threshold value. It is characterized by turning off the balance processing. For example, the threshold value may be set to a value indicating complete correction, or the threshold value may be variable by a user operation.
[0014]
According to the aspect of the present invention, the white balance adaptation rate can be expressed by a numerical value from 100% indicating complete correction to 0% indicating no white balance correction. When white balance correction is performed to achieve gray (R = G = B) in which the red (R), green (G), and blue (B) color signal levels are equal, the white balance correction amount is set to “normal”. The white balance control means defines the white balance correction amount on the printer side as
White balance correction amount on the printer side
= Normal white balance correction amount x White balance adaptation rate (%) / 100
It is characterized by determining according to.
[0015]
In addition, as described in claim 8, the printer according to the present invention further includes a “camera adaptation rate neglecting mode” for performing the normal white balance correction processing even when white balance adaptation rate information is read. There is also an aspect in which the camera adaptation rate ignoring mode can be selected by operating a selection unit.
[0016]
`` Camera adaptation rate utilization mode '' that implements white balance processing that reflects the setting of the white balance adaptation rate used in the electronic camera and `` camera adaptation rate ignore mode '' can be selected according to user operation and selected By switching the white balance control method according to the mode, it is possible to meet various user requests.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a printer system, a white balance control method thereof, an electronic camera, and a printer according to the present invention will be described in detail with reference to the accompanying drawings.
[0018]
FIG. 1 is a block diagram of a digital camera according to an embodiment of the present invention. The taking lens 12 of the camera 10 may be a single focus lens or a variable focal length such as a zoom lens. The light passing through the photographing lens 12 is imaged on a CCD image sensor (hereinafter referred to as CCD) 16 through an infrared cut filter 13 and an optical low-pass filter 14. Photosensors are arranged in a plane on the light receiving surface of the CCD 16, and red (R), green (G), and blue (B) primary color filters are arranged in a predetermined arrangement corresponding to each sensor.
[0019]
The subject image formed on the light receiving surface of the CCD 16 is converted into a signal charge of an amount corresponding to the amount of incident light by each photosensor. The CCD 16 has a so-called electronic shutter function that controls the charge accumulation time (shutter speed) of each photosensor according to the timing of the shutter gate pulse.
[0020]
The signal charges accumulated in the photosensors of the CCD 16 are sequentially read out as voltage signals (image signals) corresponding to the signal charges based on pulses given from a CCD driver (not shown). The image signal output from the CCD 16 undergoes predetermined analog signal processing such as correlated double sampling (CDS) processing and color separation processing, and then converted to a digital signal by the A / D converter 18.
[0021]
The digitized image signal is applied to the linear matrix circuit 20. In the linear matrix circuit 20, the input RGB data is expressed by the following equation. Convert according to <1> to obtain new RGB data.
[0022]
[Expression 1]

However, a to i are constants.
[0023]
The signal processed by the linear matrix circuit 20 is sent to a white balance adjustment circuit (hereinafter referred to as WB circuit) 22 and a white balance gain control unit 24. In this specification, “white balance” is abbreviated as “WB” as necessary. The WB circuit 22 includes a multiplier for increasing / decreasing digital values of RGB color signals, and each color signal is added to a corresponding multiplier. Commands for white balance correction values (gain values) Rg, Gg, and Bg are added from the WB gain control unit 24 to the multipliers for each color, and each multiplier adjusts the level of the color signal in accordance with the commands. The RGB signal whose white balance is adjusted in the WB circuit 22 is sent to the gamma conversion circuit 26. The contents of the control by the WB gain control unit 24 and the concept of the WB adaptation rate used for the control will be described later.
[0024]
The gamma conversion circuit 26 converts the input / output characteristics so that the white balance adjusted RGB signal has a desired gamma characteristic. The gamma-converted signal is sent to an RGB → YCr Cb conversion circuit (hereinafter referred to as a YC conversion circuit) 28, where the RGB signal is converted into a luminance signal Y and color difference signals Cr and Cb.
[0025]
The luminance / color difference signals (Y, Cr, Cb) obtained by the YC conversion circuit 28 are sent to the Cr Cb matrix circuit 30, and color correction of the color difference signals is performed. The image data processed by the Cr Cb matrix circuit 30 is compressed by a compression / expansion circuit 32 according to JPEG or another predetermined format, and then recorded on a recording medium 34 such as a memory card. At this time, information on the WB adaptation rate controlled by the WB gain control unit 24 is recorded on the recording medium 34 as image additional information. For example, the WB adaptation rate is written in the tag information of the image file. The recording medium 34 is not limited to a removable medium, and may be an internal memory of the camera 10.
[0026]
Next, a white balance control method for the camera 10 configured as described above will be described. AE (automatic exposure adjustment) control is performed in response to a half-pressing operation of a shutter button (not shown). In the AE control, R, G, and B signals are captured a plurality of times with a predetermined exposure value, and the subject brightness (shooting EV value) is obtained based on an integrated value obtained by integrating these R, G, and B signals. The aperture value and shutter speed at the time of shooting are finally determined based on the value. The aperture and electronic shutter (charge accumulation time) are controlled according to the determined aperture value and shutter speed when the shutter button is fully pressed.
[0027]
The R, G, B signals for one screen captured from the CCD 16 in response to the full pressing operation of the shutter button are sent to the WB gain control unit 24 via the linear matrix circuit 20. The WB gain control unit 24 divides one screen into a plurality of areas (for example, 8 × 8), obtains an average integrated value for each color of the R, G, and B signals for each divided area, and calculates an integrated value of the R signal. The ratio R / G of the integrated value of the G signal and the ratio B / G of the integrated value of the B signal and the integrated value of the G signal are obtained.
[0028]
R / G and B / G calculated for each divided area are used to determine which detection frame is included in the plurality of detection frames represented on the graph of FIG. used. Each detection frame such as a shade detection frame, a daylight color detection frame, a day white color detection frame, a white color detection frame, and a tungsten detection frame in FIG. 2 defines a color distribution range such as a light source type. Based on the number of areas that fall within the detection frame, the light source type is automatically determined, and white balance adjustment corresponding to the light source type is performed.
[0029]
FIG. 3 is an example of the camera WB adaptation rate when the photographing light source is tungsten. The horizontal axis indicates the B / G gain value, and the vertical axis indicates the R / G gain value. However, the B / G gain value and R / G gain value during daylighting are normalized to 1 and displayed (point A). In FIG. 3, when correction is made with “tungsten adaptation rate equivalent to 100% gain value” (point B), that is, R / G = 0.5, R / G = 2.0, the gray object under the tungsten light source is The image is captured in gray (R = G = B).
[0030]
On the other hand, when correction is performed with “a gain value equivalent to a tungsten adaptation rate of 70%” (point C), that is, R / G = 0.65 and B / G = 1.7, the gray object under the tungsten light source The image is captured in reddish gray with an atmosphere.
[0031]
Thus, the adaptation rate indicates the degree to which the atmosphere of the light source remains, and is defined on the graph by the distance between the daylight gain value (point A) and the complete correction point (point B). Note that the space defining the color distribution is not limited to the (R / G, B / G) space shown in FIG. 3, and an LAB color space or other chromaticity diagram can also be used.
[0032]
In the case of this example, the adaptation rate is appropriately set between 100% (complete correction) and 0% (no correction). The acclimatization rate of 100% is a case where a complete white balance is achieved, and the atmosphere of the light source does not remain at all. When the adaptation rate of 0% is selected, as a result, white balance correction is not performed and the color of the light source is output as it is. This is the same as when the manual white balance is set to “daylight (clear)”. The closer the adaptation rate is to “0%”, the more the atmosphere of the light source remains, and the closer to “100%”, the less the atmosphere of the light source.
[0033]
The camera WB adaptation rate may be automatically determined by the auto white balance (AWB) function of the camera 10 or may be manually set by the camera user. In this embodiment, the adaptation rate of AWB can be changed according to the photographer's preference. The adaptation rate may be set stepwise or may be set continuously. The set adaptation rate information is recorded together with the image on the recording medium 34 as additional information at the time of image recording.
[0034]
Next, the printer will be described. FIG. 4 is a block diagram of the printer according to the embodiment of the present invention. An image captured by the camera 10 and its additional information are transferred from the camera 10 to the printer 40 via a removable recording medium (removable medium) 34. When the image file is stored in a recording medium inside the camera, the image and its additional information are transmitted from the camera 10 to the printer 40 using wireless or wired data communication means.
[0035]
The printer 40 includes a JPEG compressed image decompression processing unit 42, a YCr Cb → RGB conversion circuit (hereinafter referred to as an RGB conversion circuit) 44, a WB correction circuit 46, a lookup table (LUT) correction circuit 48, an RGB → YMC conversion circuit ( Hereinafter, it is referred to as a YMC conversion circuit.) 50, a print engine 52, and a control unit 54 for controlling them.
[0036]
The image data read from the recording medium 34 is decompressed by the JPEG compressed image decompression processing unit 42 and then sent to the RGB conversion circuit 44. The signal converted from the YC signal to the RGB signal is sent to the WB correction circuit 46, where the gain of each color signal is adjusted. The control unit 54 analyzes the image captured from the JPEG compressed image decompression processing unit 42, determines the gain value of each color signal based on the information of the WB adaptation rate that is additional information of the image, and sends it to the WB correction circuit 46. A gain control signal is given.
[0037]
The data processed by the WB correction circuit 46 is subjected to correction processing by the LUT correction circuit 48 and then sent to the YMC conversion circuit 50. The YMC conversion circuit 50 converts the received RGB data into Y (yellow), magenta (M), and cyan (C) color signals. The image data converted into the YMC signal is sent to the print engine 52, and the image content indicated by the image data is printed on a printing paper or other printing medium. In this way, a printed matter 56 on which the image content is printed is obtained.
[0038]
The control unit 54 includes an image analysis unit, a printer AutoSetUp function unit, and a coefficient determination unit. The control unit 54 of the printer 40 reads WB adaptation rate information included in the additional information of the image, and performs white balance correction control that reflects the setting of the adaptation rate. For example, the following processes (1) to (3) are performed.
[0039]
(1) When there is no additional information on the WB adaptation rate, normal AWB processing is performed. Here, “normal AWB processing” means that the white balance of the input image data is corrected on the printer side, and the red (R), green (G), and blue (B) color signal levels are equal. The process of adjusting the gain of each color signal so as to achieve the following gray (R = G = B).
[0040]
(2) When the camera WB adaptation rate is less than 100%, the printer AWB process is turned off. Thereby, printing is performed with the white balance set on the camera side, and correction that cancels the atmosphere of the light source can be avoided. The threshold value that is a criterion for determining whether or not to turn off the printer AWB process may be fixedly set to “100%” indicating complete correction, or the threshold value setting can be changed by a user operation. It may be configured. For example, when the threshold is set to 80%, if the camera WB adaptation rate is less than 80%, the printer AWB process is turned off, and if the camera WB adaptation rate is 80% or more, the printer AWB process is executed. The control is switched.
[0041]
(3) The AWB correction amount on the printer side is <2>
[0042]
[Expression 2]
Printer AWB correction amount = Normal AWB correction amount × Adaptation rate (%) / 100... <2>
The control is performed by reflecting the setting content of the adaptation rate on the camera side in the AWB correction on the printer side. Here, “normal AWB correction amount” means a white balance correction amount by the normal AWB processing.
[0043]
In the printer 40 shown in FIG. 4, even if the additional information of the WB adaptation rate is read on the printer 40 side, normal printer AWB processing is executed without performing the AWB control reflecting the information. The aspect which provides "is also preferable.
[0044]
In other words, the printer 40 utilizes the information on the WB adaptation rate set on the camera 10 side to perform the “camera adaptation rate utilization mode” in which AWB control of the printer 40 is performed, and the “camera adaptation rate ignore mode” does not use the adaptation rate information. The mode selection means 58 is configured so that the user can select a mode as appropriate. The selection information of the mode selection means 58 is input to the control unit 54, and the control unit 54 switches the AWB control method corresponding to the selected mode.
[0045]
FIG. 5 is a flowchart showing a processing procedure of a system in which the camera 10 and the printer 40 described above are combined. First, the camera 10 acquires light source determination data (step S110), and performs light source determination based on the acquired data (step S112). Next, an adaptation rate table corresponding to the determined light source is read, and an R / G gain and a B / G gain are determined based on the light source type and the adaptation rate. The WB adaptation rate may be a value set in advance on the camera side as in step S114, or the camera WB adaptation rate can be arbitrarily set by means such as a GUI (graphical user interface). You may comprise.
[0046]
Next, a process of recording the image data captured in conjunction with the pressing of the shutter button and the additional information (including the camera WB adaptation rate) on the recording medium 34 is executed (step S118). After shooting, the recording medium 34 is taken out from the camera 10 and mounted in the media insertion slot of the printer 10. The printer 40 performs processing to read image data and additional information (including the camera WB adaptation rate) from the recording medium 34 (step S120). Based on the read image data and additional information, AWB processing on the printer side (any one of (1) to (3) above) is performed to print the target image (step S122).
[0047]
Next, an application example to a moving image recording camera (movie camera) will be described.
[0048]
When printing one scene of a moving image having no additional information related to the WB adaptation rate, normal AWB processing is performed on the printer side. On the other hand, when one scene is taken out from a moving image having additional information related to the WB adaptation rate and printing is performed, the same correspondence as in the case of printing from the camera 10 (electronic still camera) described above is performed.
[0049]
The white balance adjustment at the time of moving image shooting includes a method described below in addition to the case where the light source type and color temperature are estimated and the WB adaptation rate is set according to the estimated light source type and color temperature. That is, the WB gain is set so that the RGB integrated value or the color difference signal integrated value becomes gray for the entire screen or a part of the screen (for example, a constant region in the center). In this case, when the WB gain value necessary for the integrated value to become gray is within a certain range (in a predetermined range), an adaptation rate process for intentionally setting the WB gain to be weak is performed. Is called. An example is shown in FIG. In the figure, the area indicated by reference numeral 62 is an area that defines the range to be set to the adaptation rate 100%, and the other area (reference numeral 64) is to define the range to be set to the adaptation rate 80%. It has been established.
[0050]
For example, when the R gain and B gain necessary for achieving perfect white balance are 1.1 and 0.9, respectively, this is within the area of 100% adaptation rate indicated by reference numeral 62 in FIG. WB control is performed with gain = 1.1 and B gain 0.9.
[0051]
In addition, when the R gain and B gain necessary for taking a complete WB are 0.6 and 2.0, respectively, this is within the area of 80% adaptation rate indicated by reference numeral 64. <3>, <4>
[0052]
[Equation 3]
R gain = 1.0− (1.0−0.6) × 0.8 = 0.68 <3>
[0053]
[Expression 4]
B gain = 1.0 + (2.0−1.0) × 0.8 = 1.8 <4>
And WB control is performed with the calculated R gain and B gain.
[0054]
【The invention's effect】
As described above, according to the present invention, the information on the white balance adaptation rate set by the electronic camera is recorded together with the image on the recording medium, and at the time of printing, the information on the adaptation rate is read on the printer side and linked to the setting on the camera side. Since the white balance control is performed, it is possible to avoid a situation in which the photographer intentionally leaves the atmosphere (color) of the light source and corrects the atmosphere at the time of printing.
[Brief description of the drawings]
FIG. 1 is a block diagram of a digital camera according to an embodiment of the present invention.
FIG. 2 is a graph showing a detection frame indicating a color distribution range such as a light source type.
FIG. 3 is a graph for explaining the white balance adaptation rate set on the camera side;
FIG. 4 is a configuration diagram of a system including a printer according to an embodiment of the invention.
FIG. 5 is a flowchart showing the processing procedure of the camera and printer system of this example.
FIG. 6 is a diagram showing an example of white balance adaptation rate processing for a moving image
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Camera, 12 ... Shooting lens, 16 ... CCD, 18 ... A / D converter, 20 ... Linear matrix circuit, 22 ... WB circuit, 24 ... WB gain control part, 26 ... Gamma conversion circuit, 28 ... YC conversion circuit , 34 ... recording medium, 40 ... printer, 46 ... WB correction circuit, 48 ... LUT correction circuit, 50 ... YMC conversion circuit, 52 ... print engine, 54 ... control unit, 58 ... mode selection means

Claims (10)

In a printer system that prints an image taken with an electronic camera using a printer,
The electronic camera is
This is a white balance adaptation rate that indicates the degree to which the atmosphere of the photographic light source remains for the image signal acquired through the imaging means, and is automatically determined by a preset white balance adaptation rate and an auto white balance function. White balance correction means for performing white balance correction processing according to the white balance adaptation rate set by the user or the white balance adaptation rate set by the user ;
Before comprising recording means for recording data relating to Kiho white balance adaptation rate on the recording medium together with the captured image as the additional information of the image, and
The printer is
Information acquisition means for reading an image recorded on the recording medium and its additional information;
White balance control means for performing white balance correction processing on the image read from the information acquisition means, and when additional information is read together with the image by the information acquisition means, the white information included in the additional information A printer system comprising: white balance control means for controlling white balance processing on the printer side so as to correct the white balance of the read image with a white balance correction amount corresponding to a balance adaptation rate. A white balance control method applied to a printer system that prints an image captured by an electronic camera using a printer,
The white balance adaptation rate that indicates the degree to which the atmosphere of the photographic light source remains when taking pictures with the electronic camera, and the white balance adaptation rate automatically determined by the preset white balance adaptation rate and the auto white balance function A step of performing white balance correction processing according to the rate or the white balance adaptation rate set by the user ;
And recording the data for the previous Kiho white balance adaptation rate on the recording medium together with the captured image as the additional information of the image,
Capturing an image recorded on the recording medium and its additional information into the printer;
White balance control means for performing white balance correction processing on an image captured on the printer side, and when additional information is read together with the image by the information acquisition means, white balance included in the additional information The white balance processing on the printer side is controlled so that the white balance of the read image is corrected with the white balance correction amount corresponding to the adaptation rate , and the white balance adaptation rate setting used in the electronic camera is reflected. A process of performing printing;
A white balance control method comprising: Imaging means for converting an optical image of a subject into an electrical signal;
A white balance adaptation rate indicating the degree to which the atmosphere of the photographic light source is left for the image signal acquired through the imaging means, and is automatically determined by a preset white balance adaptation rate and an auto white balance function. White balance correction means for performing white balance correction processing in accordance with the adjusted white balance adaptation rate or the white balance adaptation rate set by the user ;
Recording means for recording on a recording medium together with the pre-captured image data on Kiho white balance adaptation rate as additional information for the image,
An electronic camera characterized by comprising: An information acquisition unit that reads information of a white balance adaptation rate indicating an image captured by an electronic camera and a degree of white balance correction for the image;
A white balance control means for correcting the white balance process with respect to image read from the information acquisition unit, when the with the image white balance adaptation rate is read by the information acquisition unit, the white balance White balance control means for controlling white balance processing at the time of printing so as to correct the white balance of the read image with a white balance correction amount corresponding to the adaptation rate ;
According to the white balance control by the white balance control means, a printing means for performing printing by white balance reflecting the setting of the white balance adaptation rate used in the electronic camera;
A printer comprising: 5. The printer according to claim 4, wherein white balance correction is performed by a white balance correction unit in the printer, and the red (R), green (G), and blue (B) color signal levels are equal. When defining white balance correction processing when achieving G = B) as "normal white balance correction processing"
The printer according to claim 1, wherein the white balance control unit performs the normal white balance correction process when the white balance adaptation rate information cannot be acquired.   The white balance control means turns off the white balance processing on the printer side when the white balance adaptation rate read from the information acquisition means is smaller than a set threshold value. 5. The printer according to 4. The printer according to claim 4, wherein the white balance adaptation rate can be expressed by a numerical value from 100% indicating complete correction to 0% indicating no white balance correction,
When white balance correction is performed by the white balance correction means inside the printer to achieve gray (R = G = B) in which the color signal levels of red (R), green (G), and blue (B) are equal. When defining the white balance correction amount as "normal white balance correction amount",
The white balance control means calculates the white balance correction amount on the printer side as follows: White balance correction amount on the printer side = normal white balance correction amount × white balance adaptation rate (%) / 100
A printer characterized by deciding according to.   6. The printer according to claim 5, further comprising a “camera adaptation rate ignoring mode” for executing the normal white balance correction processing even when white balance adaptation rate information is read. The printer is configured so that the camera adaptation rate ignoring mode can be selected.   The white balance correction means includes
  Means for automatically determining a light source type based on the acquired image signal;
  A means for performing white balance correction according to the automatically determined light source type, and correction according to the white balance adaptation rate expressed by a numerical value from 100% indicating complete correction to 0% indicating no white balance correction Means for correcting the white balance by the amount,
  The printer system according to claim 1, comprising:   The white balance correction means includes
  Means for automatically determining a light source type based on the acquired image signal;
  A means for performing white balance correction according to the automatically determined light source type, and correction according to the white balance adaptation rate expressed by a numerical value from 100% indicating complete correction to 0% indicating no white balance correction Means for correcting the white balance by the amount,
  The electronic camera according to claim 3, comprising:

Images