JP2004032245A - Image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always obtain compressed image data with corrected image quality having excellent image quality from compressed image data. <P>SOLUTION: A correction amount computing means 15 computes correction amounts of white balance correction and density correction which are to be applied to image data D1 obtained by decompressing compressed image data P1 by a first decompression means 10, and an image quality correction means 25 applies image quality processing to the image data D1 by using these correction amounts to obtain the image data D2 whose image quality is corrected. A second decompression 35 decompresses the compressed image data P2 obtained by applying compression processing to the data D2 by a compression means 30 to obtain RGB image data D3. A first change amount computing means 20 and a second change amount computing means 40 respectively compute a signal change amount S1 obtained by image quality correction executed by an image quality correction means 25, and a signal change amount S2 obtained by compression processing executed by the means 30. An object image data deciding means decides the data P2 as object image data P if the amount S1 is larger than S2, and decides the original data P1 as the data P if S1 is equal to or lower than S2. <P>COPYRIGHT: (C)2004,JPO

Description

【数２】

なお、式（２）におけるＹｍｉｄは、画像データのビット数と関連した定数であり、８ビットの画像データの場合、１２８とすることができる。
【００２１】
画質補正手段２５は、補正量算出手段１５により算出した補正量を用いて下記の式（３）に従って、画像データＤ１（Ｒ１、Ｇ１、Ｂ１）に対してホワイトバランス補正と濃度補正を行って画像データＤ２（Ｒ２、Ｇ２、Ｂ２）を得る。
【００２２】
【数３】

なお、画質補正手段１５は、式（３）に示す計算を画像データＤ１の全ての画素に対して行うものである。
【００２３】
第１の変化量算出手段２０と第２の変化量算出手段４０は、夫々下記の式（４）と式（５）に従って、画質補正手段１５が行う画質補正による信号変化量Ｓ１と圧縮手段３０が行う圧縮処理による信号変化量Ｓ２とを算出する。
【００２４】
【数４】

【数５】

第１の変化量算出手段２０と第２の変化量算出手段４０により夫々算出された信号変化量Ｓ１と信号変化量Ｓ２が、目的画像データ決定手段４５に入力される。目的画像データ決定手段４５は、信号変化量Ｓ１と信号変化量Ｓ２とを比較し、信号変化量Ｓ１が信号変化量Ｓ２以下であるとき、すなわち画質補正手段１５が行う画質補正による信号変化量が圧縮手段３０が行う圧縮処理による信号変化量Ｓ２以下であるとき、圧縮画像データＰ１を目的画像データＰとし、信号変化量Ｓ１が信号変化量Ｓ２より大きいとき、圧縮画像データＰ２、すなわち圧縮画像データＰ１を解凍して、画像補正処理を施した後に再圧縮を行うことにより得た画像データＰ２を目的画像データＰとする。目的画像データ決定手段４５により決定された目的画像データＰは、記憶手段５０に記憶される。
【００２５】
図２は、図１に示す画像処理装置Ａの動作を示すフローチャートである。図示のように、画像処理装置Ａの第１の解凍手段１０は、まず入力される圧縮画像データＰ１を解凍して、ＲＧＢ画像データＤ１を得る（Ｓ５）。補正量算出手段１５は、式（１）と式（２）に従って画像データＤ１に対するホワイトバランス補正量および濃度補正量を算出する（Ｓ１０）。画質補正手段２５は、補正量算出手段１５により算出したホワイトバランス補正量および濃度補正量を用い、式（３）に従って画像データＤ１に対してホワイトバランス補正と濃度補正を行って、補正済みＲＧＢ画像データＤ２を得る（Ｓ１２）。第１の変化量算出手段２０が、式（４）に従って、画像データ画質補正手段２５が行う画質補正処理による信号変化量Ｓ１を算出する（Ｓ１４）と共に、圧縮手段３０は、画質補正手段２５により得た画像データＤ２に対して圧縮処理を行い、圧縮画像データＰ２を得る（Ｓ１６）。画像処理装置Ａの第２の解凍手段３５は、圧縮画像データＰ２を解凍してＲＧＢ画像データＤ３を得（Ｓ１８）、第２の変化量算出手段４０は、式（５）に従って、圧縮手段３０が行う圧縮処理による信号変化量Ｓ２を算出する（Ｓ２０）。目的画像データ決定手段４５は、信号変化量Ｓ１とＳ２とを比較し（Ｓ２２）、信号変化量Ｓ１が、信号変化量Ｓ２より大きいとき、圧縮画像データＰ２を目的画像データＰに決定するが（Ｓ２２：Ｙｅｓ、Ｓ２４）、信号変化量Ｓ１が信号変化量Ｓ２以下であるとき、圧縮画像データＰ１、すなわち入力された圧縮画像データそのものを目的画像データＰに決定する（Ｓ２２：Ｎｏ、Ｓ２６）。記憶部５０は、目的画像データ決定手段４５により決定された目的画像データＰを記憶保存して処理が終了する（Ｓ３０）。
【００２６】
このように、本実施形態の画像処理装置Ａによれば、入力されてきた圧縮画像データＰ１から画質補正済み圧縮画像データ（目的画像データ）を得る際に、圧縮画像データＰ１に対して画質補正を行うことによる信号変化量Ｓ１と、画質補正した画像データ（Ｄ２）から圧縮画像データＰ２を得るために行う再圧縮による信号変化量Ｓ２を算出し、画質補正による信号変化量Ｓ１が、再圧縮による信号変化量Ｓ２より大きいときにのみ、圧縮画像データＰ１を解凍して画質補正処理を施し、再圧縮処理を行って得た圧縮画像データＰ２を目的画像データＰとし、画質補正による信号変化量Ｓ１が、再圧縮による信号変化量Ｓ２以下であるとき、すなわち画質補正による画質向上よりも、再圧縮による画質劣化のほうが大きいときには、画質補正を行わずに、元の圧縮画像データＰ１を目的画像データＰとするようにしているので、画質が最もよい目的画像データを得ることができる。
【００２７】
図３は、本発明の第２の実施形態となる画像処理装置Ｂの構成を示すブロック図である。図示のように、本実施形態の画像処理装置Ｂは、圧縮画像データＰ１を解凍してＲＧＢ画像データＤ１（Ｒ１、Ｇ１、Ｂ１）を得る解凍手段６０と、ＲＧＢ画像データＤ１に対して行うホワイトバランス補正および濃度補正の補正量を夫々算出する補正量算出手段６５と、補正量算出手段６５により算出した補正量の総和Ｓ算出すると共に、この総和Ｓが、図示しない記憶部に予め設定された閾値Ｍ以下であるときに、圧縮画像データＰ１をそのまま目的画像データＰとして後述する記憶手段９０に出力して記憶させるが、補正量の総和Ｓが閾値Ｍより大きいときに、後述する画質補正手段画像データＤ１を出力して画質補正処理を行わせる制御手段７０と、出力されてきた画像データＤ１に対して、補正量算出手段６５により算出された補正量を用いてホワイトバランス補正および濃度補正処理を行って補正済み画像データＤ２を得る画質補正手段７５と、補正済み画像データＤ２に対して圧縮処理を行って圧縮画像データＰ２を取得し、この圧縮画像データＰ２を目的画像データＰとして記憶手段９０に出力する圧縮手段８０と、制御手段７０または圧縮手段８０から出力されてきた目的画像データＰを記憶保存する記憶手段９０とを備えてなるものである。
【００２８】
図３に示す画像処理装置Ｂの補正量算出手段６５は、図１に示す画像処理装置Ａの補正量算出手段１５と同様に、上述した式（１）、式（２）を用いてホワイト補正量（ΔＲ、ΔＢ）および濃度補正量ΔＤを算出し、制御手段７０は、下記の式（６）に従って、補正量の総和Ｓを求める。
【００２９】
【数６】

補正量の総和Ｓが大きければ大きいほど、画像データＤ１に対して行う画質補正による信号変化量が大きいことを意味し、本実施形態において、制御手段７０は、この総和Ｓと予め設定された閾値Ｍとを比較し、補正量の総和Ｓが閾値Ｍより大きいときにのみ、画質補正手段画像データＤ１を出力して画質補正処理を行わせるものである。
【００３０】
閾値Ｍは、予め設定されたものであり、圧縮手段８０が行う圧縮処理による信号の最大変化量以上の数値である。
【００３１】
画質補正手段７５は、図１に示す画像処理装置Ａの画質補正手段２５と同様に、補正量算出手段６５により算出したホワイトバランス補正量および濃度補正量を用いて、式（３）に従って、制御手段７０から出力されてきた画像データＤ１に対してホワイトバランス補正および濃度補正を施すものである。
【００３２】
図４は、図３に示す画像処理装置Ｂの動作を示すフローチャートである。図示のように、本実施形態の画像処理装置Ｂは、まず、解凍手段６０により処理対象の圧縮画像データＰ１を解凍してＲＧＢ画像データＤ１を得る（Ｓ５０）。補正量算出手段６５は、画像データＤ１に対して行うホワイトバランス補正および濃度補正の補正量を夫々算出して制御手段７０に出力する（Ｓ５４）。制御手段７０は、補正量算出手段６５により算出されたホワイトバランス補正量および濃度補正量から、補正量の総和Ｓを求める（Ｓ５４）と共に、この総和Ｓが図示しない記憶部に設定された閾値Ｍ以下であるとき、圧縮画像データＰ１そのまま目的画像データＰとして記憶手段９０に記憶保存させる（Ｓ５６：Ｎｏ、Ｓ５８、Ｓ６６）が、補正量の総和Ｓが閾値Ｍより大きいとき、画質補正手段７５に画像データＤ１に出力し、画質補正を行わせる（Ｓ５６：Ｙｅｓ、Ｓ６０）。画質補正手段７５が、補正量算出手段６５により算出した補正量を用いて、制御手段７０から出力された画像データＤ１に対してホワイトバランス補正および濃度補正を施して得た画像データＤ２に対して、圧縮手段８０は、圧縮処理を行って圧縮画像データＰ２を得、この圧縮画像データＰ２を目的画像データＰとして記憶手段９０に出力する（Ｓ６２、Ｓ６４、Ｓ６６）。
【００３３】
このように、本実施形態の画像処理装置Ｂによれば、図１に示す画像処理装置Ａと同様に、画質補正処理による画質向上よりも、再圧縮による画質劣化のほうが大きいとき、画像データに対する画質補正を行わず、元の圧縮画像データ（Ｐ１）そのまま目的画像データＰにすることによって、最も画質のよい目的の圧縮画像データを得ることができるうえに、予め設定され、再圧縮処理による信号変化量の最大値となる閾値を判断基準として利用することによって、画質補正を行うか否かの判断を行う際に、実際に画像データに対して画質補正処理、圧縮処理、解凍処理を行う必要がないので、処理時間を短縮することができ、効率が良い。
【００３４】
上述において、本発明の望ましい実施形態となる画像処理装置に説明したが、本発明の画像処理装置は、上述した実施形態に限られるものではなく、本発明の主旨を変えない限り、様々な変更を加えることができる。
【００３５】
例えば、上述した２つの画像処理装置の画質補正部は、画像データに対してホワイトバランス補正と濃度補正を行うものであるが、本発明の画像処理装置は、画像データに対して行う画質補正処理は、この２つに限られるものではなく、例えば、階調補正や、シャープネス補正などを行うものであってもよい。
【００３６】
また、図１に示す画像処理装置Ａは、画質補正による信号変化量Ｓ１が再圧縮による信号変化量Ｓ２より大きいとき、元の圧縮画像データＰ１を解凍、画質補正、再圧縮して得た圧縮画像データＰ２を目的画像データとし、信号変化量Ｓ１が再圧縮による信号変化量Ｓ２以下であるとき、元の圧縮画像データＰ１を目的画像データとするようにしているが、本発明の画像処理装置は、例えば、画質補正による信号変化量Ｓ１が再圧縮による信号変化量Ｓ２のＴ倍（Ｔ：以上の正数）より大きいとき、元の圧縮画像データＰ１を解凍、画質補正、再圧縮して得た圧縮画像データＰ２を目的画像データとし、信号変化量Ｓ１が再圧縮による信号変化量Ｓ２のＴ倍以下であるとき、元の圧縮画像データＰ１を目的画像データとするように構成されてもよい。
【００３７】
また、上述した２つの実施形態の画像処理装置は、入力されてきた圧縮画像データから得た目的の圧縮画像データを記憶保存するものであるが、記憶保存された画像データを端末装置に送信したり、プリント装置に送信してプリントアウトを行わせたりするものであってもよい。
【００３８】
また、上述した画像処理装置は、圧縮画像データから画質補正済み画像データを取得するための独立した形態を有するものであるが、例えば、プリントシステムや、通信中継装置などに備えられ、画質補正の役割を担う部分として構成されたものであってもよい。
【００３９】
本発明の画像処理装置の取り扱う圧縮画像データの種類として、デジタルカメラにより撮影して得た圧縮画像データや、ネットワーク通信を行うために圧縮された画像データなど、いかなる圧縮された画像データであってもよい。
【図面の簡単な説明】
【図１】本発明の第１の実施形態となる画像処理装置Ａの構成を示すブロック図
【図２】図１に示す画像処理装置Ａの動作を示すフローチャート
【図３】本発明の第２の実施形態となる画像処理装置Ｂの構成を示すブロック図
【図４】図３に示す画像処理装置Ｂの動作を示すフローチャート
【符号の説明】
１０　　第１の解凍手段
１５　　補正量算出手段
２０　　第１の変化量算出手段
２５　　画質補正手段
３０　　圧縮手段
３５　　第２の解凍手段
４０　　第２の変化量算出手段
４５　　目的画像決定手段
５０　　記憶手段
６０　　解凍手段
６５　　補正量算出手段
７０　　制御手段
７５　　画質補正手段
８０　　圧縮手段
９０　　記憶手段
Ｄ１，Ｄ２，Ｄ３　　ＲＧＢ画像データ
Ｐ１，Ｐ２　　圧縮画像データ
Ｐ　　目的画像データ
Ｓ１，Ｓ２，Ｓ　　信号変化量
Ｍ　　閾値
ΔＲ，ΔＢ　　ホワイトバランス補正量
ΔＤ　　濃度補正量[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus that obtains compressed image data whose image quality has been corrected from image data, more specifically, compressed image data.
[0002]
[Prior art]
In recent years, various systems that provide services for digital image data (hereinafter abbreviated as image data) have appeared. For example, a system that stores and manages image data such as those obtained by scanning a negative film with a scanner and those obtained by a digital camera, and image quality correction to achieve the desired image quality There is a print service system that performs processing and prints.
[0003]
On the other hand, in the background of the rapid spread of the Internet due to the low price of terminal devices such as computers and the advance of network technology, most of the various systems described above provide services via the network.
[0004]
For example, the above-described print service system has a configuration in which image quality correction processing is performed on image data uploaded by a user using a terminal device, and then output to a printer such as a minilab connected via a network and printed out. In addition, there is a configuration in which image data subjected to image quality correction processing is held, only an address such as a URL indicating the holding location is transmitted to a minilab, and the image data to be printed is downloaded when accessed from the minilab. However, image data is transferred between the terminal device and the printer that performs printout via a network.
[0005]
Also, in the field of mobile communication, with the spread of mobile phones and enhancement of functions of mobile phones, image services using mobile phones as terminal devices are also actively performed. For example, when relaying an e-mail between mobile phones, image quality correction processing such as white balance correction and density correction is performed on the image data attached to the e-mail transmitted from the transmitting mobile phone. If the data is sent to the receiving mobile phone or the attached mobile phone cannot receive the attached file, the image data subjected to image quality correction processing is held, and an address such as a URL indicating the holding location of the image data There is a communication relay server device having an image quality correction function, such as transmitting only to a mobile phone on the receiving side, and downloading when receiving access from the mobile phone on the receiving side later. These server devices also exchange image data with a mobile phone serving as a terminal device via a network.
[0006]
On the other hand, when transferring image data via a network, the image data is compressed so as to reduce the burden on the terminal device and the network, such as shortening the communication time. That is, the image data uploaded from the terminal device is compressed, and the image data to be downloaded to the terminal device is also compressed. In the case of a mobile phone, image data obtained by photographing is compressed and stored in a storage unit of the mobile phone.
[0007]
For this reason, in an apparatus that performs image quality correction processing, firstly, a procedure for decompressing the compressed image data, performing image quality correction on the decompressed image data, and recompressing to transmit the corrected image data is necessary. It is said.
[0008]
[Problems to be solved by the invention]
However, the recompression process is intended to reduce the size of the image data, and causes image quality deterioration contrary to the image quality correction process. That is, in the various systems described above, image quality correction processing is performed to improve image quality, while recompression is also performed to degrade image quality. In some cases, the amount of degradation in image quality due to recompression may exceed the amount of improvement in image quality due to image quality correction processing. Finally, the final target image data has a higher image quality than the original image data before image quality correction processing. There is a problem that sometimes gets worse.
[0009]
The present invention has been made in view of the above circumstances, and always obtains target image data with good image quality in a system that obtains target image data by performing image quality correction processing on compressed image data and then performing recompression. An object of the present invention is to provide an image processing apparatus that can perform the above processing.
[0010]
[Means for Solving the Problems]
An image processing apparatus of the present invention is an image processing apparatus for obtaining compressed image data whose image quality has been corrected from first compressed image data,
Decompression means for decompressing the first compressed image data to obtain first image data;
Image quality correction means for performing image quality correction processing on the first image data to obtain second image data;
Compression means for performing a compression process on the second image data to obtain second compressed image data;
An image quality corrected compressed image data acquisition unit that uses the second compressed image data as the image quality corrected compressed image data;
Determination means for determining whether or not to perform the image quality correction processing on the first image data;
The image quality correcting unit performs the image quality correcting process only on the first image data determined to perform the image quality correcting process by the determining unit, and the image quality corrected compressed image data acquiring unit However, the first compressed image data corresponding to the first image data determined not to perform the image quality correction processing by the determining means is used as the image quality corrected compressed image data. It is what.
[0011]
That is, the image processing apparatus of the present invention aims to obtain compressed image data (image quality corrected compressed image data) whose image quality has been corrected from compressed image data (first compressed image data). Yes, similarly to the conventional image processing apparatus, the first image data is decompressed and subjected to the image quality correction process, and the image data subjected to the image quality correction process is recompressed to obtain the image quality corrected compressed image data The first compression determined to perform the image quality correction processing by the determination means, and determining whether to perform the image quality correction processing on the first image data. While the image data is subjected to conventional processing (the above-mentioned basic processing is also performed), the above-described basic processing is applied to the first compressed image data that is determined not to perform image quality correction processing by the determination means. The not performed, the first compressed image data itself object image data, that is, one that operates to image quality corrected compressed image data.
[0012]
In the image processing apparatus of the present invention, the determination unit includes a first change amount including a signal change amount of image data by the image quality correction process performed on the first image data by the image quality correction unit;
A signal change amount acquisition means for calculating a second change amount comprising a signal change amount of the image data by the compression processing performed on the second image data by the compression means;
Only when the first change amount obtained by the signal change amount acquisition means is larger than the second change amount, it is determined to perform the image quality processing on the first image data. be able to.
[0013]
In addition, in order to simplify the calculation and reduce the processing time, the determination unit of the present invention is configured such that the image data signal change amount by the image quality correction process performed on the first image data by the image quality correction unit. A signal change amount calculating means for calculating
Only when the signal change amount calculated by the signal change amount calculating means is larger than a predetermined threshold value, it may be determined to perform the image quality correction processing on the first image data.
[0014]
Here, it is desirable that the predetermined threshold value is around the maximum value of the signal change amount of the image data by the compression processing of the compression unit of the image processing apparatus of the present invention, and is a processing target of the image processing apparatus of the present invention. It may be set for each type based on the type of image data (photograph, medical image, etc.), and the same threshold may be set for any type of image data.
[0015]
The first compressed image data to be processed by the image processing apparatus of the present invention may be obtained by photographing with a digital camera.
[0016]
【The invention's effect】
The image processing apparatus according to the present invention converts compressed image data into compressed image data by determining whether to perform image quality correction on the compressed image data when obtaining compressed image data (target compressed image data) whose image quality has been corrected from the compressed image data. On the other hand, whether or not to perform image quality correction processing is determined, and the compressed image data itself is subjected to image quality correction processing compression without performing image quality correction processing on the compressed image data that is determined not to perform image quality correction processing. Since it is determined to be image data, it is determined to perform the image quality correction process on the compressed image data only when the signal change amount due to the image quality correction process is larger than the signal change amount due to the recompression process. Therefore, it is possible to always obtain the target compressed image data with good image quality.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0018]
FIG. 1 is a block diagram showing a configuration of an image processing apparatus A according to the first embodiment of the present invention. As shown in the figure, the image processing apparatus A according to the present embodiment decompresses the compressed image data P1 to obtain RGB image data D1 (R1, G1, B1), and the image data D1. The correction amount calculation means 15 for calculating a correction amount for performing white balance correction and density correction, and the white balance correction and density correction for the image data D1 using the correction amount calculated by the correction amount calculation means 15 The image quality correction means 25 for performing the image quality correction, the first change amount calculation means 20 for calculating the signal change amount S1 due to the image quality correction of the image quality correction means 25, and the image data D2 (R2) with the image quality correction acquired by the image quality correction means 25 , G2, B2) to perform compression processing to obtain compressed image data P2, and decompress the compressed image data P2 obtained by the compression means 30 Second decompression means 35 for obtaining the GB image data D3 (R3, G3, B3), second change amount calculation means 40 for calculating the signal change amount S2 due to the compression means 30 compressing the image data D2, Based on the first change amount S1 and the second change amount S2, the target image data determination unit 45 that determines the target image data P to be the compressed image data P1 or the compressed image data P2, and the target image data determination unit 45 And storage means P for storing the determined target image data P.
[0019]
In the present embodiment, the image quality correction processing performed on the image data is white balance correction and density correction, and the correction amount calculation means 15 uses the white balance correction amounts ΔR, (1) and (2), respectively. ΔB and density correction amount ΔD are calculated.
[0020]
[Expression 1]

[Expression 2]

Ymid in equation (2) is a constant related to the number of bits of image data, and can be set to 128 in the case of 8-bit image data.
[0021]
The image quality correction unit 25 performs white balance correction and density correction on the image data D1 (R1, G1, B1) according to the following equation (3) using the correction amount calculated by the correction amount calculation unit 15 to generate an image. Data D2 (R2, G2, B2) is obtained.
[0022]
[Equation 3]

The image quality correction means 15 performs the calculation shown in Expression (3) for all the pixels of the image data D1.
[0023]
The first change amount calculating means 20 and the second change amount calculating means 40 are respectively the signal change amount S1 and the compression means 30 by the image quality correction performed by the image quality correction means 15 according to the following equations (4) and (5). The signal change amount S2 by the compression processing performed by is calculated.
[0024]
[Expression 4]

[Equation 5]

The signal change amount S1 and the signal change amount S2 calculated by the first change amount calculation unit 20 and the second change amount calculation unit 40, respectively, are input to the target image data determination unit 45. The target image data determination unit 45 compares the signal change amount S1 and the signal change amount S2, and when the signal change amount S1 is equal to or less than the signal change amount S2, that is, the signal change amount due to the image quality correction performed by the image quality correction unit 15 When the signal change amount S2 is equal to or less than the signal change amount S2 by the compression processing performed by the compression means 30, the compressed image data P1 is the target image data P. When the signal change amount S1 is larger than the signal change amount S2, the compressed image data P2, that is, the compressed image data Image data P2 obtained by decompressing P1, performing image correction processing, and performing recompression is set as target image data P. The target image data P determined by the target image data determination unit 45 is stored in the storage unit 50.
[0025]
FIG. 2 is a flowchart showing the operation of the image processing apparatus A shown in FIG. As shown in the figure, the first decompressing means 10 of the image processing apparatus A first decompresses the input compressed image data P1 to obtain RGB image data D1 (S5). The correction amount calculation means 15 calculates the white balance correction amount and the density correction amount for the image data D1 according to the equations (1) and (2) (S10). The image quality correction unit 25 uses the white balance correction amount and the density correction amount calculated by the correction amount calculation unit 15 to perform white balance correction and density correction on the image data D1 according to Expression (3), thereby correcting the corrected RGB image. Data D2 is obtained (S12). The first change amount calculation means 20 calculates the signal change amount S1 by the image quality correction processing performed by the image data image quality correction means 25 according to the equation (4) (S14), and the compression means 30 is caused by the image quality correction means 25. A compression process is performed on the obtained image data D2 to obtain compressed image data P2 (S16). The second decompression unit 35 of the image processing apparatus A decompresses the compressed image data P2 to obtain RGB image data D3 (S18), and the second change amount calculation unit 40 performs the compression unit 30 according to the equation (5). The signal change amount S2 due to the compression processing performed is calculated (S20). The target image data determination means 45 compares the signal change amounts S1 and S2 (S22), and determines that the compressed image data P2 is the target image data P when the signal change amount S1 is larger than the signal change amount S2 ( S22: Yes, S24) When the signal change amount S1 is equal to or less than the signal change amount S2, the compressed image data P1, that is, the input compressed image data itself is determined as the target image data P (S22: No, S26). The storage unit 50 stores and saves the target image data P determined by the target image data determination unit 45, and the process ends (S30).
[0026]
As described above, according to the image processing apparatus A of the present embodiment, when obtaining compressed image data (target image data) whose image quality has been corrected from the input compressed image data P1, image quality correction is performed on the compressed image data P1. The signal change amount S1 due to the image quality correction and the signal change amount S2 due to the recompression performed to obtain the compressed image data P2 from the image data (D2) whose image quality has been corrected are calculated. The compressed image data P1 is decompressed and subjected to image quality correction processing only when it is larger than the signal change amount S2 due to the above, and the compressed image data P2 obtained by performing the recompression processing is set as the target image data P, and the signal change amount due to the image quality correction When S1 is equal to or less than the signal change amount S2 due to recompression, that is, when image quality deterioration due to recompression is larger than image quality improvement due to image quality correction, image quality compensation is performed. The without, since such an object image data P of the original compressed image data P1, it is possible to image quality get the best target image data.
[0027]
FIG. 3 is a block diagram showing a configuration of an image processing apparatus B according to the second embodiment of the present invention. As shown in the figure, the image processing apparatus B according to the present embodiment decompresses the compressed image data P1 to obtain RGB image data D1 (R1, G1, B1), and white that is performed on the RGB image data D1. A correction amount calculation means 65 for calculating the correction amounts for balance correction and density correction, and a total S for the correction amounts calculated by the correction amount calculation means 65 are calculated, and this total S is preset in a storage unit (not shown). When the value is equal to or less than the threshold value M, the compressed image data P1 is directly output to and stored in the storage means 90 described later as the target image data P. When the correction amount sum S is larger than the threshold value M, the image quality correction means described later The control means 70 that outputs the image data D1 to perform the image quality correction process, and the correction amount calculated by the correction amount calculation means 65 for the output image data D1. The image quality correcting means 75 that obtains corrected image data D2 by performing white balance correction and density correction processing using the amount, and compressing the corrected image data D2 to obtain compressed image data P2, and this compression A compression unit 80 that outputs the image data P2 as the target image data P to the storage unit 90 and a storage unit 90 that stores and saves the target image data P output from the control unit 70 or the compression unit 80 are provided. is there.
[0028]
The correction amount calculation means 65 of the image processing apparatus B shown in FIG. 3 performs white correction using the above-described equations (1) and (2), similarly to the correction amount calculation means 15 of the image processing apparatus A shown in FIG. The amount (ΔR, ΔB) and the density correction amount ΔD are calculated, and the control means 70 obtains the sum S of the correction amounts according to the following equation (6).
[0029]
[Formula 6]

The larger the correction amount sum S is, the larger the signal change amount due to image quality correction performed on the image data D1. In this embodiment, the control means 70 determines the sum S and a preset threshold value. Compared with M, only when the sum S of correction amounts is larger than the threshold value M, the image quality correction means image data D1 is output and image quality correction processing is performed.
[0030]
The threshold value M is set in advance, and is a numerical value that is equal to or greater than the maximum amount of signal change caused by the compression processing performed by the compression unit 80.
[0031]
Similar to the image quality correction unit 25 of the image processing apparatus A shown in FIG. 1, the image quality correction unit 75 uses the white balance correction amount and the density correction amount calculated by the correction amount calculation unit 65 to perform control according to Expression (3). The image data D1 output from the means 70 is subjected to white balance correction and density correction.
[0032]
FIG. 4 is a flowchart showing the operation of the image processing apparatus B shown in FIG. As shown in the figure, the image processing apparatus B of the present embodiment first decompresses the compressed image data P1 to be processed by the decompression means 60 to obtain RGB image data D1 (S50). The correction amount calculation unit 65 calculates the correction amounts for white balance correction and density correction performed on the image data D1, and outputs them to the control unit 70 (S54). The control unit 70 obtains a total S of correction amounts from the white balance correction amount and the density correction amount calculated by the correction amount calculation unit 65 (S54), and this total S is a threshold value M set in a storage unit (not shown). When the following is true, the compressed image data P1 is stored and saved in the storage unit 90 as the target image data P as it is (S56: No, S58, S66). The image data D1 is output and image quality correction is performed (S56: Yes, S60). The image quality correction unit 75 uses the correction amount calculated by the correction amount calculation unit 65 to perform image data D2 obtained by performing white balance correction and density correction on the image data D1 output from the control unit 70. The compression unit 80 performs compression processing to obtain compressed image data P2, and outputs the compressed image data P2 to the storage unit 90 as target image data P (S62, S64, S66).
[0033]
As described above, according to the image processing apparatus B of the present embodiment, as in the case of the image processing apparatus A shown in FIG. 1, when the image quality deterioration due to recompression is larger than the image quality improvement by the image quality correction process, By performing the original compressed image data (P1) as it is as the target image data P without performing image quality correction, it is possible to obtain the target compressed image data with the best image quality, and to set a signal by recompression processing that is set in advance. It is necessary to actually perform image quality correction processing, compression processing, and decompression processing on image data when determining whether or not to perform image quality correction by using the threshold value that is the maximum value of the change amount as a criterion. Therefore, the processing time can be shortened and the efficiency is high.
[0034]
In the above description, the image processing apparatus according to a preferred embodiment of the present invention has been described. However, the image processing apparatus of the present invention is not limited to the above-described embodiment, and various modifications can be made without changing the gist of the present invention. Can be added.
[0035]
For example, the image quality correction units of the two image processing apparatuses described above perform white balance correction and density correction on image data. However, the image processing apparatus of the present invention performs image quality correction processing on image data. Is not limited to these two, and for example, gradation correction or sharpness correction may be performed.
[0036]
In addition, when the signal change amount S1 due to image quality correction is larger than the signal change amount S2 due to recompression, the image processing apparatus A shown in FIG. 1 compresses the original compressed image data P1 by decompression, image quality correction, and recompression. When the image data P2 is the target image data and the signal change amount S1 is equal to or less than the signal change amount S2 due to recompression, the original compressed image data P1 is set as the target image data. For example, when the signal change amount S1 due to image quality correction is larger than T times the signal change amount S2 due to recompression (T: a positive number greater than or equal to), the original compressed image data P1 is decompressed, image quality corrected, and recompressed. The obtained compressed image data P2 is the target image data, and when the signal change amount S1 is T times or less the signal change amount S2 due to recompression, the original compressed image data P1 is set as the target image data. Good.
[0037]
The image processing apparatuses according to the two embodiments described above store and save the target compressed image data obtained from the input compressed image data, and transmit the stored and saved image data to the terminal device. Or, it may be transmitted to a printing apparatus to perform printout.
[0038]
The image processing apparatus described above has an independent form for acquiring image quality corrected image data from compressed image data. For example, the image processing apparatus is provided in a print system, a communication relay apparatus, or the like, and performs image quality correction. It may be configured as a part that plays a role.
[0039]
The type of compressed image data handled by the image processing apparatus of the present invention is any compressed image data such as compressed image data obtained by photographing with a digital camera or image data compressed for network communication. Also good.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an image processing apparatus A according to a first embodiment of the present invention. FIG. 2 is a flowchart showing an operation of the image processing apparatus A shown in FIG. FIG. 4 is a block diagram showing the configuration of an image processing apparatus B according to the embodiment of the present invention. FIG. 4 is a flowchart showing the operation of the image processing apparatus B shown in FIG.
10 first decompression means 15 correction amount calculation means 20 first change amount calculation means 25 image quality correction means 30 compression means 35 second decompression means 40 second change amount calculation means 45 target image determination means 50 storage means 60 decompression Means 65 Correction amount calculation means 70 Control means 75 Image quality correction means 80 Compression means 90 Storage means D1, D2, D3 RGB image data P1, P2 Compressed image data P Target image data S1, S2, S Signal change amount M Threshold values ΔR, ΔB White balance correction amount ΔD Density correction amount

Claims (4)

An image processing apparatus for obtaining compressed image data whose image quality has been corrected from first compressed image data,
Decompression means for decompressing the first compressed image data to obtain first image data;
Image quality correction means for performing image quality correction processing on the first image data to obtain second image data;
Compression means for performing a compression process on the second image data to obtain second compressed image data;
An image quality corrected compressed image data acquisition unit that uses the second compressed image data as the image quality corrected compressed image data;
Determination means for determining whether or not to perform the image quality correction processing on the first image data;
The image quality correction means performs the image quality correction processing only on the first image data determined to be subjected to the image quality correction processing by the determination means;
The image quality corrected compressed image data acquisition unit converts the first compressed image data corresponding to the first image data determined not to perform the image quality correction processing by the determination unit to the image quality corrected compressed image. An image processing apparatus characterized by being data. A first change amount comprising a signal change amount of image data by the image quality correction processing performed by the image quality correction unit on the first image data by the determination unit;
A signal change amount acquisition means for calculating a second change amount comprising a signal change amount of the image data by the compression processing performed on the second image data by the compression means;
Only when the first change amount obtained by the signal change amount acquisition means is larger than the second change amount, it is determined to perform the image quality processing on the first image data. The image processing apparatus according to claim 1. The determination means comprises signal change amount calculation means for calculating a signal change amount of the image data by the image quality correction processing performed on the first image data by the image quality correction means;
Only when the signal change amount calculated by the signal change amount calculation means is larger than a predetermined threshold value, it is determined to perform the image quality correction processing on the first image data. The image processing apparatus according to claim 1. The image processing apparatus according to claim 1, wherein the first compressed image data is obtained by photographing with a digital camera.

Images