JP2009268011A

JP2009268011A - Image processing apparatus

Info

Publication number: JP2009268011A
Application number: JP2008118258A
Authority: JP
Inventors: Satoshi Suzuki; 諭鈴木
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2008-04-30
Filing date: 2008-04-30
Publication date: 2009-11-12

Abstract

<P>PROBLEM TO BE SOLVED: To focus attention on neighborhood pixels, hue angle differences of surrounding pixels, an orientation of hue change as for attention-focused pixel of an input signal, and apply an appropriate correction to allow adjustment of contrast feeling. <P>SOLUTION: A hue space conversion part 2 converts the input data 1 to a hue value, a neighborhood pixel hue angle calculation part 3 calculates a hue angle between the attention-focused pixel and pixels within a neighborhood area, a surrounding pixels hue angle calculation part 4 calculates a hue angle between the attention-focused pixel and pixels within a surrounding area, and a hue correction amount calculation part 5 determines a correction amount for the original hue value using a value of the hue angles difference obtained through 3, 4 and an orientation of hue change. A hue correction part 6 provides a correction with the correction amount determined through 5 to the original hue value to output as output data 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、プラズマディスプレイ又は液晶などのカラー画像表示装置に関するものであり、着目画素と近傍領域内の画素との色相差と、近傍領域よりも大きな距離を持つ周辺領域内の画素との色相差の２つの情報から色相補正量を求め、人間の視覚特性に合わせたコントラスト調整を実現させるための画像処理装置に関するものである。 The present invention relates to a color image display device such as a plasma display or a liquid crystal, and a hue difference between a pixel of interest and a pixel in a neighboring area and a hue difference between a pixel in a peripheral area having a larger distance than the neighboring area. The present invention relates to an image processing apparatus for obtaining a hue correction amount from the two pieces of information and realizing contrast adjustment in accordance with human visual characteristics.

高齢者などの年齢経過や個人差による視覚機能の低下を補償するために、色相の変化に対してトランジェント部分の強調処理を行う。また、カラー画像の隣接するピクセル間のカラーバランスから人間の視覚特性に合致するよう色再現範囲を変換する技術がある（例えば、特許文献１及び特許文献２）。
特開平９−９７３３３号公報特開平８−１３９９５１号公報 In order to compensate for the deterioration of visual function due to the age of individuals such as the elderly and individual differences, the transient part is emphasized with respect to the change in hue. In addition, there is a technique for converting a color reproduction range so as to match a human visual characteristic from a color balance between adjacent pixels of a color image (for example, Patent Document 1 and Patent Document 2).
JP-A-9-97333 JP-A-8-139951

上記従来の手法によれば、色相変化のみに着目した強調処理であるので、例えば様々な色相を含んだテクスチャを多く含む画像などでは全てのピクセルにおいて色相が強調処理されてしまい、処理画像が原画像の色再現性を大きく損なう可能性がある。
本手法では上記問題点を解決するために、着目画素と隣接する近傍領域内の画素との情報に加えて、前記の近傍領域内画素より距離の大きい周辺領域内の画素との情報も考慮することで、シーンによって強調処理を行わない等、適切な強調処理を行うことを可能とすることを目的とする。 According to the above-described conventional method, since the emphasis process focuses only on the hue change, for example, in an image including many textures including various hues, the hue is emphasized in all pixels, and the processed image is the original. There is a possibility that the color reproducibility of the image is greatly impaired.
In this method, in order to solve the above-mentioned problem, in addition to information on the pixel of interest and pixels in the neighboring area, information on pixels in the peripheral area having a larger distance than the pixels in the neighboring area is also considered. Accordingly, an object is to enable appropriate enhancement processing, such as not performing enhancement processing depending on the scene.

第１の発明は、カラー画像において入力データから得られる色相値を補正する画像補正装置であって、入力信号のＲＧＢ信号またはＹＵＶ信号から色相空間へ変換する第１の関数により変換する色相空間変換部と、前記色相空間変換部により変換された色相値において、着目画素と近傍画素との色相角差と色相変化の向きを表す第２の関数を算出する近傍画素色相角計算部と、前記色相空間変換部により変換された色相値において、着目画素と前記近傍画素とは異なる周辺画素との色相角差と色相変化の向きを表す第３の関数を算出する周辺画素色相角計算部と、前記第２、第３の関数から着目画素に対する色相補正量を算出する第４の関数を計算する色相補正量計算部と、前記色相補正量計算部により計算された第４の関数で求められた補正量を元の色相値と合成する第５の関数を有する色相補正部とを備えることを特徴とする。
第２の発明は、前記近傍画素色相角計算部及び周辺画素色相角計算部では、前記第２、第３の関数において、着目画素と対象領域内における任意の数の画素の色相角をそれぞれ比較し、色相差と色相変化の方向を考慮した色相変化量を算出し、着目画素と対象領域内の画素に対する色変化を求めることを特徴とする。
第３の発明は、前記第４の関数において、ｍ＜ｎが成り立つ、着目画素から距離ｍを持つ近傍画素との色相変化量をＨｍとし、着目画素から距離ｎを持つ周辺画素との色相変化量をＨｎとすると、ＨｍとＨｎの値から着目画素に対する色相補正量を算出することを特徴とする。
第４の発明は、前記色相補正量算出において、Ｈｍ、Ｈｎの値がある程度小さい場合に、着目画素と周辺画素との色相値に基づいて色相補正量を算出することを特徴とする。
第５の発明は、前記色相補正量算出において、Ｈｍ、Ｈｎの値が大きい、または着目画素と周辺画素との色相が近い程、色相補正量を小さくすることを特徴とする。
第６の発明は、前記色相補正量計算について、補正する割合が強い程、着目画素と周辺領域との色相角の相対距離を大きくする補正量を算出することを特徴とする。 A first invention is an image correction apparatus for correcting a hue value obtained from input data in a color image, and is a hue space conversion that is converted by a first function that converts an RGB signal or YUV signal of an input signal into a hue space. And a neighboring pixel hue angle calculating unit that calculates a second function representing a hue angle difference between the pixel of interest and a neighboring pixel and a direction of a hue change in the hue value converted by the hue space converting unit, and the hue A peripheral pixel hue angle calculation unit that calculates a third function representing a hue angle difference and a direction of hue change between a pixel of interest and a neighboring pixel different from the neighboring pixel in the hue value converted by the space conversion unit; A hue correction amount calculation unit that calculates a fourth function for calculating a hue correction amount for the pixel of interest from the second and third functions, and a complement obtained by the fourth function calculated by the hue correction amount calculation unit. Characterized in that it comprises a hue correction portion having a fifth function for synthesizing the quantity and the original hue value.
In the second invention, the neighboring pixel hue angle calculation unit and the neighboring pixel hue angle calculation unit compare hue angles of an arbitrary number of pixels in the target region and the target region in the second and third functions, respectively. Then, the hue change amount is calculated in consideration of the hue difference and the direction of the hue change, and the color change with respect to the pixel of interest and the pixel in the target region is obtained.
In a fourth aspect of the present invention, in the fourth function, the hue change amount with a neighboring pixel having a distance m from the target pixel, where m <n, is Hm, and the hue change with a peripheral pixel having the distance n from the target pixel When the amount is Hn, the hue correction amount for the target pixel is calculated from the values of Hm and Hn.
According to a fourth aspect of the present invention, in the hue correction amount calculation, when the values of Hm and Hn are small to some extent, the hue correction amount is calculated based on the hue values of the pixel of interest and the surrounding pixels.
In a fifth aspect of the invention, the hue correction amount is decreased as the values of Hm and Hn are larger or the hues of the pixel of interest and the surrounding pixels are closer in the calculation of the hue correction amount.
The sixth invention is characterized in that the hue correction amount calculation calculates a correction amount that increases the relative distance of the hue angle between the pixel of interest and the peripheral region as the correction ratio increases.

以上のように、本発明によれば、画像内に一定のテクスチャが存在し、着目画素に隣接する近傍領域内、または周辺領域内での画素の色相変化が激しい場合には色相補正を施さず、近傍または周辺領域においてそれぞれ色相変化が少なく、近傍領域と周辺領域の色相差がある程度の距離を持つ場合にのみに着目画素に対して色相補性を施すことができる。 As described above, according to the present invention, when a certain texture exists in an image and the hue change of a pixel in a neighboring region adjacent to the target pixel or a peripheral region is severe, hue correction is not performed. Color complementarity can be applied to the pixel of interest only when there is little change in hue in the vicinity or the peripheral area and the hue difference between the vicinity area and the peripheral area has a certain distance.

本発明の具体的な例について図を用いて説明する。図１は入力カラー画像に対してシーンに適応した色相調整を行う画像補正装置のブロック図である。この画像補正装置は、図１に示すように、カラー映像信号であるＲＧＢ信号またはＹＵＶ信号の入力１から色相値に変換する色相空間変換部２、色相空間変換部により変換された色相値から着目画素に対する近傍画素との色相変化量を算出する近傍画素色相角計算部３と、着目画素に対する周辺画素との色相変化量を算出する周辺画素色相角計算部４を有する。
さらに、近傍画素色相角計算部３、周辺画素色相角計算部４で算出された色相角と領域内の色相変化量情報から着目画素に対しての色相補正量を算出する色相補正量計算部５、色相補正量計算部５で算出された補正量と色相空間変換部２を通った補正前データと合成する色相補正部６で構成されている。
近傍画素色相角計算部３は、着目画素の色相値から着目画素の近傍に配置された近傍画素の色相角を差分し、近傍領域内の画素との色相変化量を算出する。図２は着目画素と着目画素の近傍に配置された近傍領域内画素の関係を示す図である。
例として、着目画素に対して右下の画素に注目した場合、着目画素をＸ（ｉ，ｊ）、着目画素からの距離ｍを持つ近傍画素をＸ（ｉ＋ｍ，ｊ＋ｍ）とすると、２つの画素の色相角の差分をＨｍ１とした場合、次式で表される。これを対象とするｋ箇所の近傍画素に対してそれぞれＨｍ１からＨｍｋまで求める。 Specific examples of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an image correction apparatus that performs hue adjustment adapted to a scene on an input color image. As shown in FIG. 1, this image correction apparatus focuses on a hue space conversion unit 2 that converts an input 1 of an RGB signal or a YUV signal, which is a color video signal, into a hue value, and a hue value converted by the hue space conversion unit. It has a neighboring pixel hue angle calculation unit 3 that calculates a hue change amount with a neighboring pixel with respect to a pixel, and a peripheral pixel hue angle calculation unit 4 that calculates a hue change amount with a peripheral pixel with respect to the pixel of interest.
Further, a hue correction amount calculation unit 5 that calculates a hue correction amount for the pixel of interest from the hue angle calculated by the neighboring pixel hue angle calculation unit 3 and the peripheral pixel hue angle calculation unit 4 and the hue change amount information in the region. The hue correction unit 6 combines the correction amount calculated by the hue correction amount calculation unit 5 and the pre-correction data that has passed through the hue space conversion unit 2.
The neighboring pixel hue angle calculation unit 3 calculates a hue change amount with a pixel in the neighboring region by subtracting the hue angle of the neighboring pixel arranged in the vicinity of the pixel of interest from the hue value of the pixel of interest. FIG. 2 is a diagram showing the relationship between the pixel of interest and the pixels in the vicinity area arranged in the vicinity of the pixel of interest.
As an example, when attention is paid to the lower right pixel with respect to the target pixel, if the target pixel is X (i, j) and a neighboring pixel having a distance m from the target pixel is X (i + m, j + m), two pixels When the difference in hue angle is Hm1, it is expressed by the following equation. Hm1 to Hmk are obtained for k neighboring pixels for this.

次に、前記で算出されたＨｍ１からＨｍｋの色相差分値に対して次式を適応し、各近傍画素同士の色相変化量Ｈｍを算出する。このＨｍが小さいほど近傍領域内での色相変化が少ないとする。 Next, the following equation is applied to the hue difference values from Hm1 to Hmk calculated above to calculate the hue change amount Hm between the neighboring pixels. It is assumed that the smaller the Hm, the smaller the hue change in the vicinity region.

同様に、図３に示すように、ｍ＜ｎである距離ｎを持つ周辺画素に対しても次式にて色相角の差分と、周辺領域内画素の色相変化量Ｈｎを求める。 Similarly, as shown in FIG. 3, the difference in hue angle and the hue change amount Hn of the pixels in the peripheral area are also obtained for the peripheral pixels having the distance n where m <n.

Ｈｍ、Ｈｎの値が小さいほど、該当領域では色相変化が小さいと判断できるため、図４に示すように、近傍画素の色相値の平均値を色相角−１８０°〜１８０°で正規化した値をＨａｍ、周辺画素の色相値の平均を同様に正規化した値をＨａｎとし、ＨａｍとＨａｎの色相角差をＨａｎｇとすると、着目画素に対する色相補正量を次式で定義することで色相補正量ΔＨを算出する。 Since it can be determined that the hue change is small in the corresponding region as the values of Hm and Hn are small, as shown in FIG. 4, the average value of the hue values of neighboring pixels is normalized by a hue angle of −180 ° to 180 °. Is defined as the following equation, and the hue correction amount for the pixel of interest is defined by the following equation, where Han is the normalized value of the hue value of the surrounding pixels in the same manner, and Han is the hue angle difference between Ham and Han. ΔH is calculated.

図１の色相補正部６にて補正前の色相値ＸにΔＨを加算したものを補正後の色相値Ｘ’として出力データとする。例として、着目画素Ｘの色相角を１２０、Ｈａｍ＝１２０、Ｈａｎ＝２０、Ｈｍ＝０．１、Ｈｎ＝０．３、Ｈａｎｇ＝１００とした場合、下記の補正量が算出される。
ΔＨ＝（１ − ０．１）＊（１ − ０．３）＊（１８０ - １００）＊（１００／１８０） ≒２８
得られた補正量ΔＨ＝２８を、着目画素Ｘの色相値１２０に対して加算し着目画素の色相値を１４８とする。この補正により、周辺画素に対して、着目画素の色相角の相対距離を広げる。
このような処理により、本発明においては、領域内の色相変化が大きい場合はテクスチャが多いと判断し着目画素に対して色相補正を弱め、色相変化が少なく近傍領域と周辺領域との色相差が大きい場合は、周辺画素に対して色相角の相対距離が広がるように色相補正を行うことが可能である。 A value obtained by adding ΔH to the hue value X before correction in the hue correction unit 6 in FIG. As an example, when the hue angle of the pixel of interest X is 120, Ham = 120, Han = 20, Hm = 0.1, Hn = 0.3, Hang = 100, the following correction amount is calculated.
ΔH = (1−0.1) * (1−0.3) * (180−100) * (100/180) ≈28
The obtained correction amount ΔH = 28 is added to the hue value 120 of the target pixel X to set the hue value of the target pixel to 148. By this correction, the relative distance of the hue angle of the pixel of interest is expanded with respect to the surrounding pixels.
By such processing, in the present invention, if the hue change in the area is large, it is determined that there are many textures, and the hue correction is weakened for the pixel of interest, and there is little hue change and the hue difference between the neighboring area and the surrounding area is small. If it is larger, the hue correction can be performed so that the relative distance of the hue angle with respect to the surrounding pixels is widened.

本発明による画像処理装置では、多くのテクスチャから構成されるような高周波成分の多い画像に対しては画像補正を施さず、ある程度の領域を持ちその領域内にて低周波成分で構成される画像に対してのみ画質補正を施すため、画質補正が有効なシーンに対してのみ補正を施すことができる。また色相に対する補正のため、人間の視覚特性に合わせた補正量の調整が容易となるため、デジタルテレビなどの画質設定メニューなどと連動させた画質補正に有効である。 The image processing apparatus according to the present invention does not perform image correction on an image with a lot of high-frequency components, such as a lot of textures, and has a certain area and is composed of low-frequency components within that area. Since the image quality correction is performed only on the image, the correction can be performed only on the scene for which the image quality correction is effective. Further, since the correction for the hue makes it easy to adjust the correction amount according to the human visual characteristics, it is effective for the image quality correction linked with the image quality setting menu of a digital television or the like.

本発明の一実施例のカラー画像処理装置のブロック図1 is a block diagram of a color image processing apparatus according to an embodiment of the present invention. 着目画素と近傍領域内画素との色相角差を算出するための領域を示す図The figure which shows the area | region for calculating the hue angle difference of a focused pixel and the pixel in a near region 近傍領域内画素と周辺領域内領域を示す図Diagram showing the pixels in the near area and the area in the surrounding area 着目画素と周辺画素との色相関係と色相補正を示す図The figure which shows the hue relationship and hue correction of a focused pixel and a surrounding pixel

符号の説明Explanation of symbols

１入力データ
２色相空間変換部
３周辺画素色相角計算部
４周辺領域色相角計算部
５色相補正量計算部
６色相補正部
７出力データ DESCRIPTION OF SYMBOLS 1 Input data 2 Hue space conversion part 3 Peripheral pixel hue angle calculation part 4 Peripheral area hue angle calculation part 5 Hue correction amount calculation part 6 Hue correction part 7 Output data

Claims

カラー画像において入力データから得られる色相値を補正する画像補正装置であって、
入力信号のＲＧＢ信号またはＹＵＶ信号から色相空間へ変換する色相空間変換部と、
前記色相空間変換部により変換された色相値において、着目画素と近傍画素との色相角差と色相変化の向きを算出する近傍画素色相角計算部と、
前記色相空間変換部により変換された色相値において、着目画素と前記近傍画素とは異なる周辺画素との色相角差と色相変化の向きを算出する周辺画素色相角計算部と、
前記近傍画素色相角計算部と周辺画素色相角計算部の算出結果から着目画素に対する色相補正量を計算する色相補正量計算部と、
前記色相補正量計算部により計算された結果から補正量を元の色相値と合成する色相補正部とを備えることを特徴とする画像補正装置。 An image correction apparatus for correcting a hue value obtained from input data in a color image,
A hue space conversion unit for converting an RGB signal or YUV signal of the input signal into a hue space;
In the hue value converted by the hue space conversion unit, a neighboring pixel hue angle calculation unit that calculates a hue angle difference between the target pixel and a neighboring pixel and a direction of hue change;
In the hue value converted by the hue space conversion unit, a peripheral pixel hue angle calculation unit that calculates the hue angle difference and the direction of the hue change between the pixel of interest and the neighboring pixels different from the neighboring pixels;
A hue correction amount calculation unit that calculates a hue correction amount for the pixel of interest from the calculation results of the neighboring pixel hue angle calculation unit and the peripheral pixel hue angle calculation unit;
An image correction apparatus comprising: a hue correction unit that combines a correction amount with an original hue value based on a result calculated by the hue correction amount calculation unit.

前記近傍画素色相角計算部及び周辺画素色相角計算部では、着目画素と前記近傍画素及び前記周辺画素の対象領域内における任意の数の画素の色相角をそれぞれ比較し、色相差と色相変化の方向を考慮した色相変化量を算出し、着目画素と対象領域内の画素に対する色変化を求めることを特徴とする請求項１に記載の画像補正装置。 The neighboring pixel hue angle calculation unit and the neighboring pixel hue angle calculation unit compare the hue angles of an arbitrary number of pixels in the target region of the target pixel and the neighboring pixels and the neighboring pixels, respectively, and compare the hue difference and the hue change. The image correction apparatus according to claim 1, wherein a hue change amount in consideration of a direction is calculated to obtain a color change with respect to a pixel of interest and a pixel in a target region.

前記色相補正量計算部では、着目画素から距離ｍを持つ近傍画素との色相変化量をＨｍとし、着目画素から距離ｎ（ｍ＜ｎ）を持つ周辺画素との色相変化量をＨｎとすると、ＨｍとＨｎの値から着目画素に対する色相補正量を算出することを特徴とする請求項１に記載の画像補正装置。 In the hue correction amount calculation unit, assuming that a hue change amount with a neighboring pixel having a distance m from the target pixel is Hm and a hue change amount with a peripheral pixel having a distance n (m <n) from the target pixel is Hn, The image correction apparatus according to claim 1, wherein the hue correction amount for the target pixel is calculated from the values of Hm and Hn.

前記色相補正量計算部では、前記色相補正量算出において、Ｈｍ、Ｈｎの値が所定の閾値よりも小さい場合に、着目画素と周辺画素との色相値に基づいて色相補正量を算出する請求項３に記載の画像補正装置。 The hue correction amount calculation unit calculates a hue correction amount based on hue values of a pixel of interest and peripheral pixels when the values of Hm and Hn are smaller than a predetermined threshold in the hue correction amount calculation. 4. The image correction apparatus according to 3.

前記色相補正量計算部では、前記色相補正量算出において、Ｈｍ、Ｈｎの値が所定の閾値よりも大きい場合、または着目画素と周辺画素との色相が近い程、色相補正量を小さくする請求項３に記載の画像補正装置。 The hue correction amount calculation unit decreases the hue correction amount in the hue correction amount calculation when the values of Hm and Hn are larger than a predetermined threshold or when the target pixel and the surrounding pixels are closer to each other. 4. The image correction apparatus according to 3.

前記色相補正量計算部では、前記色相補正量計算において、補正する割合が強い程、着目画素と周辺領域との色相角の相対距離を大きくする補正量を算出する画像補正装置。 In the hue correction amount calculation unit, an image correction apparatus that calculates a correction amount that increases a relative distance of a hue angle between a pixel of interest and a peripheral region as the correction ratio increases in the hue correction amount calculation.