JP3791593B2 - Image processing apparatus, image processing method, program, and recording medium - Google Patents

Description

のように表される。
(2) 明度変換パラメータが負、すなわちＲL＜０の場合
図９に、ＲＧＢ空間を、点Ｒを通りグレイ軸を含む平面で切った場合の断面を示す。明度変換パラメータが負のときは、図９に示すように、点Ｐは線分ＰＫ上の点Ｐ’に変換される。
【００３８】
次に、重み付け部１２０ｃは、所望の重み付け処理を行う（Ｓ３４）。
【００３９】
まず、重み付け部１２０ｃは、図７に示すように、線分ＫＲ上に存在しない点に関しては、点Ｐがグレイ軸（線分ＷＫ）に近づくにつれて明度変換量が減少するように重み付けを行う。このときの重み付け係数は、Ｒ−Ｙ領域において、
(Ｒ−Ｂ)／Ｒとなる。
【００４０】
さらに、重み付け部１２０ｃは、明度変換パラメータが正の場合と同様に、図８に示すような色相に関する重み付け処理を行う。すなわち、Ｒの明度変換は、Ｒの頂点を含む色相（基準色相）において１で、当該基準色相から離れるに従って減少し、Ｙの頂点を含む色相（隣接する基準色相）で０になるようにする。このような重み付け係数は、(Ｒ−Ｇ)／(Ｒ−Ｂ)である。
【００４１】
したがって、ＲLが負の場合は、明度変換量ＰＰ’＝(ΔＲ,ΔＧ,ΔＢ)は、
【００４２】
【数２】

のように表される。
【００４３】
また、図１０に示すように、Ｙの明度変換における色相に関する重み付けは、Ｙの頂点を含む色相（基準色相）において１で、当該基準色相から離れるに従って減少し、Ｒの頂点を含む色相（隣接する基準色相）で０になるようにする。このような重み付け係数は、(Ｇ−Ｂ)／(Ｒ−Ｂ)である。すなわち、Ｙの明度変換における色相に関する重み付けは、Ｒの明度変換における色相に関する重み付け係数(Ｒ−Ｇ)／(Ｒ−Ｂ)を(Ｇ−Ｂ)／(Ｒ−Ｂ)に変更することによって行われる。
【００４４】
したがって、Ｙの明度変換における色相に関する重み付けは、ＹL≧０のとき
【００４５】
【数３】

であり、ＹL＜０のとき
【００４６】
【数４】

となる。
【００４７】
最終的なＲ−Ｙ領域における変換量は、ＲLに関する変換量とＹLに関する変換量とを重ね合せたものとなる。この際、ＲL，ＹLの正負によって式の形が異なる部分（(1)変換する方向（Ｗ方向またはＫ方向）、(2)グレイ軸に近づくにつれて明度変換量が減少するという重み付け）に関しては、ＲLおよびＹLに関して色相についての重み付けした結果が正または負かに基づいて決定する。
【００４８】
最終的な変換量は、
Ｌ＝(Ｒ−Ｇ)×２ＲL／255＋(Ｇ−Ｂ)×２ＹL／255 … (6)
Ｌ＞０のとき
【００４９】
【数５】

Ｌ＜０のとき
【００５０】
【数６】

となる。
【００５１】
以上のようにして、当該実施形態による画像処理装置によれば、基準色相間の領域における明度変換量を基準色相毎に独立に、且つ隣の領域との連続性が失われないように設定できるので、全色空間において良好な色変換を実現することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態にかかるプロジェクタ内の画像処理部１００の機能ブロック図である。
【図２】明度変換部１２０による処理を説明するための６つの色相領域を示す図である。
【図３】重み付け部１２０ｃによる重み付け処理を説明するための図である。
【図４】本発明の一実施形態にかかる色相判定部１１５および明度変換部１２０の動作を説明するためのフローチャートである。
【図５】各色相領域における明度変換部１２０の動作を説明するためのフローチャートである。
【図６】変換量算出部１２０ｂによる明度変換量の算出処理を説明するための図(１)である。
【図７】変換量算出部１２０ｂによる明度変換量の算出処理を説明するための図(２)である。
【図８】重み付け部１２０ｃによるＲに対する重み付け処理を説明するための図である。
【図９】変換量算出部１２０ｂによる明度変換量の算出処理を説明するための図(３)である。
【図１０】重み付け部１２０ｃによるＹに対する重み付け処理を説明するための図である。
【符号の説明】
１００ 画像処理部
１１０ Ａ／Ｄ変換部
１１５ 色相判定部
１２０ 明度変換部
１２０ａ パラメータ入力部
１２０ｂ 変換量算出部
１２０ｃ 重み付け部
１３０ Ｄ／Ａ変換部
１４０ Ｌ／Ｖ駆動部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to image processing for printers, projectors, and the like, in particular, color conversion processing of image data expressed in three colors of R (red), G (green), and B (blue) according to the use device, user preference, and the like The present invention relates to an image processing apparatus, an image processing method, a program, and a recording medium.
[0002]
[Prior art]
Color conversion in the printing process is an essential technique for correcting image quality deterioration and maintaining good color reproducibility. Also, in a display device such as a monitor / projector, color conversion processing is performed in order to perform desired color reproduction according to usage conditions.
[0003]
[Problems to be solved by the invention]
However, in the case of matrix conversion color conversion, suitable color conversion cannot be realized due to the non-linearity of the print. In addition, since the amount of lightness conversion between the six hues (reference hues) of red, blue, green, yellow (Y), cyan (C), and magenta (M) cannot be independently corrected, good color conversion is possible in the entire color space. Cannot be realized.
[0004]
The present invention has been made to solve the above-described problems, and provides an image processing apparatus, an image processing method, a program, and a recording medium that can independently correct a lightness conversion amount in an area between reference hues for each reference hue. The issue is to provide.
[0005]
[Means for Solving the Problems]
In view of the above problems, the invention according to claim 1 is an image processing apparatus that performs desired image processing on RGB image input data in an RGB color space, and the pre-conversion color point indicated by the RGB image input data A hue determination means for determining the hue of the image, a parameter input means for inputting a lightness conversion parameter for defining the lightness conversion amount, white or black depending on the determination result of the hue determination means and the input lightness conversion parameter Brightness conversion means for linearly converting the pre-conversion color point toward the image, and configured to perform brightness conversion of the RGB image input data.
[0006]
According to the image processing apparatus configured to perform desired image processing on the RGB image input data in the RGB color space configured as described above, the hue of the pre-conversion color point indicated by the RGB image input data by the hue determination unit And a lightness conversion parameter that defines the lightness conversion amount is input by the parameter input means. Then, according to the determination result of the hue determination means and the input brightness conversion parameter, the brightness conversion means linearly converts the color point before conversion toward white or black, and the brightness of the RGB image input data Conversion is performed.
[0007]
The invention according to claim 2 is the image processing apparatus according to claim 1, wherein the hue determination unit includes a plurality of pre-conversion color points indicated by the RGB image input data in the RGB color space. It is configured to determine which of the divided hue regions belongs and the lightness conversion means performs lightness conversion according to the determination result.
[0008]
Furthermore, the invention described in claim 3 is the image processing apparatus according to claim 2, wherein the hue determination unit is configured such that the pre-conversion color point indicated by the RGB image input data is an RY hue region, Y -G hue region, GC hue region, CB hue region, BM hue region, or MR hue region is configured to be determined.
[0009]
The invention described in claim 4 is the image processing apparatus according to any one of claims 1 to 3, wherein the lightness conversion means turns to white when the input lightness conversion parameter is positive. Then, the color point before the conversion is linearly converted to lightness, and when negative, the color point before conversion is linearly converted toward black.
[0010]
Furthermore, the invention according to claim 5 is the image processing apparatus according to any one of claims 1 to 4, wherein the brightness conversion parameter can be set independently for each hue of RGBCMY. Configured.
[0011]
The invention according to claim 6 is the image processing apparatus according to any one of claims 1 to 5, wherein, based on the determination result by the hue determination unit and the input brightness conversion parameter, It comprises lightness conversion amount calculating means for calculating the lightness conversion amount of the RGB image input data.
[0012]
Furthermore, the invention according to claim 7 is the image processing apparatus according to any one of claims 1 to 6, wherein the lightness conversion means is based on a hue of a color point before conversion indicated by the RGB image input data. Weighting means for applying a desired weighting process to the lightness conversion amount according to the above, and is configured to perform lightness conversion of RGB image input data based on the weighted lightness conversion amount.
[0013]
The invention according to claim 8 is the image processing apparatus according to claim 7, wherein the weighting unit performs weighting so that the lightness conversion amount decreases as the pre-conversion color point approaches the gray axis. Configured to do.
[0014]
Further, the invention according to claim 9 is the image processing apparatus according to claim 7 or 8, wherein the weighting unit has a maximum lightness conversion amount with respect to a predetermined reference hue in the reference hue, and the reference hue. It is configured so as to decrease as it moves away from the image, and to be minimized at the adjacent reference hue.
[0015]
According to a tenth aspect of the present invention, there is provided an image processing method for performing desired image processing on RGB image input data in an RGB color space, wherein the hue of a pre-conversion color point indicated by the RGB image input data is determined. A hue determination step for determining, a parameter input step for inputting a lightness conversion parameter for defining a lightness conversion amount, and toward white or black depending on the determination result of the hue determination step and the input lightness conversion parameter A brightness conversion step of linearly converting the color point before conversion, and configured to perform brightness conversion of the RGB image input data.
[0016]
The invention according to claim 11 is a program for causing a computer to execute desired image processing performed on RGB image input data in the RGB color space, the conversion indicated by the RGB image input data. According to the hue determination process for determining the hue of the previous color point, the parameter input process for inputting a lightness conversion parameter for defining the lightness conversion amount, the determination result of the hue determination process and the input lightness conversion parameter, Brightness conversion processing for linearly converting the pre-conversion color point toward white or black, and configured to cause a computer to execute image processing for performing brightness conversion of the RGB image input data.
[0017]
A twelfth aspect of the present invention is a computer-readable recording medium on which the program according to the eleventh aspect is recorded.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In this embodiment, image processing in the projector will be described.
[0019]
FIG. 1 is a functional block diagram of an image processing unit 100 in a projector according to an embodiment of the present invention.
[0020]
An image processing unit 100 in a projector according to an embodiment of the present invention includes an A / D conversion unit 110 that converts an analog image input signal into a digital signal, and a hue determination unit that determines a hue based on RGB image input data. 115, a lightness conversion unit 120 for performing a desired lightness conversion on the RGB image input signal, a D / A conversion unit 130 for converting a digital signal into an analog signal, and driving a liquid crystal light valve to project an image And an L / V (light valve) driving unit 140 for performing display.
[0021]
Further, the lightness conversion unit 120 is configured to input the lightness conversion parameter for each hue, the RGB image based on the hue determined by the hue determination unit 115 and the input lightness conversion parameter. A conversion amount calculation unit 120b that calculates a lightness conversion amount of input data, and a weighting unit 120c that performs weighting processing on the lightness conversion amount based on the hue determined by the hue determination unit. .
[0022]
FIG. 2 shows six hue regions for explaining the processing by the lightness conversion unit 120. All conversions by the lightness conversion unit 120 are performed in the RGB space.
[0023]
The hue is divided into six areas as shown in FIG. 2, and brightness conversion is performed for each area. That is, the hue determination unit 115 determines the hue based on the RGB image input data, and performs brightness conversion for each region based on the determination result.
[0024]
Then, the parameter input unit 120a inputs a lightness conversion parameter that defines the lightness conversion amount for each hue of R, G, B, C, M, and Y. The range of the input brightness conversion parameter is -128 or more and 127 or less. In each area of FIG. 2, the lightness conversion parameters for two colors of RGBCMY are related to the calculation of the lightness conversion amount. For example, in the region 1 of FIG. 2, the R and Y lightness conversion parameters are related to the calculation of the lightness conversion amount. In other words, each RGBCMY brightness conversion amount affects two adjacent hue regions. For example, if R, region 1 and region 6 are affected.
[0025]
Then, as shown in FIG. 3, for example, in the case of R, the weighting unit 120c maximizes each RGBCMY conversion amount for each primary color (the vertex of the RGB space) and decreases as it approaches the adjacent hue or gray axis. Perform weighting. By performing such weighting, the continuity of the RGB space is maintained even after the brightness conversion. The weighting process will be described in detail below.
[0026]
Operations of Hue Determination Unit 115 and Lightness Conversion Unit 120 Next, operations of the hue determination unit 115 and the lightness conversion unit 120 in the image processing unit 100 of the projector according to the embodiment of the present invention will be described with reference to FIG. To do.
[0027]
Note that the brightness conversion processing by the hue determination unit 115 and the brightness conversion unit 120 described below is performed by executing an image processing program recorded in a program storage unit (not shown) of the projector. The program storage unit constitutes a medium on which an image processing program is recorded. Further, the image processing program itself is also included within the scope of the present invention.
[0028]
First, when the use of the projector is started, the hue determination unit 115 obtains a magnitude relationship between the R, G, and B values of the RGB image input data (S10), and the RGB image input data is displayed in the hue regions 1 to 1 shown in FIG. 6 or a gray region is determined. That is, the hue determination unit 115
(1) When R ≧ G> B, it is determined that the region is the RY region (hue region 1 in FIG. 2), and brightness conversion processing is performed in the RY region (S12).
(2) When G> R ≧ B, it is determined that the region is the YG region (hue region 2 in FIG. 2), and brightness conversion processing is performed in the YG region (S14).
(3) When G ≧ B> R, it is determined that the region is the GC region (hue region 3 in FIG. 2), and brightness conversion processing is performed in the GC region (S16).
(4) When B> G ≧ R, it is determined that the area is the CB area (hue area 4 in FIG. 2), and brightness conversion processing is performed in the CB area (S18).
(5) When B ≧ R> G, it is determined that the region is the BM region (hue region 5 in FIG. 2), and brightness conversion processing is performed in the BM region (S20).
(6) When R> B ≧ G, it is determined that the region is the MR region (hue region 6 in FIG. 2), and brightness conversion processing is performed in the MR region (S22).
(7) When R = G = B, it is determined that the region is a gray region (non-conversion region), and brightness conversion processing is not performed (S24).
[0029]
Next, processing by the lightness conversion unit 120 in each hue region will be described with reference to FIG. In the present embodiment, the brightness conversion process in the case of R ≧ G> B, that is, the RY area (hue area 1 in FIG. 2) will be described. The lightness conversion process is the same as the hue region 1 for the other hue regions 2 to 6 shown in FIG.
[0030]
As shown in FIG. 5, first, a parameter that defines a lightness conversion amount (referred to as “lightness conversion parameter” in the specification) is input from the parameter input unit 120a to the conversion amount calculation unit 120b (S30). . The brightness conversion parameter is
RL: R lightness conversion parameter (−128 ≦ RL ≦ 127)
GL: G lightness conversion parameter (−128 ≦ GL ≦ 127)
BL: B lightness conversion parameter (−128 ≦ BL ≦ 127)
CL: C lightness conversion parameter (−128 ≦ CL ≦ 127)
ML: M lightness conversion parameter (−128 ≦ ML ≦ 127)
YL: Y brightness conversion parameter (−128 ≦ YL ≦ 127)
Is defined.
[0031]
Next, a lightness conversion amount calculation process is performed by the conversion amount calculation unit 120b (S32). When the lightness conversion parameter is positive, that is, RL> 0, the point P (R, G, B) is converted to the point P ′ (R ′, G ′, B ′) toward white (W) in the RGB space. The On the other hand, if the lightness conversion parameter is negative, that is, RL <0, the point P (R, G, B) is pointed to the point P ′ (R ′, G ′, B ′) toward black (K) in the RGB space. Converted.
[0032]
The following brightness conversion process will be described separately for the case where RL is positive and the case where RL is negative.
(1) When the lightness conversion parameter is positive, that is, when RL> 0, FIG. 6 shows a cross section when the RGB space is cut by a plane passing through the point R and including the gray axis. When the lightness conversion parameter is positive, the point P is converted to a point P ′ on the line segment WP as shown in FIG. When the point P is a point on the line segment WR, the relational expression:
PP ′ = 2RL × PW / 255 (1)
Is established.
[0033]
Next, the weighting unit 120c performs a desired weighting process (S34).
[0034]
First, as shown in FIG. 7, the weighting unit 120c weights points that do not exist on the line segment WR so that the lightness conversion amount decreases as the point P approaches the gray axis (line segment WK). The weighting coefficient at this time is (RB) / (255-B) in the RY region.
[0035]
Further, as shown in FIG. 8, the weighting unit 120c performs weighting processing on the hue. That is, the lightness conversion of R is 1 in the hue including the R vertex (reference hue), decreases as the distance from the reference hue increases, and becomes 0 in the hue including the Y vertex (adjacent reference hue). . Such a weighting factor is (R−G) / (R−B).
[0036]
Therefore, when RL is positive, the lightness conversion amount PP ′ = (ΔR, ΔG, ΔB) is
[0037]
[Expression 1]

It is expressed as
(2) When the lightness conversion parameter is negative, that is, when RL <0, FIG. 9 shows a cross section when the RGB space is cut by a plane passing through the point R and including the gray axis. When the lightness conversion parameter is negative, the point P is converted to a point P ′ on the line segment PK, as shown in FIG.
[0038]
Next, the weighting unit 120c performs a desired weighting process (S34).
[0039]
First, as illustrated in FIG. 7, the weighting unit 120 c performs weighting on points that do not exist on the line segment KR so that the lightness conversion amount decreases as the point P approaches the gray axis (line segment WK). The weighting coefficient at this time is in the RY region.
(RB) / R.
[0040]
Further, the weighting unit 120c performs a weighting process related to the hue as illustrated in FIG. 8 as in the case where the lightness conversion parameter is positive. That is, the lightness conversion of R is 1 in the hue including the R vertex (reference hue), decreases as the distance from the reference hue increases, and becomes 0 in the hue including the Y vertex (adjacent reference hue). . Such a weighting factor is (R−G) / (R−B).
[0041]
Therefore, when RL is negative, the lightness conversion amount PP ′ = (ΔR, ΔG, ΔB) is
[0042]
[Expression 2]

It is expressed as
[0043]
Also, as shown in FIG. 10, the weight related to the hue in the lightness conversion of Y is 1 in the hue including the Y vertex (reference hue), and decreases with increasing distance from the reference hue, and the hue including the R vertex (adjacent). The reference hue is set to 0. Such a weighting coefficient is (GB) / (RB). That is, the weighting relating to the hue in the brightness conversion of Y is performed by changing the weighting coefficient (RG) / (RB) relating to the hue in the brightness conversion of R to (GB) / (RB). Is called.
[0044]
Therefore, the weighting related to the hue in the brightness conversion of Y is when YL ≧ 0.
[Equation 3]

And when YL <0
[Expression 4]

It becomes.
[0047]
The final conversion amount in the RY region is obtained by superimposing the conversion amount related to RL and the conversion amount related to YL. At this time, with respect to the parts where the form of the expression differs depending on whether RL and YL are positive or negative ((1) the conversion direction (W direction or K direction), (2) the weighting that the lightness conversion amount decreases as it approaches the gray axis) A decision is made based on whether the weighted result for hue for RL and YL is positive or negative.
[0048]
The final conversion amount is
L = (R−G) × 2RL / 255 + (GB) × 2YL / 255 (6)
When L> 0 [0049]
[Equation 5]

When L <0 [0050]
[Formula 6]

It becomes.
[0051]
As described above, according to the image processing apparatus of the present embodiment, the lightness conversion amount in the region between the reference hues can be set independently for each reference hue and so as not to lose continuity with the adjacent region. Therefore, good color conversion can be realized in the entire color space.
[Brief description of the drawings]
FIG. 1 is a functional block diagram of an image processing unit 100 in a projector according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating six hue regions for explaining processing by the lightness conversion unit 120;
FIG. 3 is a diagram for explaining weighting processing by a weighting unit 120c.
FIG. 4 is a flowchart for explaining operations of a hue determination unit 115 and a lightness conversion unit 120 according to an embodiment of the present invention.
FIG. 5 is a flowchart for explaining the operation of a lightness conversion unit 120 in each hue region.
FIG. 6 is a diagram (1) for explaining lightness conversion amount calculation processing by a conversion amount calculation unit 120b;
FIG. 7 is a diagram (2) for explaining lightness conversion amount calculation processing by a conversion amount calculation unit 120b;
FIG. 8 is a diagram for explaining a weighting process for R by a weighting unit 120c.
FIG. 9 is a diagram (3) for explaining lightness conversion amount calculation processing by the conversion amount calculation unit 120b;
FIG. 10 is a diagram for explaining a weighting process for Y by a weighting unit 120c.
[Explanation of symbols]
100 Image Processing Unit 110 A / D Conversion Unit 115 Hue Determination Unit 120 Brightness Conversion Unit 120a Parameter Input Unit 120b Conversion Amount Calculation Unit 120c Weighting Unit 130 D / A Conversion Unit 140 L / V Drive Unit

Claims (12)

An image processing apparatus that performs desired image processing on RGB image input data in an RGB color space,
Hue determination means for determining the hue of the pre-conversion color point indicated by the RGB image input data;
Parameter input means for inputting a lightness conversion parameter that defines the lightness conversion amount;
Lightness conversion means for performing lightness conversion of the pre-conversion color point toward white or black according to the determination result of the hue determination means and the input lightness conversion parameter;
An image processing apparatus for performing brightness conversion of the RGB image input data. The image processing apparatus according to claim 1,
The hue determination means;
Determining whether the pre-conversion color point indicated by the RGB image input data belongs to a plurality of hue regions divided in the RGB color space;
An image processing apparatus in which the lightness conversion means performs lightness conversion according to the determination result. The image processing apparatus according to claim 2,
The hue determination means;
The pre-conversion color point indicated by the RGB image input data is any of an RY hue area, a YG hue area, a GC hue area, a CB hue area, a BM hue area, and an MR hue area. Image processing apparatus for determining whether the image belongs to. An image processing apparatus according to any one of claims 1 to 3, wherein
The brightness conversion means includes
Image processing for performing lightness conversion of the pre-conversion color point toward white when the input lightness conversion parameter is positive, and performing lightness conversion of the pre-conversion color point toward black when negative apparatus. An image processing apparatus according to any one of claims 1 to 4, wherein
The lightness conversion parameter can be set independently for each hue of RGBCMY. An image processing apparatus according to any one of claims 1 to 5,
An image processing apparatus comprising lightness conversion amount calculation means for calculating a lightness conversion amount of the RGB image input data based on a determination result by the hue determination means and an input lightness conversion parameter. The image processing apparatus according to any one of claims 1 to 6,
Based on the hue of the pre-conversion color point indicated by the RGB image input data, comprising weighting means for performing a desired weighting process on the lightness conversion amount by the lightness conversion means;
An image processing apparatus that performs brightness conversion of RGB image input data based on the weighted brightness conversion amount. The image processing apparatus according to claim 7,
The weighting means is
An image processing apparatus that performs weighting so that the amount of brightness conversion decreases as the pre-conversion color point approaches the gray axis. The image processing apparatus according to claim 7 or 8,
The weighting means is
An image processing apparatus, wherein a lightness conversion amount relating to a predetermined reference hue is maximized in the reference hue, decreases as the distance from the reference hue increases, and becomes minimum in an adjacent reference hue. An image processing method for performing desired image processing on RGB image input data in an RGB color space,
A hue determination step of determining a hue of a color point before conversion indicated by the RGB image input data;
A parameter input step for inputting a lightness conversion parameter for defining a lightness conversion amount;
In accordance with the determination result of the hue determination step and the input lightness conversion parameter, a lightness conversion step of performing lightness conversion of the pre-conversion color point toward white or black,
An image processing method for performing brightness conversion of the RGB image input data. A hue determination process for causing a computer to execute desired image processing performed on RGB image input data in an RGB color space, and determining a hue of a color point before conversion indicated by the RGB image input data When,
Parameter input processing for inputting a lightness conversion parameter that defines the lightness conversion amount;
Brightness conversion processing for linearly converting the pre-conversion color point toward white or black according to the determination result of the hue determination processing and the input brightness conversion parameter, and the RGB image input data A program for causing a computer to execute image processing for performing lightness conversion. A computer-readable recording medium on which the program according to claim 11 is recorded.

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