JP2002330299A - Image processor, image processing method, program and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor capable of independently correcting saturation conversion quantity in an area between reference hues in each reference hue. SOLUTION: This image processor performs desired image processing of RGB image input data in an RGB color space. A hue deciding part decides a hue of an unconverted color point shown by the RGB image input data, and a saturation converting part performs saturation conversion of the unconverted color point into a color point whose hue is the same as that of the unconverted color point and also is on a straight line almost perpendicular to a gray axis in accordance with decision results of the hue deciding part. The saturation converting part is further provided with a parameter inputting part for inputting a saturation conversion parameter that regulates saturation conversion quantity and a conversion quantity calculating part. The conversion quantity calculating part calculates saturation conversion quantity of the RGB image input data on the basis of the decision results of the hue deciding part and the inputted saturation conversion parameter. A weighting part applies desired weighting processing to the saturation conversion quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image processing for printers, projectors, etc., and more particularly to R (red) G (green) B
The present invention relates to an image processing apparatus, an image processing method, a program, and a recording medium for performing color conversion processing of image data expressed in three colors (blue) according to a device to be used, user's preference, and the like.

[0002]

2. Description of the Related Art Color conversion in print processing is an essential technique for correcting image quality deterioration and maintaining good color reproducibility. Also, in a display device such as a monitor or a projector, a color conversion process is performed in order to reproduce a desired color according to a use condition or the like.

[0003]

However, in the case of the matrix operation color conversion, it is not possible to realize a suitable color conversion due to the non-linearity of the print. Also, red, blue,
Since the saturation conversion amounts among the six hues (reference hues) of green, yellow (Y), cyan (C), and magenta (M) cannot be corrected independently, it is possible to realize good color conversion in all color spaces. Can not.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an image processing apparatus, an image processing method, and a program capable of independently correcting a saturation conversion amount in an area between reference hues for each reference hue. And a recording medium.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, an invention according to claim 1 is an image processing apparatus for performing desired image processing on RGB image input data in an RGB color space. A hue determining means for determining the hue of the pre-conversion color point indicated by the image input data; and And a saturation conversion unit for performing a saturation conversion of the pre-conversion color point to a color point, wherein the saturation conversion unit performs a saturation conversion of the RGB image input data.

According to the image processing apparatus configured as described above and performing desired image processing on RGB image input data in the RGB color space, the hue judging means
The hue of the pre-conversion color point indicated by the RGB image input data is determined, and the chroma conversion unit has the same hue as the pre-conversion color point and is substantially perpendicular to the gray axis according to the determination result of the hue determination unit. The color point before conversion is subjected to saturation conversion to a color point on a straight line. Then, saturation conversion of the RGB image input data is performed by the saturation conversion means.

[0007] The invention described in claim 2 is the first invention.
The image processing apparatus according to the above, wherein the hue determination means,
The pre-conversion color point indicated by the RGB image input data is RGB
It is configured to determine to which of the hue regions divided into a plurality in the color space the color space belongs, and according to the determination result, the saturation conversion unit performs the saturation conversion.

Further, according to a third aspect of the present invention, in the image processing apparatus according to the second aspect, the hue determining means determines that the color point before conversion indicated by the RGB image input data is R
-Y hue area, YG hue area, GC hue area, C-
It is configured to determine which one of the B hue area, the BM hue area, and the MR hue area belongs.

The invention described in claim 4 is the first invention.
The image processing apparatus according to any one of claims 1 to 3,
The saturation conversion unit is configured to include a parameter input unit for inputting a saturation conversion parameter defining a saturation conversion amount.

Further, the invention according to claim 5 is the image processing apparatus according to claim 4, wherein the saturation conversion parameter can be set independently for each hue of RGBCMY. Is done.

[0011] The invention according to claim 6 is the invention according to claim 4.
Or the image processing device according to 5, wherein a saturation conversion amount calculation for calculating a saturation conversion amount of the RGB image input data based on a determination result by the hue determination unit and an input saturation conversion parameter. Means.

Further, according to a seventh aspect of the present invention, in the image processing apparatus according to any one of the first to sixth aspects, based on a hue of a pre-conversion color point indicated by the RGB image input data, A weighting unit is provided for performing a desired weighting process on the saturation conversion amount by the saturation conversion unit, and is configured to perform the saturation conversion of the RGB image input data based on the weighted saturation conversion amount.

[0013] The invention described in claim 8 is the invention according to claim 7.
The image processing apparatus according to the above, wherein the weighting means,
The saturation conversion amount for a predetermined reference hue is configured to be maximum in the reference hue, decrease with distance from the reference hue, and minimize in the adjacent reference hue.

According to a ninth aspect of the present invention, in the image processing apparatus according to any one of the first to eighth aspects, as a result of the saturation conversion by the saturation conversion means, the color point is R.
When the color point is converted outside the GB space, the color point after the saturation conversion is converted to the outermost color point in the RGB color space.

[0015] The invention according to claim 10 is an image forming apparatus for RGB.
An image processing method for performing desired image processing on RGB image input data in a color space, comprising: a hue determining step of determining a hue of a pre-conversion color point indicated by the RGB image input data; A saturation conversion step of performing saturation conversion of the color point before conversion to a color point on a straight line that has the same hue as the color point before conversion and that is substantially perpendicular to the gray axis according to the determination result. It is configured to perform a saturation conversion of the RGB image input data by a degree conversion step.

[0016] Further, according to the present invention, the RG
A hue determination process for causing a computer to execute desired image processing performed on RGB image input data in a B color space, the hue determination process determining a hue of a pre-conversion color point indicated by the RGB image input data And a saturation conversion process of performing saturation conversion of the pre-conversion color point into a color point on a straight line that has the same hue as the pre-conversion color point and is substantially perpendicular to the gray axis, according to the determination result of the hue determination process. And performing saturation conversion of the RGB image input data by the saturation conversion processing.

According to a twelfth aspect of the present invention, there is provided a computer-readable recording medium storing the program according to the eleventh aspect.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In this embodiment, image processing in a projector will be described.

FIG. 1 shows a functional block diagram of an image processing unit 100 in a projector according to an embodiment of the present invention.

An image processing section 100 in a projector according to an embodiment of the present invention includes an A / D conversion section 110 for converting an analog image input signal into a digital signal, and an RG.
Hue determination unit 1 for determining hue based on B image input data
15, a saturation conversion unit 120 for performing desired saturation conversion on the RGB image input signal, a D / A conversion unit 130 for converting a digital signal into an analog signal, and an image by driving a liquid crystal light valve. And an L / V (light valve) driving unit 140 for performing projection display of the image.

Further, the saturation conversion section 120 includes a parameter input section 120a for inputting a saturation conversion parameter for each hue, and a hue determined by the hue determination section 115 and the input saturation conversion parameter. Based on the hue determined by the hue determination unit, and a weighting unit 120c for weighting the saturation conversion amount based on the hue determined by the hue determination unit. And is provided.

FIG. 2 shows six hue regions for explaining the processing by the saturation conversion section 120. Saturation converter 120
Are all performed in RGB space.

The hue is divided into six regions as shown in FIG. 2, and saturation conversion is performed for each region. That is,
The hue determination unit 115 determines the hue based on the RGB image input data, and performs saturation conversion for each region based on the determination result.

Then, a saturation conversion parameter for defining a saturation conversion amount is input for each of R, G, B, C, M, and Y hues by the parameter input unit 120a. The range of the input saturation conversion parameter is -128 or more and 127
It is as follows. In each area of FIG. 2, 2 of RGBCMY
The saturation conversion parameter related to the color is related to the calculation of the saturation conversion amount. For example, in region 1 of FIG. 2, the R and Y chroma conversion parameters are related to the calculation of the chroma conversion amount. In other words, each of the chroma conversion amounts of RGBCMY affects two adjacent hue regions. For example, if R, area 1
And the area 6.

Then, as shown in FIG. 3, for example, in the case of R, the weighting unit 120c maximizes each conversion amount of RGBCMY in each primary color (apex of the RGB space), and decreases as the color approaches the adjacent hue or gray axis. Weighting so that By performing such weighting, even after the saturation conversion, R
The continuity of the GB space is maintained. The weighting process will be described in detail below.

Hue determination section 115 and saturation conversion section 120
Next, referring to FIG. 4, the hue determination unit 1 in the image processing unit 100 of the projector according to the embodiment of the present invention will be described.
15 and the operation of the saturation conversion unit 120 will be described.

The saturation conversion process performed by the hue determination unit 115 and the saturation conversion unit 120 described below is performed by executing an image processing program stored 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 in the scope of the present invention.

First, when the use of the projector is started, the hue judging section 115 outputs R,
The magnitude relationship between the G and B values is determined (S10), and the RGB image input data is converted to the hue regions 1 to 6 or gray (Gra) shown in FIG.
y) Determine which of the areas belongs to. That is, (1) when R ≧ G> B, the hue determination unit 115 determines that the region is the RY region (the hue region 1 in FIG. 2) and performs the saturation conversion process in the RY region (S12). ), (2) G> R ≧
In the case of B, it is determined that the region is the YG region (hue region 2 in FIG. 2), and the saturation conversion process in the YG region is performed (S1).
4), (3) When G ≧ B> R, it is determined that the area is a GC area (hue area 3 in FIG. 2), and a saturation conversion process is performed in the GC area (S16), (4) When B> G ≧ R, C
CB area (hue area 4 in FIG. 2)
A saturation conversion process is performed on the region (S18), and (5) B
When ≧ R> G, it is determined that the region is the BM region (hue region 5 in FIG. 2), and a saturation conversion process is performed in the BM region (S20). (6) When R> B ≧ G , MR region (hue region 6 in FIG. 2), and performs a saturation conversion process in the MR region (S22). (7) When R = G = B, the gray region (no conversion) ), And does not perform the saturation conversion process (S24).

Next, with reference to FIG. 5, the processing performed by the saturation converter 120 in each hue region will be described. In this embodiment, when R ≧ G> B, that is, in the RY region (FIG. 2)
The saturation conversion processing in the hue region 1) will be described. The saturation conversion processing is performed for the other hue regions 2 to 2 shown in FIG.
6 is similar to the hue area 1, and the description thereof is omitted.

As shown in FIG. 5, first, a parameter (referred to as "saturation conversion parameter" in this specification) that defines a saturation conversion amount is input from a parameter input unit 120a to a conversion amount calculation unit 120b. Is performed (S30).
The saturation conversion parameters are as follows: Rc: Saturation conversion parameter of R (−128 ≦ Rc ≦ 127) Gc: Saturation conversion parameter of G (−128 ≦ Gc ≦ 127) Bc: Saturation conversion parameter of B (−128 ≦ Bc ≦ 127) Cc: Saturation conversion parameter of C (−128 ≦ Cc ≦ 127) Mc: Saturation conversion parameter of M (−128 ≦ Mc ≦ 127) Yc: Saturation conversion parameter of Y (−128 ≦ Yc ≦ 127) When the saturation conversion parameter is -128, all colors are converted to achromatic colors (gray), and when the saturation conversion parameter is 128, all colors are converted to the outermost color in the RGB color space. .

Next, a calculation process of the saturation conversion amount is performed by the conversion amount calculation unit 120b (S32). FIG.
The figure which looked at the RGB space from the (white) side is shown. FIG.
2 shows a cross section when the RGB space is cut by a plane including a gray axis passing through a point R ′ on a line segment RY. As shown in FIG. 6, in the saturation conversion by the saturation conversion unit 120, the predetermined color point P is a color point having the same hue as (1) the color before the conversion,
And (2) converted into a point P 'which is a color point on a straight line substantially perpendicular to the gray axis (WK axis).

6 and 7, the coordinates of the point P are (R, G, B), the coordinates of the point P 'are (R', G ', B'), and P'H = (1 + F) PH ... ( 1) Here, the point H is located on the gray axis (line segment W) from the point P.
The point Q is the intersection of the straight line passing through the points P and P ′ and the outermost contour of the RGB color space. (1) Referring to FIG. 7, the condition for color point P and color point P ′ to have the same hue is R′−G ′ = (1 + F) (RG) (2) G′−B '= (1 + F) (GB) (3) R'-B' = (1 + F) (RB) (4) (2) The condition for the straight line PH (P'H) and the straight line WK to be perpendicular is represented by R '+ G' + B '= R + G + B (5).

Equations (2) to (5) are solved for R ', G', B '. From formula (2) + formula (4) + formula (5)}, R ′ = R + F × (2R−GB) / 3 (6) From {-expression (2) + expression (3) + expression (5)}, G ′ = G + F × (−R + 2G−B) / 3 (7) Further, from {−expression (3) −expression (4) + expression (5)}, B ′ = B + F × (−RG−2B) / 3 (8)

Next, the value of F is obtained. In FIG. 8, the horizontal axis indicates the length of PH before the saturation conversion, and the vertical axis indicates the length of P′H after the saturation conversion.

As shown in FIG. 8, the saturation conversion parameters are as follows:
When Rc = 0, PH = P'H regardless of the position of the point P, and when Rc = -128, P'H = 0 regardless of the position of the point P.
When Rc = 127, P′H =
QH. When −128 <Rc <0 P′H = (128 + Rc) × PH / 128 (9) From Expressions (1) and (9), (128 + Rc) × PH / 128 = (1 + F) × PH, so that F = Rc / 128. When 0 <Rc <127 P′H = 128 × PH / (128−Rc) (10) From Equations (1) and (10), 128 × PH / (128−Rc) = (1 + F) × PH, so that F = Rc / (128−Rc). However, when Rc> 0, P′H ≦ QH must be satisfied in order to prevent P ′ from going out of the RGB space, so that the value of F is limited. Then, P'H =
The value of F at the time of QH is obtained.

As shown in FIG. 6, P'H
= QH. For example, in the case of the RY area, case 1 (C
As in the case of ase 1), Q exists on WS (R ′ =
There is a case where Q is present on KS (where B ′ = 0), as in the case of Case 2 (case 2). The value of F in each case is as follows.

In case 1, if R ′ = 255 is substituted into equation (6), 255 = R + F × (2R−GB) / 3, so that F = 3 × (255−R) / (2R −GB) (11)

In case 2, when B ′ = 0 is substituted into equation (8), 0 = B + F × (−R−G + 2B) / 3, so that F = 3B / (R + G−2B) (12) Becomes

From the above, the value of F when Rc> 0 is Rc
/ (128-Rc), 3 (255-R) / (2R-G-B), 3B /
It becomes the minimum value of (R + G-2B). Expressing this as an equation, F = min {Rc / (128−Rc), 3 (255−R) / (2R−G−B), 3B / (R + G−2B)} (13)

The value of F when Rc <0, Rc / 128
Are 3 (255−R) / (2R−GB), 3B / (R + G−2)
Since the values are always smaller than B), the cases of case 1 and case 2 can be summarized into one equation: F = min {C, 3 (255−R) / (2R−GB), 3B / ( R + G-2B)} (14) Here, when Rc <0, the value of C is C = Rc /
128, and when Rc> 0, C = Rc / (128-Rc).

Next, the weighting unit 120c performs a weighting process according to the hue on the F obtained as in the equations (13) and (14) (S34).

As shown in FIG. 9, the saturation conversion of R is 1 in the hue (reference hue) including the vertex of R, decreases as the distance from the reference hue increases, and decreases in the hue including the vertex of Y (the adjacent reference hue). Hue). Such a weighting factor is (RG) / (RB).

As shown in FIG. 10, the saturation conversion of Y is 1 in the hue (reference hue) including the vertex of Y, decreases as the distance from the reference hue increases, and decreases in the hue including the vertex of R (neighboring). (Reference hue). Such a weighting coefficient is (GB) / (RB).

To summarize the above results, when Rc <0, C1 = Rc / 128 Rc ≧ 0, C1 = Rc / (128−Rc) When Yc <0, C2 = Yc / 128 Yc ≧ 0 At this time, C2 = Yc / (128-Yc).

Therefore, F1 = (R−G) / (R−B) × min {C1, 3 (255−R) / (2R−G−B), 3B / (R + G−2B)} (15) F2 = (G−B) / (R−B) × min {C2,3 (255−R) / (2R−G−B), 3B / (R + G−2B)} (16), and the point P ( An equation for converting R, G, B) into a point P ′ (R ′, G ′, B ′) is as follows: R ′ = R + (F1 + F2) × (2R−GB) / 3 (17) G ′ = G + (F1 + F2) × (−R + 2G−B) / 3 (18) B ′ = B + (F1 + F2) × (−RG−2B) / 3 (19)

As described above, according to the image processing apparatus of the present embodiment, the saturation conversion amount in the region between the reference hues is independent for each reference hue, and the continuity with the adjacent region is not lost. Thus, 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 describing processing by a saturation conversion unit;

FIG. 3 is a diagram illustrating a weighting process performed by a weighting unit 120c.

FIG. 4 is an exemplary embodiment of a hue determination unit according to the present invention.
6 is a flowchart for explaining the operation of the saturation conversion unit 120.

FIG. 5 is a flowchart illustrating an operation of a saturation conversion unit 120 in each hue region.

FIG. 6 is a diagram (1) illustrating a calculation process of a saturation conversion amount by a conversion amount calculation unit 120b;

FIG. 7 is a diagram (2) illustrating a calculation process of a saturation conversion amount performed by a conversion amount calculation unit 120b.

FIG. 8 is a diagram (3) illustrating a calculation process of a saturation conversion amount performed by the conversion amount calculation unit 120b.

FIG. 9 is a diagram for explaining a weighting process for R by a weighting unit 120c.

FIG. 10 is a diagram illustrating a weighting process for Y by a weighting unit 120c.

[Explanation of symbols]

 Reference Signs List 100 Image processing unit 110 A / D conversion unit 115 Hue determination unit 120 Saturation conversion unit 120a Parameter input unit 120b Conversion amount calculation unit 120c Weighting unit 130 D / A conversion unit 140 L / V drive unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C262 AB11 AB17 BA01 BA02 BA03 BA18 BA19 BC09 BC19 5B057 AA11 BA25 BA26 CE17 CE18 CH08 CH18 DA16 DA17 5C077 LL19 MP08 PP32 PP33 PP37 PQ08 PQ18 SS05 TT02 5C079 HB01 HB02 HB11 MA NA01 PA03 PA05

Claims (12)

[Claims] 1. An image processing apparatus for performing desired image processing on RGB image input data in an RGB color space, comprising: a hue determination unit configured to determine a hue of a pre-conversion color point indicated by the RGB image input data; According to the determination result of the hue determination unit, a saturation conversion unit that performs the saturation conversion of the pre-conversion color point to a color point on a straight line that is the same hue as the pre-conversion color point and that is substantially perpendicular to the gray axis, An image processing apparatus, comprising: converting the RGB image input data into saturation by the saturation conversion unit. 2. The image processing apparatus according to claim 1, wherein the hue determination unit determines that the pre-conversion color point indicated by the RGB image input data is RGB.
An image processing apparatus which determines which of a plurality of divided hue regions belongs in a color space, and performs the saturation conversion by the saturation conversion unit according to the determination result. 3. The image processing apparatus according to claim 2, wherein the hue determination unit determines that the pre-conversion color point indicated by the RGB image input data is RY.
An image processing apparatus for determining which of a hue area, a YG hue area, a GC hue area, a CB hue area, a BM hue area, and an MR hue area. 4. The image processing apparatus according to claim 1, wherein the saturation conversion unit includes a parameter input unit for inputting a saturation conversion parameter that defines a saturation conversion amount. Image processing device provided. 5. The image processing apparatus according to claim 4, wherein the saturation conversion parameter can be independently set for each of RGBCMY hues. 6. The image processing apparatus according to claim 4, wherein a saturation conversion amount of the RGB image input data is based on a determination result by the hue determination unit and an input saturation conversion parameter. An image processing apparatus comprising a saturation conversion amount calculation unit for calculating a color conversion amount. 7. The image processing apparatus according to claim 1, wherein the amount of saturation conversion by the saturation conversion unit is based on a hue of a pre-conversion color point indicated by the RGB image input data. An image processing apparatus, comprising: weighting means for performing a desired weighting process on the RGB image input data based on the weighted saturation conversion amount. 8. The image processing apparatus according to claim 7, wherein the weighting unit is configured such that a saturation conversion amount relating to a predetermined reference hue is maximum in the reference hue, decreases as the distance from the reference hue decreases, and An image processing apparatus that minimizes the reference hue to be used. 9. The image processing apparatus according to claim 1, wherein a color point is RGB as a result of the saturation conversion performed by the saturation conversion unit.
If the color point is converted outside the space,
An image processing device that converts a color point into an outermost color point in a GB color space. 10. An image processing method for performing desired image processing on RGB image input data in an RGB color space, comprising: a hue determining step of determining a hue of a pre-conversion color point indicated by the RGB image input data; A saturation conversion step of performing saturation conversion of the pre-conversion color point to a color point on a straight line that is the same hue as the pre-conversion color point and that is substantially perpendicular to the gray axis according to the determination result of the hue determination step. An image processing method comprising the steps of: performing a saturation conversion of the RGB image input data in the saturation conversion step. 11. A program for causing a computer to execute desired image processing to be performed 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 A hue determination process to be determined, and, according to the determination result of the hue determination process, convert the color point before conversion into a color point on a straight line that is the same hue as the color point before conversion and that is substantially perpendicular to the gray axis A program for causing a computer to execute image processing for performing color conversion of the RGB image input data by the color conversion. 12. A computer-readable recording medium on which the program according to claim 11 is recorded.