JP2002058042A - Hue conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hue adjusting method capable of arbitrarily adjusting a desirable hue by a method wherein the desirable hue to be adjusted in color images is instructed at a hue coordinate. SOLUTION: A plurality of axes directing to an arbitrary direction are set with the origin of a UV coordinate system as a start point, and these axes are arbitrarily and independently set so as to give a deformation. A chrominance signal pinched between arbitrary two axes within the plurality of axes is changed by deforming at least one axis out of the two axes, whereby a hue of the chrominance signal in a region on both sides of the deformed axis is converted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hue conversion method in a color image signal processing apparatus such as a color television receiver and a color copying machine.

[0002]

2. Description of the Related Art Conventionally, when adjusting the hue of a color image of a color television receiver, a color copying machine, or the like, hue conversion is performed by rotating the entire hue coordinates representing the hue in a predetermined direction to be adjusted. I was going.

[0003]

In this conventional hue conversion method, all the hues are converted because the entire hue coordinates are rotated, so that a desired hue in a color image, for example, a color near a human flesh color. There was a problem that only the hue could not be adjusted.

Accordingly, the present invention provides a method for designating a desired hue to be adjusted in a color image on hue coordinates.
It is an object of the present invention to provide a hue conversion method capable of arbitrarily adjusting a desired hue.

[0005]

According to a first aspect of the present invention, there is provided a hue conversion method, wherein a color signal is expressed in a plane coordinate system formed by orthogonal axes of a first color difference signal and a second color difference signal.
A plurality of axes are set in any direction starting from the origin of the plane coordinate system, and these axes can be arbitrarily and independently displaced, and are sandwiched between any two of the plurality of axes. By changing the color signal by displacing at least one of the two axes, the hue of the color signal in the region on both sides of the displaced axis is converted.

According to the hue conversion method of the first aspect, a plurality of axes are set in arbitrary directions in a hue coordinate system expressing color signals, and these axes are independently displaced, and the axes are displaced. Since the hues of the regions on both sides of the axis are converted, it is possible to arbitrarily adjust a predetermined hue.

In addition, since the coordinate is converted by the displacement of the axis,
The gradation processing (gradation) can be changed smoothly.

In addition, since the regions on both sides of the displaced axis are subjected to hue conversion, the problem of color loss does not occur.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a hue conversion method according to the present invention will be described with reference to the drawings.

FIG. 1 and FIG. 2 are diagrams for explaining the hue conversion of the present invention. Hue coordinates of a color image signal of a color television receiver, a color copier, or the like are expressed by a plane coordinate system formed by orthogonal axes of a first color difference signal U and a second color difference signal V as shown in FIG. Is done. Here, the first
Is the RY, and the second chrominance signal V is the B-
Y. (Note that R and B are the three primary colors red and blue, and Y
Is a luminance signal. )

In FIG. 1, an arbitrary point P in a plane coordinate system (hereinafter referred to as a UV coordinate system) constituted by orthogonal axes of a first color difference signal U and a second color difference signal V is represented by P
(U, v). In this UV coordinate system, the point P
(U, v) so that the first angle θ1 passing through the origin 0
An axis A and a second axis B at an angle θ2 are set.

A coordinate system (hereinafter referred to as an AB coordinate system) is constituted by the axes A and B, and the point P is defined by the AB coordinate system.
(U, v).

First, P (u, v) is represented by referring to FIG.
When represented by coordinates α and β in the AB coordinate system,

[0014]

(Equation 1)

By transforming equation (1), the point P
(Α, β) is

[0016]

(Equation 2)

The point P can be represented by a UV coordinate system.

Next, as shown in FIG. 2, the first axis A at the angle θ1
Is displaced by an angle Δθ1 to obtain an axis A ′.
The axis B is displaced by an angle Δθ2 to be an axis B ′. In the A′B ′ coordinate system composed of the axes A ′ and B ′, the coordinates (α,
β), the point P (u, v) becomes the point P ′
(U ', v').

The point P '(u', v ') after this change is
In the A'B 'coordinate system,

[0020]

(Equation 3)

## EQU1 ##

Next, by substituting equation (2) for α and β in equation (3) and rearranging, point P ′ (u ′, v ′) after the change is obtained.
Is in the UV coordinate system

[0023]

(Equation 4)

It is expressed as follows.

As shown in equation (4), the coordinates P ′ (u ′, v ′) of the arbitrary point P after the hue conversion are converted to the coordinates P (u,
v) and a coefficient determined by the angles θ1, θ2, Δθ1, and Δθ2, and can be calculated by a simple two-dimensional determinant. In Equation (4), X11 to X22 are coefficients resulting from the equation rearrangement, and are angles θ1, θ2, Δθ1, and Δθ, respectively.
Determined by 2.

In the above description, the arbitrary point P in the area between the axis A and the axis B has been described. However, the operation of the hue conversion in the present invention extends to the area on both sides of the displaced axis.

That is, since a plurality of axes are set in the UV coordinate system, any point in this coordinate system is an area sandwiched between two axes. When one axis, for example, the axis B in FIG. 1 is displaced, the point in the region sandwiched between the axis A and the axis B is hue-converted, and the axis C is shifted as illustrated by a broken line in FIG. If provided, points in an area sandwiched between the axes B and C are also subjected to hue conversion. In this way, the hues of the regions on both sides of the displaced axis are converted correspondingly. Note that the number of axes may be at least two axes, and a predetermined hue conversion can be performed by displacing at least one of the two axes.

As described above, a plurality of axes (at least two axes A and B) are set in the UV coordinate system expressing the color signal, and these axes A and B are independently displaced, and the displaced axes are set. Since the hues of the regions on both sides of are converted, gradation processing (gradation) can also be smoothly changed. Also, the displaced axis,
For example, since the regions on both sides of the A axis are subjected to hue conversion, the problem of color loss does not occur.

FIGS. 3 and 4 show the hue conversion method of the present invention.
FIG. 3 shows an example applied to the case of eight axes, and FIG.
FIG. 4 shows a setting state of axes A1 to A8 on the coordinates, and FIG. 4 shows a block circuit of hue conversion.

In FIG. 3, axes A1 to A1 are located on a UV coordinate system.
Axis A8 is set so that axis A1 coincides with the v axis, and axis A
The axes after 2 are set at angles shifted sequentially by 45 degrees. As a result, as shown in the figure, the axis A1, the axis A3, the axis A5, and the axis A7, which are the odd axes, respectively correspond to the axes of the UV coordinates, and the axes A2, A4, A6, and A6, which are the even axes, respectively.
8 is at an angle of 45 degrees from the axis of the UV coordinates.

An area sandwiched between the axis A1 and the axis A2 is formed. Similarly, an area between the axis A2 and the axis A3,
3 and area on axis A4, area on axis A4 and axis A5, axis A5
And an axis A6, an axis A6 and an axis A7, an axis A7 and an axis A8, and an axis A8 and an axis A1.

The axes A1 to A8 can be independently displaced by arbitrary positive and negative angles. For example, when the axis A2 is displaced by the predetermined angle Δθ2 in the direction of the axis A3, the displacement of the axis A2 changes the hues of both the area and the area in relation to each other.

The hue conversion block circuit 40 shown in FIG.
The image data expressed in the V coordinate system is converted into input signals u, v
And outputs the output signals u ′ and v ′ of the converted image data having undergone the desired hue conversion processing.
It has the following components.

The area discriminating and coefficient setting device 41 receives the input signals u and v sequentially, and determines which of the areas 1 to 3 in FIG. 3 the input signal belongs to.指定 A8 are input as to whether .about.A8 are to be displaced, and in which direction, if any, are displaced, and each coefficient K1 calculated according to the area determination of the input signals u and v is input. To K4, and outputs the set coefficients K1 to K4.

The multiplier 42 multiplies the u component of the input signal by the first coefficient K1, the multiplier 43 multiplies the v component of the input signal by the second coefficient K2, and the multiplier 44 generates the u component of the input signal. Is multiplied by a third coefficient K3.
The component is multiplied by a fourth coefficient K4.

The adder 46 adds the multiplication result of the first multiplier 42 and the multiplication result of the second multiplier 43, and outputs the addition result u ′ = K1 · u + K2 · v. The multiplication result of the third multiplier 44 and the multiplication result of the fourth multiplier 45 are added, and the addition result v ′ = K3 · u + K4 · v is output. The output addition results u ′ and v ′ become converted image data that has undergone hue conversion processing.

As described above, the conversion formula in the hue conversion block 40 is as follows: u '= K1.u + K2.v (5) v' = K3.u + K4.v (6)

Each of the coefficients K1 to K1 in the equations (5) and (6)
K4 is defined as follows. K1 = (cos (a) * sin (b) * cos (Δ1) -sin (a) * sin (b) * sin (Δ1) -sin (a) * cos (b) * cos (Δ2) + sin (a) * sin (b) * sin (Δ2)} / sin (ba) = coef1 * cos (Δ1) -coef2 * sin (Δ1) -coef3 * cos (Δ2) + coef2 * sin (Δ2) (7) K2 = {-cos (a) * cos (b) * cos (Δ1) + sin (a) * cos (b) * sin (Δ1) + cos (a) * cos (b) * cos (Δ2 ) -cos (a) * sin (b) * sin (Δ2)} / sin (ba) = -coef4 * cos (Δ1) + coef3 * sin (Δ1) + coef4 * cos (Δ2) -coef1 * sin (Δ2 (8) K3 = {sin (a) * sin (b) * cos (Δ1) + cos (a) * sin (b) * sin (Δ1) -sin (a) * sin (b) * cos (Δ 2) -sin (a) * cos (b) * sin (Δ2)} / sin (ba) = coef2 * cos (Δ1) + coef1 * sin (Δ1) -coef2 * cos (Δ2) -coef3 * sin (Δ2) ・ ・ ・ (9) K4 = {-sin (a) * cos (b) * cos (Δ1) -cos (a) * cos (b) * sin (Δ1) + cos (a) * sin (b) * cos (Δ2) + cos (a) * cos (b) * sin (Δ2)} / sin (ba) = -coef3 * cos (Δ1) -coef4 * sin (Δ1) + coef1 * cos (Δ2 ) + coef4 * sin (Δ2) (10)

The angles (a), (b), (Δ1) and (Δ2) in the equations (7) to (10) are the angles (θ1), (θ2) and (Δθ1) in FIGS. ), (Δθ2)
Respectively.

Equations (7) to (10) representing coefficients K1 to K4
In, the variables coef1 to coef4 are arranged as follows. coef1 = cos (a) * sin (b) / sin (ba) coef2 = sin (a) * sin (b) / sin (ba) coef3 = sin (a) * cos (b) / sin (ba) coef4 = cos (a) * cos (b) / sin (ba)

The relationship between each of the variables coef1 to coef4 and the area is arranged as shown in the following table.

The hue conversion block circuit 40 shown in FIG.
First, the region discriminating and coefficient setting device 41 determines whether or not each of the axes A1 to A8 is displaced, and if so, the hue change designation Δθ1 in which direction and how much.
~ Δθ8 is input. Region determination and coefficient setting device 41
Are axes A1 to A8 according to hue change designations Δθ1 to Δθ8.
Are set, the coefficients K1 to K4 in each area are calculated based on the changed angles by the equations (7) to (10). The calculated coefficients K1 to K4 are stored in a memory. In this state, input signals u and v of image data expressed in the UV coordinate system are sequentially input.

Then, it is determined to which of the regions the input signals u and v sequentially input belong. In this embodiment, eight axes are set on the UV coordinate system such that the axis A1 coincides with the v axis, and the axes after the axis A2 are set at angles shifted sequentially by 45 degrees, respectively. Since it is possible to determine to which region the input signals u and v belong from the region 〜 only by comparing the magnitude of the u component and the v component of the input signals u and v and the sign thereof, a region determination circuit is configured by a simple circuit. be able to.

Based on the area determination results of the input signals u and v, coefficients K1 to K4 calculated and stored in advance are output from the area determination and coefficient setting device 41 according to the area.

From the u component and v component of the input signals u and v and the coefficients K1 to K4, multipliers 42 to 45 and adders 46 and 47 perform multiplication processing and addition processing, respectively. Output signal u ′ (= K1 · u + K2 ·
v) and v '(= K3.u + K4.v) are output.

In the examples shown in FIGS. 3 and 4, the number of axes is eight. However, the number of axes can be any number, and the set angles of each axis are not limited to uniform. Can be set to

[0047]

According to the hue conversion method of the first aspect of the present invention, a plurality of axes are set in arbitrary directions in a hue coordinate system expressing a color signal, and these axes are independently displaced. Since the hues of the regions on both sides of the displaced axis are converted, the predetermined hue can be adjusted arbitrarily.

Also, since the coordinate transformation is performed by the displacement of the axis,
The gradation processing (gradation) can be changed smoothly.

Further, since the areas on both sides of the displaced axis are subjected to the hue conversion, the problem of color loss does not occur.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining hue conversion according to the present invention.

FIG. 2 is a diagram for explaining hue conversion according to the present invention.

FIG. 3 is a diagram showing an example in which the hue conversion method of the present invention is applied to a case of eight axes.

FIG. 4 is a block diagram of hue conversion in the hue conversion method of the present invention.

[Explanation of symbols]

 A1 to A8 Set axis to area divided by axis 41 Area discriminating and coefficient setting device 42 to 45 Multiplier 46, 47 Adder

Continued on front page F term (reference) 5B057 BA28 CA01 CA08 CB01 CB08 CE17 DA08 DB02 DB06 5C066 AA03 AA05 CA05 EB01 GA02 KE04 5C077 MP08 PP36 PP37 TT06 5C079 LB12 NA02 NA05 PA02

Claims (1)

[Claims] 1. A color signal is expressed in a plane coordinate system constituted by orthogonal axes of a first color difference signal and a second color difference signal, and the origin of the plane coordinate system is set as a starting point in an arbitrary direction. A plurality of axes are set, these axes can be arbitrarily and independently displaced, and a color signal sandwiched by any two of the plurality of axes is displaced by at least one of the two axes. A hue conversion method characterized in that the hue of the color signal in the area on both sides of the displaced axis is converted by changing the hue.