JP2001128189A - Color correcting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color correcting circuit which can correct saturation and hue only in the vicinity of a specific hue point. SOLUTION: A color correcting circuit extracts only hue points in the area formed between equal-hue lines L1 and L2 in the X-Y plane when the B-Y components of color difference signals are used as the X-axis ad the R-Y components of the color difference signals are used as the Y-axis. The circuit performs saturation correction by moving the hue points in the area in the direction parallel to a specific hue line L0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color correction circuit for a display device or the like, and more particularly to a color correction circuit capable of correcting saturation and hue only near a specific hue point.

[0002]

2. Description of the Related Art There are various types of display devices for displaying video signals. For each display such as CRT, liquid crystal, and plasma, the chromaticity points of the three primary colors do not match the original chromaticity points, and are different between displays. Therefore, when a video signal is displayed on a display, a hue and a saturation shift occur in color reproduction.
Also, in the case of a video signal generated by an imaging device, a shift in saturation and hue similarly occurs due to variations in three primary colors of the imaging device.

A baseband video signal is composed of three primary color signals of red (R), green (G), and blue (B), or a luminance signal (Y) and two color difference signals (RY, BY, or Pb). , Pr) are used. The signals displayed on the display are three primary color signals of R, G, and B, and the luminance and color difference signals can be easily converted mutually by a matrix circuit. When controlling the saturation and the hue, the color difference signal is more easily processed than the three primary color signals, and thus the color difference signal is often used for the correction processing.

There are various conventional saturation and hue correction methods. In each case, the corrected chrominance signal (R-Y) and (B-Y) is replaced with the corrected chrominance signal (r). -Y), (b-
If y), a correction process equivalent to the calculation process shown in the following equation was performed. (r−y) = − A2 × sin (T2) × (B−Y) + A2 × cos
(T2) × (R−Y) (by) = A1 × cos (T1) × (B−Y) + A1 × sin (T
1) × (R−Y) Here, if A1 = A2 and T1 = T2, the (R) of two orthogonal axes
For -Y) and (B-Y), saturation correction is uniformly performed by gain control using the coefficient A1, and hue correction is uniformly performed by rotation corresponding to the angle T1. In this case, the correction amount uniformly changes over the entire hue plane of (R−Y) and (B−Y).

[0005] Further, according to T1 and T2, (R-Y) and (B-
Each rotation of Y) can be changed to a different angle, and the amplitudes of (ry) and (by) can be individually set to different values by A1 and A2. By doing this,
The correction amount can be corrected to be non-uniform on a plane having two color difference signals as axes.

[0006]

With the conventional technique described above, it is not possible to correct saturation or hue only in the vicinity of a specific hue (hereinafter referred to as color correction). Although it is possible to increase the amount of color correction in the vicinity of a specific hue to some extent relative to other hue points, it is important that all hue points change due to color correction of a certain hue point. There were serious disadvantages. SUMMARY An advantage of some aspects of the invention is to provide a color correction circuit capable of correcting saturation and hue only near a specific hue point.

[0007]

In order to achieve the above object, in a color correction circuit for correcting a color near a specific hue to be corrected, one color difference signal component of two color difference signals is converted to X. When the other color difference signal component is the Y axis, the first and second equal hue straight lines that sandwich the specific hue straight line that is the equal hue straight line corresponding to the specific hue on the X and Y planes are set, Extracting means for extracting only hue points in an area formed between the first and second equal hue straight lines including the specific hue straight line, and a direction parallel to the specific hue straight line in the area. And a color correction circuit for providing a color correction circuit.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color correction circuit according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of the color correction circuit of the present invention, FIG. 2 is a diagram for explaining the color correction circuit of the present invention, and FIG. 3 is a diagram showing the saturation correction effect of the present invention. FIG. 4 is a diagram showing a hue correction effect of the present invention. In FIG. 1, a color difference signal (R−Y), which is a Y-axis signal (hereinafter abbreviated as a signal Y) in FIG. 2, is input from an input terminal 1 and supplied to a multiplier 3, a multiplier 6 and an adder 15. ing. Similarly, the X-axis signal of FIG.
A color difference signal (abbreviated as signal X) is input to the multiplier 5, the multiplier 8, and the adder 18.

In FIG. 2, the horizontal axis X is (BY) and the vertical axis Y is
Is an X, Y plane when (RY) is obtained. This X, Y
The radius in the plane represents the saturation (color depth),
The angle from the center, which is the intersection of X and Y, represents the hue. In FIG. 2, assuming that the angle between the straight line L1 passing through the intersection of X and Y and the Y-axis is T1, the multiplier 3 multiplies the signal Y by -sin (T1) signal r1, and the multiplier 5 outputs -cos (T
1) multiplying the signal X by the signal b1 to output signals -Y * sin (T1) and -X * cos (T1), respectively. Note that the straight line L1 is a uniform hue straight line in one quadrant.

The outputs of the multipliers 3 and 5 are added by the adder 4 to obtain -Y.times.sin (T1) -X.times.cos (T1). When this value is 0, the hue point is represented by the straight line L1 in FIG.
Will be on top. The output of the adder 4 is supplied to a limiter 9, which outputs a signal V1 by limiting the negative value of the output of the adder 4 to zero. Note that the area where the signal V1 has a positive value is the area including the point A of the straight line L1 in FIG. 2 (the area on the left side of the straight line L1 in FIG. 2). This signal V1 is input to a minimum value selector (MIN) 11.

In FIG. 2, if the angle between the straight line L2 passing through the intersection of X and Y and the Y-axis is T2, the multiplier 6 becomes sin
The signal Y is multiplied by the signal r2 of (T2), and the multiplier 8
By multiplying the signal X by the signal b2 of s (T2),
The signals Y × sin (T2) and X × cos (T2), respectively
Is output. Note that the straight line L2 is a uniform hue straight line in one quadrant. The outputs of the multipliers 6 and 8 are added by the adder 7 to obtain Y × sin (T2) + X × cos (T2). When this value is 0, the hue point is on the straight line L2 in FIG. The output of the adder 7 is supplied to a limiter 10, and the limiter 10 outputs a signal V2 by limiting a negative value in the output of the adder 7 to 0.

The area where the signal V2 has a positive value is the area including the point A of the straight line L2 in FIG. 2 (the area above the straight line L2 in FIG. 2). This signal V2 is input to the minimum value selector 11. The upper limit of the output of the minimum value selector 11 is limited by the limiter 12, and the multipliers 13 and 1
4 is input. The limiter 12 limits the correction amount output from the minimum value selector 11. The minimum value selector 11 selects a signal having a smaller value from the input signals V1 and V2. By selecting the minimum value of the signals V1 and V2 on the X and Y planes, the region A is a region on the left side of the straight line L1 in FIG. 2 and on the upper side of the straight line L2. Only the hue points within the can be extracted. Outside this area A, 0 is selected.

That is, the multipliers 3 and 5, the adder 4 and the limiter 9, the multipliers 6 and 8, the adder 7 and the limiter 10,
The minimum value selector 11 for selecting the minimum value of the outputs of the limiters 9 and 10 operates as an extracting unit for extracting only the hue points in the area A on the X and Y planes. As a result, the value obtained by the minimum value selector 11 indicates how much the hue point in the area A surrounded by the straight lines L1 and L2 is to be corrected, and the hue point in the area A Only the positive value becomes 0, and becomes 0 on the straight lines L1 and L2 and in the area other than the area A. The value of the hue point in the area A represents the minimum value of the distances to the straight lines L1 and L2 (the length of the perpendicular to each straight line).

In FIG. 2, when an angle between a straight line L0 substantially in the middle of the straight lines L1 and L2 (not necessarily exactly at the center) and the Y axis is T0, the multiplier 13 converts the input signal from the limiter 12 into a Gain1. The signal V3 is multiplied to obtain a signal V3, which is supplied to the multipliers 16 and 17. The multiplier 16 uses cos (T
0) is multiplied by the signal r3, and the multiplier 17 outputs −s
By multiplying the signal V3 by the signal b3 of in (T0), the signals V3 × cos (T0) and −V3 × si
n (T0) is output. Note that the straight line L0 is a uniform hue straight line in one quadrant.

The coefficients r 3 and b 3 are calculated by the multipliers 16 and 17.
, The movement amount for actually moving the hue points in the area A in the direction parallel to the straight line L0 is obtained. That is, the multipliers 16 and 17 are
And operates as a saturation moving means for moving the hue point in a direction parallel to the straight line L0 by the correction amount output through the.
The movement direction moves in a direction away from the origin of the XY axis when Gain1 is positive, and moves in a direction approaching the origin when Gain1 is negative. The amount of movement is determined by the absolute value of Gain1.

The adders 15 and 18 add the outputs of the multipliers 16 and 17 to the signals Y and X, respectively, and output the chrominance-corrected color difference signals RY and BY components, respectively. 1
9 and 22. FIG. 3 shows the effect of correcting the hue point when T1 is 0 degree, T2 is 60 degrees, and T0 is 30 degrees in FIG. In FIG. 3, the black circles are before correction, and the white circles are after correction. At this time, the hue point is represented by a straight line L0.
, The saturation (color density) changes, and the change in hue is small.

The means for correcting the saturation in the color correction has been described above. However, description will be given because hue can be further corrected. The multiplier 14 converts the input signal from the limiter 12 into Gai
The signal V4 is obtained by multiplying by n2 and supplied to the multipliers 20 and 21. The multiplier 20 multiplies the signal V4 by the signal r4 of sin (T0), and the multiplier 17 multiplies the signal V4 by the signal b4 of cos (T0), thereby obtaining the signal V4.
* Sin (T0) and V4 * cos (T0) are output.

The coefficients r4 and b4 are calculated by the multipliers 20 and 21.
, The amount of movement for actually moving the hue points in the area A in the direction orthogonal to the straight line L0 is obtained. That is, the multipliers 20 and 21 correspond to the multiplier 1
4 operates as a hue moving means for moving the hue point in the direction orthogonal to the straight line L0 by the correction amount output via the control unit 4. The moving direction moves in a direction in which the angle from the Y axis decreases when Gain2 is positive, and in a direction in which the angle increases when negative, and the amount of movement is determined by the magnitude of the absolute value of Gain2.

FIG. 4 shows the effect of correcting the hue point when T1 is 0 degrees, T2 is 60 degrees, and T0 is 30 degrees in FIG. In FIG. 4, the black circles are before correction, and the white circles are after correction. At this time, since the hue point moves in a direction orthogonal to the straight line L0, the hue changes and the change in saturation (color density) is small. Then, the adder 19 adds the output of the multiplier 20 to the chroma-corrected color difference signal RY that is the output of the adder 15, and the chroma-corrected and hue-corrected color difference signal RY. And outputs it from the output terminal 23. Similarly, the adder 20 adds the output of the multiplier 21 to the chroma-corrected color difference signal BY that is the output of the adder 18,
Obtaining a color difference signal BY that has undergone saturation correction and hue correction,
The signal is output from the output terminal 24.

As described above, the color correction circuit according to the present invention can correct the saturation and the hue only in the vicinity of a specific hue from two color difference signals. By connecting a plurality of the configurations shown in FIG. 1 in cascade, it is possible to correct the saturation and the hue only in the vicinity of each of a plurality of specific hue points. The present invention
The present invention can be used for color correction of a specific color (for example, green) of a video signal when displaying a video signal on a display device, color correction of a specific color of a video signal input by a television camera or the like.

[0021]

According to the color correction circuit of the present invention, the hue points of the entire region do not move under the influence of the correction, and the saturation and the hue can be corrected only in the vicinity of a specific hue point.
In addition, there is an extremely excellent effect such as realization with a small circuit scale.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram for explaining the present invention.

FIG. 3 is a diagram illustrating a saturation correction effect of the present invention.

FIG. 4 is a diagram showing a hue correction effect of the present invention.

[Explanation of symbols]

1, 2, input terminal 3, 4, 6, 8, 13, 14, 16, 17, 20, 21
Multipliers 4, 7, 15, 18, 19, 22 Adders 9, 10, 12 Limiters 11 Minimum value selector (MIN) 23, 24 Output terminals

Claims (2)

[Claims] 1. A color correction circuit for correcting a color near a specific hue to be corrected, wherein one color difference signal component of two color difference signals is set to an X axis and the other color difference signal component is set to a Y axis. At this time, first and second equal hue straight lines sandwiching the specific hue straight line which is the same hue straight line corresponding to the specific hue on the X and Y planes are set, and the first and second straight hue straight lines including the specific hue straight line are set. Extraction means for extracting only hue points in an area formed between equal hue straight lines, and saturation correction means for moving hue points in the area in a direction parallel to the specific hue straight line are provided. A color correction circuit, characterized in that: 2. A color correction circuit according to claim 1, further comprising a hue correction means for moving a hue point in said area in a direction orthogonal to said specific hue straight line.