JPH06189331A - Picture signal processing device - Google Patents

Abstract

PURPOSE:To obtain the picture signal processing device implementing white balance correction with high accuracy and simple configuration in spite of its being a luminance color difference signal system. CONSTITUTION:A white balance coefficient setting means 51 is used to set a white balance coefficient of a video signal. A white balance correction coefficient decision means 52 decides two white balance correction coefficients acting on a luminance signal of the video signal based on a white balance coefficient set to the white balance coefficient setting means 51. A luminance signal arithmetic operation means 59 multiplies respectively two white balance correction coefficients and a luminance signal decided by the white balance correction coefficient decision means 52 to obtain two output signal. A 1st adder 57 adds one of the two output signals obtained by a luminance signal arithmetic operation means 59 with a 1st color difference signal of the video signal. A 2nd adder 58 adds the other of the two output signals obtained by the luminance signal arithmetic operation means 59 with a 2nd color difference signal of the video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal processing device for performing white balance correction of a color video signal composed of a luminance signal and a color difference signal.

[0002]

2. Description of the Related Art Conventionally, equipment that handles RGB video signals,
For example, in a three-tube camera for business use, when white balance is to be achieved, an appropriate optical filter is attached according to the color temperature of the light source, and the part that cannot be completely corrected is converted into an RGB signal when a white paper is photographed. The correction is performed by multiplying each of the RGB signals by a white balance coefficient that sets the ratio to 1.

As described above, in the RGB system, the deviation of the white balance is checked at the level of the RGB signal, and the correction value obtained thereby is used to correct the RGB signal. Therefore, generally, the accuracy is very high. Is. On the other hand, in a single-chip camera typified by a video movie, most of them handle a luminance signal and a color difference signal instead of the RGB system. In such a luminance / color difference signal system, the white balance coefficient of RGB cannot be directly used for correction.

At present, white balance correction in the luminance color difference signal system is performed by a method in which the luminance color difference signal is once converted into RGB signals, and the converted signal is subjected to RGB white balance correction. The following (Equation 6) shows the white balance correction formula of the luminance color difference signal system. In (Equation 6), Y is a luminance signal,
RY and BY are color difference signals, and Kr, Kg, and Kb are R respectively.
It is an amplification value for the signal, the G signal, and the B signal.

The central matrix on the right side of this equation is a matrix for converting a luminance color difference signal into an RGB signal, and the leftmost matrix on the right side is an RGB signal representing a luminance color difference signal R.
It is a matrix obtained by multiplying a matrix for changing to a GB signal by a white balance coefficient.

[0006]

[Equation 6]

Here, since Kr, Kg, and Kb have the relationship shown in the following (Equation 7) as a condition for not changing the brightness before and after the white balance correction, this equation is substituted into (Equation 6). When organized, it can be expressed as in (Equation 8).

[0008]

[Equation 7]

[0009]

[Equation 8]

When the above white balance correction formula is realized by a circuit, it is considerably complicated, the circuit scale becomes large, and the cost becomes high. Therefore, it is not suitable for incorporation into a small and simple device such as a video movie. Therefore, conventionally, in a video movie or the like, white balance is performed by using a simple color adjustment circuit that does not rely on the correction formula shown in (Equation 8). FIG. 1 is a circuit block diagram of a main part of a conventional image signal processing device of a luminance / color difference signal system having such an adjusting circuit. This image signal processing device includes a color CCD sensor 91 and a color adjusting circuit 92.
And a gamma correction circuit 93 and an encoder 94. The color CCD sensor 91 outputs a luminance signal Y and color difference signals R-Y and B-Y according to the captured image. The color adjustment circuit 92 performs white balance correction on the luminance signal Y and the color difference signals RY and BY from the color CCD sensor 91. The gamma correction circuit 93 performs gamma correction on the output signal of the color adjustment circuit 92. The encoder 94 converts the output signal of the gamma correction circuit 93 into an NTSC signal.

In this conventional image signal processing device, the white balance correction is performed by the color adjusting circuit 92 based on the following (Equation 9). However, Kr and Kb in the equation are white balance coefficients.

[0012]

[Equation 9]

[0013]

The qualitative meaning of the above equation 4 is to move the coordinates of the input video signal in parallel on the color difference plane consisting of the two color difference signals R-Y and B-Y. The white color can be corrected to an arbitrary color, but for other colors, the more saturated the color is from the origin, the more balanced the color is, and the correct correction cannot be performed. Table 1 shows a comparison result between the ideal luminance color difference value at the time of white balance correction and the luminance color difference signal value according to the conventional method. In the conventional method, Kr = −0.03 and Kb = 0.07 are set so that no error occurs at R = G = B = 0.5. According to (Table 1), in the conventional method, the colors are shifted as a whole, and the BY signal is shifted by 50% or more particularly at R = 0, G = 0. 2, and B = 0. This is a very different color in terms of color. Table 2 shows the luminance color difference values obtained in Table 1 converted to RGB and expressed in 256 gradations. From Tables 1 and 2, it is confirmed that the conventional method is totally deviated from the ideal color.

[0014]

[Table 1]

[0015]

[Table 2]

Therefore, an object of the present invention is to propose an image processing apparatus which can realize white balance correction of a luminance / color difference signal system with a small number of parts and a small circuit scale. Another object of the present invention is to propose an image processing apparatus capable of performing white balance correction without greatly disturbing the balance of highly saturated colors apart from the origin white.

Still another object of the present invention is to provide an image processing apparatus capable of realizing a correction substantially equivalent to the correction by the white balance correction formula shown in (Equation 8) with a simpler configuration than (Equation 8). To provide. Still another object of the present invention is to provide an image processing apparatus capable of adjusting hue and saturation in addition to white balance correction.

[0018]

In order to achieve the above object, the invention of claim 1 is an image processing apparatus for performing adjustment including white balance correction on a luminance color difference signal, and two correction coefficients to be applied to the luminance signal. A matrix of 2 rows and 1 column, a correction coefficient generating means for generating a matrix of 2 rows and 2 columns consisting of four correction coefficients that act on two color difference signals, and a matrix of 2 rows and 1 column and a luminance signal. Obtained from first multiplying means for multiplying, second multiplying means for multiplying the matrix of 2 rows and 2 columns and a matrix of 2 rows and 1 column consisting of two color difference signals, and first and second multiplying means. And an addition unit that obtains the correction value of the two color difference signals by obtaining the sum of a matrix of 2 rows and 1 column consisting of two multiplication values.

According to a second aspect of the present invention, the matrix of 2 rows and 1 column generated by the correction coefficient generating means is

[0020]

[Equation 10]

And the matrix of 2 rows and 2 columns is

[0022]

[Equation 11]

It is characterized in that However,
K _r and K _b are amplification factors for the R signal and the B signal. According to a third aspect of the present invention, the matrix of 2 rows and 1 column generated by the correction coefficient generating means is

[0024]

[Equation 12]

It is characterized in that the matrix of 2 rows and 2 columns is a unit matrix. According to a fourth aspect of the present invention, the matrix of 2 rows and 1 column generated by the correction coefficient generating means is

[0026]

[Equation 13]

And the matrix of 2 rows and 2 columns is

[0028]

[Equation 14]

It is characterized in that

[0030]

According to the first and second aspects of the present invention, the strict white balance correction formula for the luminance and color difference signals (Equation 8) is much simpler than the case where it is constituted by a logic circuit. Since the performance itself is handled by simply ignoring the luminance signal, there is an effect that it is not much different from the correction performance of (Equation 8).

According to the invention of claim 3, the performance of white balance correction is slightly deteriorated, but the circuit scale is further simplified. According to the invention of claim 4, in addition to the white balance correction, the saturation and hue can be adjusted with a simple structure.

[0032]

(Embodiment 1) FIG. 2 is a circuit block diagram of a main part of an image signal processing apparatus according to a first embodiment of the present invention. This image signal processing apparatus includes a white balance coefficient setting means 11 and a white balance. Correction coefficient determination means 12 and first register 13
, The second register 14, the first multiplier 15, and the second
Multiplier 16, a third register 18, a fourth register 19, a fifth register 20, and a sixth register 21
A third multiplier 22, a fourth multiplier 23, a fifth multiplier 24, a sixth multiplier 25, an R adder 26,
B adder 27, first adder 29, and second adder 3
It has 0 and. The first register 13, the second register 14, the first multiplier 15, and the second multiplier 16 constitute a luminance signal calculation means 32, and the third register 18
And fourth register 19, fifth register 20, sixth register 21, third multiplier 22, fourth multiplier 23, fifth multiplier 24, sixth multiplier 25 and R adder 26 and B
The adder 27 constitutes a matrix calculation means 33. The white balance coefficient setting means 11 is for setting the amplification ratio of red (R), green (G), and blue (B) of the video signal, that is, the white balance coefficients Kr, Kg, Kb.
Specifically, for example, a variable resistor (not shown) or the like may be provided and configured manually, or may be configured automatically based on an input signal. Since the white balance coefficients Kr, Kg, Kb have the relationship of the above-mentioned (Equation 7), only the white balance coefficients Kr, Kb are finally output from the white balance coefficient setting means 11. The white balance correction coefficient determination means 12 is based on the white balance coefficients Kr and Kb from the white balance coefficient setting means 11 and is composed of a first white balance correction coefficient group A1 composed of two white balance correction coefficients to be applied to the luminance signal Y. , A2,
A second white balance correction coefficient group B composed of four white balance correction coefficients to be applied to the two color difference signals R-Y and B-Y.
A total of six white balance coefficients of 1, B2, B3, and B4 are determined. First white balance correction coefficient group A1, A2 and second white balance correction coefficient group B1, B2, B3, B4
Is shown in the following (Equation 15) to (Equation 20).

[0033]

[Equation 15]

[0034]

[Equation 16]

[0035]

[Equation 17]

[0036]

[Equation 18]

[0037]

[Formula 19]

[0038]

[Equation 20]

The first register 13 has a white balance correction coefficient A determined by the white balance correction coefficient determining means 12.
1 is set. The white balance correction coefficient A2 determined by the white balance correction coefficient determination means 12 is set in the second register 14. The first multiplier 15 multiplies the white balance correction coefficient A1 set in the first register 13 and the luminance signal Y. The second multiplier 16 has a second
White balance correction coefficient A2 set in the register 14 of
And the luminance signal Y are multiplied. The third register 18 is
The white balance correction coefficient B1 determined by the white balance correction coefficient determination means 12 is set. Fourth register 1
In 9, the white balance correction coefficient B2 determined by the white balance correction coefficient determination means 12 is set. The white balance correction coefficient B3 determined by the white balance correction coefficient determining unit 12 is set in the fifth register 20. Sixth
The white balance correction coefficient B4 determined by the white balance correction coefficient determining means 12 is set in the register 21 of FIG. The third multiplier 22 receives the white balance correction coefficient B1 set in the third register 18 and the input color difference signal R
-Multiply with Y. The fourth multiplier 23 multiplies the white balance correction coefficient B2 set in the fourth register 19 and the input color difference signal RY. Fifth multiplier 2
4 multiplies the white balance correction coefficient B3 set in the fifth register 20 and the input color difference signal BY. The sixth multiplier 25 receives the white balance correction coefficient B4 set in the sixth register 21 and the input color difference signal B
-Multiply with Y. The R adder 26 is the third multiplier 2
The multiplication result by 2 and the multiplication result by the fifth multiplier 24 are added. The B adder 27 adds the multiplication result of the fourth calculator 23 and the multiplication result of the sixth multiplier 25.
The first adder 29 adds the multiplication result of the first multiplier 15 and the addition result of the R adder 26. The second adder 30 adds the multiplication result of the second multiplier 16 and the addition result of the B calculator 27.

The color difference signals (RY) 'and (BY)' obtained as a result of the calculation by the adders 26, 27, 29, 30 and the multipliers 15, 16, 22 to 25 are input. When expressed using the luminance color difference signals Y, RY, and BY, (Equation 21)
become that way. It can be seen from (Equation 21) that the white balance-corrected color difference signal is expressed by an addition formula of the luminance signal Y and the color difference signals R-Y and B-Y.

[0041]

[Equation 21]

Here, when (Equation 21) is compared with (Equation 8), which is a strict white balance correction formula, (Equation 21) expresses (Equation 8) as (RY) 'and (BY)'. It is understood that it is a summary of. That is, it can be said that (Equation 21) intentionally ignores the luminance signal Y ′ of (Equation 8).
By the way, depending on how much the white balance correction is affected by ignoring one signal component, the present inventors considered as follows. That is, white balance correction becomes substantially impossible if important signal components such as the color difference signals RY or BY are ignored, but white balance correction is made even if the luminance signal having a low contribution to white balance is ignored. I thought that it would not have much effect on.

This is a theoretical consideration of the white balance correction ignoring the luminance signal component Y ', but it has been confirmed that the white balance correction can be realized with considerable accuracy in practice when the white balance correction is performed based on (Equation 21). . Table 3 shows a comparison between the luminance color difference signal component based on the white balance correction of (Equation 8) and the luminance color difference signal component based on the white balance correction of (Equation 21) for various input signals. . From this table, for most input signals, the white balance correction of (Equation 21) differs from that of (Equation 8) by at most about 0.01 to 0.02, and there is no big difference, and therefore, the highly accurate white balance correction. It can be understood that the correction can be performed. From the viewpoint of the circuit configuration, it can be understood that 6 multipliers and 4 adders are sufficient, and a great simplification can be achieved as compared with the case where (Equation 8) is realized by a logic circuit.

Further, (Table 4) shows the luminance color difference values of (Table 3) converted into RGB and expressed in 256 gradations. It can be confirmed from this table that a highly accurate white balance has been achieved.

[0045]

[Table 3]

[0046]

[Table 4]

(Embodiment 2) FIG. 3 shows a second embodiment of the present invention. In this embodiment, the circuit configuration is further simplified as compared with the first embodiment, and the white balance coefficient setting means 51
A white balance correction coefficient determining means 52, a first register 53, a second register 54, and a first multiplier 55.
, A second multiplier 56, a first adder 57, and a second adder 58. The first register 53, the second register 54, the first multiplier 55, and the second multiplier 56.
And constitute a luminance signal calculation means 59. The white balance coefficient setting means 51 uses the red (R), green (G),
Amplification ratio of blue (B), that is, white balance coefficients Kr, Kg,
It is for setting Kb. The white balance correction coefficient determining means 52 determines two white balance correction coefficients A1 and A2 to be applied to the luminance signal Y based on the white balance coefficients Kr and Kb from the white balance correction coefficient determining means 51. These white balance correction coefficients A1 and A2 are the same as A1 and A2 in the first embodiment. First
In the register 53, the white balance correction coefficient A1 determined by the white balance correction coefficient determination means 52 is set. The second register 54 has a white balance correction coefficient A2 determined by the white balance complementary coefficient determination means 52.
Is set. The first multiplier 55 has a first
The white balance positive coefficient A1 set in the register 53 is multiplied by the luminance signal Y. The second multiplier 56 multiplies the white balance correction coefficient A2 set in the second register 4 by the luminance signal Y. The first adder 57 adds the output of the first multiplier 55 and the input color difference signal RY. The second adder 58 adds the output of the second multiplier 56 and the input color difference signal BY. The color difference signals (RY) ′ and (BY) ′ obtained as a result of the calculation by the multipliers 55 and 56 and the adders 57 and 58 are converted into Y, RY, and BY on the input side. It can be expressed by using (Equation 22).

[0048]

[Equation 22]

In the above (Equation 22), the color difference signal (R-
Y) ′ and (B−Y) ′ are given by the addition of Y and R−Y and B−Y. The formulas are represented by the white balance correction formula (Equation 21) in the first embodiment. It can be said that they have commonality. Rather, the coefficient of RY and BY in (Equation 21) is changed to 1 (Equation 22).
Is. In this way, the R-Y and B-Y coefficients are forcibly set to 1
Table 5 shows how much the white balance correction is affected when the value is changed to. However, in the table, the obtained luminance color difference value is a value corrected by using (Equation 8) as in the case of the corresponding one in (Table 3). As can be seen from (Table 5), most of the luminance color difference values in this embodiment are 0.01 to 0.02 as compared with those corrected using (Equation 8).
The difference is up to a degree, and it is the highest that the BY signal makes a difference of 0.07 when R = G = 0 and B = 0.6.
Therefore, as compared with the conventional method of (Table 1), the difference in luminance color difference value is sufficiently small. In fact, it can be understood that when the white balance correction according to the present embodiment is performed, what kind of reproduced color is obtained for each input color is quite faithful as shown in (Table 6). Note that (Table 6) is (Table 5)
The luminance color difference value of is converted into RGB and is expressed in 256 gradations.

[0050]

[Table 5]

[0051]

[Table 6]

(Embodiment 3) FIG. 4 is a circuit block of an essential part of a printer device equipped with an image signal processing device according to a third embodiment of the present invention. This printer device comprises a YC separation circuit 61 and a decoder 62. , A / D converter 63, frame memory 64, hue / color adjustment value setting means 65, white balance coefficient setting means 66, and white balance / color adjustment circuit 6
7, an image processing circuit 68, a head drive circuit 69, a thermal head 70, a D / A converter 71, an encoder 72, and a mixing circuit 73. The YC separation circuit 61 converts the input NTSC signal into luminance signals Y and C.
Separated into signal.

The decoder 62 converts the C signal from the YC separation circuit 61 into color difference signals RY and BY. The A / D converter 63 converts the luminance signal Y from the YC separation circuit 61 and the color difference signals RY and BY from the decoder 62 from analog into digital. The frame memory 64 stores the luminance signal Y and the color difference signals RY and BY for one screen. The hue / saturation adjustment value setting means 65 is for setting an adjustment value for adjusting the hue and saturation of the video signal stored in the frame memory 64.

The white balance coefficient setting means 66 is for setting the amplification ratio of red (R), green (G) and blue (B) of the video signal, that is, the white balance coefficients Kr, Kg and Kb.
The same structure as that described in the first and second embodiments is used. The white balance / color adjustment circuit 67 performs white balance correction and color adjustment based on each set value given from the hue / saturation adjustment value setting means 65 and the white balance coefficient setting means 66. The image processing circuit 68 subjects the output signal of the white balance / color adjustment circuit 67 to, for example, edge enhancement processing, color correction processing, color conversion processing, etc., and outputs a Ye signal and a Mg signal based on the print amounts of yellow, magenta, and cyan. , Cy
Output a signal. The head drive circuit 69 outputs a pulse signal based on the Ye signal, the Mg signal, and the Cy signal from the image processing circuit 68, and the thermal head 70 prints an image. The D / A converter 71 converts the luminance signal Y and the color difference signals (RY) ′ and (BY) ′, which have been subjected to white balance correction and color adjustment by the white balance / color adjustment circuit 67, into analog values. . The encoder 72 is a D / A converter 71
The color difference signals (R-Y) 'and (B-Y)' are converted into C signals. The mixing circuit 73 synthesizes the luminance signal Y from the D / A converter 71 and the C signal from the encoder 72 to generate an NTSC signal. This NTSC signal is CR
Displayed on T. The luminance signal Y and the color difference signals (RY) ′ and (BY) ′ input to the D / A converter 71.
Are the same as the luminance signal Y and the color difference signals (RY) ′ and (BY) input to the image processing circuit 68.

FIG. 5 is a circuit block of the white balance / color adjusting circuit 67.
01, the first register 102, and the second register 10
3, a first multiplier 104, a second multiplier 105,
The third register 107, the fourth register 108, the fifth register 109, the sixth register 110, and the third register 107.
Multiplier 111, the fourth multiplier 112, the fifth multiplier 113, the sixth multiplier 114, and the R adder 115.
And a B adder 116, a first adder 118, and a second adder 119. First register 102
The second register 103, the first multiplier 104, and the second multiplier 105 constitute the luminance signal calculation means 201, and the third register 107, the fourth register 108, and the fifth register 109. And sixth register 110, third multiplier 111, fourth multiplier 112 and fifth multiplier 113
And sixth multiplier 114, R adder 115, and B adder 11
6 constitutes the matrix calculation means 202. MP
U101 consists of, for example, a one-chip microcomputer,
The hue adjustment value θ and the saturation adjustment value S given from the hue / saturation adjustment value setting means 65, and the white balance coefficient setting means 6
6, the red signal amplification factor, that is, the white balance coefficient Kr, and the blue signal amplification factor, that is, the white balance coefficient K
b from the first color difference signal correction coefficient group C1, C2 and the second
Color difference signal correction coefficient groups D1, D2, D3, D4 are calculated, and they are calculated by the first to sixth registers 102, 103, 1
Set to 07-110. The above C1, C2, D1 to D4
The respective coefficients are shown in the following (Equation 23) to (Equation 28).

[0056]

[Equation 23]

[0057]

[Equation 24]

[0058]

[Equation 25]

[0059]

[Equation 26]

[0060]

[Equation 27]

[0061]

[Equation 28]

The multipliers 104, 105, 111 to 1 shown in FIG.
If the arithmetic operation performed by 14 and the adders 115, 116, 118, and 119 is expressed by an equation, the following (Formula 29) is obtained.

[0063]

[Equation 29]

However, C1, C2 and D1 to D4 are coefficients given by the above (Equation 23) to (Equation 28). here,
(Equation 29) can be rewritten as Equation 30 below.

[0065]

[Equation 30]

The expression (30) can be considered as a value obtained by rotating the white balance corrected value of the first embodiment by the hue adjustment value θ and increasing the value by the saturation adjustment value S.
Next, the operation of the apparatus shown in FIG. 4 will be described. First, when an NTSC signal is input, the YC separation circuit 61 separates the NTSC signal into a luminance signal Y and a C signal, supplies the luminance signal Y to the A / D converter 63, and supplies the C signal to the decoder 62. Supply.
This causes the decoder 62 to convert the C signal to the color difference signal RY,
It is decoded into BY and supplied to the A / D converter 63. As a result, the A / D converter 63 sequentially supplies the luminance signal Y and the color difference signals RY and BY to the frame memory 64. As a result, the frame memory 64 stores the luminance signal Y and the color difference signals RY and BY for one frame. On the other hand, the operator inputs the white balance coefficients Kr and Kb to the white balance coefficient setting means 66 and the hue / saturation adjustment value setting means 6
5, the hue adjustment value θ and the saturation adjustment value S are respectively set, and when the respective values are input, the MPU 101 calculates each color difference signal correction coefficient C1, C2, D1 to D4, and the color difference signal correction coefficient C1. To the first register 102, the color difference signal correction coefficient C2 to the second register 103, the color difference signal correction coefficient D1 to the third register 107, the color difference signal correction coefficient D2 to the fourth register 108, and the color difference signal correction coefficient. D3
Is set in the fifth register 109, and the color difference signal correction coefficient D4 is set in the sixth register 110. And the first
Of the luminance signal Y from the frame memory 64 and the color difference signal correction coefficient C1 from the first register 102.
And the second multiplier 105
4 and the color difference signal correction coefficient C2 from the second register 103, and the third multiplier 111
The color difference signal R-Y from the frame memory 64 is multiplied by the color difference signal correction coefficient D1 from the third register 107, and the fourth multiplier 112 calculates the color difference signal R-Y signal from the frame memory 64 and the fourth color difference signal R-Y. Of the color difference signal correction coefficient D2 from the register 108 and the fifth multiplier 113 multiplies the color difference signal BY signal from the frame memory 64 by the color difference signal correction coefficient D3 from the fifth register 109. And then the 6th
Of the color difference signal BY from the frame memory 64 is multiplied by the color difference signal correction coefficient D4 from the sixth register 110. Then, the R adder 115 adds the multiplication result by the third multiplier 111 and the multiplication result by the fifth multiplier 113, and the B adder 116 adds the multiplication result by the fourth multiplier 112 and the sixth result. And the result of multiplication by the multiplier 114 are added. Then, the first adder 118
A new color difference signal (RY) ′ is obtained by adding the multiplication result of the first multiplier 104 and the addition result of the R adder 115.
Of the image processing circuit 68 and the D / A converter 71.
And the second adder 119 supplies the second multiplier 105
And the addition result of the B adder 116 are added to obtain a new color difference signal (BY) ′, which is supplied to the image processing circuit 68 and the D / A converter 71. Thus, the color difference signals (RY) 'and (BY)' are obtained.

As a result, the image processing circuit 68 performs edge enhancement processing, color correction processing, and color conversion on the new color difference signals (RY) ', (BY)' and the unprocessed luminance signal Y. By processing, the Ye signal, the Mg signal, and the Cy signal based on the print amounts of yellow, magenta, and cyan are generated and supplied to the head drive circuit 69. As a result, the head drive circuit 69 converts the Ye signal, the Mg signal, and the Cy signal into pulse signals and supplies them to the thermal head 70. As a result, the thermal head 70 prints an image that has been color-adjusted with the white-balance-corrected signal.

Further, the D / A converter 71 D / A converts the new color difference signals (RY) 'and (BY)' and the unprocessed luminance signal Y into an analog color difference signal. (R-
Y) ′ and (B−Y) ′ are supplied to the encoder 72, and the analog luminance signal Y is supplied to the mixing circuit 73. As a result, the encoder 72 causes the color difference signal (R-
Y) 'and (B-Y)' are converted to C signals and supplied to the mixing circuit 73. As a result, the mixing circuit 73
An NTSC signal is produced by synthesizing the C signal and the luminance signal Y. The NTSC signal is input to a CRT (not shown) so that the color of the image finally displayed on the CRT and the color of the image printed by the thermal head 70 are almost the same. In this way, the white balance coefficient setting means 66 for setting the white balance coefficients Kr and Kb of the video signal, and the MPU 101.
The first white balance correction coefficient, which is realized by the above-mentioned method, and which acts on the luminance signal Y based on the white balance coefficients Kr and Kb set in the white balance coefficient setting means 66.
Second white balance correction coefficient group B1, B2, B consisting of four white balance correction coefficient groups A1 and A2 and four white balance correction coefficients applied to the two color difference signals RY and BY.
A total of 6 white balance correction coefficients A1 and A of 3 and B4
A white balance correction coefficient determining means for determining 2, B1, B2, B3, and B4 and a part of the hue / saturation adjustment value setting means 65 are provided to set a hue adjustment value θ for adjusting the hue of the video signal. A saturation adjustment value setting means for setting the saturation adjustment value S for adjusting the saturation of the video signal, which is realized by a part of the hue adjustment value setting means and the hue / saturation adjustment value setting means 65. Means and the hue adjustment value θ set in the hue adjustment value setting means and the saturation adjustment value S set in the saturation adjustment value setting means, which is realized by the MPU 101.
Color adjustment coefficient determining means for determining a color adjustment coefficient group consisting of four color adjustment coefficients to be applied to one color difference signal RY and BY, and realized by the MPU 101 and determined by the white balance correction coefficient determining means. It is applied to the luminance signal Y based on the first white balance correction coefficient group A1, A2 and the color adjustment coefficient group determined by the color adjustment coefficient determination means 2
First color difference signal correction coefficient groups C1 and C2 composed of two color difference signal correction coefficients;
A second white balance correction coefficient group B realized by the MPU 101 and determined by the white balance correction coefficient determination means.
Two color difference signals R− based on 1, B2, B3, B4 and the color adjustment coefficient group determined by the color adjustment coefficient determining means.
Second coefficient calculation means for newly determining a second color difference signal correction coefficient group D1, D2, D3, D4 composed of four color difference signal correction coefficients to be applied to Y and BY, and a first coefficient calculation means. Luminance signal calculation means 201 for obtaining two output signals by respectively multiplying the two color difference signal correction coefficients C1 and C2 of the first color difference signal correction coefficient group determined by Four color difference signal correction coefficients D1 and D of the second color difference signal correction coefficient group determined by the means.
2, D3, D4 and two color difference signals RY, BY
A matrix calculation means 202 for performing a matrix operation of × 2 to obtain two output signals, one of the two output signals of the luminance signal calculation means 201, and the matrix calculation means 20.
A first adder 118 for adding one of the two output signals of 2; the other of the two output signals of the luminance signal calculation means 201 and the other of the two output signals of the matrix calculation means 202. And a second adder 119 for adding and, the color adjustment is performed using the signal of which the white balance of the video signal has been corrected. Therefore, when the white balance is corrected, a color having a large saturation is obtained. However, the color does not deviate from the color actually desired. Further, as described above, by reflecting the color adjustment coefficient in the coefficient applied to the luminance signal Y as well, a printer device capable of performing correction equivalent to performing color adjustment on the signal after white balance correction is provided. It can be realized with a simple configuration. If the color adjustment coefficient is not reflected in the coefficient to be applied to the luminance signal Y, it becomes meaningless as a process of performing color adjustment on a signal that does not have white balance and then performing white balance correction. .

At present, most printers capable of color adjustment are provided with the matrix calculating means 202, and therefore the white balance coefficient setting means 66, the luminance signal calculating means 201, and the first and second adders 118. , 119, and by performing calculation based on the above equation 29, both accurate white balance correction and color adjustment can be realized.

Table 7 shows three input signals RGB = (0.
The luminance and color difference values obtained by the apparatus of the first embodiment for 6 0 0) (0 0.6 0) (0 0 0.6) are obtained by rotating the hue (θ) by ± 10 ° and the saturation S is set to 0.5 times. The result obtained by multiplying by 1.5 is represented by a luminance color difference value.
Table 8 shows the same input signal as RGB values of 256 gradations. Further, FIG. 6 is a plot of (Table 7) on the BY and RY planes. From these tables and figures, it can be seen that the color adjustment of the signal after the white balance correction can be performed without destroying the white balance correction.

[0071]

[Table 7]

[0072]

[Table 8]

In each of the above embodiments, the operator sets the white balance coefficient, but the white balance coefficient is automatically obtained from the information of the input image using fuzzy inference or the like and set. May be. Further, in each of the above embodiments, the MPU 101 realizes the white balance correction coefficient determination means, the color adjustment coefficient determination means, and the first and second coefficient calculation means, but each means is made to have a single function and each function is performed. The configuration may be shared.

Further, in the third embodiment, the hue and saturation are adjusted for the color difference signal which is the white balance correction value of the first embodiment, but the white balance correction of the second embodiment is performed. Of course, the hue and saturation may be adjusted with respect to the value. In that case, the circuit configuration becomes simpler.

[0075]

As described above, according to the first and second aspects of the invention, the strict white balance correction formula (equation 8) for the luminance and color difference signals is remarkably simple as compared with the case where the logic circuit is used. In addition, since the performance of white balance correction itself is handled by simply ignoring the luminance signal, there is an effect that it is not much different from the correction performance of (Equation 8).

Further, according to the invention of claim 3, the performance of white balance correction is slightly deteriorated, but there is an effect that the circuit scale is further simplified. According to the invention of claim 4, in addition to the white balance correction, the saturation and hue can be adjusted with a simple structure.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional image processing apparatus.

FIG. 2 is a diagram showing an image processing apparatus as an embodiment of the present invention.

FIG. 3 is a diagram showing an image processing apparatus as another embodiment of the present invention.

FIG. 4 is a diagram showing an application example of the present invention.

FIG. 5 is a diagram showing still another embodiment of the present invention.

FIG. 6 is a diagram showing changes in three RGB values due to hue adjustment and saturation adjustment.

[Explanation of symbols]

 11 white balance coefficient setting means 12 white balance correction coefficient determining means 29 first adder 30 second adder 32 luminance signal calculating means 33 matrix calculating means 51 white balance coefficient setting means 52 white balance correction coefficient determining means 57 first Adder 58 Second adder 59 Luminance signal calculation means 65 Hue / saturation adjustment value setting means 66 White balance coefficient setting means 101 MPU 118 First adder 119 Second adder 201 Luminance signal calculation means 202 Matrix Computing means

Claims (7)

[Claims] 1. An image processing apparatus for performing adjustment including white balance correction on a luminance color difference signal, wherein a matrix of 2 rows and 1 column made up of two correction coefficients acting on the luminance signal and acting on the two color difference signals. A correction coefficient generating means for generating a matrix of 2 rows and 2 columns consisting of four correction coefficients, and a first for multiplying the matrix of 2 rows and 1 column by the luminance signal.
2 consisting of a matrix of 2 rows and 2 columns and two color difference signals
2 consisting of a second multiplication means for multiplying the matrix of row 1 column and two multiplication values obtained from the first and second multiplication means
An image processing apparatus comprising: an addition unit that obtains a sum of a row-one-column matrix to obtain a correction value of two color difference signals. 2. The 2 rows 1 generated by the correction coefficient generating means
The matrix of columns is And the matrix of 2 rows and 2 columns is The image processing apparatus according to claim 1, wherein
However, K _r and K _b are amplification degrees for the R signal and the B signal. 3. The 2 rows 1 generated by the correction coefficient generating means
The matrix of columns is 2. The image processing apparatus according to claim 1, wherein the matrix of 2 rows and 2 columns is a unit matrix. However,
Kr and Kb are amplification degrees for the R signal and the B signal. 4. Two lines 1 generated by the correction coefficient generating means
The matrix of columns is And the matrix of 2 rows and 2 columns is The image processing apparatus according to claim 1, wherein
Here, K _{r and} K _b are the R and B signal amplification levels, S is the saturation adjustment value, and θ is the hue adjustment value. 5. An image processing apparatus for performing white balance correction on a color difference signal, comprising: a white balance coefficient setting means for setting a white balance coefficient of a video signal; and a white balance set in the white balance coefficient setting means. 2) It acts on the luminance signal of the video signal based on the coefficient.
White balance correction coefficient determining means for determining two white balance correction coefficients, and a luminance signal for obtaining two output signals by multiplying the two white balance correction coefficients and the luminance signal determined by the white balance correction coefficient determining means, respectively. A calculation unit, a first adder that adds one of the two output signals obtained by the luminance signal calculation unit and the first color difference signal of the video signal, and the luminance signal calculation unit. A second adder that adds the other of the two output signals and the second color difference signal of the video signal, and the added value of the first adder is output as the white balance correction value of the first color difference signal. An image processing apparatus comprising: a first output unit; and a second output unit that outputs the added value of the second adder as a white balance correction value of a second color difference signal. 6. An image processing device for performing white balance correction on a color difference signal, comprising: a white balance coefficient setting means for setting a white balance coefficient of a video signal; and a white balance set in the white balance coefficient setting means. A first white balance correction coefficient group consisting of two white balance correction coefficients acting on the luminance signal based on the coefficient, and a second white balance correction coefficient consisting of four white balance correction coefficients acting on the two color difference signals. A white balance correction coefficient determining means for determining a total of six white balance correction coefficients for the group; and a first white balance correction coefficient determining means for determining the white balance correction coefficient.
Luminance signal calculation means for obtaining two output signals by respectively multiplying the two white balance correction coefficients of the white balance correction coefficient group and the luminance signal, and the second white balance correction coefficient determined by the white balance correction coefficient determination means.
2 × 2 matrix calculation of the four white balance correction coefficients of the white balance correction coefficient group and the two color difference signals is performed to obtain 2
Matrix calculating means for obtaining one output signal; a first adder for adding one of the two output signals of the luminance signal calculating means and one of the two output signals of the matrix calculating means; A second adder for adding the other of the two output signals of the luminance signal calculation means and the other of the two output signals of the matrix calculation means, and a first output means having the same contents as in claim 5. An image processing apparatus comprising: a second output unit having the same contents as claim 5. 7. An image processing device for performing white balance correction, hue and saturation adjustment on a color difference signal, comprising: a white balance coefficient setting means for setting a white balance coefficient of a video signal; On the basis of the white balance coefficient set in the means, a first white balance correction coefficient group consisting of two white balance correction coefficients acting on the luminance signal and four white balance correction coefficients acting on two color difference signals. White balance correction coefficient determining means for determining a total of six white balance correction coefficients of the second white balance correction coefficient group, and hue adjustment value setting means for setting a hue adjustment value for adjusting the hue of the video signal. A saturation adjustment value setting unit for setting a saturation adjustment value for adjusting the saturation of the video signal; a hue adjustment value set in the hue adjustment value setting unit and the saturation adjustment; A color adjustment coefficient determining means for determining a color adjustment coefficient group consisting of four color adjustment coefficients to be applied to the two color difference signals based on the saturation adjustment value set in the setting means; and the white balance correction coefficient determining means. First determined by
Based on the white balance correction coefficient group and the color adjustment coefficient group determined by the color adjustment coefficient determination means, a first color difference signal correction coefficient group including two color difference signal correction coefficients to be applied to the luminance signal is newly added. A first coefficient calculating means for determining, and a second coefficient determined by the white balance correction coefficient determining means.
Based on the white balance correction coefficient group and the color adjustment coefficient group determined by the color adjustment coefficient determination means, a second color difference signal correction coefficient group including four color difference signal correction coefficients to be applied to the two color difference signals is generated. Newly determined second coefficient calculating means, and two outputs by multiplying each of the two color difference signal correction coefficients and the luminance signal of the first color difference signal correction coefficient group determined by the first coefficient calculating means. A luminance signal calculation means for obtaining a signal, and a 2 × 2 matrix calculation of four color difference signal correction coefficients of the second color difference signal correction coefficient group and two color difference signals determined by the second coefficient calculation means. Matrix computing means for obtaining two output signals by means of a first addition means for adding one of the two output signals of the luminance signal computing means and one of the two output signals of the matrix computing means. A second adder for adding the other of the two output signals of the luminance signal calculating means and the other of the two output signals of the matrix calculating means, and a second adder corresponding to claim 5. An image processing apparatus, comprising: a first output unit having the same content; and a second output unit having the same content as the one corresponding to claim 5.