JP3264107B2 - Contour correction circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction circuit used for improving image quality in video signal processing of an image pickup device or the like.

[0002]

2. Description of the Related Art In recent years, in an image pickup apparatus or the like, a contour correction circuit has been increasingly regarded as important in order to reproduce an image having a natural and clear contour with respect to an image of a flesh color portion.

Hereinafter, a conventional contour correction circuit will be described. FIG. 8 shows a block diagram of this conventional contour correction circuit. In FIG. 8, 1 is a digital three primary color input video signal, 2 is an IQ signal generation circuit, 6 is a coring circuit, 7 is a contour correction signal generation circuit, 8 is an arbitrary set value X,
9 is a contour correction signal output, and 24 is a hue detection circuit. FIG. 9 is a block diagram showing the configuration of the hue detection circuit 24.
10 is an I signal input, 11 is an arbitrary set value Imax, 12
Is an arbitrary set value Imin, 13 is a Q signal input, 14 is an arbitrary set value Qmax, 15 is an arbitrary set value Qmin, 1
6 is a subtractor, 25 is a single area determination circuit, and 26 is a coring amount output.

[0004] The operation of the contour correction circuit configured as described above will be described below.

[0005] First, an IQ signal generation circuit 2 generates I and Q signals from digital three primary color input video signals 1 by calculations shown in (Equation 1) and (Equation 2).

[0006]

(Equation 1)

[0007]

(Equation 2)

[0008] The generated IQ signal is supplied to a hue detection circuit 24.
To determine the hue of the digital three primary color input video signal 1. In the hue detection circuit 24, as shown in FIG.
Arbitrary upper limit value Im of I axis corresponding to skin color portion on Q plane
ax11, an arbitrary lower limit Imin12, and an arbitrary upper limit Qmax14 and an arbitrary lower limit Qmin15 on the Q axis.
An area surrounded by dots is set, and four subtracters 16 are used to determine whether the hue of the digital primary color input video signal 1 exists inside or outside the area (Equation 3).
From (6), and the operation results I1, I2,
Q1 and Q2 are input to the single area determination circuit 25. If all are positive, it is determined that the digital three primary color input video signal 1 is within the area, and if at least one is negative, it is determined to be outside the area. Only the preset value is output as the coring amount output 26
Output as

[0009]

(Equation 3)

[0010]

(Equation 4)

[0011]

(Equation 5)

[0012]

(Equation 6)

At the same time as the above operation, a contour correction signal is generated by the contour correction circuit 7 from the digital three primary color input video signal 1 and input to the coring circuit 6. The coring circuit 6 slices the contour correction signal to a zero value by regarding a value equal to or smaller than a value obtained by adding an arbitrary predetermined value X set in advance and the coring amount output 26 of the hue detection circuit 24 as noise, The corrected contour correction signal 9 is output.

As described above, in the conventional contour correction circuit,
The flesh color area is determined by one quadrangular area. When the hue of the digital three primary color input video signal 1 is in a preset flesh color area, as shown in FIG. Apply coring with a larger value,
By lowering the contour correction signal level, the image quality is prevented from deteriorating due to the contour correction signal of the skin color portion.

[0015]

However, in the above-mentioned conventional configuration, since there is only one skin color detection area, the input image may be such that the hue of the skin color such as a human face changes delicately and continuously. In the case of input, there is a problem that the coring amount output of the hue detection circuit 24 is not stable at the hue near the boundary of the flesh color detection area, and there is a part where the coring is applied or not in the flesh color area.

The present invention solves the above-mentioned conventional problems, and determines a skin color portion of an input image by dividing it into a plurality of regions.
An object of the present invention is to provide a contour correction circuit that performs appropriate coring processing on skin colors and colors at skin color boundaries by setting a stepwise coring amount for each region, and obtains a more natural image. And

[0017]

In order to achieve this object, a contour correction circuit according to the present invention comprises: an IQ signal generating circuit for generating I and Q signals from an arbitrary digital three primary color input video signal; A contour correction signal generating circuit for generating a contour correction signal from a primary color input video signal;
The difference between the arbitrary upper limit value Imax and the arbitrary lower limit value Imin set on the axis and the I signal generated by the IQ signal generation circuit is taken, and the arbitrary upper limit value Qmax and the arbitrary upper limit value set on the Q axis on the IQ plane are taken. Any lower limit Qmin and IQ
A plurality of subtracters each taking a difference from the Q signal generated by the signal generation circuit, and a plurality of subtracter outputs are input , and a plurality of subtracters are inputted.
Judge each value of the subtractor output and based on this judgment result
A plurality of coincidence detection circuits that output signals; a plurality of region detection circuits that determine a hue by specifying a position on the IQ plane of the digital three primary color input video signal from the plurality of coincidence detection circuit outputs;
A selection circuit which is controlled by the output of the plurality of area determination circuits and selects and outputs one of a plurality of set values; and a zero value of the contour correction circuit output equal to or less than a value obtained by adding an arbitrary set value X and the output of the selection circuit. Has a coring circuit.

[0018]

According to the present invention, an IQ signal is generated by an IQ signal generation circuit from a digital three primary color input video signal, and a match detection circuit and a plurality of area determination circuits determine and select a skin color portion by dividing it into a plurality of areas. By outputting a circuit control signal and setting a stepwise coring amount for each region in the selection circuit, appropriate coring processing can be performed on skin colors and colors at skin color boundaries.

[0019]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a contour correction circuit according to the first embodiment of the present invention. FIG.
1 is a digital three primary color input video signal, 2 is an IQ signal generation circuit, 7 is an outline correction signal generation circuit, 6 is a coring circuit 8 is an arbitrary set value X, and 9 is an outline correction signal output. It is similar to the example. Reference numeral 3 denotes a hue detection area determination circuit, which outputs digital 3
The hue of the primary color input video signal 1 is determined, and a preset IQ
It determines which of a plurality of regions on the plane belongs to and outputs a selection circuit control signal 19. A selection circuit 4 is controlled by a selection circuit control signal 19 of the hue detection circuit 3 and selects one from a plurality of coring amounts 5 set in advance.
Output to the coring circuit 6. FIG. 2 is a block diagram showing the configuration of the hue detection area determination circuit 3. In FIG. 2, 1
0 is an I signal input, 11 is an arbitrary set value Imax, 12 is an arbitrary set value Imin, 13 is a Q signal input, 14 is an arbitrary set value Qmax, 15 is an arbitrary set value Qmin, 16
Is a subtractor, which is the same as the conventional example.
A coincidence detection circuit 17 determines whether the input signal is negative or an arbitrary positive number. Reference numeral 18 denotes a plurality of area determination circuits which determine from the outputs of the coincidence detection circuits 17a, 17b, 17c, and 17d which of a plurality of areas on the IQ plane a hue of the digital three primary color input video signal 1 belongs to. , And outputs a selection circuit control signal 19.

The operation of the contour correction circuit of the present embodiment configured as described above will be described below. FIG.
As shown in FIG. 4 and FIG. 4, when the hue of the digital primary color input video signal 1 is in any of a plurality of preset skin color regions, the contour correction circuit of this embodiment sets a core that is set stepwise for each region. The ring level is output to the coring circuit 6, added to an arbitrary set value X8, and the coring amount of the flesh color portion is increased stepwise to perform coring, thereby obtaining a contour correction signal from flesh color to flesh color peripheral color. Thus, an appropriate coring process is performed.

First, an IQ signal generating circuit 2 generates I and Q signals from digital three primary color input video signals 1 by the operations shown in (Equation 1) and (Equation 2).

The generated IQ signal is input to the hue detection area determination circuit 3 and determines the hue of the digital primary color input video signal 1. In the hue detection region determination circuit 3, as shown in FIG. 3, the upper limit value Imax11 and the lower limit value Imin12 of the I axis corresponding to the skin color portion on the IQ plane, and the upper limit value Qmax14 and the lower limit value Qmin15 of the Q axis. Set the area to be enclosed. In order to determine whether the hue of the digital three primary color input video signal 1 exists inside or outside the area, and at which position inside the area,
The arithmetic operation of (Equation 3) is performed by (Equation 3) with two subtracters 16, and
The operation results I1, I2, Q1, and Q2 are compared with the match detection circuit 1
Enter 7 The coincidence detection circuit 17 determines whether the input signal is negative or an arbitrary positive number, so that the hue of the input digital primary color input video signal is set to the set value Ima.
It detects how far away it is from x, Imin, Qmax, Qmin and outputs as shown in Table 1.

[0024]

[Table 1]

The multiple area determination circuit 18 performs a logical operation on the outputs of the coincidence detection circuits 17a, 17b, 17c, and 17d as shown in (Equation 7), (Equation 8), (Equation 9), (Equation 10), and (Equation 11). In the formulas, + indicates a logical sum and * indicates a logical product. By performing the operations shown in Table 2, any region into which the hue of the digital three primary color input video signal 1 is divided as shown in FIG. And outputs a selection circuit control signal 19.

[0026]

(Equation 7)

[0027]

(Equation 8)

[0028]

(Equation 9)

[0029]

(Equation 10)

[0030]

[Equation 11]

[0031]

[Table 2]

At the same time as the above operation, a contour correction signal is generated by the contour correction circuit 7 from the digital three primary color input video signal 1 and input to the coring circuit 6. The coring circuit 6 sets a value equal to or less than a value obtained by adding an arbitrary preset value X of the contour correction signal and the output of the selection circuit 4 to a zero value, and outputs a corrected contour correction signal 9.

As described above, according to the present embodiment, the hue detection area determination circuit 3 is constituted by the coincidence detection circuit 17 and the multiple area determination circuit 18 and the selection circuit 4 is provided, so that the digital three primary color input video signals 1 Is determined in a plurality of regions set on the IQ plane, and by setting a gradual coring amount in each region, an appropriate coring process is performed on the contour correction signal from skin color to skin color peripheral color. It can be carried out.

FIG. 5 is a block diagram of a hue detection circuit according to a second embodiment of the present invention. In FIG.
Is an I signal input, 11 is an arbitrary set value Imax, 12 is an arbitrary set value Imin, 13 is a Q signal input, 16 is a subtractor, 17 is a coincidence detection circuit, 18 is a multiple area determination circuit,
Reference numeral 9 denotes a selection circuit control signal, which is the same as that of the embodiment shown in FIG. The difference from FIG.
3 is provided, and an arbitrary set value α20 and an arbitrary set value β21
And (I−Imin) multiplied by the multipliers 22 and 23 are replaced with the set values Qmax and Qmin in FIG. In the embodiment shown in FIG. 2, since the area is divided by a rectangle as shown in FIG. 3, when setting a skin color area that normally exists around the I axis, it is necessary to include many hues other than the skin color. In other words, there is a problem that coring is applied to colors other than flesh color, and this embodiment will be described as a method for solving this problem.

The operation of the contour correction circuit configured as described above will be described below. Any set value α2
It is assumed that 0 and any set value β21 satisfy the relationship of −α = β. α and β and (I−Imin) are multiplied by a multiplier 22,
By replacing the value multiplied by 23 with the set values Qmax and Qmin in FIG. 2, Qmax and Qmin become (I-Imi) as shown in (Equation 12) and (Equation 13).
n). Therefore, Qmax and Qmin increase as the I signal increases, and a triangular area can be set as shown in FIG.

[0036]

(Equation 12)

[0037]

(Equation 13)

The operation after the area is set is described in claim 1.
This is the same as the embodiment of the present invention. As described above, according to the present embodiment, an arbitrary set value α20 and an arbitrary set value β21,
By providing a value obtained by multiplying (I−Imin) by the multipliers 22 and 23 as a signal corresponding to the set values Qmax and Qmin in FIG. 2, a flesh color region can be set as a triangle, and a hue other than flesh color can be set. Since a hue detection circuit to which the coring process does not reach much can be provided, a contour correction signal with higher accuracy can be obtained.

[0039]

As described above, the present invention provides an IQ signal generating circuit for generating I and Q signals from an arbitrary digital three primary color input video signal, and a contour correction signal from the arbitrary digital three primary color input video signal. A contour correction signal generating circuit,
Taking the difference of any upper limit Imax and I signal generated by the IQ signal generation circuit and any lower limit Imin which has been set on the I axis on the IQ plane, respectively, Q on the IQ plane
A plurality of subtractors each taking a difference between an arbitrary upper limit value Qmax and an arbitrary lower limit value Qmin set on the axis and the Q signal generated by the IQ signal generation circuit ; and Determine each value of multiple subtractor outputs
A plurality of coincidence detecting circuits for outputting signals based on the judgment result; and a plurality of area judging circuits for judging a hue by specifying a position on the IQ plane of the digital three primary color input video signal from the plurality of coincidence detecting circuits. A selection circuit controlled by an output of the plurality of area determination circuits to select and output one of a plurality of set values, and an output of a contour correction circuit having a value equal to or less than a value obtained by adding an arbitrary set value X and the output of the selection circuit. By providing a coring circuit that sets a zero value to, the skin color area is divided into a plurality of areas, and a stepwise coring amount is set for each area, so that a natural contour correction signal is applied to the skin color part. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a contour correction circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a hue detection circuit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a flesh-tone area according to the first embodiment of the present invention;

FIG. 4 is a diagram showing a setting state of a coring amount in a flesh color region according to the first embodiment of the present invention.

FIG. 5 is a block diagram of a hue detection circuit according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a flesh-tone area according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a setting state of a coring amount in a flesh color region according to a second embodiment of the present invention.

FIG. 8 is a block diagram of a conventional contour correction circuit.

FIG. 9 is a block diagram of a conventional hue detection circuit.

FIG. 10 is a diagram showing a skin color area in a conventional example.

FIG. 11 is a diagram showing a setting state of a coring amount in a flesh color region in a conventional example.

[Explanation of symbols]

 Reference Signs List 1 digital primary color input video signal 2 IQ signal generation circuit 3 hue detection area circuit 4 selection circuit 5 coring amount 6 coring circuit 7 contour correction signal generation circuit 8 arbitrary set value X 9 contour correction signal output 10 I signal input 11 Arbitrary set value Imax 12 Arbitrary set value Imin 13 Q signal input 14 Arbitrary set value Qmax 15 Arbitrary set value Qmin 16 Subtractor 17 Match detection circuit 18 Multiple area judgment circuit 19 Selection circuit control output 20 Arbitrary coefficient α 21 Any coefficient β 22,23 multiplier 24 hue detection circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/14-5/217 H04N 9/44-9/78

Claims (2)

(57) [Claims] 1. An IQ signal generation circuit for generating I and Q signals from an arbitrary digital three primary color input video signal, a contour correction signal generation circuit for generating an outline correction signal from the arbitrary digital three primary color input video signal, Any upper limit value Imax and any lower limit value Imin set on the I axis on the IQ plane
And the difference between the I signal generated by the IQ signal generation circuit and
Taking each of a plurality of subtractors for taking each the difference between any upper limit Qmax and the Q signal generated by the IQ signal generation circuit and any lower limit Qmin set on the Q axis on the IQ plane, the plurality Input of the subtractor of
Each value of the output of the subtractor is determined, and based on this determination result,
A plurality of coincidence detection circuits that output signals based on the plurality of coincidence detection circuits; a plurality of region determination circuits that determine a hue by specifying a position on the IQ plane of the digital three primary color input video signal from the plurality of coincidence detection circuits; A selection circuit which is controlled by a circuit output and selects and outputs one of a plurality of set values;
A contour correction circuit comprising a coring circuit for setting an output of the contour correction circuit equal to or less than a value obtained by adding an arbitrary set value X and an output of the selection circuit to a zero value. Means for multiplying the I signal output from the IQ signal generation circuit by an arbitrary coefficient α;
The output of the means for multiplying the arbitrary coefficient α by changing to the arbitrary set value Qmax according to claim 1 is given, and the output of the means for multiplying the arbitrary coefficient β by changing to the arbitrary set value Qmin of claim 1 is given. 2. The contour correction device according to claim 1, wherein the correction is performed.