JP2002281346A - Gradation correcting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently suppress various adverse effects such as crush of gradation caused by gradation correction. SOLUTION: This gradation correcting device is provided with a gradation correction means 1 to calculate gradation correction characteristics based on brightness distribution of an input signal and to perform gradation correction of the input signal by using the calculated gradation correction characteristics, a difference of brightness detecting means 2 to detect prescribed characteristics from the input signal, correction means 3 and a control means 5 to control the gradation correction to be performed by the gradation correction means 1 based on a detection result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a gradation correction apparatus and a program for improving the gradation of a video signal.

[0002]

2. Description of the Related Art Generally, when an image that does not use the entire dynamic range is input, for example, an apparatus having a dynamic range of 256 gradations from "0" to "255" has a luminance value of "100". ~ "200"
When the signals up to are input, the signal processing for adjusting the contrast and the DC level is performed so that the luminance value “100” becomes “0” and the luminance value “200” becomes “255”.

In an image in which certain luminance values are concentrated, a process of increasing the contrast of the luminance level to make the image highly visible (hereinafter referred to as gradation correction) is also performed.

[0004] When the above-described signal processing is performed, as a result of increasing the gradation of a signal in which the amplitude of the input signal is small over a wide area, a false contour which cannot be seen in the original video signal (hereinafter referred to as a false contour). Occurs). In the above example,
Since the luminance value has been expanded from “100 to 200” to “0 to 255”, the signal amplitude has been expanded to about 2.5 times.

[0005] Considering the case where pixels of luminance "150" and luminance "152" are adjacent to each other in the input signal, when the gradation correction is not performed, the luminance difference is "2". As a result of the gradation correction, the luminance difference is also enlarged to a luminance difference of “2” × 2.5 × = “5”, and the displayed image appears to have an outline between the pixels. I will.

A technique for suppressing the false contour will be briefly described as a conventional example.

[0007] In FIG. 15, the luminance distribution of the video signal input from the input terminal Din is detected by the frame memory 12 and the CPU 113. From the detection result, in order to increase the gradation around the luminance level where the dispersion is small, the gradation conversion table 114 changes the input / output characteristics around the luminance level to increase the gradation. Since the false contour is generated by increasing the gradation, the LPF 115 performs a two-dimensional low-pass filter (LPF) process on the output signal of the gradation conversion table 114 in order to remove the false contour. Further, in an HPF (high pass filter) 116, an outline is extracted from the video signal before gradation conversion, and a coring process for removing noise is performed on the result in a coring 118, and an edge portion of the input video signal is extracted. Extract.

LPF 115 which has been subjected to two-dimensional LPF processing
Is added to the output signal from the coring 118, which is the edge of the input video signal that has undergone coring, to compensate for the edge lost in the LPF.

[0009]

However, in the above-described processing, since the LPF processing is performed on the entire signal after the gradation correction, a false contour at a portion where the luminance variance is small can be removed. LPF processing is also performed on a portion where a large false contour does not occur.

In addition, when the high-frequency component is not correctly extracted, or only the LPF processing is performed on intermediate frequency components that are not detected as high-frequency components, even if the edge portion of the input signal is corrected, the intermediate frequency that is not a target of correction There is a problem that the components are subjected to the LPF processing, and the entire screen excluding the edge portions is subjected to the LPF processing.

As described above, performing the gradation correction may cause various other adverse effects. Hereinafter, such an adverse effect will be described.

First, when an input image includes a region having a gradation in which the luminance changes gently, the gradation of the region having the gradation is reduced because the frequency of the luminance in the region having the gradation is small. And the change in luminance may be crushed.

That is, when an input image includes a region having a gradation, as a result of performing the gradation correction on the input image, the gradation characteristic of the region having the gradation is reduced, so that the change in luminance is reduced. There is a problem that.

If the input image is, for example, a photographic image in which a background that is not interesting is shown in the background and a plant such as a flower of interest is shown in the center, a person may be in the middle of the image in which the flower is shown. There is no interest in the surrounding area where the area is interested and the background is reflected. However, when such an image is subjected to gradation correction, if the frequency of luminance of the region of interest is smaller than the frequency of luminance of the region of no interest, the gradation of luminance of the region of interest is reduced. As a result, visibility deteriorates.

That is, as a result of performing the gradation correction, there is a problem that the gradation of an area of interest of the input image is reduced, and the visibility may be reduced.

In general, in a liquid crystal panel or the like, an ideal gamma curve is not obtained because a gamma curve is broken or discontinuous in a low luminance portion and a high luminance portion. for that reason,
If processing is performed to greatly change the gradation of the input signal in a portion corresponding to the low / high luminance portion, noise enlargement, gradation collapse, and the like are conspicuous.

That is, tone correction is performed on an input image,
When the gradation of the low luminance portion or the high luminance portion is greatly increased, and when the image is displayed on a liquid crystal panel or the like, there is a problem that noise enlargement, gradation collapse, and the like are conspicuous.

Further, as described above, false contours are generated as a result of performing tone correction on an input image, and when the false contours are suppressed, an image in a portion where no false contours are generated is adversely affected. Problem.

Further, when a large area having a single brightness exists in the input image or the like, as a result of performing the gradation correction on the input image, the gradation of other areas is reduced.

That is, when a large area having a single luminance exists in an input image, for example, as a result of performing gradation correction on the input image, the gradation of other areas is reduced. There is.

When the gradation correction characteristic for making the luminance of the input image correspond to the luminance after the gradation correction is represented by a broken line, when the gradation correction is performed with the gradation correction characteristic, gradation is obtained. In a region, a false contour may occur in a portion of a pixel having a luminance corresponding to a broken line portion of the gradation correction characteristic. When such false contours are suppressed in the same manner as described in the related art, the image of a portion where no false contours are generated is adversely affected as described above.

That is, when the gradation correction characteristic is represented by a polygonal line, a pixel portion having a luminance corresponding to the polygonal line portion of the gradation correction characteristic among the pixels in the gradation region of the input image includes: There is a problem that a false contour may occur after gradation correction.

As described above, performing the gradation correction causes various adverse effects.

According to the present invention, in consideration of the above problem, when an input image includes an area having a gradation, a change in luminance of the area having the gradation is reduced as a result of performing gradation correction on the input image. It is an object of the present invention to provide a tone correction device and a program without any.

According to the present invention, there is provided a gradation correcting apparatus which does not reduce the gradation of an area of interest of an input image as a result of performing the gradation correction in consideration of the above-mentioned subject.
And programs.

Further, in consideration of the above-mentioned problem, the present invention provides a gradation which does not cause noise enlargement, gradation collapse, etc. to appear remarkably even when an input image is subjected to gradation correction and displayed on a liquid crystal panel or the like. It is an object to provide a correction device and a program.

Another object of the present invention is to provide a gradation correction apparatus and a program which do not cause false contours even when gradation correction is performed on an input image, in consideration of the above-mentioned problems.

Further, in consideration of the above-mentioned problem, the present invention considers the above problem, and when a large area having a single luminance exists in an input image or the like, even if gradation correction is performed on the input image, the gradation of another area is not affected. It is an object of the present invention to provide a gradation correction device and a program that are not deteriorated.

Another object of the present invention is to provide a tone correction device and a program which do not generate false contours even when the tone correction characteristic is represented by a polygonal line in consideration of the above problems. It is assumed that.

[0030]

In order to solve the above-mentioned problems, a first aspect of the present invention (corresponding to claim 1) calculates a gradation correction characteristic based on a luminance distribution of an input signal and calculates the gradation correction characteristic. Tone correction means for performing tone correction of the input signal using the obtained tone correction characteristic, feature detection means for detecting a predetermined feature from the input signal, and the tone based on the detection result. And a control unit for controlling the gradation correction performed by the correction unit.

The second invention (corresponding to claim 2)
In the formula, the predetermined feature is gradation, the feature detection unit detects a region having the gradation, and the control unit corresponds to a luminance of a pixel belonging to the detected region having the gradation. Correcting the luminance distribution so as to increase the frequency of appearance of the luminance in the luminance distribution, and the gradation correction means calculates the gradation correction characteristic based on the corrected luminance distribution. The tone correction device according to the above.

The third invention (corresponding to claim 3)
The feature correcting means according to the second aspect of the present invention, wherein the feature detecting means detects the area having the gradation by detecting an area in which a difference in luminance of the input signal is smaller than a predetermined value. .

The fourth invention (corresponding to claim 4)
Among the regions where the difference in luminance is smaller than the predetermined value, for a region composed of substantially the same luminance,
A gradation correction device according to a third aspect of the present invention, which is not a detection target.

The fifth invention (corresponding to claim 5)
Is the area having a predetermined intermediate luminance, the characteristic detecting means detects an area having the predetermined intermediate luminance, and the control means detects the area having the predetermined intermediate luminance. Corresponding to the luminance of the pixels belonging to the region having the, the luminance distribution is corrected so as to increase the frequency of appearance of the luminance in the luminance distribution, and the gradation correction means, based on the corrected luminance distribution FIG. 1 is a gradation correction apparatus according to a first aspect of the present invention for calculating gradation correction characteristics.

The sixth invention (corresponding to claim 6)
The predetermined feature is a region where the luminance is substantially the same, the feature detecting unit detects a region where the luminance is substantially the same, and the control unit detects that the detected luminance is the same. Corresponding to the luminance of the pixels belonging to the substantially same region, the luminance distribution is corrected so as to reduce the frequency of appearance of the luminance in the luminance distribution, and the gradation correction means adjusts the corrected luminance distribution. A gradation correction apparatus according to a first aspect of the present invention, wherein the gradation correction characteristic is calculated based on the gradation correction characteristic.

The seventh invention (corresponding to claim 7)
The predetermined feature is a position on a display screen, the feature detecting means detects the position in each area of the input signal, and the control means detects the detected position of each area. According to the luminance of the luminance distribution corresponding to the luminance of the pixels belonging to the area, the gradation correction means, the gradation correction means, based on the corrected luminance distribution, the gradation correction characteristics FIG. 4 is a gradation correction apparatus according to a first aspect of the present invention for calculating.

The eighth invention (corresponding to claim 8)
Calculating a gradation correction characteristic based on the luminance distribution of the input signal, and using the calculated gradation correction characteristic to perform gradation correction of the input signal; and Determine the degree of gradation correction based on the gradation correction characteristics,
Control means for correcting the luminance distribution or the gradation correction characteristic according to a predetermined reference, wherein the gradation correction means performs gradation using the corrected luminance distribution or the gradation correction characteristic. This is a gradation correction device that performs correction.

The ninth invention (corresponding to claim 9)
Is the gradation correction device according to the eighth aspect of the present invention, wherein the predetermined reference is a frequency of appearance of luminance in a luminance distribution or a gradient of the gradation correction characteristic.

A tenth aspect of the present invention (corresponding to claim 10) is the gradation correction apparatus according to the eighth or ninth aspect of the present invention, wherein the predetermined reference differs depending on the degree of luminance. .

In the eleventh aspect of the present invention (corresponding to claim 11), the difference between the gradation correction characteristics is that the inclination that each part of the gradation correction characteristic can take is equal to the gradation correction characteristic. An eighth or ninth aspect of the present invention is the tone correction apparatus according to the present invention, wherein the portion corresponding to the intermediate luminance of the characteristic is larger and the portion other than the intermediate luminance is smaller than the portion corresponding to the intermediate luminance.

According to a twelfth aspect of the present invention (corresponding to claim 12), a gradation correction characteristic is calculated based on a luminance distribution of an input signal, and the input signal is calculated using the calculated gradation correction characteristic. A tone correction unit for performing tone correction of the above, a feature detection unit for detecting a predetermined feature from the input signal or a signal after the tone correction of the input signal, and a case where the tone correction characteristic is represented by a broken line After the input signal has been subjected to the gradation correction, if a pixel having a luminance corresponding to a bending point of the gradation correction characteristic has a predetermined characteristic as the detection result, the luminance of the pixel is changed to the vicinity of the pixel. And a correction unit that corrects using the luminance of the predetermined pixel after the gradation correction.

According to a thirteenth aspect of the present invention (corresponding to claim 13), the predetermined feature is gradation.
The feature detecting means is a gradation correcting apparatus according to a twelfth aspect of the present invention for detecting the gradation-containing area.

According to a fourteenth aspect of the present invention (corresponding to claim 14), the gradation area is detected by detecting an area where the difference in luminance of the input signal is smaller than a predetermined value. 4 is a gradation correction device according to the present invention.

Further, according to a fifteenth aspect of the present invention (corresponding to claim 15), in an area in which the difference in luminance is smaller than the predetermined value, an area having substantially the same luminance is detected. It is a gradation correction device according to a fourteenth invention which is not targeted.

According to a sixteenth aspect of the present invention (corresponding to claim 16), the tone correction characteristic of the tone correcting apparatus according to the first aspect of the present invention is calculated based on the luminance distribution of the input signal. A gradation correction unit that performs gradation correction of the input signal using the calculated gradation correction characteristics, a feature detection unit that detects a predetermined feature from the input signal, and based on the detection result,
This is a program for causing a computer to function as all or part of a control unit that controls the gradation correction performed by the gradation correction unit.

According to a seventeenth aspect of the present invention (corresponding to claim 17), the tone correction characteristic of the tone correcting apparatus according to the eighth aspect of the present invention is calculated based on the luminance distribution of the input signal. A gradation correction unit that performs gradation correction of the input signal using the calculated gradation correction characteristic, and a degree of gradation correction based on the luminance distribution or the gradation correction characteristic is determined, and a predetermined level is determined. This is a program for causing a computer to function as all or a part of control means for correcting the luminance distribution or the gradation correction characteristic according to a predetermined standard.

According to an eighteenth aspect of the present invention (corresponding to claim 18), the tone correction device according to the twelfth aspect of the invention calculates a tone correction characteristic based on a luminance distribution of an input signal, and Tone correction means for performing tone correction of the input signal using the calculated tone correction characteristic, and feature detection means for detecting a predetermined feature from the input signal or the signal after tone correction of the input signal When the gradation correction characteristic is represented by a polygonal line, after the input signal is subjected to the gradation correction, a pixel having a luminance corresponding to a bending point of the gradation correction characteristic is determined as the detection result. In a case where the computer has the characteristic described above, the program is a program for causing a computer to function as all or a part of correction means for correcting the luminance of the pixel by using the luminance after gradation correction of a predetermined pixel around the pixel.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example of the present invention, in the case where the characteristics of an input signal are detected and the gradation is changed based on the detection result, an area where the luminance difference of the input video signal is small is detected. Then, by controlling the luminance distribution state of the input video signal based on the result, an effect of preventing the adverse effect due to the gradation correction is provided.

Also, the present invention focuses on, for example, a gradation correction means for changing input / output characteristics in accordance with the luminance distribution of an input video signal, and a method for focusing an input signal on a fixed area of m dots × n lines. Luminance difference detecting means for detecting a luminance difference between video signals in the image signal; comparing means for comparing an output of the luminance difference detecting means with a threshold; luminance distribution detecting means for detecting a luminance distribution of an input video signal; By providing control means for weighting the result of the detection means on the basis of the result of the comparison means, it has an effect of preventing adverse effects due to gradation correction.

Further, as an example of the present invention, when the characteristics of an input signal are detected and the gradation is changed based on the detection result, the distance of the input video signal from the center of the screen is detected. By controlling the luminance distribution state of the input video signal based on the result, an effect of preventing the adverse effect due to the gradation correction is provided.

The present invention also includes, as an example, a gradation correcting means for changing input / output characteristics in accordance with a luminance distribution of an input video signal, and a screen position detecting means for detecting a distance of a target input signal from the center of the screen. A luminance distribution detecting means for detecting the luminance distribution of the input video signal; and a control means for weighting the result of the luminance distribution detecting means based on the result of the screen position detecting means. Has the effect of preventing

Further, as an example of the present invention, when the characteristics of an input signal are detected and the gradation is changed based on the detection result, an intermediate luminance area of the input video signal is detected, and By controlling the luminance distribution state of the input video signal based on this, it has an effect of preventing the adverse effect due to the gradation correction.

The present invention also provides, as an example, a gradation correcting means for changing input / output characteristics according to a luminance distribution of an input video signal, an intermediate luminance detecting means for detecting an intermediate luminance of an input signal of interest, A luminance distribution detecting means for detecting a luminance distribution of a signal and a control means for weighting the result of the luminance distribution detecting means based on the result of the intermediate luminance detecting means are provided to prevent the adverse effects due to gradation correction. Has an action.

As an example of the present invention, when the characteristics of an input signal are detected and the gradation is changed based on the detection result, an offset is added to the luminance distribution state of the input video signal, and the offset is added. The amount has an effect that the tone improvement effect can be expanded by controlling the tone correction range to be constant.

Further, as an example of the present invention, a gradation correction means for changing input / output characteristics in accordance with a luminance distribution of an input video signal, and a correction range for obtaining a gradation correction range from control contents of the gradation correction means. Calculating means, a luminance distribution detecting means for detecting a luminance distribution of the input video signal, and an offset correcting means for correcting a result of the luminance distribution detecting means based on a result of the correction range detecting means. This has the effect that the tone improving effect can be expanded.

Further, as an example of the present invention, when the characteristics of the input signal are detected and the gradation is changed based on the detection result, the degree of concentration of the input video signal to a specific luminance is detected. By controlling the luminance distribution status of the input video signal based on the result, the effect of improving the gradation improving effect can be obtained.

The present invention also provides, as an example, a gradation correcting means for changing input / output characteristics according to a luminance distribution of an input video signal, and a specific luminance detecting means for detecting whether or not the input signal is concentrated at a specific luminance. Means, a luminance distribution detecting means for detecting the luminance distribution of the input video signal, and a control means for weighting the result of the luminance distribution detecting means based on the result of the specific luminance detecting means, thereby improving the gradation. Has the effect of being able to expand.

Further, as an example of the present invention, in the case where the characteristics of an input signal are detected and the gradation is changed based on the detection result, the gradation is controlled based on the luminance distribution state of the input video signal. Since a plurality of straight lines are approximated to each other and the correction range of each straight line can be set independently, there is an effect that the effect of improving the tone can be expanded while preventing the adverse effect of the tone correction.

Further, as an example, the present invention provides a gradation correction means for changing input / output characteristics by approximation using a plurality of straight lines in accordance with a luminance distribution of an input video signal, and a luminance distribution detecting the luminance distribution of the input video signal. Detecting means and, when performing tone correction according to the luminance distribution, by providing a limiter that independently defines a tone correction range according to each linear region of tone correction, while preventing the adverse effects of tone correction, This has the effect that the gradation improvement effect can be expanded.

The present invention is also applicable to the case where the characteristics of an input signal are detected and the gradation is changed based on the detection result. Is approximated by a plurality of straight lines, and by applying LPF to a portion where the luminance change at the joint between the straight lines is small, the gradation improving effect can be expanded.

As an example of the present invention, a gradation correction means for changing input / output characteristics by approximation by a plurality of straight lines according to a luminance distribution of an input video signal, and a luminance distribution detecting the luminance distribution of the input video signal A detecting means, a luminance difference detecting means for focusing an input signal on a fixed area of m dots × n lines, and detecting a luminance difference of a video signal in the area; Means, a seam detecting means for detecting a seam for detecting a seam of each straight line by linear approximation in the gradation correcting means, and calculating an output of the comparing means, an output of the gradation correcting means, The output of the seam detecting means is input and the LPF means for applying a low-pass filter to the output signal of the tone correcting means in accordance with the output signal of the comparing means to perform a filtering process, thereby enhancing the tone improving effect. When you can Cormorant having an effect.

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

(Embodiment 1) FIG. 1 is an example of a configuration diagram of a gradation correction apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes gradation correction means for improving the gradation of an input video signal, reference numeral 2 denotes a luminance difference detection means for dividing an input video signal into a certain area and detecting a luminance difference in the area, and
Is a comparing means for comparing the output of the luminance difference detecting means 2 with a threshold value, 4 is a luminance distribution detecting means for detecting a luminance distribution in the input video signal, and 5 is a comparison of the result of the luminance distribution detecting means 2 Control means for weighting control based on the result of the means 3.

Next, the operation of this embodiment will be described.

FIG. 2 is a diagram showing the frequency of the luminance level of a conventional input signal, and FIG. 3 is a diagram showing the input / output characteristics at that time.

FIG. 4 is a diagram showing the frequency of the luminance level of the input signal according to the first embodiment of the present invention, and FIG. 5 is a diagram showing the input / output characteristics at that time.

First, the input video signal is input to the gradation correcting means 1 and the luminance difference detecting means 2.

The following description is based on the assumption that the gradation correction characteristics used when the gradation correction means 1 performs gradation correction on an input video signal are approximated by broken lines with four straight lines for simplification.

Needless to say, the same applies to other than the four straight lines, for example, an eight-line approximation.

The video signal input to the gradation correcting means 1 is
From the result of the normal luminance distribution detecting means 4, gradation correction is performed so as to increase the gradation around a luminance level having a large frequency.

The luminance difference detecting means 2 focuses an input signal on an m × n region of m dots vertically and n lines horizontally, for example.
A maximum luminance and a minimum luminance of n pixels are detected, and a luminance difference value is output.

The comparing means 3 outputs the luminance difference detecting means 2
Is compared with a preset threshold value. When the difference value is smaller than the threshold value, it can be determined that the gradation change is conspicuous when m × n pixels have a small luminance change and gradation correction is performed. As described above, the comparing unit 3 detects the gradation area by detecting that the above-described difference value is smaller than the threshold value.

The operation of the tone correcting means 1 and the control means 5 will be described below in comparison with the conventional tone correcting means.

An example of the operation of the conventional gradation correcting means will be described with reference to FIG. First, the luminance distribution of the input video signal is detected. The luminance level to be detected is 256 of the input signal "0 to 255".
The gradation is "0-63", "64-127", "128-1"
The luminance level is divided into four luminance levels of “91” and “192 to 255”, and the luminance level of each pixel of the image is detected. FIG. 2 shows an example of the detected frequency of each luminance level. This example shows a detection result in which the number of pixels at the luminance levels “0 to 63” is small and the number of pixels at the luminance levels “64 to 127” is large. This detection result means that the number of pixels at the luminance levels “0 to 63” is small when viewed from the whole image, and thus the gradation is not so important.
That is, since the number of pixels of "27" is large, this level of gradation is important. As a result, input / output characteristics according to the number of pixels at four luminance levels are realized.

FIG. 3 shows input / output characteristics in the case of the above example. At the luminance levels "0 to 63", the output is small with respect to the input because the gradation is not important. Conversely, at the luminance levels "64 to 127", the output is large with respect to the input to increase the gradation. Become. As described above, the gradation correction means 1 performs gradation correction according to the luminance distribution situation and outputs a video signal.

However, the fact that the frequency is small does not necessarily mean that the gradation may be sacrificed. For example, in the case of gradation in which the luminance gradually changes, if the gradation is reduced, the change in the luminance may be crushed.

At the luminance levels "0 to 63" in FIG. 3, the gradation of the output signal is significantly lower than that of the input signal. On the other hand, in a high-frequency region where the change in luminance is large, a slight difference in change in luminance does not cause any particular problem. Therefore, the control unit 5 of the present embodiment controls the gradation correction unit 1 so that the gradation correction unit 1 does not treat the above-mentioned portion such as the gradation as the high-frequency region. That is, the control unit 5 can suppress the collapse of the gradation by weighting the frequency of the portion such as the gradation.

That is, as described above, the control means 5 sets the gradation area detected by the comparing means 3 as follows.
By weighting the frequency, the gradation correction unit 1 suppresses the collapse of the gradation in the gradation portion when performing the gradation correction.

FIG. 4 shows this state. The control unit 5 weights the frequency of the part determined as gradation by the comparison unit 3 at the luminance level “0 to 63” as shown by the hatched portion in the figure. For example, the frequency of the gradation portion is doubled. Then, the gradation correction unit 1 performs gradation correction using the input / output characteristics corrected by the control unit 5.

As a result, as shown in FIG. 5, a decrease in the gradation of the luminance levels "0 to 63" is prevented, and it is understood that the adverse effect of the gradation correction is suppressed.

According to this configuration, when the characteristics of the input signal are detected and the gradation is changed based on the detection result, an area where the luminance difference of the input video signal is small is detected, and based on the detection result. By controlling the luminance distribution state of the input video signal, it is possible to prevent adverse effects due to gradation correction.

Note that the luminance difference detecting means 2 and the comparing means 3 of the present embodiment are examples of the characteristic detecting means of the present invention, and the luminance distribution of the input video signal of the present embodiment is the same as that of the input signal of the present invention. This is an example of a luminance distribution, the input / output characteristics of the present embodiment are examples of the gradation correction characteristic of the present invention, and the frequency of the present embodiment is an example of the frequency of appearance of the luminance of the present invention.

(Embodiment 2) Next, Embodiment 2 will be described with reference to FIGS. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 6, reference numeral 6 denotes a horizontal counter.
7 is a vertical counter, and 8 is a screen position detecting means. FIG. 7 is an example of weighting according to the screen position.

The horizontal counter 6 in FIG. 6 counts up in the horizontal direction according to the position of the screen. On the other hand, the vertical counter 7 counts up in the vertical direction according to the screen position.

The screen position detecting means 8 determines how far from the center of the screen both horizontal and vertical positions are.

For example, as shown in FIG. 7, area A is closest to the center of the screen, and becomes farther toward areas B and C.
The control means 5 performs frequency weighting according to the areas A, B, and C.

For example, area A is four times, area B is three times, area C
Is twice as large. By doing so, by controlling the frequency in the luminance distribution to be more important as the position is closer to the center of the screen, it is possible to prevent adverse effects due to gradation correction.

Although the present embodiment has been described on the assumption that the frequency is weighted according to the distance from the center of the screen,
However, the present invention is not limited to this. For example, weighting may be performed according to the distance from the region of interest on the screen, such as weighting the frequency according to the distance from the upper left end of the screen or the lower right end of the screen.

Further, the H counter 6, the V counter 7, and the screen position detecting means 8 of this embodiment are examples of the characteristic detecting means of the present invention.

(Embodiment 3) Next, Embodiment 3 will be described with reference to FIG. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 8, reference numeral 9 denotes an intermediate luminance detecting means.

In general, the liquid crystal panel does not have an ideal gamma curve because the gamma curve is broken or discontinuous in the low luminance portion and the high luminance portion. Therefore, if a process that greatly changes the gradation of the input signal is performed on a portion corresponding to the low / high luminance portion, noise enlargement, gradation collapse, and the like are conspicuous. Therefore, the intermediate luminance is detected by the intermediate luminance detecting means 9, and the intermediate luminance part is weighted by the control means 5, so that the gradation is not corrected so much in the low / high luminance part, and the gradation characteristic in the intermediate luminance part is reduced. The main effect of the correction is that it is possible to prevent the adverse effects of the gradation correction.

The intermediate luminance detecting means 9 according to the present embodiment
Is an example of the feature detecting means of the present invention.

(Embodiment 4) Next, Embodiment 4 will be described with reference to FIGS. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 9, reference numeral 10 denotes a correction range calculating means, and reference numeral 11 denotes an offset correcting means. FIG. 10 is a diagram showing a state of offset correction.

The correction range calculation means 10 designates the allowable range of the inclination of each straight line to be set in the gradation correction means 1. For example, if it is considered that large gradation correction is not desirable, the inclination is set to 0.
The range is defined as 9 to 1.1 times. Conversely, if a greater gradation correction effect is desired, the range is defined as a gradient of 0.6 to 1.5 times. The difference between the specified range and the inclination to be actually set in the gradation correction means 1 is detected, and as shown in FIG. Try to match the tolerance. By doing so, the gradient of the straight line having the largest gradation correction effect among the four straight lines always reaches the limit of the allowable range, and the gradation improvement effect can be maximized.

The correction range calculating means 1 according to the present embodiment
0 and the offset correction means 11 are examples of the control means of the present invention.

(Fifth Embodiment) Next, a fifth embodiment will be described with reference to FIG. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 11, reference numeral 12 denotes a specific luminance detecting means.

The specific luminance detecting means detects, for example, a single luminance of the screen background. It is necessary to assign a large gradation to a gradation or the like having gradation, but a single luminance of a large area does not need to be assigned a gradation even if the frequency is large. The gradation improvement effect can be maximized.

Note that the specific luminance detecting means 1 of this embodiment
2 is an example of the feature detecting means of the present invention.

(Embodiment 6) Next, Embodiment 6 will be described with reference to FIG. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 12, reference numeral 13 denotes a limiter. In the fourth embodiment, the allowable range of the inclination is defined. In the sixth embodiment, the limiter 4 changes the allowable range of the inclination for each straight line. That is, as described above, the low / high luminance part where the adverse effect of the gradation correction is large has a narrow allowable range of inclination, and the intermediate luminance for which large gradation correction is desired has a wide allowable range of inclination. By doing so, while preventing the adverse effects of gradation correction,
The gradation improvement effect can be maximized.

The correction range calculating means 1 according to the present embodiment
Reference numeral 13 which is considered to be 0 and offset correction means 11 is an example of the control means of the present invention.

(Embodiment 7) Next, Embodiment 7 will be described with reference to FIGS. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 13, reference numeral 14 denotes joint detection means, and reference numeral 15 denotes an LPF. FIG. 14 is a diagram showing the relationship between the linear approximation and the joint.

Based on the distance from the joint of each straight line by the joint detecting means 14 and the result of the gradation judgment from the comparing means 3, a control signal for performing filtering by the LPF 15 is output to the gradation area near the joint. LP
In F15, the signal subjected to gradation correction according to the control signal is LP
By applying F, the false contour can be suppressed.

The brightness difference detecting means 2 and the comparing means 3 of the present embodiment are examples of the feature detecting means of the present invention, and the joint detecting means 14 and the LPF 15 of the present embodiment are the correcting means of the present invention. It is an example.

The tone correction devices described in the first to seventh embodiments may have the functions of the tone correction devices described in the other embodiments.

For example, the gradation correction device of the first embodiment may have the function of the gradation correction device of the fifth embodiment. In this case, when detecting the gradation region, the gradation correction device does not treat a region substantially composed of pixels having a single luminance as a gradation region. That is, the comparing means 3 compares the difference between the maximum luminance and the minimum luminance output from the luminance difference detecting means 2 with a preset threshold value, and if the difference value is smaller than the threshold value, the difference is substantially If it is 0 above, it is determined to be a region composed of pixels of a single luminance, and is excluded from the detection target as a gradation region. Then, a region composed of pixels having a single luminance is processed in the same manner as described in the fifth embodiment.

Further, the feature detecting means of the present invention is not limited to detecting predetermined features of the input image such as gradation from the input image as in the present embodiment, and may perform gradation correction based on the luminance distribution of the input image. A predetermined feature may be detected from the image subjected to the processing.

As described above, according to the present embodiment, when the gradation is changed by the gradation correction, it is possible to suppress the adverse effect of the gradation correction by controlling the luminance distribution detection result from the characteristics of the input signal. Becomes

Note that the present invention provides all or a part of the above-described tone correction device of the present invention (or device, element,
This is a program for causing a computer to execute the functions of a circuit, a unit, and the like, and is a program that operates in cooperation with the computer.

It should be noted that some of the means (or devices, elements, circuits, units, etc.) of the present invention mean some of the plurality of means, or one of the means. Means some of the functions.

Further, a computer-readable recording medium on which the program of the present invention is recorded is also included in the present invention.

[0117] One use form of the program of the present invention may be such that the program is recorded on a computer-readable recording medium and operates in cooperation with the computer.

[0118] One embodiment of the program of the present invention may be a mode in which the program is transmitted through a transmission medium, read by a computer, and operates in cooperation with the computer.

[0119] The recording medium includes a ROM and the like, and the transmission medium includes a transmission medium such as the Internet, light, radio waves, and sound waves.

Further, the computer of the present invention described above has a C
It is not limited to pure hardware such as PU, but may include firmware, OS, and peripheral devices.

As described above, the configuration of the present invention may be realized by software or hardware.

[0122]

As is clear from the above description,
The present invention can provide a gradation correction device and a program that can suppress various adverse effects due to gradation correction when changing gradation by gradation correction.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of detected luminance variance according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a gradation correction characteristic according to the first embodiment of the present invention;

FIG. 4 is a diagram illustrating an example of detection of luminance variance according to the first embodiment of the present invention;

FIG. 5 is a diagram showing an example of a gradation correction characteristic according to the first embodiment of the present invention.

FIG. 6 is a block diagram of a tone correction device according to a second embodiment of the present invention.

FIG. 7 is a diagram showing an example of weighting according to a screen position in the gradation correction device according to the second embodiment of the present invention.

FIG. 8 is a block diagram of a tone correction device according to a third embodiment of the present invention.

FIG. 9 is a block diagram of a tone correction device according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a state of offset correction according to a fourth embodiment of the present invention.

FIG. 11 is a block diagram of a tone correction device according to a fifth embodiment of the present invention.

FIG. 12 is a block diagram of a tone correction device according to a sixth embodiment of the present invention.

FIG. 13 is a block diagram of a tone correction device according to a seventh embodiment of the present invention.

FIG. 14 is a diagram showing a relationship between a straight line approximation and a joint according to the seventh embodiment of the present invention;

FIG. 15 is a block diagram showing a configuration of a conventional tone correction device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gradation correction means 2 Luminance difference detection means 3 Comparison means 4 Luminance distribution detection means 5 Control means 6 H counter 7 V counter 8 Screen position detection means 9 Intermediate luminance detection means 10 Correction range calculation means 11 Offset correction means 12 Specific luminance detection Means 13 Limiter 14 Joint detection means 15 LPF

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 5/36 G09G 5/36 520P (72) Inventor Hideki Abe 1006 Odakadoma, Kadoma City, Osaka Matsushita Electric Industrial F term in reference (reference) 5C021 PA12 PA33 PA34 PA53 PA66 PA79 PA80 PA87 RB03 XA35 5C080 BB05 DD03 EE19 EE29 GG07 GG08 JJ01 JJ02 JJ05 5C082 AA02 BA35 BA41 CA11 CA54 CA81 CA85 MM10

Claims (18)

[Claims] 1. A gradation correction unit that calculates a gradation correction characteristic based on a luminance distribution of an input signal and performs gradation correction of the input signal using the calculated gradation correction characteristic. A gradation correction device comprising: a characteristic detection unit configured to detect a predetermined characteristic from a signal; and a control unit configured to control gradation correction performed by the gradation correction unit based on the detection result. 2. The method according to claim 1, wherein the predetermined characteristic is a gradation, the characteristic detecting unit detects an area having the gradation, and the control unit is configured to detect a luminance of a pixel belonging to the detected area having the gradation. And correcting the luminance distribution so as to increase the appearance frequency of the luminance in the luminance distribution, wherein the gradation correction unit calculates the gradation correction characteristic based on the corrected luminance distribution. 2. The gradation correction device according to 1. 3. The gradation correcting apparatus according to claim 2, wherein said characteristic detecting means detects the area having the gradation by detecting an area where a difference in luminance of the input signal is smaller than a predetermined value. 4. The gradation correction device according to claim 3, wherein, of the regions in which the difference in luminance is smaller than the predetermined value, a region having substantially the same luminance is not subjected to the detection. 5. The predetermined feature is an area having a predetermined intermediate luminance. The feature detecting means detects an area having the predetermined intermediate luminance. The control means detects the area having the predetermined intermediate luminance. The luminance distribution is corrected so as to increase the appearance frequency of the luminance in the luminance distribution corresponding to the luminance of the pixels belonging to the region having the intermediate luminance of the luminance distribution means. The gradation correction device according to claim 1, wherein the gradation correction characteristic is calculated based on the gradation correction characteristic. 6. The predetermined feature is a region in which luminance is substantially the same, the feature detecting means detects a region in which the luminance is substantially the same, and the control means detects the region in which the luminance is substantially the same. The luminance distribution is corrected so as to reduce the frequency of occurrence of luminance in the luminance distribution, which corresponds to the luminance of pixels belonging to an area where the luminance is substantially the same, and the gradation correction unit corrects the corrected luminance distribution. The tone correction device according to claim 1, wherein the tone correction characteristic is calculated based on a luminance distribution. 7. The predetermined feature is a position on a display screen, the feature detection unit detects the position in each region of the input signal, and the control unit detects the position of each region. Corresponding to the luminance of the pixels belonging to the area,
2. The tone correction device according to claim 1, wherein the tone appearance frequency is changed in the brightness distribution, and the tone correction unit calculates the tone correction characteristic based on the corrected brightness distribution. 3. 8. A gradation correction unit that calculates a gradation correction characteristic based on a luminance distribution of an input signal, and performs a gradation correction of the input signal using the calculated gradation correction characteristic; Control means for determining a distribution or a degree of gradation correction based on the gradation correction characteristic, and correcting the luminance distribution or the gradation correction characteristic according to a predetermined reference. A tone correction device for performing tone correction using the corrected luminance distribution or the tone correction characteristic. 9. The gradation correction device according to claim 8, wherein the predetermined reference is a frequency of appearance of luminance in a luminance distribution or a gradient of the gradation correction characteristic. 10. The gradation correction device according to claim 8, wherein the predetermined reference differs depending on a degree of luminance. 11. The difference according to the degree of the luminance means that the inclination of each part of the gradation correction characteristic is large in a part corresponding to the intermediate luminance of the gradation correction characteristic, The tone correction device according to claim 8, wherein a portion other than the portion corresponding to the intermediate luminance is smaller than a portion corresponding to the intermediate luminance. 12. A gradation correction unit that calculates a gradation correction characteristic based on a luminance distribution of an input signal, and performs a gradation correction of the input signal using the calculated gradation correction characteristic; A characteristic detecting means for detecting a predetermined characteristic from the signal or the signal after the gradation correction of the input signal; and if the gradation correction characteristic is represented by a broken line, after the input signal is subjected to the gradation correction. When a pixel having a luminance corresponding to a bending point of the gradation correction characteristic has a predetermined characteristic as the detection result, the luminance of the pixel is determined using the luminance of the predetermined pixel around the pixel after the gradation correction. And a correcting means for performing correction. 13. The gradation correction device according to claim 12, wherein the predetermined feature is gradation, and the feature detection unit detects an area having the gradation. 14. The gradation correction device according to claim 13, wherein the detection of the gradation area is performed by detecting an area where a difference in luminance of the input signal is smaller than a predetermined value. 15. The gradation correction apparatus according to claim 14, wherein, of the regions where the difference in luminance is smaller than the predetermined value, a region having substantially the same luminance is not detected. 16. The tone correction device according to claim 1, wherein a tone correction characteristic is calculated based on a luminance distribution of the input signal, and the calculated tone correction characteristic is utilized by using the calculated tone correction characteristic. And / or a tone correction means for performing correction, a feature detection means for detecting a predetermined feature from the input signal, and a control means for controlling tone correction performed by the tone correction means based on the detection result. A program that causes a computer to function as part. 17. The tone correction device according to claim 8, wherein a tone correction characteristic is calculated based on a luminance distribution of the input signal, and the calculated tone correction characteristic is utilized by using the calculated tone correction characteristic. Gradation correction means for performing correction, and control for determining the degree of gradation correction based on the luminance distribution or the gradation correction characteristic and correcting the luminance distribution or the gradation correction characteristic based on a predetermined reference. A program for causing a computer to function as all or part of the means. 18. The tone correction device according to claim 12, wherein a tone correction characteristic is calculated based on a luminance distribution of the input signal, and the calculated tone correction characteristic is used by using the calculated tone correction characteristic. Tone correction means for performing correction; feature detection means for detecting a predetermined feature from the input signal or the signal after tone correction of the input signal; and inputting when the tone correction characteristic is represented by a polygonal line. After the signal has been subjected to the tone correction, if a pixel having a brightness corresponding to a turning point of the tone correction characteristic has a predetermined characteristic as the detection result, the brightness of the pixel is changed to a predetermined value around the pixel. A program for causing a computer to function as all or a part of a correction unit that corrects using the luminance of a pixel after gradation correction.