JP2527165B2 - Image processing method and apparatus - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and apparatus, and more particularly, to an image processing method for effectively performing gradation correction when recording a visible image from a video signal representing a still image on an image recording medium. And equipment.

Background Art For example, receiving a video signal read from a video signal recording medium such as a video floppy disk or a video tape,
A still image recording apparatus that reproduces a visible image on an image recording medium such as photographic paper has been proposed.

In such an apparatus, for example, RGB color signals obtained from an input video signal are sequentially input to a high-intensity black and white CRT for recording, and a lens and a three-color separation filter are arranged in front of the display screen of the recording CRT. Then, the image displayed on the screen is formed on the color photographic paper. In this case, the color image is formed by coloring the CMY dye on the color photographic paper to form a color image.The RGB signal obtained from the input video signal and the signal input to the high-intensity black and white CRT for coloring the CMY dye are The levels need to be reversed. That is, for example, in a bright image portion where the RGB signal level is high, it is necessary to reduce the color development of the CMY pigments to represent the brightness, and therefore the output needs to be reduced.

In addition, the density of each color of the image represented by the input video signal is different from the actual one due to, for example, the illumination condition at the time of shooting, the camera used for shooting, etc., and it is necessary to compensate for this. For example, in reality, the RGB signals to be input may have different maximum levels, even though each RGB color has a white portion of the same level and the highest level. In such a case, if the input RGB signal is output as it is, for example, a portion that should be white is recorded on the recording medium as a color that is mixed with one of the colors due to the difference in the level of the RGB signal. .

In order to compensate for this, gradation correction is performed for each input RGB signal by a lookup table. That is, gradation correction is performed using a look-up table composed of output level data corresponding to the input signal. By this gradation correction, the above-mentioned level inversion is also performed.

If the image in the lookup table has white parts, the highest level point is the highlight point and the lowest level point is the shadow point for each RGB input signal.
The output levels of the highlight point and the shadow point of each of the B input signals are set to match. By doing so, the white portion is expressed as white because the RGB signals are output with the same intensity.

The highlight point and the shadow point are obtained by creating a cumulative histogram showing the frequency distribution of the video signal of each pixel of the input video signal forming one frame image. Then, for example, the point where the cumulative histogram is 99% is set as the highlight point.
That is, the input video signal having a level of 99% or less of the signal of each pixel is set as the highlight point.

By the way, since the input video signal is generally subjected to the process of emphasizing the contour when the image is captured by an electronic still camera, when a cumulative histogram is created from the video signal of each pixel of the input video signal, the pixel whose level is changed by the contour enhancement is used. The cumulative histogram is affected by, and the highlight point and the shadow point cannot be accurately determined.

Further, since noise is usually mixed in the input video signal, the cumulative histogram is also affected by noise, and this point also has a drawback that the highlight point and the shadow point cannot be accurately determined. .

Aim The present invention solves the above-mentioned drawbacks of the prior art, and performs edge enhancement processing or removes the influence of noise to accurately obtain a highlight point or a shadow point, and image processing capable of performing effective gradation correction. It is an object to provide a method and a device.

DISCLOSURE OF THE INVENTION According to the present invention, an image processing method of image-processing an input video signal based on lookup table data and outputting the set image data, receives the input video signal, and sets a highlight point and a shadow point of the input video signal. A step of creating a lookup table data corresponding to the input video signal based on the set highlight point and shadow point, and performing image processing based on the lookup table data corresponding to the input video signal, The setting of the highlight point and the shadow point is performed from the input video signal whose signal level change is reduced by the input signal level change buffering process.

Further, according to the present invention, the image processing device includes image processing means for performing image processing of the input video signal based on the look-up table data and outputting the same, and a highlight point and a shadow of the input video signal upon receiving the input video signal. Highlight point and shadow point setting means for setting points, and lookup table creation for creating lookup table data according to an input video signal based on the set highlight points and shadow points and outputting to the image processing means The highlight point and shadow point setting means sets the highlight point and the shadow point from the input video signal whose signal level change is reduced by the input signal level change buffering means.

Description of Embodiments Embodiments of an image processing method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an image recording apparatus using the image processing apparatus according to the present invention.

For example, a video signal from a video signal source such as a video floppy reproducing device is input into analog-digital (A / D) conversion circuits 10R, 10G and 10B in the form of three primary color signals R, G and B, 52R, 52G and 52B.
Is supplied to. A / D conversion circuits 10R, 10G, and 10B are synchronous signals.
In response to SYNC54, the input video signals 52R, 52G, 52B are converted into corresponding digital data and outputs 56R, 56G, 56B are output to the sharpness circuits 12R, 12G, 12B.

Sharpness circuits 12R, 12G, 12B are A / D conversion circuits 10R, 1
It is a circuit that converts video signals input from 0G and 10B into sharper or softer. The sharpness circuits 12R, 12G, and 12B set the sharpness enhancement coefficient so that the input digital video signal 56R, 5R
This is a matrix circuit that converts the sharpness of 6G and 56B.

For example, if the sharpness enhancement coefficient is set to convert the input signal to sharper, the input video signal 56
R, 56G, and 56B are edge-enhanced. That is, since the signal level of the contour portion where the signal level changes in the input video signals 56R, 56G, and 56B is processed so as to change more rapidly, the contour is emphasized.

Conversely, if the sharpness enhancement coefficient is set to convert the input signals 56R, 56G, 56B more softly, the input image signals 56R, 56G, 56B that have been edge-enhanced are converted to the signals before edge enhancement. To be done. That is, the input video signal
In 56R, 56G, and 56B, since the signal level of the emphasized contour portion is processed so as to change more gradually, the contour emphasis is removed.

Sharpness circuit 12R, 12G, 12B output 58R, 58G, 58B
Is input to the frame memories 14R, 14G and 14B.

The frame memories 14R, 14G, 14B store the signal data of each pixel forming an image for one frame. Output signals 60R, 60G, and 60B from the frame memories 14R, 14G, and 14B are input to the gradation correction units 16R, 16G, and 16B, respectively.

The gradation correction units 16R, 16G, 16B are set with lookup tables LUTR, LUTG, LUTB for gradation correction,
A parameter correction unit that performs gradation correction. The look-up tables LUTR, LUTG, and LUTB are each the input video signal 60.
It is composed of data for converting R, 60G, and 60B into signals to be input to the high-intensity black and white CRT 26 in order to develop the CMY pigments on the color photographic paper 32. Further, by converting the signal levels by the look-up tables LUTR, LUTG, and LUTB, the difference due to the lighting condition in which the image represented by the input video signal is photographed is compensated, and the color tone is approximated to the actual one.

Here, look-up table LUT for gradation correction
R, LUTG, and LUTB will be described.

Second example of lookup tables LUTR, LUTG, LUTB
Shown in the figure. In the figure, the horizontal axis represents the level of the input video signal v, and the vertical axis represents the level of the density signal D that is output.
Such RGB look-up tables LUTR, L
The UTG and LUTB convert the RGB input video signals v into output signals representing the density D.

In the figure, points RH, GH, and BH that are respectively closest to the highest level of the input video signal RGB are highlight points, and points RS, GS, and BS that are closest to the lowest level are shadow points.
The density D of the output signal corresponding to the highlight points RH, GH, BH of the input video signal RGB is set to a constant value DH, and similarly, the density of the output signal corresponding to the shadow points RS, GS, BS of the input video signal RGB. D is also set to a constant value DS. When setting a curve like the one shown in the figure showing the data of the lookup tables LUTR, LUTG, LUTB, highlight points RH, GH, BH
And the shadow points RS, GS and BS are emphasized.

For example, in setting the curve of the lookup table LUTR, a curve is set so as to pass through two points, a highlight point (RH, DH) and a shadow point (RS, DS).

The highlight point and the shadow point are obtained as follows.

A cumulative histogram as shown in FIG. 3 is created for each input video signal of RGB. This figure is a cumulative histogram for the R signal. This shows, for example, the frequency distribution of the video signal of each pixel representing an image of one frame. In the figure, the horizontal axis is the level of the input video signal, and the vertical axis is the point on the curve of the histogram, and the cumulative number of pixels having the video signal level equal to or lower than the input video signal level is included in the image of one frame. The ratio (%) to the total number of pixels is shown. It should be noted that the cumulative histogram may be created from sampled data instead of data of all pixels representing an image of one frame.

Therefore, in the figure, the highlight point RH is the video signal of each pixel and 99% or less of it is below this level RH.
Is shown. In this way, the highlight point is usually set at the point where the cumulative histogram is 99%. Similarly, the shadow point RS indicates that the video signal of each pixel whose level is equal to or lower than this level RS is 1% of the whole, and the shadow point is usually set to a point where the cumulative histogram is 1%.

The output densities corresponding to the highlight point and the shadow point set in this way are set to the predetermined values DH and DS as described above, and by using these, the highlight point (R
H, DH) and the shadow point (RS, DS), the curve of the lookup table LUTR is set.

Returning to FIG. 1, the outputs 62R, 62G, and 62B subjected to the gradation correction by the gradation correction units 16R, 16G, and 16B are the color correction units 18R, 18G, and 18B, and the gradation correction units 20R, 20G, and 20B, respectively. And through the digital analog (D / A) conversion circuit 22R, 22G, 22B,
Switch 24 on the one hand and video monitor 80 on the other hand
Is input to

The outputs 68R, 68G and 68B input to the switch 24 are selectively selected by the switch 24 and input to the high brightness black and white CRT 26 for recording. A lens is in front of the display screen of the recording CRT 26.
28 and a three-color separation filter 30 are arranged so that the image displayed on the screen is formed on the color photographic paper 32.

The color correction units 18R, 18G, and 18B are color correction matrix MTXA.
Is set, thereby compensating the difference in hue characteristics between the signal source of the input video signal and the photosensitive material. For example, when the input signal source is a TV camera, matrix coefficients for compensating the hue characteristics of the TV camera and the printing paper 32 are used for the color correction matrix MTXA. As a result, the video signal data in which the hue is corrected to the target density is output to the outputs 64R, 64G, 64B.

The gradation correction units 20R, 20G, and 20B are set with gradation correction lookup tables LUT-2R, LUT-2G, and LUT-2B, which are parameters for compensating the gradation characteristics of the recording CRT 26 and the printing paper 32. It is a correction unit. The outputs 66R, 66G, 66B of the gradation correction units 20R, 20G, 20B are input to the D / A conversion circuits 22R, 22G, 22B and converted into corresponding analog signals. Analog signal output from D / A converter circuits 22R, 22G, 22B 68R, 68G, 6
8B is input to the switch 24 on the one hand and to the video monitor device 80 on the other hand.

The outputs 68R, 68G and 68B input to the switch 24 are selectively selected by the switch 24 and input to the high brightness black and white CRT 26 for recording. A lens is in front of the display screen of the recording CRT 26.
28 and a three-color separation filter 30 are arranged so that the image displayed on the screen is formed on the color photographic paper 32.

The switch 24 selectively selects the three-separated color signals 68R, 68G, 68B output from the D / A conversion circuits 22R, 22G, 22B to record C.
It is a selection circuit to supply to the RT 80.

Analog signal output from D / A conversion circuit 22R, 22G, 22B 68
R, 68G, and 68B are also input to the video monitor device 80, and the video monitor device 80 displays the image after gradation correction. The operator sees this image and performs necessary operations as described later.

The control device 82 is a control device that controls the operation of the entire device, and is advantageously constituted by a processing system such as a microprocessor. The control device 82 is connected to the sharpness circuits 12R, 12G, 12B, the color correction units 18R, 18G, 18B, the gradation correction units 20R, 20G, 20B, and is also used for sharpness processing in the sharpness circuits 12R, 12G, 12B. Sharpness enhancement factor values and color correction matrix
MTXA and lookup table LUT-2R, LUT-2G, LU
A storage unit 84 for storing various parameter values set as T-2B is connected.

The control device 82 includes a keyboard or the like for the operator to select or modify the image processing parameters such as the value of the sharpness enhancement coefficient or the look-up table LUT-2R, and to give necessary instructions such as image recording instructions. Input operation device
86 is connected.

Output from frame memories 14R, 14G, 14B 60R, 60G, 6
0B is also input to the cumulative histogram creation units 42R, 42G, 42B.

The cumulative histogram creation units 42R, 42G, and 42B arrange the levels of the signals of the respective pixels representing the image of one frame in the order of their magnitudes, and calculate the ratio of the cumulatives below the respective input video signal levels to the whole, A cumulative histogram as shown in FIG. 3 is created. It should be noted that the cumulative histogram may be created from sampled data instead of data of all pixels representing an image of one frame as described above.

And the cumulative histogram creation unit 42R, 42G, 42B is 99%
Output 72 representing the highlight point of 1% and the shadow point of 1%
The R, 72G, and 72B are output to the LUT conversion units 44R, 44G, and 44B, respectively.

The output 74 from the standard lookup table storage unit 46 is also input to the LUT conversion units 44R, 44G, 44B. The standard lookup table storage unit 46 stores a standard lookup table L0 for tone correction.

The LUT conversion units 44R, 44G, and 44B are output from the cumulative histogram creation units 42R, 42G, and 42B based on the output 74 of the standard lookup table L0 read from the standard lookup table storage unit 46. The outputs 72R, 72G, and 72B representing the highlight points and the shadow points are taken into consideration and converted to create the look-up table data for this image. LUT converter 44R, 44G, 44B output 76R, 76G, 76
B is output to the gradation correction units 16R, 16G, 16B respectively, and the gradation correction units 16R, 16G, 16B are output 76R, 76G of the lookup table data sent from the LUT conversion units 44R, 44G, 44B,
The tone correction of the input video signals 60R, 60G, and 60B is performed by the 76B.

The standard look-up table data L0 read from the standard look-up table storage unit 46 is a standard curve as shown in FIG. This curve is represented by D = −2.21og v. Where v is the level of the input video signal, D
Is the output density, and the coefficient 2.2 is the reciprocal of the gamma of the video system.

In the LUT converters 44R, 44G, 44B, this standard curve L0
Is converted so as to pass through these points according to the values of highlight points and shadow points output from the cumulative histogram creation units 42R, 42G, 42B.

Lookup table L for gradation correction units 16R, 16G, and 16B
The input video signals 60R, 60G, and 60B are subjected to gradation correction by the UTR, LUTG, and LUTB, and output. Gradation correction section 16R, 16G, 16
The signals 62R, 62G, and 62B output from B are the color correction units 18R and 1R.
Through 8G, 18B, gradation correction section 20R, 20G, 20B and digital-analog (D / A) conversion circuits 22R, 22G, 22B, one of them is selectively selected by the switch 24, and a high-intensity monochrome CRT for recording
A color image is formed on the photographic printing paper 32 by being input to the photographic paper 32. The other is input to the video monitor device 80.

In this embodiment, when the cumulative histogram is created, the operator inputs the sharpness enhancement coefficient of the sharpness circuits 12R, 12G, 12B into a value for converting the input video signals 56R, 56G, 56B into a softer input operation device 86. Set from. A / D conversion circuit 10R, 10G, 10B to sharpness circuit 12
If the video signal input to R, 12G, and 12B is a signal with edge enhancement, this video signal is output to the sharpness circuits 12R and 12B.
The contour enhancement is removed in G and 12B, and the signal is converted into the original signal without contour enhancement. Also, sharpness circuit 12R, 1
The portions where the level of the input video signal changes abruptly are converted into gentle changes by 2G and 12B, so that the high frequency portion is removed and the noise included in the input video signals 56R, 56G, and 56B is removed.

Therefore, the cumulative histogram creation units 42R, 42G, 42B
In, a cumulative histogram is created from the original signal with no edge enhancement and noise removed, so the highlight points and shadow points obtained from this cumulative histogram are used as the highlight points and shadow points of the input video signal. It is accurate, and based on this highlight point and shadow point, the lookup table conversion units 44R, 44G,
Look-up table LUTR and LUT created in 44B
According to G and LUTB, gradation correction of the input video signal can be accurately performed.

In this way the lookup tables LUTR, LUTG, LU
After setting TB, the operator has the sharpness circuit 12R, 12G,
Sharpness circuit 1 by changing the sharpness enhancement coefficient of 12B
Set 2R, 12G, 12B to output the input video signals 56R, 56G, 56B as they are without converting them to software. As a result, the edge-enhanced input video signals 56R, 56G, and 56B output from the A / D conversion circuits 10R, 10G, and 10B are the sharpness circuit 1
It is output as it is without being changed by 2R, 12G and 12B and is input to the frame memories 14R, 14G and 14B. If more sharpness enhancement is required, the operator may set sharpness enhancement coefficients of the sharpness circuits 12R, 12G, 12B so as to enhance the contour of the input video signal.

Then, for the edge-enhanced input video signals 60R, 60G, and 60B output from the film memories 14R, 14G, and 14B, it is appropriate to use the look-up table set as described above in the gradation correction units 16R, 16G, and 16B. It is possible to perform various gradation corrections.

In a conventional device, such a sharpness circuit
Input video signal 56R with contour enhancement by 12R, 12G, 12B,
Since the contour enhancement of 56G and 56B was not removed, the cumulative histogram creation unit 42R, 4
It was input to 2G and 42B and a cumulative histogram was created. Further, the signal containing noise was directly input to the cumulative histogram creation units 42R, 42G, 42B.

Therefore, the highlight points or shadow points obtained from the cumulative histogram are inaccurate due to the influence of contour enhancement or noise, and the lookup tables LUTR, LU created by such highlight points or shadow points are inaccurate.
Proper gradation correction could not be performed with TG and LUTB.

According to the present embodiment, the effects of contour enhancement and noise are removed as described above to create a cumulative histogram.
The highlight point and the shadow point can be accurately obtained, and appropriate gradation correction can be performed.

Further, since the effect of the edge enhancement of the edge-enhanced input video signal is also removed by the sharpness circuit for performing the edge enhancement, it is not necessary to provide means only for removing the edge enhancement, and the efficiency is improved. Is good.

Note that when the edge enhancement is removed by the sharpness circuits 12R, 12G, and 12B, the signal of the small area portion of the image is removed, but the small area portion has little effect on human vision, so Does not mean

In the above embodiment, the sharpness circuit 12R, 12G,
Although the influence and noise of the edge emphasis of the input video signal are removed by setting the sharpness emphasis coefficient of 12B, a low pass filter may be used instead of the sharpness circuits 12R, 12G and 12B. In this case, the input video signal is passed through the low pass filter and the high frequency component is removed. This removes contour enhancement and noise.

The input image signal from which the edge enhancement and the noise have been removed as described above is input to the cumulative histogram creation units 42R, 42G, and 42B, and the cumulative histogram is created. Then, the edge-enhanced input video signals 60R, 60G, and 60B are applied to the gradation correction unit 16R,
Gradation correction is performed in 16G and 16B to obtain a hard copy.

Further, when the input video signal is a luminance signal and a color difference signal, the sharpness circuit described above is applied only to the luminance signal.
After performing the processing of removing the edge enhancement by 12R, 12G, 12B or the low-pass filter, each RGB color signal may be created from the luminance signal and the color difference signal to create each cumulative histogram. In this way, the noise of the luminance signal with a lot of noise is removed, so that the noise of the video signal input to the cumulative histogram creation units 42R, 42G, 42B can be reduced. An accurate cumulative histogram can be obtained.

Although the above embodiments have described the method and apparatus used in the image recording apparatus, the image processing method and apparatus of the present invention is not limited to recording a visible image on an image recording medium, and various types displayed on a CRT. Can be used for processing images.

Effect According to the present invention, the processing for reducing the change in the signal level of the input video signal input to the cumulative histogram creating means is performed. Therefore, when the input video signal is a contour-enhanced signal, the contour enhancement is removed. The accumulated original histogram can be obtained and a cumulative histogram can be created. Also, noise can be removed from the input video signal to create a cumulative histogram.

Therefore, since an accurate cumulative histogram can be created to obtain a look-up table, gradation correction can be appropriately performed.

[Brief description of drawings]

FIG. 1 is a block diagram of an image recording apparatus using an image processing apparatus according to the present invention, and FIG. 2 shows an example of lookup tables LUTR, LUTG, LUTB stored in the gradation correction unit of FIG. FIG. 3 is a diagram showing an example of a cumulative histogram of the input video signal of FIG. 1, and FIG. 4 is a standard look-up table L0 stored in the standard look-up table storage unit of FIG. It is a figure. Explanation of symbols for main parts 12R, 12G, 12B …… Sharpness circuit 14R, 14G, 14B …… Frame memory 16R, 16G, 16B …… Gradation correction unit 26 …… Recording CRT 32 …… Printing paper 42R, 42G, 42B: Cumulative histogram creation unit 44R, 44G, 44B: Look-up table conversion unit 46: Standard look-up table storage unit 82: Control device 86: Input operation device

Front page continued (72) Inventor Osamu Shimazaki 798 Miyadai, Kaisei-cho, Ashigarakami-gun, Kanagawa Fuji Photo Film Co., Ltd. (56) References JP-A-60-37878 (JP, A) JP-A-57-56843 (JP) , A)

Claims (12)

(57) [Claims] 1. An image processing method for image-processing an input video signal having a change in signal level due to the effect of edge enhancement based on lookup table data and outputting the image signal, the method comprising: An input signal level change buffering process for processing a video signal with a reduced signal level change so as to eliminate the effect of the signal level, and a video signal received by the video signal processed in the input signal level change buffering process Setting step of setting the highlight point and the shadow point of the above, and a lookup table creating step of creating lookup table data according to the video signal based on the highlight point and the shadow point set in the setting step. And, based on the look-up table data created in the look-up table creation step, the input video signal An image processing step of image processing, wherein the setting step creates a cumulative histogram for setting a highlight point and a shadow point from the video signal processed in the input signal level change buffer processing step. A creation step, the lookup table creation step creates lookup table data based on highlight points and shadow points in the cumulative histogram, the image processing step, by the input signal level change buffering step, An image processing method characterized in that at least an input video signal whose signal level has not been changed is subjected to image processing based on the look-up table data. 2. The image processing method according to claim 1, wherein the image processing method is used in an image recording method for reproducing a visible image on an image recording medium. 3. The method according to claim 2, wherein the look-up table creating step represents the intensity of light for irradiating the image recording medium with the input video signal based on the look-up table data. An image processing method, characterized in that a density signal is obtained by converting the signal into a signal and performing gradation correction according to a shooting condition of the input video signal. 4. The method according to any one of claims 1 to 3, wherein the input signal level change buffer processing step changes the sharpness coefficient set in a sharpness circuit, An image processing method characterized in that a change in a signal level of an input video signal is moderated. 5. An image processing method according to any one of claims 1 to 3, wherein the input signal level change buffer processing step is performed by a low-pass filter. 6. The method according to any one of claims 1 to 3, wherein the input signal level change buffering step changes the signal level of only the luminance signal of the input video signal. An image processing method characterized by reducing the number of images. 7. An image processing apparatus for performing image processing on an input video signal having a change in signal level due to the effect of contour enhancement based on lookup table data and outputting the same, wherein the apparatus enhances the input video signal by the contour enhancement. Input signal level change buffer processing means for processing a video signal with a reduced signal level change so as to eliminate the effect of the above; and the video signal received by the video signal processed by the input signal level change buffer processing means. Highlight point and shadow point setting means for setting a highlight point and a shadow point of a signal, and the input signal level change based on the highlight point and the shadow point set by the highlight point and shadow point setting means A look-up table data corresponding to the video signal processed by the buffer processing means is created and the look-up table data is output to the image processing means. Up table creating means, and image processing means for image-processing and outputting the input video signal based on the look-up table data created by the look-up table creating means. The setting means includes a cumulative histogram creating means for creating a cumulative histogram for setting highlight points and shadow points from the video signal processed by the input signal level change buffer processing means, and the look-up table creating means includes Look-up table data is created based on highlight points and shadow points in the cumulative histogram, and the input signal level conversion buffer processing means performs the setting processing in the highlight point and shadow point setting means. The input image to the light point and shadow point setting means The video signal whose change in signal level of the signal is reduced, and the input signal level change buffer processing unit further reduces the signal level change in the image processing unit when performing image processing in the image processing unit. An image characterized by supplying an input video signal that has not been processed, and wherein the image processing means image-processes the input video signal supplied from the input signal level change buffer processing means based on the lookup table data. Processing equipment. 8. The image processing device according to claim 7, wherein the image processing means is used in an image recording device for reproducing a visible image on an image recording medium. 9. The apparatus according to claim 8, wherein the image processing means has a gradation correction means for storing the look-up table data, and the gradation correction means causes the input image to be input. An image processing apparatus, wherein a signal is converted into a signal representing the intensity of light applied to the image recording medium, and gradation correction is performed according to shooting conditions of the input video signal to obtain a density signal. 10. The apparatus according to any one of claims 7 to 9, wherein the input signal level change buffer processing means changes the sharpness coefficient to be set and outputs a signal to the input video signal. An image processing apparatus, which is a sharpness circuit capable of performing processing for gradual change in level. 11. An image processing apparatus according to claim 7, wherein said input signal level change buffer processing means is a low-pass filter. 12. The apparatus according to any one of claims 7 to 9, wherein the input signal level change buffer processing means is one of the input video signals input to the cumulative histogram creating means. Only the luminance signal,
An image processing apparatus characterized by performing processing for reducing a change in signal level.