JP2020145538A - Image processing device, image processing method, and program - Google Patents

Abstract

To realize an emphasis process in which deterioration of an emphasis effect is prevented particularly even in a dark background.SOLUTION: An image processing device comprises means (301, 302, 303, 304, 306, 308, 309) for processing an undershoot component of an image signal as an overshoot component in an edge emphasis process. In a case where the luminance level of the image signal is lower than a threshold, the device performs adjustment (300) to raise the luminance level of the image signal and thereafter inputs the image signal to the edge emphasis process.SELECTED DRAWING: Figure 3

Description

The present invention relates to a technique for processing an image signal captured by an image sensor.

In the past, when shooting a night view or a starry sky, it was necessary to prepare equipment and set shooting conditions in advance. On the other hand, in recent years, there is a digital camera equipped with a shooting mode to make it easier to shoot night views and starry sky. It has become. In addition, some digital cameras have a function of performing image processing such as star enhancement processing that makes it easier to recognize stars even when conditions such as weather and sky brightness are bad. Further, Patent Document 1 discloses a method of optimizing an overshoot and an undershoot by independently controlling the gain in the star enhancement process.

Japanese Unexamined Patent Publication No. 2016-15600

Here, as the enhancement process when a subject such as a slightly bright spot exists in a dark background as in the star enhancement process, there is, for example, an edge enhancement process. However, when the edge enhancement process equivalent to the edge enhancement amount in a normal bright scene is performed as the enhancement process for a subject such as a star in a dark background, for example, when the background is particularly dark, the undershoot is clipped. This will weaken the emphasis effect on the subject star.

Therefore, an object of the present invention is to enable an inconspicuous enhancement process of undershoot, and to realize an enhancement process in which the enhancement effect is not weakened even in a particularly dark background.

The image processing apparatus of the present invention includes a level adjusting means for adjusting the brightness level of the image signal and an edge enhancing means for performing edge enhancing processing on the image signal, and the edge enhancing means is for the edge enhancing processing. The level adjusting means includes a processing means for processing the undershoot component of the image signal as an overshoot component, and the level adjusting means increases the brightness level of the image signal when the brightness level of the image signal is lower than the threshold value. It is characterized in that it is input to the edge enhancing means after adjusting to.

According to the present invention, it is possible to realize an enhancement process in which the enhancement effect is not weakened even on a particularly dark background.

It is a figure which shows the schematic structure of the image pickup apparatus which is an application example of an image processing apparatus. It is a figure which shows the structural example of an image processing circuit. It is a figure which shows the structural example of the star enhancement circuit among the image processing circuits. It is a flowchart of a star emphasis processing.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The configuration shown in the following embodiments is only an example, and the present invention is not limited to the illustrated configuration.
FIG. 1 is a diagram showing a schematic configuration of an image pickup apparatus 100 as an application example of the image processing apparatus of the present embodiment. In this embodiment, a digital camera is taken as an example of the image pickup apparatus 100.
The photographing lens 10 is an optical lens including a focus lens, a zoom lens, and the like. The shutter 12 is a mechanical shutter having an aperture function. The image sensor 14 converts an optical image incident through an optical system such as a photographing lens 10 and a shutter 12 into an electric signal. The A / D converter 16 is an analog / digital converter that converts an analog signal output from the image sensor 14 into a digital signal.

The timing generation circuit 18 is a circuit that supplies a clock signal and a control signal to the image sensor 14 and the A / D converter 16. The timing generation circuit 18 is controlled by the memory control circuit 22 and the system control circuit 50. As the control regarding the exposure time, in addition to the mechanical time control by the shutter 12, the accumulation time control by the electronic shutter control in which the timing generation circuit 18 controls the reset timing of the image sensor 14 is also performed. The accumulation time control by the electronic shutter can be used for moving image shooting and the like.

The image processing circuit 20 performs predetermined pixel interpolation processing, color conversion processing, development processing, and the like on the data from the A / D converter 16 or the data read from the memory 30 via the memory control circuit 22. .. Further, the image processing circuit 20 realizes an electronic zoom function by cutting out an image and performing scaling processing. Further, the image processing circuit 20 performs a predetermined arithmetic processing using the captured image data, and sends the result of the arithmetic processing to the system control circuit 50. The system control circuit 50 controls AF (autofocus) operation and processing in the distance measuring control unit 42, and controls AE (autoexposure) operation and processing in the exposure control unit 40 based on the calculation result from the image processing circuit 20. , EF (flash dimming) processing is controlled. Further, the image processing circuit 20 also performs AWB (auto white balance) processing.

The imaging device 100 of the present embodiment also has a subject detection unit 74. The subject detection method in the subject detection unit 74 is not particularly limited as known methods such as pattern matching and feature point extraction can be applied. Further, as an example, the subject detected by the subject detection unit 74 may be a person's face or the like. When face detection is performed, the subject detection unit 74 outputs the coordinates of the face region (area information), the coordinates of the eyes, and the like as the detection result. Further, the subject detection unit 74 may detect another subject (subject area) by using a known subject detection method, and the detected subject is not limited.

The memory control circuit 22 controls the A / D converter 16, the timing generation circuit 18, the image processing circuit 20, the memory 30, and the compression / expansion circuit 32 under the instruction of the system control circuit 50. For example, the memory control circuit 22 writes the data of the A / D converter 16 to the memory 30 directly via the image processing circuit 20 or the memory control circuit 22, or the data from the A / D converter 16.

The image display unit 28 displays an image or the like on a display device including a TFT, an LCD, or the like. The image data for display written in the memory 30 is sent to the image display unit 28 via the memory control circuit 22, and the image display unit 28 displays an image based on the image data for display on the screen of the display device. .. In addition, when the captured image data is sequentially displayed, the electronic finder function is realized. Further, the image display unit 28 can arbitrarily turn on / off the display according to the instruction of the system control circuit 50, and when the display is turned off, the power consumption of the image pickup apparatus 100 can be significantly reduced. ..

The memory 30 is a memory capable of storing captured still image and moving image data, and has a sufficient storage capacity for storing a predetermined number of still images and moving images for a predetermined time. As a result, the memory 30 can store a large amount of image data at high speed even in the case of continuous shooting or panoramic shooting in which a plurality of still images are continuously shot. The memory 30 can also be used as a work area of the system control circuit 50.

The compression / decompression circuit 32 is a circuit that compresses / decompresses image data by adaptive discrete cosine transform (ADCT) or the like, reads an image stored in a memory 30 and performs compression processing or decompression processing, and stores the processed data in memory. Write in 30.

The exposure control unit 40 drives and controls the shutter 12 having an aperture function. The exposure control unit 40 also controls the flash dimming function by interlocking with the flash 48.
The distance measurement control unit 42 drives the focus lens of the photographing lens 10 and controls focusing. The zoom control unit 44 drives the zoom lens of the photographing lens 10 and controls zooming.
The exposure control unit 40 and the distance measurement control unit 42 are controlled by the system control circuit 50.
The flash 48 has an AF auxiliary light projection function and a flash dimming function.

The system control circuit 50 controls the entire image pickup apparatus 100. For example, when performing control using the TTL method, the system control circuit 50 has an exposure control unit 40 and a distance measurement control unit based on the calculation result of performing a predetermined calculation process on the captured image data by the image processing circuit 20. 42 is controlled.

The mode dial 60, the shutter switches 62 and 64, the display changeover switch 66, the operation unit 70, and the zoom switch 72 are operation devices for the user to input various operation instructions to the system control circuit 50. These are composed of a single unit or a combination of a switch, a dial, a touch panel, a pointing by eye-gaze detection, a voice recognition device, and the like.

The mode dial 60 is a dial operated by the user when switching and setting each function mode such as power off, automatic shooting mode, shooting mode, HDR shooting mode, panoramic shooting mode, movie shooting mode, playback mode, and PC connection mode. Is.

The shutter switch 62 is a switch SW1 that is turned on during the operation of pressing the shutter button (so-called half-press). When the switch SW1 is turned on, the system control circuit 50 instructs the start of operations such as AF (autofocus) processing, AE (autoexposure) processing, and AWB (auto white balance) processing.

The shutter switch 64 is a switch SW2 that is turned on when the operation of pressing the shutter button is completed (so-called full pressing). When the switch SW2 is turned on, the system control circuit 50 exposes the image sensor 14 for the exposure time determined by the AE process. When flash photography is performed, when the switch SW2 is turned on, the system control circuit 50 exposes the image sensor 14 for the exposure time determined by the AE process after performing the EF (flash pre-flash) process. In the case of flash photography, the system control circuit 50 causes the flash 48 to emit light during this exposure period, and at the same time as the end of the exposure period, the exposure of the image sensor 14 is completed via the exposure control unit 40. Further, the system control circuit 50 controls a series of processing operations from imaging by the image sensor 14 to recording processing for writing image data to the recording medium 120. The series of processing includes A / D conversion by the A / D converter 16, writing / reading processing of image data to the memory 30 via the memory control circuit 22, and calculation by the image processing circuit 20 and the memory control circuit 22. Processing, compression / expansion processing of the compression / expansion circuit 32, and the like.

The display changeover switch 66 is a switch for switching the display of the image display unit 28. In addition to the switch operated by the user, the display changeover switch 66 may be, for example, a proximity detection sensor that detects that the user brings his / her face close to the optical finder 104. The system control circuit 50 controls the display switching of the image display unit 28 based on the output of the display switching switch 66. For example, when taking a picture using the optical finder 104, the system control circuit 50 can save power by cutting off the current supply to the image display unit 28.

The operation unit 70 includes various buttons, a touch panel, a rotary dial, and the like. The operation unit 70 includes a menu button, a set button, a macro button, a multi-screen playback page break button, a flash setting button, a single shooting / continuous shooting / self-timer switching button, and the like. In addition, the operation unit 70 has a menu move + (plus) button, a menu move- (minus) button, a playback image move + (plus) button, a playback image- (minus) button, a shooting image quality selection button, and an exposure compensation button. A date / time setting button and the like are also included.

The zoom switch 72 is a switch for a zoom operation in which the user gives an instruction to change the magnification of the captured image. The zoom switch 72 includes a teleswitch that changes the imaging angle of view to the telephoto side and a wide switch that changes the imaging angle of view to the wide-angle side. The system control circuit 50 instructs the change of the shooting angle of view of the shooting lens 10 via the zoom control unit 44 based on the output of the zoom switch 72. As a result, the optical zoom operation is performed. Further, the system control circuit 50 can also control the electronic zooming change of the imaging angle of view by cutting out an image by the image processing circuit 20 or performing pixel interpolation processing based on the output of the zoom switch 72.

The power supply 86 is a power supply unit including a primary battery such as an alkaline battery, a secondary battery such as a NiCd battery, a NiMH battery, and a Li ion battery, and an AC adapter.
The optical finder 104 is a finder used when taking a picture without using the electronic finder function by the image display unit 28.

The I / F 90 is an interface unit for exchanging data with a recording medium 120 such as a memory card or a hard disk. The connector 92 is a connector portion for connecting to a recording medium such as a memory card or a hard disk.
The communication unit 110 is a communication function unit for performing various communications such as USB, IEEE1394, LAN, wireless communication, and the like.
The connector 112 is a connector unit for connecting the image pickup device 100 of the present embodiment to another device via the communication unit 110. The connector 112 may include an antenna for wireless communication.
The recording medium 120 includes a recording unit 122 composed of a semiconductor memory (memory card or the like) or a magnetic disk (hard disk or the like), an I / F 124 between the image pickup device 100, a connector 126 for connecting to the image pickup device 100, and the like. It has.

Here, the imaging device 100 of the present embodiment is provided with a shooting mode for facilitating shooting of the night view or the starry sky, for example, when shooting the night view or the starry sky. According to this shooting mode, it is easier to shoot an appropriate exposure setting and focus position even in a dark place. Further, the image pickup apparatus 100 of the present embodiment is capable of executing an enhancement process that makes it easy to recognize a star even when conditions such as weather and sky brightness are bad in a shooting mode of a night view or a starry sky. In the image pickup apparatus 100 of the present embodiment, when a slightly bright star-like subject exists in a dark background, the enhancement process is performed by the image processing circuit 20.

FIG. 2 is a diagram showing a schematic configuration example of the image processing circuit 20 according to the present embodiment.
An image signal output from the image sensor 14 and A / D converted by the A / D converter 16 is input to the image processing circuit 20. It is assumed that the image signal from the image sensor 14 is a so-called bayer array signal. The luminance generation unit 201 generates a luminance signal Y from the signals in the bayer array. The color generation unit 202 generates a color difference signal UV from the signals of the bayer array. The edge enhancement unit 203 performs edge enhancement processing on the input image signal. Then, the YUV signal obtained by the processing of the luminance generation unit 201, the color generation unit 202, and the edge enhancement unit 203 is sent to the post-processing unit 204 and the detection system 205. The post-processing unit 204 performs post-processing such as resizing processing, saturation changing processing, and edge enhancement processing on the YUV signal according to the shooting scene and the like. The detection system 205 performs detection processing for detecting the brightness level of the entire image or the subject, detecting the face, detecting the scene, and the like. Then, the detection system 205 appropriately sets various parameters used in each processing in the brightness generation unit 201, the color generation unit 202, the edge enhancement unit 203, and the post-processing unit 204 based on the detected brightness level, face, scene, and the like. change.

3 (a) to 3 (e) are views of the image processing circuit 20 according to the present embodiment, which is used for a configuration and an explanation thereof for emphasizing a subject such as a star.
FIG. 3A is a diagram showing a configuration in which a subject such as a star is emphasized. In the present embodiment, an example in which the star enhancement process for emphasizing the stars in the night sky is performed by the edge enhancement process of the edge enhancement unit 203 is performed, but it is performed during the edge enhancement process of the post-processing in the post-processing unit 204. You may.

In FIG. 3A, the addition / subtraction circuit 300 is a level adjustment circuit capable of adjusting the luminance level by shifting the luminance level of the input image signal. The luminance level shift by the addition / subtraction circuit 300 is performed based on, for example, the luminance level of the image detected by the detection system 205 of FIG. 2 and the luminance level of the subject area. For example, when the luminance level is lower than a predetermined threshold value, the detection system 205 changes the parameters of the addition / subtraction circuit 300 so that the addition / subtraction circuit 300 adjusts the level to raise the luminance level of the image. As a result, in the addition / subtraction circuit 300, when the brightness level of the image is lower than a predetermined threshold value, a process of shifting to raise the brightness level is performed. When the detected luminance level is equal to or higher than a predetermined threshold value, the detection system 205 sets the parameters of the addition / subtraction circuit 300 so that the level adjustment for raising the luminance level is not performed in the addition / subtraction circuit 300.

The image signal output from the addition / subtraction circuit 300 is input to the non-inverting input terminal (+ side terminal) of the subtraction circuit 302, the inverting input terminal (-side terminal) of the subtraction circuit 303, and the low-pass filter (LPF) 301. .. Further, the image signal after the low-pass filter processing by the low-pass filter 301 is input to the inverting input terminal of the subtraction circuit 302 and the non-inverting input terminal of the subtraction circuit 303. Here, FIG. 3B is a diagram showing a part of the horizontal waveform of the image signal input to the addition / subtraction circuit 300, in which the vertical axis direction is the brightness level and the horizontal axis direction is the horizontal direction of the image. It is assumed that it represents coordinates. FIG. 3C is a diagram showing a signal waveform after the signal of FIG. 3B is processed by the low-pass filter 301. As shown in FIG. 3C, the signal waveform after the low-pass filter processing is a signal waveform in which high frequency components are substantially removed from the signal of FIG. 3B.

In the subtraction circuit 302 and the subtraction circuit 303, the difference between the image signal output from the addition / subtraction circuit 300 and the image signal processed by the low-pass filter 301 is obtained. At this time, by not considering the negative signal, a signal of an overshoot component, which is an edge signal convex toward the high luminance side, can be obtained from the subtraction circuit 302. FIG. 3D shows the signal waveform after processing by the subtraction circuit 302. In the subtraction circuit 302, the image signal after the low-pass filter processing of FIG. 3 (c) is subtracted from the image signal of FIG. 3 (b), so that the shaded portion 311 in FIG. 3 (d) becomes an overshoot component. A signal is obtained.

On the contrary, from the subtraction circuit 303, a signal in which the undershoot component, which is an edge signal convex toward the low luminance side, is inverted can be obtained. FIG. 3E shows the signal waveform after processing by the subtraction circuit 303. In the subtraction circuit 303, the shaded portion 321 in FIG. 3 (e) is an undershoot component by subtracting the image signal of FIG. 3 (b) from the image signal after the low-pass filter processing of FIG. 3 (c). The inverted signal of is obtained.

The signal output from the subtraction circuit 302 is input to the gain circuit (AMP) 304. Further, the signal output from the subtraction circuit 303 is input to the gain circuit 306. The gain circuit 304 performs a clip process for limiting the gain and amplitude on the signal of the overshoot component by the control signal from the gain control circuit (CTRL) 305. Further, the gain circuit 306 of the present embodiment is subjected to a clip process for limiting the gain and amplitude with respect to the signal in which the undershoot component is inverted by the control signal from the gain control circuit 307. In the present embodiment, when the signal value to which the undershoot component is added (that is, the absolute value of the undershoot component is subtracted from the original signal) becomes a negative value in calculation as in the normal edge enhancement processing, the signal value is set. It is treated as zero. Therefore, in the normal edge enhancement process, when the background is a dark image, the signal value to which the undershoot component is added suddenly sticks to zero. Therefore, the gain circuit 304 functions as a circuit that performs clipping processing so as to suppress a sudden change in the edge enhancement effect when the signal value sticks to zero as described above.

The output signal of the gain circuit 304 is input to the adder circuit 308. The addition circuit 308 adds the original image signal before being input to the addition / subtraction circuit 300 and the signal after the signal of the overshoot component is clipped by the gain circuit 304. Then, the output signal of the adder circuit 308 is input to the adder circuit 309.
Further, the output signal of the gain circuit 306 is input to the adder circuit 309. The adder circuit 309 adds the output signal of the adder circuit 308 and the output signal of the gain circuit 306. That is, the addition circuit 309 adds the original image signal before being input to the addition / subtraction circuit 300 and the signal of the overshoot component after the clip processing by the gain circuit 304, and the undershoot after the clip processing by the gain circuit 306. The signal with the inverted component is added. Then, the output signal of the addition circuit 309 becomes a signal after the enhancement process.

As described above, in the configuration of FIG. 3A, when the edge enhancement process is performed, the undershoot component of the image signal is subtracted without being added to be treated as an overshoot component. Therefore, as described above, the signal value does not stick to zero due to the addition of the undershoot component. In such a case, if the gain circuit 306 that performs the clipping process is passed through, the overshoot component obtained by inverting the undershoot component will be rather suppressed. Therefore, in the configuration of FIG. 3A, when the brightness level of the image is lower than a predetermined threshold value, the brightness level of the image is raised by the level at which the undershoot component of edge enhancement due to the low brightness level of the subject is not clipped. After that, it is configured to be input to the edge enhancement processing. Further, in the configuration in which the enhancement processing such as stars is performed instead of inputting to the edge enhancement processing after increasing the brightness level of the image, the signal before the gain of the clip processing is applied by the gain circuit (304, 306) is used. The edge enhancement process may be performed.

The low-pass filter 301 used here is, for example, a filter that replaces the value of the pixel of interest with the pixel of interest and the pixel adjacent thereto at a ratio of 1: 2: 1 (/4). And.
Further, in the present embodiment, the difference between the image signal output from the addition / subtraction circuit 300 and the image signal after the low-pass filter processing is obtained, but the difference is not limited to this, and a signal containing a high frequency component and a signal not containing a high frequency component It is only necessary to be able to obtain the difference between.

FIG. 4 is a flowchart showing the flow of processing when the imaging device 100 of the present embodiment performs enhancement processing for a subject such as a star. The processing of the flowchart of FIG. 4 is mainly performed by the image processing circuit 20, but a part of the processing is related to the system control circuit 50.

In FIG. 4, when the shutter switch 64 is operated and the ON signal of the switch SW2 is received, the system control circuit 50 starts the photographing operation in the image pickup apparatus 100 as the process of step S401. When shooting is started in step S401, the image processing circuit 20 acquires the average luminance level of the captured image captured by the image sensor 14 and input from the A / D converter 16 as the process of step S402.

Next, when the process proceeds to step S403, the image processing circuit 20 performs a level determination process for comparing the threshold value preset for the luminance level with the average luminance level acquired in step S402. Then, when the image processing circuit 20 determines that the average brightness level is lower than the threshold value, the image processing circuit 20 proceeds to step S404. On the other hand, the image processing circuit 20 proceeds to step S405 when it is determined that the average brightness level is equal to or higher than the threshold value, that is, when the brightness is high to some extent.

Proceeding to step S404, in the image processing circuit 20, the addition / subtraction circuit 300 performs a process of shifting so as to raise the brightness level of the image.
After that, when the image processing circuit 20 proceeds to step S405, the image processing circuit 20 performs edge enhancement as an enhancement process for a subject such as a star.

The acquisition of the brightness level performed in step S402 is described on the premise that the average value of the brightness level of the entire image is obtained. However, for example, the sky and the ground, the building, and the like are detected, and the predetermined area is, for example, the empty area. You may want to get the average value of the luminance levels for. In this case, in the subsequent step S403, the average value of the brightness levels in the empty region and the threshold value are compared.

As described above, according to the present embodiment, by preventing the undershoot component of edge enhancement due to the low brightness level of the image from being clipped, it is possible to enhance the undershoot component inconspicuously. Further, according to the present embodiment, it is possible to realize an enhancement process in which the enhancement effect is not weakened even on a particularly dark background.

Although each embodiment of the present invention has been described in detail above, the present invention is not limited to these embodiments, and various embodiments within the scope of the gist of the present invention are also included in the present invention.
Further, the processing of each function and the flowchart related to the image processing device of the above-described embodiment may be realized only by the hardware configuration, or may be configured as a software module by executing a program by a CPU or the like. Further, a part may be configured as a hardware configuration and the rest may be configured as a software module. The program for configuring this software module is not only when it is prepared in advance and stored in an internal memory or the like, but also when it is acquired from a recording medium such as an external memory or via a network (not shown). You may.

Further, in the above-described embodiment, an example of application to a digital camera has been given, but it can also be applied to, for example, a surveillance camera, an industrial camera, an in-vehicle camera, a medical camera, a smartphone having a photographing function, a tablet terminal, and the like.

A program that realizes one or more functions in signal processing according to the present invention can be supplied to a system or device via a network or storage medium, and is read and executed by one or more processors of the computer of the system or device. It is feasible by being done. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

The above-described embodiments are merely examples of implementation of the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. That is, the present invention can be implemented in various forms without departing from the technical idea or its main features.

100: image pickup device, 14: image sensor, 20: image processing circuit, 50: system control circuit

Claims (9)

Level adjustment means for adjusting the brightness level of the image signal,
It has an edge enhancement means for performing edge enhancement processing on the image signal.
The edge enhancing means includes a processing means for processing an undershoot component of the image signal as an overshoot component during the edge enhancing process.
The image processing apparatus is characterized in that, when the brightness level of the image signal is lower than the threshold value, the level adjusting means adjusts the brightness level of the image signal so as to increase the brightness level and then inputs the image signal to the edge enhancing means. The edge enhancement process includes a clip process that limits the gain and amplitude of the signal.
The level adjusting means is characterized in that when the brightness level of the image signal is lower than the threshold value, the brightness level of the image signal is increased by the level at which the undershoot component is not clipped by the edge enhancement processing. The image processing apparatus according to claim 1. When the average luminance level of the entire image by the image signal or the average luminance level of a predetermined region in the image signal is lower than the threshold value, the level adjusting means performs the adjustment of the luminance level. The image processing apparatus according to claim 1 or 2. A level determination means for determining the luminance level of an image signal and
It has an edge enhancement means for performing edge enhancement processing on the image signal.
The edge enhancement process includes a clip process that limits the gain and amplitude of the signal.
The edge enhancing means
A processing means for processing an undershoot component of the image signal as an overshoot component during the edge enhancement process is included.
An image processing apparatus characterized in that when the luminance level of the image signal is determined by the level determining means to be lower than the threshold value, the edge enhancement processing is performed using the signal before the clipping processing is performed. The level determining means is characterized in that it determines whether or not the average luminance level of the entire image based on the image signal or the average luminance level of a predetermined region in the image signal is lower than the threshold value. The image processing apparatus according to 4. The processing means according to claim 1, wherein the undershoot component is processed as the overshoot component by subtracting the undershoot component from the image signal at the time of the edge enhancement processing. 5. The image processing apparatus according to any one of 5. An image processing method executed by an image processing device.
A level adjustment process that adjusts the brightness level of the image signal,
It has an edge enhancement step of performing edge enhancement processing on the image signal.
The edge enhancement step includes a processing step of processing an undershoot component of the image signal as an overshoot component during the edge enhancement process.
In the level adjusting step, when the brightness level of the image signal is lower than the threshold value, the image processing method is characterized in that the brightness level of the image signal is adjusted to be raised and then input to the edge enhancement step. An image processing method executed by an image processing device.
The level determination process for determining the brightness level of the image signal and
It has an edge enhancement step of performing edge enhancement processing on the image signal.
The edge enhancement process includes a clip process that limits the gain and amplitude of the signal.
The edge enhancement step is
A processing step of processing an undershoot component of the image signal as an overshoot component during the edge enhancement process is included.
An image processing method characterized in that when the brightness level of the image signal is determined to be lower than the threshold value by the level determination step, the edge enhancement process is performed using the edge signal before the clip process is performed. A program for causing a computer to function as each means of the image processing apparatus according to any one of claims 1 to 6.

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