KR102401018B1 - Apparatus for correcting low visibility digital image able to forcible set within the correction section and method thereof - Google Patents

Abstract

The present invention relates to a low-visibility digital image correction apparatus capable of forced setting within a correction section and a method thereof. According to the present invention, the low-visibility digital image correction apparatus comprises: an input unit receiving a target image to be corrected from an image server; a pre-processing unit acquiring a pixel value corresponding to blue (B) from RGB and a pixel value corresponding to brightness for each of a plurality of pixels included in the target image; an initial value extraction unit using the pixel value corresponding to the brightness to acquire a first histogram, using the pixel value corresponding to the blue (B) to acquire a second histogram, acquiring a first initial value from the first histogram, and acquiring a second initial value from the second histogram; a correction section extraction unit smoothing the first histogram to acquire a first reference value, smoothing the second histogram to acquire a second reference value, and using the first reference value and the second reference value to acquire each correction section; a control unit matching a correction interval for the brightness acquired through the first reference value with the correction interval for blue (B) acquired through the second reference value and using the matched correction interval to determine a final correction interval; and a correction unit calculating an average value of the pixel values included in the extracted final correction section and forcibly correcting the brightness of the target image in response to the calculated average value.

Description

Apparatus for correcting low visibility digital image able to forcible set within the correction section and method thereof

The present invention relates to a low-visibility digital image correction apparatus and method capable of forcibly setting within a correction section, and in more detail, sets correction standard data for image data, and corrects the image based on the set correction standard data It relates to a low-visibility digital image correction apparatus and method therefor.

Digital image processing refers to converting a photographic image composed of an analog signal into a digital signal using various algorithms depending on the purpose. In digital image processing, pixel point processing, area processing, geometry processing, and frame processing may be performed to correct brightness or increase sharpness to increase image recognition rate.

However, when converting an analog signal to a digital signal, the amount of data becomes vast, so it takes 16 to 24 hours to send a digital signal through a medium (wired, radio) with the same frequency bandwidth than to send an analog signal. or 16 to 24 times the number of media is required to send them at the same time.

Accordingly, various technologies have been developed for compressing the amount of data that is inevitably increased due to digitization while minimizing deterioration in image quality and sound quality.

However, since large-capacity data is repeatedly compressed and decompressed according to the data processing limit of the transmission network and intermediate equipment, loss of image data may occur. In addition, when the received image is finally expressed due to data loss, the output image is output more dimly or darker than the initial image, thereby deteriorating the discrimination power of the image.

CCTV cameras installed for various purposes, such as crime prevention, crime, and fire, convert light incident through an image sensor into a digital image signal, and transmit the converted digital image signal to a server. At this time, when the atmospheric environment is clean, the image sensor can generate a clear image image, but if the atmospheric environment is not clean due to fog, snow, rain, etc., it generates a blurred image image, so it is very difficult to recognize an object from the image image there was Therefore, in order to increase object identification, there is a need for a technique for analyzing and processing a video image generated by a CCTV camera at a remote location.

The technology that is the background of the present invention is disclosed in Korean Patent Registration No. 10-0555755 (published on March 3, 2006).

As described above, according to the present invention, it is to provide a digital image correction apparatus and method for setting correction standard data for image data and correcting an image based on the set correction standard data.

According to an embodiment of the present invention for achieving this technical problem, in the low visibility digital image correction device capable of compulsory setting within a correction section, an input unit for receiving a target image to be corrected from an image server, a plurality of target images included in the target image A preprocessor that obtains a pixel value corresponding to the light and dark pixel value for each pixel and a pixel value corresponding to blue (B) among RGB, obtains a first histogram using the pixel value corresponding to the light and dark, and corresponds to the blue (B) an initial value extractor that obtains a second histogram using pixel values of to obtain a first reference value, obtain a second reference value by smoothing the second histogram, and then extract each correction interval using the first reference value and the second reference value; A control unit that matches the correction section for the contrast obtained through the reference value and the correction section for the blue (B) obtained through the second reference value, and extracts the final correction section using the matched correction section, and the extracted final and a correction unit that calculates an average value of pixel values included in the correction section and forcibly corrects the contrast of the target image in response to the calculated average value.

The preprocessor may convert the RGB value of the target image into a YCrCb value, and then extract only a Y value from the converted YCrCb value to obtain a pixel value corresponding to lightness and darkness.

The initial value extraction unit extracts, as a first initial value, a pixel value corresponding to the brightness and darkness corresponding to a value having the highest frequency of pixels in the first histogram, and sets the pixel value in the second histogram to a value with the highest frequency. A pixel value corresponding to the corresponding blue (B) may be extracted as a second initial value.

The correction section extractor extracts a value obtained by subtracting a first initial value from the first reference value as a first lower limit value, and extracts a value increased by the first initial value from the first reference value as a first upper limit value, and then A range greater than the first lower limit value and smaller than the first upper limit value may be set as a correction section for the contrast.

The correction section extractor extracts a value obtained by subtracting a second initial value from the second reference value as a second lower limit value, and extracts a value increased by a second initial value from the second reference value as a second upper limit value, and then 2 A range greater than the lower limit value and smaller than the second upper limit value may be set as a correction section for blue (B).

The correction period for the blue (B) may be greater than a second lower limit and less than a second upper limit, the second lower limit may be greater than the first lower limit, and the second upper limit may be smaller than the first upper limit.

When the second reference value is smaller than the first reference value, the controller may determine a final correction interval from the second lower limit value to the first reference value.

When the second reference value is greater than or equal to the first reference value and the second lower limit is less than the first reference value, the controller may determine a final correction interval from the second lower limit to the second upper limit.

When the second lower limit value and the second reference value are greater than the first reference value, the controller may determine a final correction interval from the first reference value to the second reference value.

The compensator may forcibly adjust the contrast of the target image by converting a histogram of a plurality of pixels included in the target image in response to an average value of pixel values included in the final compensation section.

In addition, according to an embodiment of the present invention, in the low-visibility digital image correction method capable of forcibly setting within a correction section using a low-visibility digital image correction device, receiving an image to be corrected from an image server, the target image obtaining a pixel value corresponding to blue (B) from among the pixel values corresponding to the brightness and the RGB for each of a plurality of pixels included in the , obtaining a first histogram using the pixel values corresponding to the brightness, obtaining a second histogram using the pixel values corresponding to B), obtaining a first initial value from the first histogram, and obtaining a second initial value from the second histogram; obtaining a first reference value by smoothing, obtaining a second reference value by smoothing the second histogram, and then extracting each correction section using the first reference value and the second reference value, the first reference value Matching the correction period for the contrast obtained through the correction period for the blue (B) obtained through the second reference value and extracting the final correction period using the matched correction period, and the extracted final correction period and calculating an average value for a plurality of pixel values included in , and forcibly correcting the contrast of the target image in response to the calculated average value.

As described above, according to the present invention, since the correction data range for RGB color is set and the final correction range for the input image is extracted within the set correction data range, the time required for extracting the correction range for the image can be reduced. have.

In addition, according to the present invention, since the image is corrected within the set correction data range, the recognition rate for the image can be increased, the image can be corrected without separate noise processing, and the correction value using the contrast and blue (B) Since , it is possible to alleviate the blurring of only one area of the image due to the luminance.

1 is a block diagram of a low visibility digital image correction apparatus according to an embodiment of the present invention.
2 is a flowchart illustrating a low-visibility digital image correction method using a low-visibility digital image correction apparatus according to an embodiment of the present invention.
FIG. 3 is an exemplary diagram for explaining a method of acquiring a first initial value in step S230 illustrated in FIG. 2 .
4 is an exemplary view for explaining the correction section for the contrast in step S240 shown in FIG.
FIG. 5 is an exemplary diagram for explaining a correction section for blue (B) in step S240 shown in FIG. 2 .
FIG. 6 is an exemplary view for explaining a method of determining a final correction section in step S250 shown in FIG. 2 .
FIG. 7 is an exemplary diagram for explaining step S260 shown in FIG. 2 .

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of explanation.

In addition, the terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to intentions or customs of users and operators. Therefore, definitions of these terms should be made based on the content throughout this specification.

Hereinafter, a low visibility digital image correcting apparatus according to an embodiment of the present invention will be described in more detail with reference to FIG. 1 .

1 is a block diagram of a low visibility digital image correction apparatus according to an embodiment of the present invention.

As shown in FIG. 1 , the low visibility digital image correction apparatus 100 according to an embodiment of the present invention includes an input unit 110 , a preprocessor 120 , an initial value extractor 130 , and a correction section extractor 140 . ), a control unit 150 and a correction unit 160 .

First, the input unit 110 receives a target image to be corrected.

The pre-processing unit 120 obtains a pixel value corresponding to brightness and a pixel value corresponding to blue (B) from the input target image, respectively.

That is, the preprocessor 120 obtains a pixel value corresponding to lightness and darkness for each of a plurality of pixels included in the target image. In addition, the preprocessor 120 obtains a pixel value corresponding to blue (B) for each of a plurality of pixels included in the target image.

At this time, when the input target image is a color image, the preprocessor 120 converts the RGB value of the target image to a YCrCb value, and then extracts only the Y value from the converted YCrCb values to obtain a pixel value corresponding to the contrast. .

Next, the initial value extraction unit 130 extracts an initial value using the acquired pixel value.

In other words, the initial value extractor 130 generates a first histogram by using pixel values corresponding to light and dark, and extracts a first initial value from the generated first histogram.

Then, the initial value extractor 130 generates a second histogram by using a pixel value corresponding to blue (B), and extracts a second initial value from the generated second histogram.

The correction section extractor 140 extracts a correction section using the extracted first and second initial values.

In detail, the correction section extractor 140 smoothes the first histogram and obtains a first reference value from the smoothed first histogram. Then, the correction interval extractor 140 extracts a first lower limit value by subtracting the first initial value from the obtained first reference value, and increases the first reference value by the first initial value to extract the first upper limit value.

The correction section extractor 140 extracts a range larger than the first lower limit and smaller than the first upper limit as a correction section for the contrast.

Also, the correction section extractor 140 smoothes the second histogram and obtains a second reference value from the smoothed second histogram. Then, the correction interval extractor 140 extracts a second lower limit value by subtracting a second initial value from the obtained second reference value, and increases the second initial value by a second initial value to extract a second upper limit value.

The correction section extractor 140 extracts a range larger than the second lower limit and smaller than the second upper limit as a correction section for blue (B).

When the extraction of the correction section is completed, the controller 150 determines the final correction section by matching the correction section for the contrast with the correction section for the blue (B).

Finally, the compensator 150 calculates an average value of pixels included in the final correction section, and forcibly corrects the contrast of the target image corresponding to the calculated average value.

Hereinafter, a low visibility digital image correction method using the low visibility digital image correcting apparatus 100 according to an embodiment of the present invention will be described in more detail with reference to FIGS. 2 to 7 .

2 is a flowchart illustrating a low-visibility digital image correction method using a low-visibility digital image correction apparatus according to an embodiment of the present invention.

As shown in FIG. 2 , the low visibility digital image correction apparatus 100 according to an embodiment of the present invention receives a target image to be corrected from an image server (not shown) ( S210 ).

In other words, the user selects a target image to be corrected from among a plurality of digital images collected in an image server (not shown). Then, the image server transmits the target image selected by the user to the low visibility digital image correction apparatus 100 .

In this case, the input target image may be a still image or a moving image.

Next, the preprocessor 120 extracts a pixel value from the input target image (S220).

In other words, every image is made up of a set of pixels. Therefore, the preprocessor 120 obtains each pixel value corresponding to the contrast and blue (B) from a plurality of pixels included in the target image.

That is, the preprocessor 120 obtains a pixel value corresponding to lightness and a pixel value corresponding to blue (B) for each pixel, respectively.

On the other hand, when the input target image is a color image, the preprocessor 120 converts the RGB value of the target image into a YCrCb value, and then extracts only the Y value from the converted YCrCb value to obtain a pixel value corresponding to the contrast. .

In the present invention, a pixel value corresponding to light and dark is obtained by converting RGB values into YCrCb values, but the present invention is not limited thereto, and a pixel value corresponding to light and dark may be obtained by converting an input target image into a gray scale form. have.

When step S220 is completed, the initial value extraction unit 130 generates each histogram using a pixel value corresponding to light and dark and a pixel value corresponding to blue (B), and obtains an initial value through the generated histogram. (S230)

First, the initial value extraction unit 130 measures the frequency of pixel values corresponding to the contrast from 0 to i, and applies the measured result to a graph in which the X-axis is the pixel value and the Y-axis is the frequency to obtain a first histogram. create

FIG. 3 is an exemplary diagram for explaining a method of acquiring a first initial value in step S230 illustrated in FIG. 2 .

For example, as shown in FIG. 3 , the initial value extraction unit 130 calculates the frequency by using pixel values corresponding to the brightness and darkness of a 4*4 matrix. Then, the initial value extractor 130 generates a first histogram by using the calculated frequency, and extracts a value with the highest frequency of pixels in the first histogram, that is, “1” as the first initial value.

Next, the initial value extraction unit 130 extracts the second initial value in the same manner as the method illustrated in FIG. 3 . That is, the initial value extractor 130 measures the frequency of pixel values corresponding to blue (B) from 0 to i, and generates a second histogram by using the measured frequency.

In addition, the initial value extractor 130 extracts a pixel value corresponding to a value having the highest frequency of pixels in the second histogram as a second initial value.

When step S230 is completed, the correction section extractor 140 performs a smoothing process on the first histogram and the second histogram to extract a correction section for contrast and a correction section for blue (S240).

FIG. 4 is an exemplary diagram for explaining a correction section for contrast in step S240 shown in FIG. 2 .

First, the correction interval extractor 140 calculates a cumulative frequency based on the first histogram, and normalizes the calculated cumulative frequency to a cumulative sum to obtain a first reference value k.

As shown in FIG. 4 , the correction section extractor 140 extracts the first lower limit value k1 by subtracting the first initial value from the first reference value k. Then, the correction interval extractor 140 extracts the first upper limit value k1' by increasing the first reference value k by the first initial value.

Then, the correction section extractor 140 sets a range greater than the first lower limit value k1 and smaller than the first upper limit value k1 ′ as the correction section for the contrast.

FIG. 5 is an exemplary diagram for explaining a correction section for blue (B) in step S240 shown in FIG. 2 .

The correction interval extractor 140 calculates a cumulative frequency based on the second histogram, and normalizes the calculated cumulative frequency to a cumulative sum to obtain a second reference value b.

As shown in FIG. 5 , the correction section extractor 140 extracts the second lower limit value b1 by subtracting the second initial value from the second reference value b. Then, the correction section extractor 140 extracts the second upper limit value b1' by increasing the second reference value b by the second initial value.

Then, the correction section extractor 140 sets a range greater than the second lower limit value b1 and smaller than the second upper limit value b1 ′ as the correction section for blue (B).

In this case, the second lower limit value b1 is greater than the first lower limit value k1 , and the second upper limit value b1 ′ is smaller than the first upper limit value k1 ′.

When the setting of the correction section is completed, the controller 150 determines the final correction section by matching the correction section for the contrast with the correction section for the blue (B) (S250).

The low visibility digital image correcting apparatus 100 according to an exemplary embodiment of the present invention performs correction within an upper limit value and a lower limit value for contrast. In this case, as the input pixel value is set to the upper limit value, the target image may become brighter and some regions may be dimmed, and as the input pixel value is set to the upper limit value, the target image may become darkened toward the lower limit value, thereby making the distinction between some regions ambiguous. Accordingly, the low visibility digital image compensating apparatus 100 is included in the contrast correction section, but applies the blue (B) correction section to perform color correction as well as the contrast of the target image to increase the discrimination.

Accordingly, the control unit 150 matches the correction period for the contrast and the correction period for the blue (B), compares the pixel values of the first reference value (k) and the second reference value (b), and then according to the comparison result Each different method determines the final calibration interval.

Hereinafter, a method of determining the final correction section according to the magnitudes of the first reference value k and the second reference value b will be described with reference to FIGS. 6A to 6C .

FIG. 6 is an exemplary view for explaining a method of determining a final correction section in step S250 shown in FIG. 2 .

As shown in FIG. 6A , when the second reference value b is smaller than the first reference value k, the control unit 150 uses the second lower limit value b1 to the first reference value k as the final correction section. decide In other words, the controller 150 determines the section from the second lower limit value b1 to the second reference value b and the section from the second reference value b to the first reference value k as the final correction section.

As shown in FIG. 6B , when the second reference value b is greater than or equal to the first reference value k, and the second lower limit value b1 is smaller than the first reference value k, the control unit 150 controls the second lower limit value ( From b1) to the second upper limit value b1' is determined as the final correction section. In other words, the control unit 150 includes a section from the second lower limit value (b1) to the first reference value (k) or the second reference value (b), and the second upper limit value from the first reference value (k) or the second reference value (b). The section up to (b1') is determined as the final correction section.

As shown in FIG. 6C , when the second lower limit value b1 and the second reference value b are greater than the first reference value k, the control unit 150 controls from the first reference value k to the second reference value b. is determined as the final calibration interval. In other words, the control unit 150 determines the section from the first reference value (k) to the second lower limit value (b1) and the section from the second lower limit value (b1) to the second reference value (b) as the final correction section.

That is, as shown in FIGS. 6A to 6C , the first lower limit value k1 , the first reference value k, the first upper limit value k1 ′, and the second lower limit value b1 , the second reference value b, and the second The final correction section is determined according to the order of magnitude of the upper limit value b1', and the controller 150 determines the section corresponding to the second to fourth sizes in the order of the sizes as the final correction section.

Finally, the corrector 160 calculates an average value of pixel values included in the determined final correction section, and corrects the contrast of the target image using the calculated average value ( S260 ).

FIG. 7 is an exemplary diagram for explaining step S260 shown in FIG. 2 .

7 , the correction unit 160 calculates an average value of pixel values included in the final correction section, and forcibly transforms a histogram of a plurality of pixels included in the target image in response to the calculated average value.

As described above, the low visibility digital image correcting apparatus according to the present invention sets a correction data range for RGB colors and extracts the final correction period for the input image within the set correction data range, so it takes time to extract the correction period for the image. time can be shortened.

In addition, the low visibility digital image correcting apparatus according to the present invention corrects the image within the set final correction section, so it is possible to increase the recognition rate of the image, and it is possible to correct the image without separate noise processing, and the contrast and blue (B) ) to obtain a correction value, it is possible to alleviate the blurring of only one area of the image due to the luminance.

Although the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, those of ordinary skill in the art will understand that various modifications and equivalent other embodiments are possible therefrom. will be. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the following claims.

100: low visibility digital image correction device
110: input unit
120: preprocessor
130: initial value extraction unit
140: correction section extraction unit
150: control unit
160: correction unit

Claims (20)

In the low visibility digital image correction device capable of forcibly setting within the correction section,
an input unit that receives the target image to be corrected from the image server;
A pre-processing unit for obtaining a pixel value corresponding to the contrast and a pixel value corresponding to blue (B) among RGB for each of a plurality of pixels included in the target image;
A first histogram is obtained using a pixel value corresponding to the contrast, a second histogram is obtained using a pixel value corresponding to the blue (B), and a first initial value is obtained from the first histogram, , an initial value extractor for obtaining a second initial value from the second histogram;
A correction interval in which a first reference value is obtained by smoothing the first histogram, a second reference value is obtained by smoothing the second histogram, and then each correction interval is extracted using the first reference value and the second reference value extractor,
A control unit that matches the correction period for the contrast obtained through the first reference value and the correction period for blue (B) obtained through the second reference value, and extracts the final correction period using the matched correction period, and
Low visibility including a correction unit calculating an average value of pixel values included in the extracted final correction section, and converting a histogram of a plurality of pixels included in the target image in response to the calculated average value to adjust the contrast of the target image Digital image correction device. According to claim 1,
The preprocessor is
Low visibility digital image compensating apparatus for converting RGB values of the target image into YCrCb values, and then extracting only Y values from the converted YCrCb values to obtain pixel values corresponding to brightness and darkness. 3. The method of claim 2,
The initial value extraction unit,
extracting, as a first initial value, a pixel value corresponding to the brightness and darkness corresponding to a value having the highest frequency of pixels in the first histogram;
and extracting, as a second initial value, a pixel value corresponding to the blue (B) corresponding to a value having the highest pixel frequency in the second histogram. 4. The method of claim 3,
The correction interval extraction unit,
A value obtained by subtracting a first initial value from the first reference value is extracted as a first lower limit value,
After extracting a value increased by the first initial value from the first reference value as a first upper limit value,
A low visibility digital image correcting apparatus for setting a range greater than the first lower limit value and smaller than the first upper limit value as a correction section for contrast. 5. The method of claim 4,
The correction interval extraction unit,
A value obtained by subtracting a second initial value from the second reference value is extracted as a second lower limit value,
After extracting a value increased by a second initial value to the second reference value as a second upper limit value,
A low visibility digital image compensating apparatus for setting a range greater than the second lower limit value and smaller than the second upper limit value as a correction section for blue (B). 6. The method of claim 5,
The correction period for the blue (B) is greater than the second lower limit value and smaller than the second upper limit value,
The second lower limit value is greater than the first lower limit value, and the second upper limit value is smaller than the first upper limit value. 7. The method of claim 6,
The control unit is
When the second reference value is smaller than the first reference value, the low visibility digital image correction apparatus determines a final correction interval from the second lower limit value to the first reference value. 7. The method of claim 6,
The control unit is
When the second reference value is greater than or equal to the first reference value and the second lower limit value is less than the first reference value,
A low visibility digital image compensating apparatus for determining a range from the second lower limit value to the second upper limit value as a final correction section. 7. The method of claim 6,
The control unit is
When the second lower limit value and the second reference value are greater than the first reference value,
A low visibility digital image compensating apparatus for determining a period from the first reference value to the second reference value as a final correction section. 7. The method of claim 6,
The correction unit,
A low visibility digital image compensating apparatus for forcibly adjusting the contrast of the target image by converting a histogram of a plurality of pixels included in the target image corresponding to an average value of pixel values included in the final compensation section. In the low visibility digital image correction method capable of forcibly setting within a correction section using a low visibility digital image correction device,
receiving the target image to be corrected from the image server;
obtaining a pixel value corresponding to blue (B) from among a pixel value corresponding to light and dark for each of a plurality of pixels included in the target image and RGB;
A first histogram is obtained using a pixel value corresponding to the contrast, a second histogram is obtained using a pixel value corresponding to the blue (B), and a first initial value is obtained from the first histogram, , obtaining a second initial value from the second histogram;
obtaining a first reference value by smoothing the first histogram, obtaining a second reference value by smoothing the second histogram, and then extracting each correction section using the first reference value and the second reference value;
Matching the correction period for the contrast obtained through the first reference value and the correction period for the blue (B) obtained through the second reference value, and extracting the final correction period using the matched correction period, and
Calculating an average value for a plurality of pixel values included in the extracted final correction section, and converting a histogram of a plurality of pixels included in the target image in response to the calculated average value to correct the contrast of the target image A low-visibility digital image correction method. 12. The method of claim 11,
The step of obtaining the pixel value comprises:
A low visibility digital image correction method for converting RGB values of the target image into YCrCb values, and then extracting only Y values from the converted YCrCb values to obtain pixel values corresponding to brightness and darkness. 13. The method of claim 12,
The step of obtaining the initial value includes:
extracting, as a first initial value, a pixel value corresponding to the brightness and darkness corresponding to a value having the highest frequency of pixels in the first histogram;
A low visibility digital image correction method for extracting a pixel value corresponding to the blue (B) corresponding to a value having the highest frequency of pixels in the second histogram as a second initial value. 14. The method of claim 13,
The step of extracting the correction section,
A value obtained by subtracting a first initial value from the first reference value is extracted as a first lower limit value,
After extracting a value increased by the first initial value from the first reference value as a first upper limit value,
A low visibility digital image correction method for setting a range greater than the first lower limit value and smaller than the first upper limit value as a correction section for contrast. 15. The method of claim 14,
The step of extracting the correction section,
A value obtained by subtracting a second initial value from the second reference value is extracted as a second lower limit value,
After extracting a value increased by a second initial value to the second reference value as a second upper limit value,
A low visibility digital image correction method for setting a range greater than the second lower limit and smaller than the second upper limit as a correction section for blue (B). 16. The method of claim 15,
The correction period for the blue (B) is greater than the second lower limit value and smaller than the second upper limit value,
The second lower limit value is greater than the first lower limit value, and the second upper limit value is smaller than the first upper limit value. 17. The method of claim 16,
The step of determining the final correction section is,
When the second reference value is smaller than the first reference value, a low visibility digital image correction method for determining a final correction interval from the second lower limit value to the first reference value. 17. The method of claim 16,
The step of determining the final correction section is,
When the second reference value is greater than or equal to the first reference value and the second lower limit value is less than the first reference value,
A low visibility digital image correction method for determining from the second lower limit value to the second upper limit value as a final correction section. 17. The method of claim 16,
The step of determining the final correction section is,
When the second lower limit value and the second reference value are greater than the first reference value,
A low visibility digital image correction method for determining from the first reference value to the second reference value as a final correction section. 17. The method of claim 16,
The step of correcting the contrast of the target image,
A low visibility digital image correction method for forcibly adjusting the contrast of the target image by converting a histogram of a plurality of pixels included in the target image corresponding to the average value of the pixels calculated within the final correction section.

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