CN117036204B - Image quality enhancement method for visual interphone - Google Patents
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Abstract
The invention relates to the technical field of image data processing, in particular to an image quality enhancement method for a visual interphone, which comprises the following steps: obtaining a judging coefficient corresponding to the gray value by analyzing the number proportion of each gray value in the face image and the distance relation between the corresponding pixel points, obtaining an atmospheric light value of the face image according to the size of the judging coefficient, combining the atmospheric light value with a deviation result of the pixel points reflecting the detail part in the face image in the transverse direction and the longitudinal direction, obtaining the retention parameters of the pixel points, and carrying out enhancement processing on the face image according to the retention parameters and combining a dark channel priori defogging algorithm. According to the invention, the transmissivity of the dark channel prior defogging algorithm is optimally adjusted through the reserved parameters, so that the image enhancement effect on the face image is greatly improved under the condition of reserving a certain degree of fog effect, and the adaptability of the visible intercom to the atmosphere illumination environment is further enhanced.
Description
Technical Field
The invention relates to the technical field of image data processing, in particular to an image quality enhancement method for a visual interphone.
Background
The visual interphone is mainly used for communicating with the indoor in an apartment gate so as to confirm the identity of a visitor to control the entrance and exit, so that the image quality of a face image obtained by the visual interphone is very important for visitor identification, along with the development of digital technology, the image quality of the face image is greatly improved due to the appearance of the digital visual interphone, but the shooting condition of the visual interphone is not ideal due to unexpected change of illumination under the outdoor complex atmospheric environment, and the face image obtained by the visual interphone is poor due to the fact that the illumination is too large in fog or strong illumination in the air and the like, so that the confirmation of the identity of the visitor by a user is influenced.
In order to solve the problem that the image quality is easily affected by environmental changes, a dark channel prior defogging algorithm is generally adopted in the prior art to directly defogging and enhancing a face image shot by a visual interphone, but in the practical application process, the depth of field information in the face image can be represented by fog with a certain concentration, so that the fog in the face image needs to be reserved to a certain extent by a parameter adjustment method, and a better visual effect is obtained.
Disclosure of Invention
The invention provides an image quality enhancement method for a visual interphone, which aims to solve the existing problems.
The invention relates to an image quality enhancement method for a visual interphone, which adopts the following technical scheme:
the invention provides an image quality enhancement method for a visual interphone, which comprises the following steps:
a visible intercom is utilized to obtain a face image;
obtaining a gray coefficient according to a pixel point with the maximum partial gray value in the dark channel image corresponding to the face image; obtaining gray scale ratio parameters of gray scale values according to the number of pixel points corresponding to any gray scale value in the face image, and adjusting the any gray scale value by using the gray scale ratio parameters and the gray scale coefficients to obtain the gray scale parameters of the gray scale values; acquiring the distance between pixel points corresponding to any gray value in a face image as a distance factor, and regulating the average value of the distance factor by using the gray ratio parameter to obtain a distance parameter of the gray value; the fusion result of the distance parameter and the gray scale parameter is marked as a gray scale value judging coefficient, and the gray scale value corresponding to the maximum judging coefficient is used as the atmospheric light value of the face image;
acquiring a first-order partial derivative and a second-order partial derivative of any pixel point in a face image, respectively marking different fusion results of the first-order partial derivative and the second-order partial derivative as a first factor and a second factor, marking the difference between the first factor and the second factor as a curvature difference value of the pixel point, and marking the fusion result of the curvature difference value and an atmospheric light value as a retention parameter of the pixel point;
and optimizing the transmissivity by using the retention parameters, and carrying out enhancement processing on the face image to obtain an enhanced image corresponding to the face image, thereby completing the enhancement of the image quality of the visual interphone.
Further, the step of obtaining the gray coefficient according to the pixel point with the maximum gray value of the part of the dark channel image corresponding to the face image comprises the following specific steps:
recording the number of all pixel points in the face image as a second number, acquiring a dark channel image corresponding to the face image by using a dark channel priori defogging algorithm, acquiring a pixel point sequence according to the pixel points in the dark channel image, and acquiring the front part in the pixel point sequenceThe first pixel points are marked as second pixel points, and the average value of gray values corresponding to the second pixel points in the face image at the same position is obtained as a gray coefficient according to the position of the second pixel points in the dark channel image, whereinThe preset super-parameters are indicated to be present,representing a second number.
Further, the method for obtaining the pixel point sequence comprises the following steps:
and (3) acquiring all pixel points in the dark channel image corresponding to the face image, marking the pixel points as first pixel points, and sequencing the first pixel points according to the sequence of gray values from large to small to obtain a pixel point sequence.
Further, the gray scale ratio parameter of the gray scale value is obtained according to the number of the pixel points corresponding to any gray scale value in the face image, and the method comprises the following specific steps:
and obtaining the number of corresponding pixel points of any gray value in the face image, marking the number as a first number, and marking the ratio of the first number to the second number as a gray ratio parameter of the corresponding gray value.
Further, the gray scale parameter for adjusting any gray scale value to obtain a gray scale value by using the gray scale duty ratio parameter and the gray scale coefficient comprises the following specific steps:
an arbitrary gray value is used as an input of a logarithmic function based on a gray coefficient, an output of the logarithmic function is referred to as a first output, and a product result of a gray duty ratio parameter and the first output is referred to as a gray parameter of the gray value.
Further, the distance between the pixel points corresponding to any gray value in the obtained face image is recorded as a distance factor, and the average value of the distance factor is adjusted by using the gray ratio parameter to obtain a distance parameter of the gray value, which comprises the following specific steps:
firstly, marking Euclidean distances between every two corresponding pixel points of any gray value in a face image as distance factors of gray values, and acquiring the average value of the distance factors between all the pixel points of any gray value;
then, the gray scale duty ratio parameter of any gray scale value is taken as an input of an exponential function taking a natural constant as a base, the output of the exponential function is recorded as a second output, and the product result of the second output and the average value of the distance factors among all pixel points of any gray scale value is recorded as a distance parameter of the gray scale value.
Further, the step of marking the fusion result of the distance parameter and the gray scale parameter as the judgment coefficient of the gray scale value comprises the following specific steps:
wherein,representing gray values in a face imageIs a judgment coefficient of (a);representing gray value in face image asDistance parameters between pixels;representing gray values in a face imageGray scale parameters of (a);an exponential function based on a natural constant is represented.
Further, the step of obtaining a first-order partial derivative and a second-order partial derivative of any pixel point in the face image, and recording different fusion results of the first-order partial derivative and the second-order partial derivative as a first factor and a second factor respectively includes the following specific steps:
firstly, respectively utilizing a Sobel operator and a Laplace operator to obtain a first-order partial derivative and a second-order partial derivative of any pixel point in a face image in the transverse direction and the longitudinal direction;
then, the specific calculation method of the first factor and the second factor is as follows:
wherein,representing the first of the face imagesA first factor for each pixel;representing the first of the face imagesA second factor for each pixel;representing the first of the face imagesA lateral first-order bias guide of each pixel point;representing the first of the face imagesA horizontal second-order bias derivative of each pixel point;representing the first of the face imagesLongitudinal first-order bias guide of each pixel point;representing the first of the face imagesLongitudinal second-order partial derivatives of the pixel points;representing the first of the face imagesThe crossed second-order bias of the pixel points.
Further, the step of marking the difference between the first factor and the second factor as a curvature difference value of the pixel point and marking the fusion result of the curvature difference value and the atmospheric light value as a retention parameter of the pixel point comprises the following specific steps:
firstly, recording the absolute value of the difference between the absolute value of the first factor and the absolute value of the second factor as the curvature difference value of the pixel point;
then, the specific calculation method of the retention parameters is as follows:
wherein,representing the first of the face imagesA retention parameter for each pixel;representing the first of the face imagesIndividual pixel pointsIs a curvature difference value of (a);an atmospheric light value representing a face image;representing a preset hyper-parameter.
Further, the method optimizes the transmissivity by using the retention parameter, and enhances the face image to obtain an enhanced image corresponding to the face image, thereby enhancing the image quality of the visual interphone, and comprises the following specific steps:
firstly, taking the reserved parameters as adjustment parameters for controlling brightness enhancement in the transmissivity of a dark channel prior defogging algorithm to obtain an optimized dark channel prior defogging algorithm;
and then, enhancing the face image by using an optimized dark channel prior defogging algorithm to obtain an enhanced image, and visualizing the enhanced image in a display screen of the visual interphone.
The technical scheme of the invention has the beneficial effects that: the method comprises the steps of obtaining a judging coefficient corresponding to a gray value by analyzing the number proportion of each gray value in a face image and the distance relation between corresponding pixel points, obtaining an atmospheric light value of the face image according to the size of the judging coefficient, combining the atmospheric light value with a deviation result of the pixel points reflecting the detail part in the face image in the transverse direction and the longitudinal direction, obtaining a retention parameter of the pixel points, optimizing and adjusting the transmissivity of a dark channel priori defogging algorithm through the retention parameter, and greatly improving the image enhancement effect of the face image under the condition of retaining a certain degree of fog effect, and further enhancing the adaptability of the visual interphone to the atmospheric illumination environment.
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In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flowchart of steps of an image quality enhancement method for a video interphone according to the present invention.
Detailed Description
In order to further describe the technical means and effects adopted by the invention to achieve the preset aim, the following is a detailed description of specific embodiments, structures, features and effects of an image quality enhancement method for a visual interphone according to the invention with reference to the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" means that the embodiments are not necessarily the same. Furthermore, the particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The following specifically describes a specific scheme of an image quality enhancement method for a visual interphone provided by the invention with reference to the accompanying drawings.
Referring to fig. 1, a flowchart of steps of a method for enhancing image quality of a visual interphone according to an embodiment of the present invention is shown, the method includes the following steps:
and S001, acquiring a face image by using the visual interphone and preprocessing.
Firstly, shooting an image of an intercom person through a visual intercom, and recording the image as a first image;
noise influence can be inevitably generated in the shooting process, so that the image quality is reduced, and errors occur in the subsequent analysis of various parameters of the first image, so that in order to reduce the influence of the noise on the first image, denoising is needed;
then, denoising the acquired first image by using a Gaussian filter algorithm to obtain a second image;
finally, in order to facilitate the subsequent analysis of the second image, the second image needs to be subjected to graying processing, and the grayed second image is obtained and recorded as a face image.
Thus, a face image is obtained.
Step S002, obtaining the judgment coefficient according to the number of the pixels corresponding to different gray levels in the face image and the distance between the pixels, and obtaining the atmospheric light value of the face image according to the size of the judgment coefficient.
The dark channel prior defogging algorithm is calculated based on an atmospheric scattering model in a reasoning manner, so that the atmospheric light value A of the dark channel prior defogging algorithm must be estimated if a defogging image is to be obtained.
The lower the fog concentration in the image, the darker the corresponding dark channel image, the brighter the corresponding dark channel image with higher fog concentration, and the larger the pixel point value, so that the dark channel image can better reflect the fog concentration information. For the face image captured by the interphone to analyze, the main part in the face image is the face part of the interphone, and only the background area except the face can capture the atmospheric light value, but because the background area can generate complex light interference, the error easily occurs when the atmospheric light value A is obtained only by the gray value, and for the part of the white area in the face image, the brightest area in the face image is not the area corresponding to the sky but the white area, and the white area is possibly caused by overexposure, so that the estimation error of the atmospheric light value A is easily caused.
Because the sky area or the fog area is continuous and occupies a larger area in the face image, the comprehensive judgment can be performed by combining the brightness and the area of the area corresponding to the brightness in order to more accurately predict the atmospheric light value.
When the brightness of a partial area in the face image is high, the area is relatively large and the distribution is discrete, the area can be judged to be a sky area or a fog area, and the whole gray scale of the area is used as an atmospheric light value A of a dark channel priori defogging algorithm.
Firstly, the number of corresponding pixel points of any gray value in a face image is recorded as a first number, the number of all pixel points in the face image is recorded as a second number, and the ratio of the first number to the second number is recorded as a gray ratio parameter of the corresponding gray value; recording Euclidean distances between every two corresponding pixel points of any gray value in the face image as distance factors of the gray value, and obtaining the average value of all the distance factors of the any gray value;
then, a dark channel prior defogging algorithm is utilized to obtain a dark channel image corresponding to the face image, all pixel points in the dark channel image corresponding to the face image are marked as first pixel points, and the number of the first pixel points is the same as the second number; sequencing the first pixel points according to the sequence from the large gray value to the small gray value to obtain a pixel point sequence, and obtaining the first pixel point sequence beforeThe first pixel points are marked as second pixel points, and the average value of gray values corresponding to the second pixel points in the face image at the same position is obtained as a gray coefficient according to the position of the second pixel points in the dark channel image, whereinThe preset super-parameters are indicated to be present,representing a second number;
it should be noted that the super parameters are preset according to experienceThe content is 0.1%, which can be adjusted according to practical conditions, and the present embodiment is not particularly limited.
Secondly, acquiring a judgment coefficient of a gray level value according to the average value of the gray level coefficient, the gray level duty ratio parameter and the distance factor, wherein the specific calculation method comprises the following steps:
wherein,representing gray valuesIs a judgment coefficient of (a);representing gray values asDistance parameters between pixels;representing gray valuesGray scale parameters of (a);an exponential function based on a natural constant;representing gray valuesGray scale ratio parameter of (2);representing gray values；Representing a gray coefficient;representing gray valuesIs the average of all distance factors of (a);
since the image area photographed by the visual interphone for calculation is a high-brightness area which has been screened out by the dark channel image, the gray value is very high, so that the gray value becomes very low in the evaluation coefficient, the suppression is performed by a logarithmic function, and the point with relatively low gray value is further suppressed based on the average value of the gray values. By multiplying the number of gray values by this, points with a large proportion and relatively high gray values can be further screened out.
The distribution of the pixel points of the atmospheric light value is relatively uniform, so that whether the position relation between every two gray level pixel points is discrete or not needs to be calculated, the average distance between the gray level pixel points is obtained by calculating the distance between every two pixel points, the result of the final discrete degree is affected by different numbers of each gray level, if the number of the pixel points of a certain gray level is small, the sufficient discrete between the pixel points can be indicated only by keeping a larger average distance, and therefore, the gray level distance parameter with smaller occupied number proportion is smaller under the same average distance. However, the distance parameter and the gray scale parameter should be kept within a certain range to have better effect, if the distance parameter is too close, the pixel points are too concentrated, the corresponding judgment coefficient is possibly lowered due to local exposure, and if the distance parameter is too far, the pixel points are too weak in dispersion and the corresponding judgment coefficient is also lowered, so that the distribution of the judgment coefficient should conform to Gaussian distribution;
and finally, obtaining the judging coefficients corresponding to all the gray values according to the gray parameters and the distance parameters of all the pixel points in the face image, and taking the gray value corresponding to the maximum judging coefficient as the atmospheric light value A of the face image.
Thus, the atmospheric light value of the face image is obtained.
Step S003, obtaining a first factor and a second factor according to partial derivatives of pixel points in the face image, and obtaining a retention parameter according to curvature difference corresponding to the first factor and the second factor and combining an atmospheric light value.
Because dust impurities exist in the air, a layer of light mist generally exists in human eyes, and in order to meet the common visual effect of human eyes, the strengthened face image is more real, so that part of mist in the image is reserved by adding a reserved constant factor.
In addition, because the visible intercom acquires the face image in real time, the atmospheric light value corresponding to the face image can change, and therefore fixed parameters cannot be set to keep fog in the face image.
When the atmospheric light value in the face image is large, the face image is brighter at the moment, and the visual effect is better, so that more fog can be reserved, and conversely, if the atmospheric light value in the face image is low, the brightness of the face image is darker, and the atmospheric light value of which part reflects the brightness needs to be reserved to ensure the visibility of the image.
The details in the face image are calculated by using the existing differential curvature algorithm, and the more the details are, the lower the fog concentration is, so that more fog needs to be reserved, and otherwise, less fog needs to be reserved.
In order to adaptively adjust the retention degree of brightness and details in a face image, the embodiment obtains retention parameters of pixel points according to partial derivatives of the pixel points in the face image, and the specific obtaining method comprises the following steps:
firstly, respectively utilizing a Sobel operator and a Laplace operator to obtain a first-order partial derivative and a second-order partial derivative of any pixel point in a face image in the transverse direction and the longitudinal direction; according to the first-order partial derivative and the second-order partial derivative of the pixel point, a first factor and a second factor are respectively obtained, and the specific calculation method comprises the following steps:
wherein,representing the first of the face imagesA first factor for each pixel;representing the first of the face imagesA second factor for each pixel;representing the first of the face imagesA lateral first-order bias guide of each pixel point;representing the first of the face imagesA horizontal second-order bias derivative of each pixel point;representing the first of the face imagesLongitudinal first-order bias guide of each pixel point;representing the first of the face imagesLongitudinal second-order partial derivatives of the pixel points;representing the first of the face imagesCrossed second-order partial derivatives of the pixel points;
it should be noted that, the Sobel operator and the laplace operator are existing image processing operators, so this embodiment is not repeated, and in addition, the chinese name of the Sobel operator is a Sobel operator.
Then, the absolute value of the difference between the absolute value of the first factor and the absolute value of the second factor is recorded as the curvature difference value of the pixel point; the retention parameters of the pixel points are obtained according to the atmospheric light value and the curvature difference value, and the specific calculation method comprises the following steps:
wherein,representing the first of the face imagesA retention parameter for each pixel;representing the first of the face imagesCurvature difference values of the individual pixel points;an atmospheric light value representing a face image;representing preset super parameters;an exponential function based on a natural constant is represented.
It should be noted that the super parameters are preset according to experienceThe value of 0.9 can be adjusted according to practical situations, and the embodiment is not particularly limited.
The curvature difference result reflects detail information of pixel points in the face image, and the greater the curvature difference value is, the more detail is. The retention parameter is influenced by the atmospheric light value and the curvature difference value, and the higher the atmospheric light value is, the higher the brightness of the face image is; the higher the brightness, the smaller the retention parameter, the more the detail in the face image is rich, the more the fog is retained, and the larger the retention parameter, the less the fog is retained, because the concentration of the fog can show the depth of field, therefore, the fog needs to be retained to a certain extent, and the retention parameter cannot be too small, in the embodiment, the super parameter is presetControlling the value range of the reserved parameterAt the position ofAnd (3) inner part.
So far, the retention parameters of the pixel points are obtained.
And S004, optimizing a dark channel prior defogging algorithm by using the retention parameters, and enhancing the face image to obtain an enhanced image.
Firstly, taking the reserved parameters as adjustment parameters for controlling brightness enhancement in the transmissivity of a dark channel prior defogging algorithm, and optimizing the dark channel prior defogging algorithm according to relevant features in a face image to obtain an optimized dark channel prior defogging algorithm;
and then, enhancing the face image by using an optimized dark channel prior defogging algorithm to obtain an enhanced image, and visualizing the enhanced image in a display screen of the visual interphone.
The following examples were usedThe model is only used for representing that the result output by the negative correlation and the constraint model is inIn the section, other models with the same purpose can be replaced in the specific implementation, and the embodiment only usesThe model is described as an example, and is not particularly limited, whereinRefers to the input of the model.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (8)
1. An image quality enhancement method for a visual interphone, comprising the steps of:
a visible intercom is utilized to obtain a face image;
obtaining a gray coefficient according to a pixel point with the maximum partial gray value in the dark channel image corresponding to the face image; obtaining gray scale ratio parameters of gray scale values according to the number of pixel points corresponding to any gray scale value in the face image, and adjusting the any gray scale value by using the gray scale ratio parameters and the gray scale coefficients to obtain the gray scale parameters of the gray scale values; acquiring the distance between pixel points corresponding to any gray value in a face image as a distance factor, and regulating the average value of the distance factor by using the gray ratio parameter to obtain a distance parameter of the gray value; the fusion result of the distance parameter and the gray scale parameter is marked as a gray scale value judging coefficient, and the gray scale value corresponding to the maximum judging coefficient is used as the atmospheric light value of the face image;
acquiring a first-order partial derivative and a second-order partial derivative of any pixel point in a face image, respectively marking different fusion results of the first-order partial derivative and the second-order partial derivative as a first factor and a second factor, marking the difference between the first factor and the second factor as a curvature difference value of the pixel point, and marking the fusion result of the curvature difference value and an atmospheric light value as a retention parameter of the pixel point;
optimizing the transmissivity by using the retention parameters, and carrying out enhancement processing on the face image to obtain an enhanced image corresponding to the face image, thereby completing the image quality enhancement of the visual interphone;
the gray scale parameters for obtaining the gray scale value by adjusting any gray scale value by using the gray scale duty ratio parameters and the gray scale coefficient comprise the following specific steps:
taking any gray value as the input of a logarithmic function taking a gray coefficient as a base, marking the output of the logarithmic function as a first output, and marking the product result of the gray duty ratio parameter and the first output as a gray parameter of the gray value;
the distance between the pixel points corresponding to any gray value in the obtained face image is recorded as a distance factor, and the average value of the distance factor is adjusted by using the gray ratio parameter to obtain the distance parameter of the gray value, comprising the following specific steps:
firstly, marking Euclidean distances between every two corresponding pixel points of any gray value in a face image as distance factors of gray values, and acquiring the average value of the distance factors between all the pixel points of any gray value;
then, the gray scale duty ratio parameter of any gray scale value is taken as an input of an exponential function taking a natural constant as a base, the output of the exponential function is recorded as a second output, and the product result of the second output and the average value of the distance factors among all pixel points of any gray scale value is recorded as a distance parameter of the gray scale value.
2. The method for enhancing image quality of a visual interphone according to claim 1, wherein the step of obtaining the gray scale coefficient according to the pixel point with the largest part of gray scale values in the dark channel image corresponding to the face image comprises the following specific steps:
recording the number of all pixel points in the face image as a second number, acquiring a dark channel image corresponding to the face image by using a dark channel priori defogging algorithm, acquiring a pixel point sequence according to the pixel points in the dark channel image, and acquiring the front part in the pixel point sequenceThe first pixel points are marked as second pixel points, and the gray value mean value of the second pixel points corresponding to the second pixel points in the face image at the same position is obtained as a gray coefficient according to the position of the second pixel points in the dark channel image, wherein ∈>The preset super-parameters are indicated to be present,representing a second number.
3. The image quality enhancement method for a visual interphone according to claim 2, characterized in that the acquisition method of the pixel point sequence is as follows:
and (3) acquiring all pixel points in the dark channel image corresponding to the face image, marking the pixel points as first pixel points, and sequencing the first pixel points according to the sequence of gray values from large to small to obtain a pixel point sequence.
4. The method for enhancing image quality of a visual interphone according to claim 2, wherein the step of obtaining the gray-scale duty ratio parameter of the gray-scale value according to the number of the pixel points corresponding to the arbitrary gray-scale value in the face image comprises the following specific steps:
and obtaining the number of corresponding pixel points of any gray value in the face image, marking the number as a first number, and marking the ratio of the first number to the second number as a gray ratio parameter of the corresponding gray value.
5. The image quality enhancement method for a visual interphone according to claim 1, characterized in that the step of recording the fusion result of the distance parameter and the gray scale parameter as the judgment coefficient of the gray scale value comprises the following specific steps:
wherein,representing gray values in a face image>Is a judgment coefficient of (a); />Representing gray value of +.>Distance parameters between pixels; />Representing gray values in a face image>Gray scale parameters of (a); />An exponential function based on a natural constant is represented.
6. The method for enhancing image quality of a visual interphone according to claim 1, wherein the steps of obtaining a first-order partial derivative and a second-order partial derivative of any pixel point in a face image, and recording different fusion results of the first-order partial derivative and the second-order partial derivative as a first factor and a second factor respectively, comprise the following specific steps:
firstly, respectively utilizing a Sobel operator and a Laplace operator to obtain a first-order partial derivative and a second-order partial derivative of any pixel point in a face image in the transverse direction and the longitudinal direction;
then, the specific calculation method of the first factor and the second factor is as follows:
wherein,representing the +.>A first factor for each pixel; />Representing the +.>A second factor for each pixel; />Representing the +.>A lateral first-order bias guide of each pixel point; />Representing the +.>A horizontal second-order bias derivative of each pixel point; />Representing the +.>Longitudinal first-order bias guide of each pixel point; />Representing the +.>Longitudinal second-order partial derivatives of the pixel points; />Representing the +.>The crossed second-order bias of the pixel points.
7. The method for enhancing image quality of a visual interphone according to claim 5, wherein the step of recording the difference between the first factor and the second factor as a curvature difference value of the pixel and recording the fusion result of the curvature difference value and the atmospheric light value as a retention parameter of the pixel comprises the following specific steps:
firstly, recording the absolute value of the difference between the absolute value of the first factor and the absolute value of the second factor as the curvature difference value of the pixel point;
then, the specific calculation method of the retention parameters is as follows:
wherein,representing the +.>A retention parameter for each pixel; />Representing the +.>Curvature difference values of the individual pixel points; />An atmospheric light value representing a face image; />Representing a preset hyper-parameter.
8. The method for enhancing image quality of a visual interphone according to claim 1, wherein the steps of optimizing the transmittance by using the retention parameter and enhancing the face image to obtain an enhanced image corresponding to the face image, and enhancing the image quality of the visual interphone are as follows:
firstly, taking the reserved parameters as adjustment parameters for controlling brightness enhancement in the transmissivity of a dark channel prior defogging algorithm to obtain an optimized dark channel prior defogging algorithm;
and then, enhancing the face image by using an optimized dark channel prior defogging algorithm to obtain an enhanced image, and visualizing the enhanced image in a display screen of the visual interphone.
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