Inclined image dodging processing method and device

Abstract

The invention provides an inclined image dodging processing method and device, and is applied to the technical field of aerial remote sensing. The method comprises the following steps: carrying out observation geometric calculation and illumination geometric calculation according to imaging parameters and position attitude data of an inclined camera; determining atmospheric influence parameters from the atmospheric correction parameter lookup table according to a calculation result, determining theoretical radiance of each pixel in the original inclined image based on the atmospheric influence parameters, determining standard brightness, and unifying a brightness reference of the theoretical radiance based on the standard brightness; calculating a cosine quadruple proportion coefficient of an actual correction angle of oblique observation of the camera, and correcting the theoretical radiance of each pixel based on the cosine quadruple proportion coefficient; and converting the processed original inclined image and the reference image from a first color space to a second color space, performing histogram matching on each channel, and then turning back to the first color space to obtain a uniform light normalized image.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aerial remote sensing technology, and in particular to a tilt image dodging processing method and device. BACKGROUND

[0002] In the field of aerial remote sensing, image dodging is an important means to ensure the uniformity and consistency of color tone of large-area images. The tilt camera system adopts a front-back and left-right downward imaging mode, and the differences between different viewing angles are significant. The same shooting moment is affected by the environment, and the color tone and contrast of different viewing angle images under the same imaging parameters differ greatly, which will affect the subsequent real scene three-dimensional processing, and therefore, pre-normalization processing is required.

[0003] There are two main schemes for existing tilt image dodging processing: one is the traditional statistical method, which performs dodging through stretching processing and the like; and the other is the manual adjustment mode, which relies on manual interaction to adjust the image color tone to achieve dodging effect.

[0004] However, the automatic processing mode of the traditional statistical method cannot avoid the systematic imaging differences caused by different imaging viewing angles, and it is difficult to achieve ideal dodging effect and realize effective automatic adjustment of image color tone. The manual adjustment mode requires a large amount of manual interaction, and the adjustment effect is greatly influenced by the experience of the operator, which is highly subjective, low in efficiency, and difficult to ensure the consistency and stability of the processing results. Therefore, the existing methods cannot automatically and efficiently solve the dodging problem of tilt images. SUMMARY

[0005] The present application provides a tilt image dodging processing method and device, which can automatically and efficiently solve the dodging problem of tilt images.

[0006] The application provides a tilt image dodging processing method, comprising: acquiring original image data, wherein the original image data comprises an original tilt image, tilt camera imaging parameters, position and attitude data, and imaging time information; performing observation geometry calculation according to the tilt camera imaging parameters and the position and attitude data to obtain an observation azimuth and an observation zenith; performing illumination geometry calculation according to the imaging time information to obtain a sun elevation angle and a sun azimuth; determining an atmospheric influence parameter from an atmospheric correction parameter lookup table according to the observation azimuth, the observation zenith, the sun elevation angle, and the sun azimuth, and determining a theoretical radiance of each pixel in the original tilt image based on the atmospheric influence parameter, and determining a standard brightness and unifying a brightness reference of the theoretical radiance based on the standard brightness, wherein the atmospheric correction parameter lookup table is used to describe a parameter set of atmospheric influence on light; calculating a cosine fourth power proportional coefficient of an actual correction angle of camera tilt observation, and correcting the theoretical radiance of each pixel based on the cosine fourth power proportional coefficient; and converting the processed original tilt image and a reference image from a first color space to a second color space, performing histogram matching on each channel respectively, and converting back to the first color space to obtain a dodging normalized image.

[0007] The application also provides a tilt image dodging processing device, comprising the following modules: an acquisition module and a processing module; the acquisition module is used to acquire original image data, wherein the original image data comprises an original tilt image, tilt camera imaging parameters, position and attitude data, and imaging time information; the processing module is used to perform observation geometry calculation according to the tilt camera imaging parameters and the position and attitude data to obtain an observation azimuth and an observation zenith; perform illumination geometry calculation according to the imaging time information to obtain a sun elevation angle and a sun azimuth; determine an atmospheric influence parameter from an atmospheric correction parameter lookup table according to the observation azimuth, the observation zenith, the sun elevation angle, and the sun azimuth, and determine a theoretical radiance of each pixel in the original tilt image based on the atmospheric influence parameter, and determine a standard brightness and unify a brightness reference of the theoretical radiance based on the standard brightness, wherein the atmospheric correction parameter lookup table is used to describe a parameter set of atmospheric influence on light; calculate a cosine fourth power proportional coefficient of an actual correction angle of camera tilt observation, and correct the theoretical radiance of each pixel based on the cosine fourth power proportional coefficient; and convert the processed original tilt image and a reference image from a first color space to a second color space, perform histogram matching on each channel respectively, and convert back to the first color space to obtain a dodging normalized image.

[0008] The present application also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method for uniform light processing of oblique images according to any one of the above when executing the program.

[0009] The present application also provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the method for uniform light processing of oblique images according to any one of the above.

[0010] The present application also provides a computer program product comprising a computer program, wherein the computer program, when executed by a processor, implements the method for uniform light processing of oblique images according to any one of the above.

[0011] The present application provides a method and device for uniform light processing of oblique images, which can calculate an observed azimuth and an observed zenith according to oblique camera imaging parameters and position and posture data, obtain a solar altitude and a solar azimuth in combination with imaging time information, and thus accurately capture geometric conditions during image imaging, thereby providing accurate basic data support for subsequent radiation correction. The present application can determine atmospheric influence parameters from an atmospheric correction parameter lookup table based on the above geometric parameters, and calculate a theoretical radiance of each pixel, thereby effectively eliminating atmospheric scattering, absorption and other factors affecting the radiation of images at different viewing angles, and unifying the radiance reference under atmospheric influence. The present application can correct the radiance by a cosine fourth power proportional coefficient of an actual correction angle and a theoretical correction angle, thereby targetedly compensating for systematic differences in radiance caused by oblique observation of the camera, and solving the problem of uneven brightness and hue caused by angle deviation during imaging at different viewing angles. The present application can perform channel-by-channel histogram matching of the processed image and a reference image in a color space, thereby further eliminating subtle random radiation differences, and making the hue and brightness distribution of all oblique images highly consistent with the reference image. In this way, through the synergistic effect of geometric parameter calculation, atmospheric influence correction, oblique angle compensation and statistical fine-tuning, the present application realizes automatic light uniformization of oblique images, avoids subjectivity and inefficiency of manual adjustment, provides high-quality image data with uniform hue and consistent radiation for subsequent real scene three-dimensional processing, and significantly improves the application value of oblique image data. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0013] Figure 1is a flowchart of a tilt image light uniformity processing method provided by the present application.

[0014] Figure 2 is a structural diagram of a tilt image light uniformity processing device provided by the present application.

[0015] Figure 3 is a structural diagram of an electronic device provided by the present application. DETAILED DESCRIPTION

[0016] For the purpose of making the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of the present application.

[0017] It should be noted that in the embodiments of the present application, the words such as "exemplary" or "for example" are used to mean serving as an example, instance, or illustration. Any embodiment or design presented as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or advantageous than other embodiments or design solutions. In fact, the use of the words such as "exemplary" or "for example" is intended to present related concepts in a specific manner.

[0018] It should be noted that in the present document, the terms "comprising", "containing" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a list of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent in such a process, method, article or device. Without more limitations, the element defined by the phrase "comprising a" does not exclude the presence of additional identical elements in the process, method, article or device that includes the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, but can also include performing functions in a substantially simultaneous manner or in a reverse order, for example, the described method can be performed in an order different from the described order, and various steps can also be added, omitted or combined. In addition, the features described with reference to certain examples can be combined in other examples.

[0019] In order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first", "second", etc. are used to distinguish the same items or similar items with basically the same functions and effects, and those skilled in the art can understand that the words "first", "second", etc. are not limited to the number and execution order.

[0020] The embodiments of the present application describe some exemplary embodiments for the purpose of illustration, it is to be understood that the present application can be implemented in other ways not specifically shown in the drawings.

[0021] As shown in Figure 1 The embodiments of the present application provide a tilt image light uniformity processing method, which can be applied to a tilt image light uniformity processing device. The tilt image light uniformity processing method can include S101-S105: S101, the tilt image light uniformity processing device acquires original image data.

[0022] Among them, the above-mentioned original image data includes original tilt image, tilt camera imaging parameter, position and attitude data and imaging time information.

[0023] Due to the differences in imaging viewing angle, sunlight, atmospheric conditions, etc., the images obtained by the tilt camera system through multi-view shooting will have inconsistent problems in tone and contrast. The original tilt image, i.e. the unprocessed image data directly obtained by the tilt camera system, is the object of light uniformity processing.

[0024] The tilt camera imaging parameter refers to the key parameter describing the camera hardware characteristics, including focal length, pixel size, pixel position, etc.

[0025] The position and attitude data refers to the spatial position (such as longitude, latitude, and elevation) and attitude information (such as heading angle, pitch angle, and roll angle) of the camera when shooting, recorded by the position and orientation system (POS), also known as POS data.

[0026] The imaging time information refers to the specific time of shooting each image by the camera.

[0027] S102, the tilt image light uniformity processing device performs observation geometry calculation according to the tilt camera imaging parameter and the position and attitude data to obtain the observation azimuth and observation zenith; performs illumination geometry calculation according to the imaging time information to obtain the solar elevation angle and solar azimuth angle.

[0028] In tilt image processing, when cameras with different viewing angles shoot the same area, due to the difference in shooting angle, it will cause systematic deviation of image tone and brightness. These deviations are essentially directly related to the "direction of camera observation of ground objects", that is, the observation direction is different, the receiving path of light reflection and atmospheric influence is also different, and finally it shows the difference of image radiation characteristics. Therefore, the core purpose of observation geometry calculation is to accurately describe the shooting direction of each pixel.

[0029] Optionally, the oblique image homogenization processing device performs observation geometry calculations based on the oblique camera imaging parameters and the position and attitude data to obtain the observation azimuth angle and the observation zenith angle, including: calculating the coordinates of the ground feature point corresponding to each pixel in the original oblique image in the image space auxiliary coordinate system using rotation transformation based on the oblique camera imaging parameters and the position and attitude data to obtain the image auxiliary coordinates of the ground feature point; determining the line of sight direction based on the line connecting the projection center in the image space auxiliary coordinate system and the image auxiliary coordinates of the ground feature point; calculating the angle between the projection of the line of sight direction on the plane and the due north direction to obtain the observation azimuth angle of each pixel; and calculating the angle between the line of sight direction and the vertical direction to obtain the observation zenith angle of each pixel.

[0030] Specifically, the tilted image homogenization processing device can first calculate the coordinates of the ground feature points corresponding to each pixel in the original tilted image in the image space auxiliary coordinate system based on the rotation transformation. The line connecting the projection center and the image auxiliary coordinates of the ground feature points in the image auxiliary coordinate system constitutes the line of sight. The angle between the projection of the line of sight on the plane and the due north direction is the observation azimuth angle. The angle between the line of sight and the vertical direction is the observation zenith angle. The image auxiliary coordinates of the ground feature points can be solved by formula (1): (1) in, This represents the auxiliary coordinates of a ground feature image in the image space auxiliary coordinate system. This represents the rotation matrix from the image space coordinate system to the auxiliary image space coordinate system. Image space coordinates representing the parallel flight direction, Image space coordinates representing the vertical flight direction. This represents the negative value of the camera's focal length, i.e., the z-value in image space coordinates.

[0031] like , representing a pixel p Located in the first and fourth quadrants, the observation azimuth angle can be: (2) like , representing a pixel p Located in the second and third quadrants, the observation azimuth angle can be: (3) The observed zenith angle can be: (4) Since the sun's position changes over time, and sunlight is the main source of image radiation characteristics, its angle directly affects the brightness and hue of images from different perspectives. Therefore, imaging time information can be used to calculate the solar altitude angle and solar azimuth angle in "illuminance geometry".

[0032] Optionally, the oblique image vignetting processing device performs illumination geometry calculation according to the imaging time information to obtain the solar elevation angle and the solar azimuth angle, including: determining illumination geometry time parameters based on the imaging time information, the illumination geometry time parameters including a ground target point latitude, a solar declination and a solar hour angle; calculating a solar zenith angle according to the ground target point latitude, the solar declination and the solar hour angle, and determining the solar elevation angle based on the solar zenith angle, the solar zenith angle and the solar elevation angle being reciprocal; and calculating the solar azimuth angle according to the solar elevation angle, the solar hour angle and the solar declination.

[0033] Specifically, the solar zenith angle is an angle between a solar ray and a ground normal line, and is reciprocal to the solar elevation angle; and is determined by a ground target point latitude , a solar declination and a solar hour angle , and their relationship is shown in formula (5): (5) The solar declination is an angle between a solar incident light and an equator of the earth, and the solar declination periodically changes with time due to the rotation and revolution of the earth, and the solar declination calculation is shown in formula (6) through Fourier series expansion: (6) wherein, , is a Julian day, =0.006918; =0.3999912; =0.070257; =0.006758; =0.000907; =0.002697; =0.001480.

[0034] The solar hour angle can be calculated by , wherein , is a true solar time, is a local time, is a time difference, , is a target point longitude, is a Greenwich time, , , =0.000075; =0.001868; =0.032077; =0.014615; = 0.040849.

[0035] Solar azimuth The angle between the projection of the sun's rays on the ground and the local meridian, the azimuth is zero at the north direction, clockwise rotation is positive, the solution is shown as formula (7): (7) Wherein, Determined by and .

[0036] S103, the tilt image light processing device determines the atmospheric influence parameter from the atmospheric correction parameter lookup table according to the observation azimuth, the observation zenith, the solar elevation angle and the solar azimuth, and determines the theoretical radiance of each pixel in the original tilt image based on the atmospheric influence parameter, and determines the standard brightness and unifies the brightness reference of the theoretical radiance based on the standard brightness.

[0037] Wherein, the above-mentioned atmospheric correction parameter lookup table is used to describe the parameter set of the influence of atmosphere on light.

[0038] Optionally, before determining the atmospheric influence parameter from the atmospheric correction parameter lookup table according to the observation azimuth, the observation zenith, the solar elevation angle and the solar azimuth, the tilt image light processing device can calculate the atmospheric influence parameter under different weather conditions by using the internationally common 6S (Second Simulation of the Satellite Signal in the Solar Spectrum) atmospheric radiation transmission model, to establish the atmospheric correction parameter lookup table under different weather conditions.

[0039] Optionally, the tilt image light processing device can determine the atmospheric influence parameter from the above-mentioned atmospheric correction parameter lookup table according to the observation azimuth, the observation zenith, the solar elevation angle and the solar azimuth, which can include: the path radiative reflectivity , the path radiative radiance , the atmospheric ball albedo , the atmospheric transmittance , the atmospheric layer top radiation flux , the spectral response function integral , the normalized solar downward radiation flux , the total upward transmittance , the total downward transmittance , the upward direct transmittance , the downward direct transmittance , the upward scattering transmittance , downscatter transmittance , and atmospheric corrected reflectance .

[0040] After that, the oblique image light uniformity processing device can calculate the theoretical radiance of each pixel in the original oblique image based on the atmospheric influence parameter and the radiative transfer formula. Finally, the radiance of the nadir image center point is taken as the "standard luminance", and the proportional coefficient of the theoretical radiance of each pixel of other cameras to the standard luminance is calculated. Through coefficient adjustment, the radiance reference of all pixels is consistent. For example, if the theoretical radiance of a certain oblique pixel is 1.2 times that of the nadir center, it is adjusted to match the standard value through the proportional coefficient, eliminating the systematic brightness deviation caused by different viewing angles. Specifically, the DN values of the R, G, and B channels of the image can be corrected through the proportional coefficient.

[0041] The radiative transfer formula is: ; Wherein, represents the total radiance (i.e. the theoretical radiance in this specification) of the radiation reaching the sensor through surface reflection and atmospheric path, represents the uplink direct component of the total radiance, represents the uplink scattering component of the total radiance, represents the atmospheric path component of the total radiance, represents the observation target reflectance, represents the solar zenith angle, , represents the target reflectance after eliminating the adjacent effect through atmospheric correction processing, represents the observation zenith angle, represents the solar azimuth angle, represents the observation azimuth angle.

[0042] S104, the oblique image light uniformity processing device calculates the cosine fourth power proportional coefficient of the actual correction angle and the theoretical correction angle of the camera oblique observation, and corrects the theoretical radiance of each pixel based on the cosine fourth power proportional coefficient.

[0043] When the camera is tilted to shoot, the light propagation path and the reflection angle of the ground object are different from vertical shooting (nadir). Due to the non-uniform light transmission characteristics of the camera lens, the radiance of the same ground object on the oblique image deviates from the theoretical value (vertical nadir reference value). Therefore, the deviation needs to be eliminated through "proportional conversion" to unify the radiance reference of images with different tilt angles.

[0044] The theoretical compensation amount is: ; After derivation, the actual compensation amount required by the oblique camera is: ; wherein, represents the angle between the target light and the center line of the main optical axis of the lens, represents the angle between the target light and the vertical downward-looking light, represents the tilt camera tilt installation angle, i.e. the angle between the direction of the main optical axis of the camera lens and the downward-looking direction.

[0045] Divide the above theoretical compensation amount and the actual required compensation amount, i.e. the compensation proportionality coefficient K: ; Since the camera will compensate by default according to the theoretical compensation amount, the two will produce a system proportionality coefficient difference due to and angle inconsistency and camera tilt installation, therefore, based on the cosine fourth power proportionality coefficient K, the theoretical radiance of each pixel can be corrected by the proportionality coefficient, so as to correct the radiance of the tilt camera to the radiance reference of the downward-looking camera.

[0046] S105, the tilt image light uniformization processing device converts the processed original tilt image and the reference image from the first color space to the second color space, respectively performs histogram matching on each channel, and converts back to the first color space to obtain a light uniformization normalized image.

[0047] After completing the above two-step systematic light energy compensation, the image is normalized by statistical methods, such as image histogram matching, to eliminate subtle random differences, thereby completing the light uniformization normalization of all images in the measurement area.

[0048] Optionally, the first color space is an RGB color space, and the second color space is a Lab color space.

[0049] Specifically, the original tilt image and the reference image processed by the above processing are converted from the RGB color space to the Lab color space, and the reference image can be a central downward-looking image. Each channel (L, a, b) of the Lab color space is respectively histogram matched. Finally, the matched image is converted back to the RGB color space to obtain a light uniformization normalized image.

[0050] In the embodiments of the present application, the geometric conditions during image imaging can be accurately captured, and accurate basic data support is provided for subsequent radiation correction, because the observation azimuth and the observation zenith can be calculated according to the tilt camera imaging parameters and the position and posture data, and the solar elevation angle and the solar azimuth can be obtained in combination with the imaging time information; the atmospheric influence parameters can be determined from the atmospheric correction parameter lookup table based on the above-mentioned geometric parameters, and the theoretical radiance of each pixel can be calculated accordingly, so that the radiation interference of different view angle images caused by atmospheric scattering, absorption and other factors can be effectively eliminated, and the radiance reference under the influence of the atmosphere is unified; the radiance can be corrected by the cosine fourth power proportional coefficient of the actual correction angle and the theoretical correction angle, so that the systematic difference of the radiation brightness caused by the camera tilt observation can be targeted compensated, and the brightness and tone unevenness problems caused by the angle deviation of different view angle imaging can be solved; the processed image and the reference image can be matched in the color space through channel histograms, so that the subtle random radiation difference can be further eliminated, and the tone and brightness distribution of all the tilt images can be highly consistent with the reference image. In this way, through the synergistic effect of geometric parameter calculation, atmospheric influence correction, tilt angle compensation and statistical fine adjustment, the automatic light uniformity normalization of the tilt image is realized, the subjectivity and inefficiency of manual adjustment are avoided, high-quality image data with uniform tone and consistent radiation is provided for subsequent real scene three-dimensional processing, and the application value of the tilt image data is significantly improved.

[0051] The above describes the scheme provided by the embodiments of the present application mainly from the perspective of the method. To realize the above functions, the hardware structure and / or software module corresponding to the execution of each function are included. Those skilled in the art should easily realize that, in combination with the units and algorithm steps of the examples described in the embodiments disclosed in the present application, the embodiments of the present application can be realized in the form of hardware or the combination of hardware and computer software. Whether a certain function is realized in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0052] The execution subject of the tilt image light uniformity processing method provided by the embodiments of the present application can be a tilt image light uniformity processing device, or a control module for tilt image light uniformity processing in the tilt image light uniformity processing device. In the embodiments of the present application, the tilt image light uniformity processing device is taken as an example to execute the tilt image light uniformity processing method, and the tilt image light uniformity processing device provided by the embodiments of the present application is described.

[0053] It should be noted that the embodiments of the present application can divide the functional modules of the tilt image dodging processing device according to the above method examples, for example, each functional module can be divided according to each function, or two or more functions can be integrated in one processing module. The above integrated module can be realized in the form of hardware or in the form of a software functional module. Optionally, the division of the modules in the embodiments of the present application is illustrative, and is only a logical functional division, and another division mode can be used in actual implementation.

[0054] As shown in Figure 2 The embodiments of the present application provide a tilt image dodging processing device 200. The tilt image dodging processing device 200 includes an acquisition module 201 and a processing module 202. The acquisition module 201 can be used to acquire original image data, and the original image data includes an original tilt image, tilt camera imaging parameters, position and attitude data, and imaging time information. The processing module 202 can be used to perform observation geometry calculation according to the tilt camera imaging parameters and the position and attitude data to obtain an observation azimuth angle and an observation zenith angle; perform illumination geometry calculation according to the imaging time information to obtain a sun elevation angle and a sun azimuth angle; determine an atmospheric influence parameter from an atmospheric correction parameter lookup table according to the observation azimuth angle, the observation zenith angle, the sun elevation angle, and the sun azimuth angle, and determine a theoretical radiance of each pixel in the original tilt image based on the atmospheric influence parameter, and determine a standard brightness and unify a brightness reference of the theoretical radiance based on the standard brightness, and the atmospheric correction parameter lookup table is used to describe a parameter set of the influence of the atmosphere on light; calculate a cosine fourth power proportional coefficient of an actual correction angle of camera tilt observation, and correct the theoretical radiance of each pixel based on the cosine fourth power proportional coefficient; convert the processed original tilt image and a reference image from a first color space to a second color space, perform histogram matching on each channel respectively, and then convert back to the first color space to obtain a dodging normalized image.

[0055] Optionally, the processing module 202 can be used to calculate the coordinates of a ground object point corresponding to each pixel in the original tilt image in an image space auxiliary coordinate system based on the tilt camera imaging parameters and the position and attitude data by using rotation transformation to obtain a ground object point image auxiliary coordinate; determine a line of sight direction according to a line connecting a projection center in the image space auxiliary coordinate system and the ground object point image auxiliary coordinate; calculate an included angle between a projection of the line of sight direction on a plane and a north direction to obtain an observation azimuth angle of each pixel; and calculate an included angle between the line of sight direction and a vertical direction to obtain an observation zenith angle of each pixel.

[0056] Optionally, the processing module 202 can be configured to determine an illumination geometry time parameter based on the imaging time information, the illumination geometry time parameter comprising a ground target point latitude, a solar declination and a solar hour angle; calculate a solar zenith angle according to the ground target point latitude, the solar declination and the solar hour angle, and determine a solar altitude angle based on the solar zenith angle, the solar zenith angle and the solar altitude angle being mutually exclusive; and calculate a solar azimuth angle according to the solar altitude angle, the solar hour angle and the solar declination.

[0057] Optionally, the processing module 202 can be further configured to calculate an atmospheric influence parameter under different weather conditions by using a 6S atmospheric radiation transfer model, so as to establish an atmospheric correction parameter lookup table under different weather conditions.

[0058] Optionally, the atmospheric influence parameter comprises a path radiance reflectance, a path radiance radiance, an atmospheric ball albedo, an atmospheric transmittance, an atmospheric layer top radiation flux, a spectral response function integral, a normalized solar downward radiation flux, an upward total transmittance, a downward total transmittance, an upward direct transmittance, a downward direct transmittance, an upward scattering transmittance, a downward scattering transmittance, and an atmospheric corrected reflectance.

[0059] Optionally, the first color space is an RGB color space, and the second color space is an Lab color space.

[0060] In the embodiments of the present application, the observation azimuth angle and the observation zenith angle can be calculated according to the tilt camera imaging parameter and the position and attitude data, the solar altitude angle and the solar azimuth angle can be obtained by combining the imaging time information, the geometric conditions during image imaging can be accurately captured, accurate basic data support is provided for subsequent radiation correction, the atmospheric influence parameter can be determined from the atmospheric correction parameter lookup table based on the above-mentioned geometric parameters, the theoretical radiance of each pixel can be calculated, the atmospheric scattering, absorption and other factors can be effectively eliminated to unify the radiance reference under the influence of the atmosphere, the radiance can be corrected by the cosine fourth power proportional coefficient of the actual correction angle and the theoretical correction angle, the systematic difference of the radiance caused by the camera tilt observation can be compensated, the brightness and hue unevenness caused by the angle deviation of different view angle imaging can be solved, the processed image and the reference image can be matched in the color space by channel histogram, the subtle random radiance difference can be further eliminated, the hue and brightness distribution of all tilt images can be highly consistent with the reference image. In this way, through the synergistic effect of the geometric parameter calculation, the atmospheric influence correction, the tilt angle compensation and the statistical fine adjustment, the automatic uniform light normalization of the tilt image is realized, the subjectivity and inefficiency of manual adjustment are avoided, the hue uniform and radiance consistent high-quality image data is provided for subsequent real scene three-dimensional processing, and the application value of the tilt image data is significantly improved.

[0061] Figure 3 An example of a schematic diagram of a physical structure of an electronic device is shown in Figure 3 The electronic device can include a processor 310, a communications interface 320, a memory 330, and a communications bus 340, wherein the processor 310, the communications interface 320, and the memory 330 communicate with each other through the communications bus 340. The processor 310 can invoke a logical instruction in the memory 330 to execute a tilt image dodging processing method, which includes: obtaining original image data, the original image data including an original tilt image, tilt camera imaging parameters, position and attitude data, and imaging time information; performing observation geometry calculation according to the tilt camera imaging parameters and the position and attitude data to obtain an observation azimuth angle and an observation zenith angle; performing illumination geometry calculation according to the imaging time information to obtain a solar elevation angle and a solar azimuth angle; determining an atmospheric influence parameter from an atmospheric correction parameter lookup table according to the observation azimuth angle, the observation zenith angle, the solar elevation angle, and the solar azimuth angle, and determining a theoretical radiance of each pixel in the original tilt image based on the atmospheric influence parameter, and determining a standard brightness and unifying a brightness reference of the theoretical radiance based on the standard brightness, the atmospheric correction parameter lookup table being used to describe a parameter set of atmospheric influence on light; calculating a cosine fourth power proportional coefficient of an actual correction angle of camera tilt observation, and correcting the theoretical radiance of each pixel based on the cosine fourth power proportional coefficient; and converting the processed original tilt image and a reference image from a first color space to a second color space, performing histogram matching on each channel respectively, and converting back to the first color space to obtain a dodging normalized image.

[0062] In addition, the logical instruction in the memory 330 described above can be implemented in the form of a software function unit and sold or used as an independent product, which can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or parts of the prior art that make contributions or parts of the technical solutions can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the method described in the embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0063] In another aspect, the present application also provides a computer program product, which comprises a computer program stored on a non-transitory computer readable storage medium, and the computer program is executable by a processor to cause a computer to perform the tilt image vignetting processing method provided by any of the above methods, which comprises: obtaining original image data, the original image data comprising an original tilt image, tilt camera imaging parameters, position and attitude data, and imaging time information; performing observation geometry calculation according to the tilt camera imaging parameters and the position and attitude data to obtain an observation azimuth angle and an observation zenith angle; performing illumination geometry calculation according to the imaging time information to obtain a solar elevation angle and a solar azimuth angle; determining an atmospheric influence parameter from an atmospheric correction parameter lookup table according to the observation azimuth angle, the observation zenith angle, the solar elevation angle, and the solar azimuth angle, and determining a theoretical radiance of each pixel in the original tilt image based on the atmospheric influence parameter, and determining a standard brightness and unifying a brightness reference of the theoretical radiance based on the standard brightness, the atmospheric correction parameter lookup table being used to describe a parameter set of atmospheric influence on light; calculating a cosine fourth power proportional coefficient of an actual correction angle of camera tilt observation, and correcting the theoretical radiance of each pixel based on the cosine fourth power proportional coefficient; and converting the processed original tilt image and a reference image from a first color space to a second color space, converting back to the first color space after performing histogram matching on each channel respectively, to obtain a vignetting normalized image.

[0064] In yet another aspect, the present application also provides a non-transitory computer readable storage medium having stored thereon a computer program, which, when executed by a processor, implements the tilt image vignetting processing method provided by any of the above methods, and the method comprises: obtaining original image data, the original image data comprising an original tilt image, tilt camera imaging parameters, position and attitude data, and imaging time information; performing observation geometry calculation according to the tilt camera imaging parameters and the position and attitude data to obtain an observation azimuth angle and an observation zenith angle; performing illumination geometry calculation according to the imaging time information to obtain a solar elevation angle and a solar azimuth angle; determining an atmospheric influence parameter from an atmospheric correction parameter lookup table according to the observation azimuth angle, the observation zenith angle, the solar elevation angle, and the solar azimuth angle, and determining a theoretical radiance of each pixel in the original tilt image based on the atmospheric influence parameter, and determining a standard brightness and unifying the brightness reference of the theoretical radiance based on the standard brightness, the atmospheric correction parameter lookup table being used to describe a parameter set of the influence of the atmosphere on light; calculating a cosine fourth power proportional coefficient of an actual correction angle of camera tilt observation, and correcting the theoretical radiance of each pixel based on the cosine fourth power proportional coefficient; and converting the processed original tilt image and a reference image from a first color space to a second color space, performing histogram matching on each channel respectively, and converting back to the first color space to obtain a vignetting normalized image.

[0065] The device embodiments described above are merely illustrative, wherein the units illustrated as separate components can or can not be physically separated, and the components illustrated as units can or can not be physical units, i.e., can be located in one place, or can be distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0066] From the above description of the embodiments, those skilled in the art can clearly understand that the embodiments can be implemented by means of software plus necessary universal hardware platforms, and of course can also be implemented by hardware. Based on such understanding, the above technical solutions, essentially or in terms of the contribution to the prior art, can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, etc., and includes a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods described in each embodiment or some parts of the embodiments.

[0067] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for homogenizing oblique images, characterized in that, include: Acquire raw image data, which includes raw tilted images, tilted camera imaging parameters, position and attitude data, and imaging time information; Based on the imaging parameters of the tilting camera and the position and attitude data, observation geometry calculations are performed to obtain the observation azimuth angle and the observation zenith angle; based on the imaging time information, illumination geometry calculations are performed to obtain the solar altitude angle and the solar azimuth angle. The atmospheric influence parameters are determined from the atmospheric correction parameter lookup table based on the observed azimuth angle, the observed zenith angle, the solar altitude angle, and the solar azimuth angle. The theoretical radiance of each pixel in the original oblique image is determined based on the atmospheric influence parameters. A standard radiance is determined and a luminance benchmark is unified based on the standard luminance. The atmospheric correction parameter lookup table is used to describe the set of parameters that describe the influence of the atmosphere on light. Calculate the cosine fourth power scaling factor between the actual correction angle and the theoretical correction angle of the camera tilt observation, and correct the theoretical radiance of each pixel based on the cosine fourth power scaling factor. The processed original tilted image and reference image are converted from the first color space to the second color space. Histogram matching is performed on each channel and then converted back to the first color space to obtain a uniformly normalized image.

2. The method for homogenizing oblique images according to claim 1, characterized in that, Based on the imaging parameters of the tilting camera and the position and attitude data, observation geometry calculations are performed to obtain the observation azimuth angle and the observation zenith angle, including: Based on the imaging parameters of the tilted camera and the position and attitude data, the coordinates of the ground feature points corresponding to each pixel in the original tilted image are calculated in the image space auxiliary coordinate system using rotation transformation, so as to obtain the image auxiliary coordinates of the ground feature points. The line of sight is determined by connecting the projection center in the image space auxiliary coordinate system with the auxiliary coordinates of the ground feature image. Calculate the angle between the projection of the line of sight onto the plane and the due north direction to obtain the observation azimuth angle of each pixel; calculate the angle between the line of sight and the vertical direction to obtain the observation zenith angle of each pixel.

3. The method for homogenizing oblique images according to claim 1, characterized in that, The step of performing illumination geometry calculations based on the imaging time information to obtain the solar altitude angle and solar azimuth angle includes: The illumination geometric time parameters are determined based on the imaging time information, and the illumination geometric time parameters include the latitude of the ground target point, the solar declination, and the solar hour angle. The solar zenith angle is calculated based on the latitude of the ground target point, the solar declination, and the solar hour angle, and the solar altitude angle is determined based on the solar zenith angle, wherein the solar zenith angle and the solar altitude angle are complementary. Calculate the solar azimuth angle based on the solar altitude angle, the solar hour angle, and the solar declination.

4. The method for homogenizing oblique images according to claim 1, characterized in that, Before determining the atmospheric influence parameters from the atmospheric correction parameter lookup table based on the observed azimuth angle, the observed zenith angle, the solar altitude angle, and the solar azimuth angle, the method further includes: Using the 6S atmospheric radiation transfer model, atmospheric influence parameters under different weather conditions are calculated to establish a lookup table of atmospheric correction parameters under different weather conditions.

5. The method for homogenizing oblique images according to claim 1 or 4, characterized in that, The atmospheric influence parameters include: path radiative reflectance, path radiative radiance, balloon albedo, atmospheric transmittance, atmospheric top radiation flux, spectral response function integral, normalized solar down-going radiation flux, upward total transmittance, downward total transmittance, upward direct transmittance, downward direct transmittance, upward scattering transmittance, downward scattering transmittance, and atmospherically corrected reflectance.

6. The method for homogenizing oblique images according to claim 1, characterized in that, The first color space is the RGB color space, and the second color space is the Lab color space.

7. A device for homogenizing light in oblique images, characterized in that, include: Acquisition module and processing module; The acquisition module is used to acquire raw image data, which includes raw tilt images, tilt camera imaging parameters, position and attitude data, and imaging time information. The processing module is used to perform observation geometry calculations based on the imaging parameters of the tilted camera and the position and attitude data to obtain the observation azimuth angle and the observation zenith angle; perform illumination geometry calculations based on the imaging time information to obtain the solar altitude angle and the solar azimuth angle; determine atmospheric influence parameters from an atmospheric correction parameter lookup table based on the observation azimuth angle, the observation zenith angle, the solar altitude angle, and the solar azimuth angle, and determine the theoretical radiance of each pixel in the original tilted image based on the atmospheric influence parameters, and determine a standard radiance and a luminance benchmark to unify the theoretical radiance based on the standard luminance. The atmospheric correction parameter lookup table is used to describe the set of parameters that describe the influence of the atmosphere on light; calculate the cosine fourth power scaling factor of the actual correction angle of the camera tilted observation, and correct the theoretical radiance of each pixel based on the cosine fourth power scaling factor; convert the processed original tilted image and reference image from a first color space to a second color space, perform histogram matching on each channel, and then convert back to the first color space to obtain a uniformly normalized image.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the tilted image homogenization processing method as described in any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the tilted image homogenization processing method as described in any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the tilted image homogenization processing method as described in any one of claims 1 to 6.

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