WO2013044642A1 - Brightness function obtaining method and related apparatus - Google Patents

Abstract

Disclosed are a brightness function obtaining method and a related apparatus, used for obtaining a brightness function of a display screen at any angle. The method of an embodiment of the present invention comprises: obtaining a first picture of a display screen taken from a first angle; obtaining a second picture and a brightness picture of the display screen taken from a second angle; calculating camcorder parameters according to the first picture; establishing a first coordinate mapping relationship according to the camcorder parameters and location parameters of the display screen; establishing a second coordinate mapping relationship according to the first picture and the second picture; obtaining a third coordinate mapping relationship through calculation according to the first coordinate mapping relationship and the second coordinate mapping relationship; and obtaining a linearization brightness function of the display screen through calculation according to the third coordinate mapping relationship and the brightness picture.

Description

 The present invention claims the priority of the Chinese patent application filed on September 27, 2011, the Chinese Patent Office, the application number is 201110301810.7, and the invention name is "the brightness function acquisition method and related device", the entire contents thereof This is incorporated herein by reference. Technical field

 The present invention relates to the field of image processing, and in particular, to a brightness function acquisition method and related apparatus. Background technique

 The display screen is an optical radiation surface for displaying an image, and may specifically include a flat or curved projection display screen and a flat panel display, wherein the projection display screen includes a front projection and a rear projection display screen, and the light radiation manner is a reflection, a transmission, and a self-lighting manner. One or a combination thereof.

 Under the current state of the art, a projection display system consisting of a single projector may not be able to meet the display requirements of large resolution, so multiple projector combinations can be used to display an image together, breaking the resolution limit. A single projector may not be able or difficult to achieve a better display on the surface, and some researchers have used a multi-projector to fused display to achieve a combined display on a curved surface such as a curved surface or a spherical surface. This multi-projector combination display method is collectively referred to as a multi-projector fusion display system.

 Geometric correction and gamut fusion techniques are key technologies in multi-projector seamless fusion display systems. Geometric correction achieves the coherence of the spatial position of the object in the scene, while gamut fusion achieves the continuity of the multi-projector gamut transition. The geometric alignment and gamut fusion effects are not good, which directly leads to the splitting of the fusion display in the fusion zone.

 The goal of gamut fusion is to control the inconsistency of the color field of the projector screen beyond the physiological limits of the human eye's perception. The image is usually color corrected using a color gamut fusion algorithm and then output to the projector. Studies have shown that the color aliasing algorithm of the single tube attenuates the image red, green and blue (RGB, Red Green Blue) values, and it is easy to present color stripes in the transition zone. The gamut fusion algorithm requires the spatial brightness distribution function of the projection display screen. Among them, the spatial brightness distribution function of these projection display screens may be related to the anisotropy of the projection display screen and the spatial brightness attenuation function of the projector.

Single flat panel display shows system limitations in terms of resolution, display area and viewing angle Sex, some people use multiple flat panel display combination to break through this limitation. In a video conferencing application scenario using multiple flat panel displays, there may be a large difference in brightness between flat panel displays, which results in a splitting of the screen and affects display quality. In this case, the difference in brightness can be automatically corrected using software or circuitry, and the correction of these differences requires the use of a spatial luminance distribution function.

 The "acquisition of the luminance function" refers to the acquisition of the spatial distribution information of the luminance. The operation of "acquisition" includes the process of sensing and data calculation, and is not limited to sensing. When the data to be acquired cannot be directly obtained, the data calculation method is needed to process the sensor data that can be obtained, thereby obtaining indirectly. The data that needs to be obtained. "Luminance function" is a function of brightness with respect to spatial coordinates and may be described as "luminance variations", "luminance distribution", "photometric variations", "," The luminance response, or the "luminance surface", is a different description of the same object as the "luminance function" in this paper. The "luminance function" in this paper describes the difference in brightness between different spatial values. It is not necessary to obtain an absolute lumen value. The ratio of the function value of the obtained luminance function to its lumen value at each spatial position is unknown but equal. constant. In many applications, the acquisition of standard lumen values is not necessary. That is, brightness can refer to relative values.

 The acquisition of the spatial luminance distribution function is a key technique in known display screen color correction or brightness correction schemes. At present, the industry usually uses a camera to capture a brightness image, and then performs a coordinate conversion method to achieve the display screen space brightness function.

 However, in the prior art, the angle at which the camera acquires the brightness image of the display screen is generally the angle at which the camera is calibrated, and since the angle at which the camera is calibrated is generally on the side, when the display screen is viewed from the side, the brightness of each part of the entire screen is Inconsistent (non-Lambertian surface) results in inaccurate color correction or brightness correction of the display screen based on the brightness image acquired by the camera. Summary of the invention

 Embodiments of the present invention provide a brightness function acquisition method and related apparatus for acquiring a brightness function of a display screen at an arbitrary angle.

 The method for obtaining a brightness function provided by the present invention includes:

Obtaining a first image of a display screen taken from a first angle, the first angle being used for imaging a camera-calibrated shooting angle; acquiring a second image of the display screen taken from the second angle and the brightness image, the second angle being an arbitrary shooting angle specified by the user; calculating camera parameters according to the first image; a parameter and a position parameter of the display screen establish a first coordinate mapping relationship from coordinates of the display screen to image coordinates taken from the first angle; establishing a slave according to the first image and the second image a second coordinate mapping relationship of the image coordinates captured by the first angle to the captured image coordinates of the second angle; and calculating from the display screen according to the first coordinate mapping relationship and the second coordinate mapping relationship Coordinates to a third coordinate mapping relationship of image coordinates taken from the second angle; a linearized luminance function of the display screen is calculated according to the third coordinate mapping relationship and the luminance image.

 The brightness function acquiring device provided by the present invention includes:

 a first acquiring unit, configured to acquire a first image of the display screen taken from the first angle, the first angle is a shooting angle for camera calibration, and a second acquiring unit, configured to acquire a display photographed from the second angle a second image of the screen and a brightness image, the second angle being an arbitrary shooting angle specified by the user; a first calculating unit, configured to calculate a camera parameter according to the first image; a first establishing unit, configured to a parameter and a position parameter of the display screen establish a first coordinate mapping relationship from a coordinate of the display screen to an image coordinate taken from the first angle; a second establishing unit, configured to: according to the first image and the The second image establishes a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle; a third establishing unit, configured to map according to the first coordinate relationship And calculating, by the second coordinate mapping relationship, a third coordinate from coordinates of the display screen to image coordinates captured from the second angle Shot relation; second calculating means for obtaining a linear luminance function of the display screen according to the third coordinate mapping relationship between the luminance image is calculated.

 The brightness function acquisition system provided by the invention comprises:

a camera device, a display device, and a brightness function acquiring device; the camera device includes at least two lenses, respectively capturing a display screen of the display device from a first angle and a second angle, wherein the first angle is used for camera calibration a shooting angle, the second angle is an arbitrary shooting angle specified by the user; the display device is configured to display an image in the display screen; the brightness function acquiring device is configured to separately capture from the camera device from the first angle a first image of the display screen, and a second image of the display screen taken from the second angle and the brightness image, calculating camera parameters according to the first image; establishing a slave image according to the camera parameter and the position parameter of the display screen a first coordinate mapping relationship of coordinates of the display screen to image coordinates captured from the first angle; And establishing, according to the first image and the second image, a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle; according to the first coordinate mapping The relationship and the second coordinate mapping relationship calculate a third coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the second angle; calculating the image according to the third coordinate mapping relationship and the brightness image The linearized luminance function of the display screen.

 As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages:

 The present invention acquires a first image of a display screen photographed from a first angle, a second image of a display screen photographed from a second angle, and a brightness image with which coordinates from the display screen are established to from the first a first coordinate mapping relationship of the image coordinates of the angle shot, using the first image and the second image to establish a second coordinate map of the image coordinates captured from the first angle to the captured image coordinates of the second angle And obtaining, by the conversion of the first coordinate mapping relationship and the second coordinate mapping relationship, a third coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the second angle, and finally according to the third coordinate The mapping relationship performs coordinate transformation on the brightness image captured from the second angle to obtain a linearized brightness function of the display screen; since the present invention respectively performs shooting from the first angle and the second angle, the first angle is a shooting angle for camera calibration, The second angle can be any angle specified by the user; thus, when performing luminance image acquisition Then, the second angle can be set to an angle observed by the user, so that the brightness of the display screen captured from the second angle is uniform (close to the Lambertian surface), and the brightness image can be used to better perform color correction or brightness correction of the display screen. . DRAWINGS

 In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings may be obtained based on these drawings without any creative work.

1 is a schematic flowchart of a method for acquiring a luminance function according to an embodiment of the present invention; FIG. 2 is another schematic flowchart of a method for acquiring a luminance function according to an embodiment of the present invention; FIG. 3 is an application scenario of a method for acquiring a luminance function according to an embodiment of the present invention; 4 is a schematic diagram showing the logical structure of a luminance function acquiring apparatus according to an embodiment of the present invention; and FIG. 5 is a schematic diagram showing the logical structure of a luminance function acquiring system according to an embodiment of the present invention. detailed description

 Embodiments of the present invention provide a luminance function acquisition method and related apparatus for acquiring a luminance function of a display screen at an arbitrary angle.

 Referring to FIG. 1 , an embodiment of a method for acquiring a luminance function in an embodiment of the present invention includes:

101. Acquire a first image of a display screen taken from a first angle;

 The brightness function acquisition means acquires a first image of the display screen taken from the first angle, the first angle being a shooting angle for camera calibration. In an embodiment of the invention, the camera captures the display screen from a first angle, which may be a projection screen or a flat panel display.

 The brightness function acquiring device calculates the geometric information of the object in the three-dimensional space from the first image acquired by the camera, and thereby reconstructs and recognizes the object; the process of the camera calibration mainly determines the geometric and optical parameters of the camera, and determines the camera relative to the world coordinate system. Orientation.

 102. Acquire a second image of the display screen taken from the second angle and the brightness image; the brightness function acquiring means acquires the second image of the display screen photographed from the second angle and the brightness image, the second angle is any shooting specified by the user Angle; the brightness image is brightness data information corresponding to the second image.

 The camera photographed from the first angle and the camera photographed from the second angle may be the same camera or two different cameras, depending on the actual situation, which is not limited herein.

 103. Calculate camera parameters according to the first image.

 The brightness function acquiring device calculates the camera parameter according to the first image acquired from the first angle. Specifically, the brightness function acquiring device calculates the geometric information of the object in the three-dimensional space according to the first image (such as the three-dimensional coordinates of the four corners of the display screen). , using the determined geometric information and the corresponding algorithm to calculate the camera.

 104. Establish a first coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the first angle according to the camera parameters and the position parameters of the display screen;

 The brightness function acquiring means performs geometric calibration based on the camera parameters and the position parameters of the display screen, and establishes a first coordinate mapping relationship from coordinates of the display screen to image coordinates taken from the first angle.

The position parameter of the display screen may be locally preset data, or may be a parameter that the brightness function acquiring device locates the display screen according to the camera parameter, which is determined according to actual conditions, and is not limited herein; The position parameter may specifically be a three-dimensional upper contour curve and a three-dimensional lower contour curve of the display screen. 105. Establish a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle according to the first image and the second image;

 The brightness function acquiring means respectively extracts geometric information from the first image and the second image acquired from the first angle and the second angle, and establishes image coordinates captured from the first angle to the second according to the extracted geometric information. The second coordinate mapping relationship of the image coordinates of the angled image.

 In the embodiment of the present invention, since the angle at which the camera calibration is performed (ie, the first angle) and the angle at which the luminance image is acquired (ie, the second angle) are different, the first coordinate mapping relationship may not be directly used to perform the display screen. The calculation of the brightness function requires coordinate conversion from the first angle to the second angle to obtain a coordinate mapping relationship from the display screen to the position of the camera corresponding to the second angle, so it is necessary to first calculate the image from the first angle. The second coordinate mapping relationship of the captured image coordinates to the second angle of the image coordinates.

 106. Calculate, according to the first coordinate mapping relationship and the second coordinate mapping relationship, a third coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the second angle;

 The luminance function acquiring means calculates a third coordinate mapping relationship from the coordinates of the display screen to the image coordinates photographed from the second angle based on the first coordinate mapping relationship and the second coordinate mapping relationship.

 107. Perform coordinate transformation on the luminance image according to the third coordinate mapping relationship.

 The luminance function acquiring means calculates a linearized luminance function of the display screen based on the third coordinate mapping relationship and the luminance image.

 In the embodiment of the present invention, if the brightness image of the display screen captured from the second angle is linearized data, the brightness function acquiring device directly obtains the coordinate image after performing coordinate transformation on the brightness image according to the third coordinate mapping relationship. a linearized brightness function of the display screen;

 If the brightness image of the display screen taken from the second angle is non-linearized data, the brightness image may be coordinate-transformed according to the third coordinate mapping relationship to obtain a brightness function of the display screen coordinates, and then the display screen coordinates are The brightness function is linearized to obtain a linearized brightness function of the display screen; or the brightness image may be linearized to obtain a linearized brightness image captured by the second angle, and then according to the third coordinate mapping relationship The linearized luminance image is coordinate-transformed to obtain a linearized luminance function of the display screen. The specific coordinate transformation or the linearization processing may be performed according to actual conditions, which is not limited herein.

The present invention acquires a first image of a display screen taken from a first angle, a second image of a display screen taken from a second angle, and a brightness image, with which the sitting from the display screen is established Marking a first coordinate mapping relationship of image coordinates taken from the first angle, using the first image and the second image to establish image coordinates captured from the first angle to the second angle of the captured image a second coordinate mapping relationship of the image coordinates, and obtaining, by the conversion of the first coordinate mapping relationship and the second coordinate mapping relationship, a third coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the second angle Finally, performing coordinate transformation on the brightness image captured from the second angle according to the third coordinate mapping relationship to obtain a linearized brightness function of the display screen; since the present invention respectively performs shooting from the first angle and the second angle, the first angle is used The angle of the camera is calibrated, and the second angle can be any angle specified by the user; thus, when the brightness image is acquired, the second angle can be set to the angle observed by the user, so that the image is captured from the second angle. The brightness of the display screen is uniform (close to the Lambertian surface), and the brightness image can be used to better display the screen. Color correction or luminance correction.

 The following is a description of the method for obtaining the brightness function in the embodiment of the present invention in the application scenario in which the display screen is the projection screen. Another embodiment of the method for acquiring the brightness function in the embodiment of the present invention includes:

 201. Acquire a first image of a projection screen taken from a first angle;

 The brightness function acquiring means acquires a first image of the projection screen taken from the first angle, the first angle being a shooting angle for camera calibration.

 In the embodiment of the present invention, the display screen is a projection screen, the projector projects a solid color image to the projection screen, and the "solid color" refers to the same color of each pixel of the input image of the projector, such as pure white, pure yellow or pure red. . The solid color image is projected onto the projection screen for the purpose of facilitating the extraction of the contour image of the projection screen and for facilitating the extraction of the luminance image of the projection screen.

 In the embodiment of the present invention, if the projection system is composed of a plurality of projectors, the brightness function acquiring device may image the images projected by each projector one by one by the first angle of the camera, or may be unified from the first angle by the camera. Take a picture group (no overlap area) projected by each projector.

 202: Acquire a second image of the projection screen taken from the second angle and the brightness image; the brightness function acquiring means acquires the second image of the projection screen taken from the second angle and the brightness image, the second angle is any shooting specified by the user Angle; the brightness image is brightness data information corresponding to the second image.

In the embodiment of the present invention, the brightness function acquiring device captures an image (second image) projected by the projector from a second angle through a camera, and acquires a brightness image corresponding to the second image according to the second image. Since the second angle can be any angle specified by the user, the user can take the second angle It is set to the angle at which the user observes the projection screen such that the radiation of the respective positions on the entire projection screen is substantially the same.

 203. Calculate camera parameters according to the first image.

 The luminance function acquiring means calculates the camera parameters from the first angle acquired from the first angle as described above.

 The camera parameters may specifically include:

 The internal parameters of the camera include: focal length, the optical center coordinate of the camera, the coordinates of the center point of the image, and the first-order coefficient of the radial distortion of the lens;

 The external parameters of the camera include: a rotation matrix and a translation vector between the three-dimensional world coordinate system and the camera coordinate system.

 In the embodiment of the present invention, it is assumed that the projection screen is a vertically extruded curved surface, and the vertically extruded curved surface is a curved surface obtained by sweeping a certain distance along a direction perpendicular to the plane in which the two-dimensional curved line is perpendicular.

 The brightness function acquiring device extracts the contour coordinates of the projection screen in the first image, and the contour coordinates may specifically be three-dimensional coordinates of the four corners of the projection screen; then, the brightness function acquiring device performs CANNY on the first image according to the contour coordinates. Extracting the edge of the operator to obtain the edge image; removing the edge data of the edge image except the upper contour and the lower contour to obtain the upper contour coordinate and the lower contour coordinate; respectively using the polynomial model and the least square method to the upper contour coordinate and The lower contour coordinates are fitted to the upper edge and the lower edge to obtain an upper contour curve and a lower contour curve. Finally, the nonlinear iterative optimization algorithm is used to initially estimate the camera parameters according to the contour coordinates, the upper contour curve and the lower contour curve.

 204. Determine a position parameter of the projection screen according to the camera parameter.

 The brightness function acquiring means determines the positional parameter of the projection screen according to the camera parameter, and the positional parameter of the projection screen is specifically a three-dimensional upper contour curve and a three-dimensional lower contour curve.

 Specifically, the brightness function acquiring device connects any point on the upper contour curve to the optical center of the camera to obtain a second line, and the second line intersects the plane where the three-dimensional upper contour curve is located, and the intersection point is a three-dimensional upper contour point, according to The set of contour points on the three-dimensional shape determines a three-dimensional upper contour curve; then, the three-dimensional lower contour curve can be obtained by the same method as determining the three-dimensional upper contour curve, or the three-dimensional upper contour curve can be translated downward by a distance equal to the height of the projection screen. A three-dimensional lower contour curve is obtained.

Optionally, in order to further improve the estimation accuracy of the camera parameter, the brightness function acquiring device may further use the camera parameter obtained in the above step 203 as an initial camera parameter, and calculate the initial camera parameter by using an upper contour curve and a lower contour curve of the projection screen. Estimated error, specific, After determining the three-dimensional upper contour curve and the three-dimensional lower contour curve, the brightness function acquiring device maps the three-dimensional lower contour curve back to the camera image according to the initially estimated camera parameter to obtain a re-casting contour curve, and re-casts the contour curve and the image. The error between the actual curves is used as the estimation error of the camera parameters. The estimation error of the specific camera parameters can be defined in various ways. As long as it is proved that the accuracy requirements are met when calculating the camera parameters, for example, the left end points of the two curves are connected, the right end points are connected, and the enclosed area is calculated. After obtaining the estimation error, the brightness function acquisition device uses a nonlinear iterative optimization algorithm to estimate a new set of camera parameters. Using this new camera parameter, a new estimation error can be obtained, and iteratively, until the estimation error is small. When the requirements are met, high-precision camera parameters can be obtained.

 205. Establish a first coordinate mapping relationship from coordinates of the projection screen to image coordinates captured from the first angle according to the camera parameters and the position parameters of the projection screen;

 The brightness function acquiring device acquires an arbitrary point coordinate of the first image in the imaging plane of the camera according to the camera parameter, and connects any point in the imaging plane with the optical center of the camera to obtain a first line; and restores according to the position parameter of the projection screen The curved surface of the projection screen (since the embodiment of the present invention assumes that the projection screen is a vertically extruded curved surface, therefore, after obtaining the three-dimensional upper contour curve and the three-dimensional lower contour curve, the curved surface of the projection screen can be obtained), wherein the first straight line Intersecting the curved surface of the projection screen, the coordinates of the obtained intersection point are mapped one by one with the coordinates of the arbitrary point; the brightness function acquiring means can establish the projection screen from the projection screen to the first according to the coordinates of each arbitrary point and the coordinates of the corresponding intersection point The first coordinate mapping relationship of the angle.

 In the embodiment of the present invention, after acquiring the position parameters (the three-dimensional upper contour curve and the three-dimensional lower contour curve) of the projection screen, the brightness function acquiring device restores the curved surface of the projection screen according to the position parameter of the projection screen; and in other application scenarios In the display screen is a pure plane (such as a flat panel display), when determining the surface of the display screen, it is not necessary to calculate the three-dimensional upper contour curve and the three-dimensional lower contour curve of the display screen, and directly through the three-dimensional coordinates of the four corners of the display screen. Determining the surface of the display screen; or, in an application scenario where the display screen is an irregular plane, the brightness function acquiring means may construct the surface of the display screen using a triangulation technique based on stereo image matching point extraction according to the position parameter of the display screen. The positional parameters of the display screen are parameters that are calibrated using a three-dimensional calibration template.

 206. Establish a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle according to the first image and the second image;

The brightness function acquiring means firstly obtains the first picture obtained from the first angle and the second angle, respectively And extracting the geometric information from the image and the second image. Specifically, the brightness function acquiring device respectively extracts the first feature point and the second feature point of the first image and the second image, where the first feature point and the second feature point are respectively used Position information indicating the first image and the second image; the image formed by the feature points may be a checkerboard image or a bitmap image;

 Then, the brightness function acquiring device searches the first feature point and the second feature point of the one-to-one mapping by using the feature point detection algorithm. Specifically, if the image formed by the feature points is a checkerboard image, the brightness function acquiring device uses the chessboard The grid detection algorithm respectively detects the checkerboard corner points in the first image and the second image, and since the images taken from the first angle and the second angle are the same as the projection screen, the first image and the second image have a common The standard checkerboard, through the mapping relationship between the checkerboards, can obtain the one-to-one mapping relationship of the checkerboard corner coordinates of the first image and the second image; finally, according to the first feature point and the second feature of the map The point establishes a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle.

 The luminance function acquiring device may also detect the Gaussian feature points of each dot in the bitmap image by using the centroid detection method, and then establish a mapping relationship between the Gaussian feature points, and calculate the coordinate points of the mapped feature points. The coordinate mapping relationship between these two images. For example, first assume that the coordinate mapping relationship between two images conforms to the rational Bessel model, and then use these known-mapped feature point coordinates to solve the parameters of the optimal rational Bessel model. After these parameters are obtained, the one-to-one mapping between the image and the image is known. Practice has proved that, at least in many cases, the coordinate mapping relationship between image and image has little error with the rational Bessel model, so the assumption of rational Bessel model is reasonable. For the solution of the parameters of the rational Bessel model, a constrained nonlinear optimization algorithm can be used. The model of the mapping relationship between images and images includes but is not limited to the rational Bessel model.

 In the embodiment of the present invention, since the angle at which the camera calibration is performed (ie, the first angle) and the angle at which the luminance image is acquired (ie, the second angle) are different, the first coordinate mapping relationship may not be directly used to perform the projection screen. The calculation of the brightness function requires coordinate conversion from the first angle to the second angle to obtain a coordinate mapping relationship from the projection screen to the position of the camera corresponding to the second angle, so it is necessary to first calculate the image from the first angle. The second coordinate mapping relationship of the captured image coordinates to the second angle of the image coordinates.

 207. Calculate, according to the first coordinate mapping relationship and the second coordinate mapping relationship, a third coordinate mapping relationship from coordinates of the projection screen to image coordinates captured from the second angle;

The brightness function acquiring means calculates the relationship between the first coordinate mapping relationship and the second coordinate mapping relationship A third coordinate mapping relationship from the coordinates of the projection screen to the image coordinates captured from the second angle described above is calculated.

 208. Perform coordinate transformation on the luminance image according to the third coordinate mapping relationship.

 The brightness function acquiring means performs coordinate transformation on the brightness image of the projection screen taken from the second angle according to the third coordinate mapping relationship, and obtains a brightness function of the projected screen coordinates.

 209. Linearize the brightness function of the projection screen coordinates.

 The luminance function acquiring means linearizes the luminance function of the projection screen coordinates to obtain a linearized luminance function of the display screen. In the embodiment of the present invention, since the luminance image of the projection screen photographed from the second angle is nonlinearized data, it is necessary to linearize the luminance function.

 Specifically, the brightness function acquiring means linearizes the brightness function of the projection screen coordinates according to an inverse function of the nonlinear brightness transfer function of the camera. The nonlinear brightness transfer function can be directly provided by the camera manufacturer or indirectly according to the color management standard used by the camera supplier. For example: Some SLR cameras (a type of camera) suppliers claim to use the sRGB color management standard. The sRGB standard defines the camera's luminance transfer function, and the inverse function of the luminance transfer function is also determined accordingly. Therefore, the luminance transfer function of the luminance transfer function of these cameras is relatively close to the luminance transfer function of the camera defined by the sRGB standard, and the luminance transfer function defined by the sRGB standard can be directly used as the luminance transfer function in the embodiment of the present invention.

 In the embodiment of the present invention, how the brightness function acquiring device obtains an accurate brightness function in a scene in which the display screen is a projection screen is described, so that the user can obtain the brightness function acquiring device according to the embodiment of the present invention. Brightness function for better color correction of the projector.

If the display screen is an application scenario of the flat panel display, the method flow for obtaining the brightness function is basically the same as the method flow of the above embodiment, and the difference is: (1) the calculation method of the camera parameter; calculating the camera parameter according to the first image When the display area of the flat panel display is usually a rectangle with a known size, the position information of the flat panel display can be directly determined according to the three-dimensional coordinates of the four corners of the flat panel display, and the three-dimensional coordinates of the four corners of the flat panel display can be measured with a ruler in advance. , no additional surface calculation is needed; according to the three-dimensional coordinates of the four corners, the brightness function acquisition device can obtain the camera parameters by using the nonlinear iterative optimization algorithm; (2) the calculation method of the first coordinate mapping relationship; After the parameter is acquired, the relative spatial position of the camera and the flat panel display is determined, and the intersection point of the first straight line and the flat panel display plane forms a mapping relationship with the starting point of the first straight line in the imaging plane of the camera. , using multiple sets of such mappings The first coordinate line can be obtained from the flat panel display to the first angle; the first straight line is a line connecting the first image from the optical center of the camera at any point in the imaging plane of the camera.

 For ease of understanding, the method for acquiring the luminance function described in the foregoing embodiment is further described in detail in a specific application scenario, specifically:

 As shown in the figure, there is a projection system composed of three projectors, wherein the projector No. 0 and the projector No. 1, and the projector No. 1 and the projector No. 2 respectively form an overlapping area of two projections, The overlapping area is a bright band caused by the superposition of the projected light; the brightness of the bright band is obviously higher than other display areas, causing the viewer to have a color splitting effect on the screen, and therefore, it is necessary to perform color correction on the display image projected by the projector. Before performing color correction, it is necessary to obtain the brightness function of the projection screen.

 It has been mentioned in the above embodiment of FIG. 2 that the display surface of the projection screen is approximately a vertical extruded curved surface. In the embodiment of the present invention, the display screen is photographed at two angles by two cameras, and the first angle is a shooting angle for performing camera calibration. The second angle is the angle at which the viewer observes the projection screen. Since the angle at which the viewer observes the projection screen is on the front side, the bright band display of the captured projection screen is relatively uniform, close to the Lambertian surface.

 The brightness function acquiring device respectively acquires the first image captured from the first angle and the second image captured from the second angle by the two cameras; the brightness function acquiring device calculates the camera parameter through the first image (the specific calculation process may Referring to the description of steps 203 and 204 above, the camera parameters can be divided into internal parameters and external parameters. The internal parameters include: the focal length of the camera, the optical center coordinates of the camera, the coordinates of the center point of the image, and the first-order coefficient of the radial distortion of the lens. The external parameters include: a rotation matrix R and a translation vector T between the three-dimensional world coordinate system and the camera coordinate system.

 If the camera coordinate system is in the direction of the world coordinate system: the angle (α) is rotated counterclockwise around the X axis, the angle (β) is rotated counterclockwise around the 轴 axis, and the angle (γ) is rotated counterclockwise around the Ζ axis. The rotation matrix is:

其中， , 和¹分别为从世界坐标系到相机坐标系变换的沿三个坐标 轴的平移量 (旋转之后)。

Where, , and ¹ are the amount of translation along the three coordinate axes (after rotation) from the world coordinate system to the camera coordinate system, respectively.

 After acquiring the camera parameters, the brightness function acquiring device connects any point on the upper contour curve with the optical center of the camera to obtain a second line, which intersects the plane where the three-dimensional upper contour curve is located, and the intersection point is three-dimensionally a contour point, determining a three-dimensional upper contour curve according to the set of contour points on the three-dimensional contour; and then shifting the three-dimensional upper contour curve downward by a distance equal to a height of the projection screen to obtain a three-dimensional lower contour curve; the brightness function acquiring device passes the three-dimensional upper contour The curve and the 3D lower contour curve determine the surface of the projection screen.

 The brightness function acquiring device acquires an arbitrary point coordinate of the first image in the imaging plane of the camera according to the camera parameter, and connects any point in the imaging plane with the optical center of the camera to obtain a first line; wherein, the first line Intersecting with the curved surface of the projection screen, the coordinates of the intersecting point and the coordinates of the arbitrary point are mapped; the brightness function acquiring means can establish the coordinates from the projection screen to the first according to the coordinates of each arbitrary point and the coordinates of the corresponding intersection point. The first coordinate mapping relationship of the angle.

 The brightness function acquiring means establishes a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle according to the first image and the second image, and the calculation method of the specific second coordinate mapping relationship may be Refer to the description of step 206 above. The brightness function acquiring device further calculates a third coordinate mapping relationship from the coordinates of the display screen to the image coordinates captured from the second angle according to the first coordinate mapping relationship and the second coordinate mapping relationship, and then uses the third coordinate mapping relationship to The brightness image of the projection screen of the two-angle shooting is subjected to coordinate transformation and linearization processing to obtain a linearized luminance function of the projection screen. The process of specific coordinate transformation and linearization processing can be referred to the description of steps 208 and 209 above.

 After obtaining the linearized luminance function of the projection screen, the color correction device can perform color correction on the overlapping area on the projection screen, specifically:

The color correction device acquires the width of the overlapping area as w, and acquires the coordinates (mx, my) of a point P in the overlapping area on the projection screen, which is a distance d from the left boundary of the projection area of the projector No. 1. The method for specifically obtaining the width w and the left boundary distance d is: according to the linearized brightness function of the obtained projection screen, the projection boundary of each projector can be extracted (specifically, image segmentation can be used) The method, the edge extraction method, or the manual editing method performs extraction), and the distance between the left boundary of the display area 1 and the right boundary of the 0 display area is the width w of the first overlap area. The distance from P _m ( mx,my ) to the left boundary of the display area of No. 1 is d.

 The chromaticity coordinates of the projection area generated by the No. 0 projector alone are , y. ), its standard color system

(CIE-XYZ, X stands for red primary color, Y stands for green primary color, Ζ stands for blue primary color, these three primary colors are not physical real colors, but fictional imaginary colors) The color vector under space is (X., X, Z.); alone

The chromaticity coordinates of the projection area of the projector No. 1 are ( , y) , and the color vector under the CIE-XYZ space is ( , ); the chromaticity coordinates of the two in the overlap region are CIE-XYZ space. The color vector below is a linear system that assumes a projection screen approximation,

( ₁ , y ₀₁ ) = T(dKx ₀ , y ₀ ) + (lT(d))(x _l , y ₁ )

( ^X 01')l' ^Z 0l) = (Χ ₀ ')' ^Ζ θ)+( ^Χ 1'Χ' ^Ζ ΐ)

 Where r (d) is the transition function of the chromaticity coordinates, r (d) = ( 1 + cos (; rd/w) )/2 can be defined, and other τ (d) can be designed as needed.

| ^B o =( ^X o, ), ^Z o)

Remember =( ^Χ ι,Χ, ^Ζ ι) ,

 Let (A, be the solution to the following equations:

χοΑ ^Β ο + ^χ ι ^Β ι y ₀ A ^B o + Υι ^Β ι +(l- _r (d)) _Xl ), Wd)y. + (l- r(d)) _yi )) . (i- · )

 As can be seen from the above formula, as long as the brightness of the projection area of the projector No. 0 is attenuated. Times, the overlap area of the projections of No.1 and No.0 is attenuated by A times. Therefore, the chromaticity coordinates of the overlapping area can be made to transition according to the r (d) function, and the attenuation is called attenuation, which is called chromatic smoothing attenuation. Function, under mural coordinates β = y5(mx, my).

 The above B PB i is the brightness response of the projection screen of the No. 0 projector and the No. 1 projector independently of the projection screen at point P. Since the brightness function is the mapping relationship between the brightness and the projection screen coordinates, the brightness function value corresponding to the P point coordinate on the projector screen of No. 0 is the brightness response of the projector independently at the point P of the No. 0 projector, therefore, The linearized luminance function obtained by the luminance function obtaining means can obtain the values of ^ and ^.

 After the color correction device transitions the chromaticity coordinates of the overlap region according to the r (d) function, the chromaticity correction of the projection screen can be completed.

After performing the chromaticity correction, the spatial luminance function under the projection screen coordinates is subjected to β attenuation. In order to obtain the overall brightness distribution under the projection screen coordinates, although the brightness distribution eliminates the smearing of the chromaticity, but does not eliminate the splitting feeling on the brightness, the color correction device also needs to perform the brightness correction method.

 First, the color correction device obtains a spatial brightness function of each projection area at the projection screen coordinates, and the brightness function may be a linearized brightness function acquired by the brightness function acquiring device, or may be a spatial brightness distribution after the attenuation is performed, and specifically The choice depends on whether the user needs chromaticity correction. In some cases where the requirements are not high, the chromaticity correction can be omitted. Both the spatial luminance function and the function are two-dimensional functions of the mural coordinates. The multiplication of the two functions is the operation of the attenuation, and the product is the spatial luminance distribution after the implementation of the attenuation.

 Then, the color correction device adds the input spatial luminance functions at the same position to obtain a composite spatial luminance function. The color correction device uses the integrated spatial luminance function as an input and uses the luminance smoothing algorithm to obtain the target spatial luminance function. Then divide the target luminance function by the input spatial luminance function to obtain a luminance smoothing attenuation function, which is recorded as = (dish, my) at the coordinates of the projection screen. The brightness smoothing algorithm for solving the target space luminance function can be considered as an optimization problem with constraints. The constraint is that the difference in brightness is not perceptible by the human eye, and the goal of optimization is to maximize the sum of the dynamic ranges of each pixel.

After linearizing the input image and multiplying it by the integrated luminance decay function α, a color corrected linear image is obtained. In the case where chromaticity correction and luminance correction are required, the luminance comprehensive luminance attenuation function _α = β^, where only luminance correction is required " = α = β where only chromaticity correction is required. The input image linearization is performed according to the common luminance transfer function of the display device.

 Finally, the color correction device non-linearizes the color-corrected linear image and outputs it to the input end of the display device to complete the color correction operation. The non-linearized operation requires an inverse function of the transfer function of the luminance function corresponding to the display device.

 The color contains brightness and chromaticity. Both the brightness and the chromaticity can be corrected according to the method described in this embodiment, and the requirement can be lowered to correct only the brightness or the chromaticity.

 The application scenario in the embodiment of the present invention has been described above by using only some examples. It can be understood that there are more application scenarios in the actual application, which are not limited herein.

 An embodiment of the brightness function acquiring device of the present invention for performing the above-described brightness function obtaining method is described below. For the logical structure, please refer to FIG. 4. An embodiment of the brightness function acquiring device in the embodiment of the present invention includes:

The first obtaining unit 401 is configured to acquire a first image of the display screen taken from the first angle, The first angle is a shooting angle for camera calibration;

 a second acquiring unit 402, configured to acquire a second image of the display screen taken from the second angle and a brightness image, where the second angle is an arbitrary shooting angle specified by the user;

 a first calculating unit 403, configured to calculate a camera according to the first image

 a first establishing unit 404, configured to establish a first coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the first angle according to the camera parameter and the position parameter of the display screen; the second establishing unit 405 is configured to The first image and the second image establish a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle;

 The third establishing unit 406 is configured to calculate, according to the first coordinate mapping relationship and the second coordinate mapping relationship, a third coordinate mapping relationship from the coordinates of the display screen to the image coordinates captured from the second angle;

 The second calculating unit 407 is configured to obtain a linearized brightness function of the display screen according to the third coordinate mapping relationship and the brightness image.

 The second calculating unit 407 in the embodiment of the present invention may include: a first coordinate transforming module 4071 and a first linearization module 4072, or a second coordinate transforming module 4074 and a second linearizing module 4073.

 The first coordinate transformation module 4071 is configured to perform coordinate transformation on the brightness image according to the third coordinate mapping relationship, and if the brightness image captured from the second angle is nonlinear data, obtain a brightness function of the display screen coordinates. And triggering the first linearization module 4072; if the luminance image captured from the second angle is linear data, directly obtaining a linearized luminance function of the display screen coordinates;

 a first linearization module 4072, configured to linearize the brightness function of the display screen coordinates to obtain a linearized brightness function of the display screen;

 a second linearization module 4073, configured to linearize the brightness image, obtain a linearized brightness image captured from the second angle, and trigger a second coordinate transformation module 4074; a second coordinate transformation module 4074, Performing coordinate transformation on the linearized luminance image according to the third coordinate mapping relationship to obtain a linearized luminance function of the display screen.

 The first calculating unit 403 in the embodiment of the present invention may include:

 a first extraction module 4031, configured to extract a contour coordinate of the display screen according to the first image;

a first obtaining module 4032, configured to acquire an upper contour curve of the display screen according to the contour coordinates And the lower contour curve;

 The estimation module 4033 is configured to estimate the camera parameters according to the contour coordinates, the upper contour curve and the lower contour curve using the nonlinear iterative optimization algorithm.

 The first establishing unit 404 in the embodiment of the present invention may include:

 a second acquisition block 4041, configured to acquire an arbitrary point coordinate of the first image in an imaging plane of the camera;

 a third obtaining module 4042, configured to connect an arbitrary point in the imaging plane to an optical center of the camera to obtain a first straight line;

 a fourth obtaining module 4043, configured to restore a curved surface of the display screen according to a position parameter of the display screen, where the first straight line intersects a curved surface of the display screen to obtain intersection point coordinates, and the coordinates of the arbitrary point and the intersection point coordinate Mapping

 The first establishing module 4044 is configured to establish, according to each of the foregoing arbitrary point coordinates and the intersection point coordinates corresponding to the arbitrary point coordinates, a first coordinate mapping relationship from the coordinates of the display screen to the image coordinates captured from the first angle.

 The second establishing unit 405 in the embodiment of the present invention may include:

 a second lifting block 4051, configured to respectively extract a first feature point and a second feature point of the first image and the second image, wherein the first feature point and the second feature point are respectively used to represent the first image And location information of the second image;

 The searching module 4052 is configured to search, by using a feature point detection algorithm, the first feature point and the second feature point of the mapping;

 a second establishing module 4053, configured to establish, according to the first feature point and the second feature point of the mapping, a second coordinate mapping relationship between the image coordinates captured from the first angle and the captured image coordinates of the second angle .

The specific interaction process of each unit in the brightness function acquiring device in the embodiment of the present invention is as follows: The first obtaining unit 401 acquires a first image of the display screen taken from the first angle, and the first angle is a shooting angle for camera calibration. In an embodiment of the invention, the camera captures the display screen from a first angle, and the display screen may be a projection screen or a flat panel display. The second acquiring unit 402 takes a second image of the display screen taken from the second angle and a brightness image, and the second angle is an arbitrary shooting angle specified by the user; the brightness image is brightness data information corresponding to the second image. The camera photographed from the first angle and the camera photographed from the second angle may be the same camera or two different cameras, which may be determined according to actual conditions, and are not limited herein. After acquiring the first image, the first calculating unit 403 calculates the camera parameters according to the above-described first image acquired from the first angle. The camera parameters are divided into internal parameters and external parameters. The internal parameters of the camera include: focal length, the optical center coordinate of the camera, the coordinates of the center point of the image, the first-order coefficient of the radial distortion of the lens; the external parameters of the camera include: 3D space world coordinates The rotation matrix and translation vector between the camera and the camera coordinate system.

 Specifically, the first extraction module 4031 of the first calculating unit 403 may extract the contour coordinates of the display screen in the first image, and the contour coordinates may specifically be three-dimensional coordinates of the four corners of the display screen; the first calculating unit 403 The first obtaining module 403 performs edge extraction of the CANNY operator on the first image according to the contour coordinate to obtain an edge image; and removes edge data of the edge image except the upper contour and the lower contour to obtain upper contour coordinates and lower contour Coordinates: The upper and lower edges are respectively fitted to the upper and lower contours using a polynomial model and a least squares method to obtain an upper contour curve and a lower contour curve; the estimation module 4033 of the first calculating unit 403 utilizes The linear iterative optimization algorithm initially estimates the camera parameters according to the contour coordinates, the upper contour curve and the lower contour curve. Further, in order to improve the estimation accuracy of the camera parameters, the estimation module 4033 may also use the obtained camera parameters as the initial camera. Parameters, and use the upper contour curve and lower of the display screen The profile curve calculates the estimation error of the initial camera parameter. Specifically, after determining the three-dimensional upper contour curve and the three-dimensional lower contour curve, the brightness function acquiring device maps the three-dimensional lower contour curve back to the camera according to the initially estimated camera parameter. The image obtains a re-casting contour curve, and the error between the contour curve and the actual curve in the image is taken as the estimation error of the camera parameter. The estimation error of the specific camera parameters can be defined in various ways. As long as it is proved that the accuracy requirements are met when calculating the camera parameters, for example, the left end points of the two curves are connected, and the right end points are connected to calculate the enclosed area. After obtaining the estimation error, the brightness function acquisition device uses a nonlinear iterative optimization algorithm to estimate a new set of camera parameters. Using this new camera parameter, a new estimation error can be obtained, and iteratively, until the estimation error is small. When the requirements are met, high-precision camera parameters can be obtained.

After acquiring the camera parameters, the first establishing unit 404 establishes a first coordinate mapping relationship from the coordinates of the display screen to the image coordinates captured from the first angle according to the camera parameters and the position parameters of the display screen; specifically, may be first The second obtaining module 4041 of the establishing unit 404 acquires any point coordinates of the first image in the imaging plane of the camera; and the third acquiring module 4042 of the first establishing unit 404 connects any point in the imaging plane to the optical center of the camera. Obtaining a first straight line; the fourth obtaining module 4043 of the first establishing unit 404 is configured according to the position parameter of the display screen Restoring the curved surface of the display screen, the first straight line intersects the curved surface of the display screen to obtain the intersection point coordinates, the arbitrary point coordinates and the intersection point coordinate-map; finally, the first establishing module by the first establishing unit 404 4044 establishes a first coordinate mapping relationship from the coordinates of the display screen to the image coordinates captured from the first angle according to each of the above-mentioned arbitrary point coordinates and the intersection point coordinates corresponding to the arbitrary point coordinates.

 Optionally, if the display screen is a vertical extruded surface, the fourth obtaining module 4043 can obtain the curved surface of the projected screen by using the three-dimensional upper contour curve and the three-dimensional lower contour curve; if the display screen is a pure plane (such as a flat panel display), determining When the surface of the screen is displayed, it is not necessary to calculate the three-dimensional upper contour curve and the three-dimensional lower contour curve of the display screen, and the fourth obtaining module 4043 can directly determine the curved surface of the display screen by displaying the three-dimensional coordinates of the four corners of the display screen; or, in the display In the application scenario where the screen is an irregular plane, the fourth obtaining module 4043 may construct a curved surface of the display screen according to a positional parameter of the display screen, using a triangulation technique based on stereo image matching point extraction, where the position parameter of the display screen is three-dimensional The calibration template is used to calibrate the parameters.

 After acquiring the first image and the second image, the second establishing unit 405 establishes a second coordinate map of the image coordinates captured from the first angle to the captured image coordinates of the second angle according to the first image and the second image. Specifically, the first feature point and the second feature point of the first image and the second image may be respectively extracted by the second extraction module 4051 of the second establishing unit 405, where the first feature point and the second feature point are respectively For displaying the position information of the first image and the second image, the image formed by the feature points may be a checkerboard image or a bitmap image; and the lookup module 4052 of the second establishing unit 405 searches using the feature point detection algorithm- Mapping the first feature point and the second feature point; specifically, if the image formed by the feature point is a checkerboard image, the brightness function acquiring device detects the first image and the second image respectively by using a checkerboard detection algorithm a checkerboard corner point, since the image taken from the first angle and the second angle is the same as the projection screen, therefore, the first image and the second image Having a common standard checkerboard, through the mapping relationship between the checkerboards, a one-to-one mapping relationship of the checkerboard corner coordinates of the first image and the second image is obtained; the second establishing module 4053 of the second establishing unit 405 And establishing, according to the first feature point and the second feature point of the mapping, a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle.

In the embodiment of the present invention, since the angle at which the camera calibration is performed (ie, the first angle) and the angle at which the luminance image is acquired (ie, the second angle) are different, the first coordinate mapping relationship may not be directly used to perform the projection screen. The calculation of the brightness function needs to be from the first angle to the second The coordinate conversion is performed to obtain the coordinate mapping relationship of the position of the camera corresponding to the second angle from the projection screen, so it is necessary to first calculate the image coordinates captured from the first angle to the captured image coordinates of the second angle. The second coordinate mapping relationship.

 After obtaining the first coordinate mapping relationship and the second coordinate mapping relationship, the third establishing unit 406 calculates a third coordinate mapping relationship from the projection screen to the second angle according to the first coordinate mapping relationship and the second coordinate mapping relationship. That is, the coordinate mapping relationship from the projection screen to the position of the camera corresponding to the second angle).

 Finally, the second calculating unit 407 calculates the linearized luminance function of the display screen by the third coordinate mapping relationship and the luminance image.

 In the embodiment of the present invention, specifically, if the brightness image of the display screen taken from the second angle is nonlinearized data, the first coordinate transformation module 4071 of the second calculation unit 407 may be configured according to the third coordinate mapping. Correlate the coordinate image of the brightness image to obtain a brightness function of the display screen coordinates, and trigger the first linearization module 4072 to linearize the brightness function of the display screen coordinate to obtain a linearized brightness function of the display screen; or The second linearization module 4073 of the second calculating unit 407 may first linearize the brightness image to obtain a linearized brightness image captured from the second angle, and trigger the second coordinate transformation module 4074 according to the above The three-coordinate mapping relationship performs coordinate transformation on the linearized luminance image to obtain a linearized luminance function of the display screen.

 If the brightness image of the display screen taken from the second angle is linearized data, the first coordinate transformation module 4071 can directly obtain the linearization of the display screen after performing coordinate transformation on the brightness image according to the third coordinate mapping relationship. Brightness function.

 An embodiment of the brightness function acquisition system of the present invention for performing the above-described brightness function acquisition method is described below. For a logical structure, please refer to FIG. 5. An embodiment of the brightness function acquisition system in the embodiment of the present invention includes:

 Camera device 501, display device 502, brightness function acquisition device 503;

The camera device 501 includes at least two lenses, and respectively captures a display screen of the display device 502 from a first angle and a second angle, the first angle is a shooting angle for camera calibration, and the second angle is specified by a user. Any angle of shooting. The camera device 501 may be composed of one or two cameras. If it is a camera, the camera includes at least two lenses. If two cameras are used, the two cameras are respectively displayed from the first angle and the second angle. Device 502 takes a picture. The display device 502 is for displaying an image in a display screen. The display device 502 can be a flat panel display or a projection display system; if it is a projection display system, the projection screen is a display screen of the display device 502, and the projection display system can include a plurality of projectors, The images projected by multiple projectors make up the image that needs to be displayed.

 The brightness function acquiring means 503 is configured to respectively acquire, from the camera device 501, a first image of the display screen photographed from the first angle, and a second image of the display screen photographed from the second angle and the brightness image, according to the first Calculating camera parameters according to an image; establishing a first coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the first angle according to the camera parameters and position parameters of the display screen; And the second image establishes a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle; according to the first coordinate mapping relationship and the second coordinate The mapping relationship calculates a third coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the second angle; calculating linearity of the display screen according to the third coordinate mapping relationship and the brightness image The brightness function.

 For the specific operation process of the brightness function acquisition system of the present invention, reference may be made to the process of the embodiment of FIG. 2, and details are not described herein again.

 In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the device embodiments described above are merely illustrative. For example, the division of the unit is only a logical function division. In actual implementation, there may be another division manner, for example, multiple units or components may be combined or Can be integrated into another system, or some features can be ignored, or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be electrical, mechanical or otherwise. The components displayed for the unit may or may not be physical units, ie may be located in one place, or may be distributed over multiple network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solution of the embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. The integrated unit, if implemented in the form of a software functional unit and sold or used as a standalone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may contribute to the prior art or all or part of the technical solution may be embodied in the form of a software product stored in a storage medium. A number of instructions are included to cause a computer device (which may be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: a U disk, a removable hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and the like, which can store program codes. .

 The above is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention. It should be covered by the scope of the present invention. Therefore, the scope of the invention should be determined by the scope of the claims.

Claims

Rights request A method for acquiring a brightness function, comprising:  Acquiring a first image of the display screen taken from the first angle, the first angle being a shooting angle for camera calibration;  Acquiring a second image of the display screen taken from the second angle and the brightness image, the second angle being an arbitrary shooting angle specified by the user;  Calculating camera parameters according to the first image;  Establishing a first coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the first angle according to the camera parameter and a position parameter of the display screen;  And establishing, according to the first image and the second image, a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle;  Calculating, according to the first coordinate mapping relationship and the second coordinate mapping relationship, a third coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the second angle;  A linearized luminance function of the display screen is calculated based on the third coordinate mapping relationship and the luminance image.  2. The method according to claim 1, wherein if the luminance image captured from the second angle is nonlinear data, the calculating according to the third coordinate mapping relationship and the luminance image The linearized brightness function of the display screen, including:  And performing coordinate transformation on the brightness image according to the third coordinate mapping relationship to obtain a brightness function of the display screen coordinates, and linearizing the brightness function of the display screen coordinates to obtain linearized brightness of the display screen. Function  Or,  And linearizing the brightness image to obtain a linearized brightness image captured from the second angle, and performing coordinate transformation on the linearized brightness image according to the third coordinate mapping relationship to obtain the display screen. Linearization brightness function;  If the brightness image captured from the second angle is linear data, calculating the linearized brightness function of the display screen according to the third coordinate mapping relationship and the brightness image, including: according to the third coordinate The mapping relationship performs coordinate transformation on the luminance image to obtain a linearized luminance function of the display screen. The method according to claim 1, wherein the camera parameters comprise: internal parameters and external ^t; The internal parameters include: a focal length, a center of the camera, a coordinate of the center point of the image, and a first-order coefficient of the radial distortion of the lens;  The external parameters include: a rotation matrix and a translation vector between the three-dimensional world coordinate system and the camera coordinate system.  4. The method of claim 1 wherein:  The calculating camera parameters according to the first image includes:  Extracting contour coordinates of the display screen according to the first image;  The upper contour curve and the lower contour curve of the display screen are acquired according to the contour coordinates; the camera parameters are estimated from the contour coordinates, the upper contour curve, and the lower contour curve using a nonlinear iterative optimization algorithm.  The method according to claim 4, wherein the acquiring the upper contour curve and the lower contour curve of the display screen according to the contour coordinates comprises:  Performing edge extraction of the CANNY operator on the first image to obtain an edge image; removing edge data of the edge image except the upper contour and the lower contour to obtain upper contour coordinates and lower wheel coordinates;  The upper and lower edges are fitted to the upper and lower contour coordinates using a polynomial model and a least squares method, respectively, to obtain an upper contour curve and a lower contour curve.  6. The method according to claim 5, wherein after estimating the camera parameters based on the contour coordinates, the upper contour curve and the lower contour curve using a nonlinear iterative optimization algorithm, the method further comprises:  Using the estimated camera parameter as an initial camera parameter;  Calculating an estimated error of the initial camera parameter using the upper contour curve and the lower contour curve;  The camera parameters are again estimated using the estimation error and the nonlinear iterative optimization algorithm.  The method according to claim 4, wherein the establishing, from the camera parameter and the position parameter of the display screen, a first from a coordinate of the display screen to an image coordinate taken from the first angle Coordinate mapping relationship, including:  Obtaining an arbitrary point coordinate of the first image in an imaging plane of the camera; Connecting any point in the imaging plane to the optical center of the camera to obtain a first straight line; restoring a curved surface of the display screen according to a position parameter of the display screen, the first straight line and the display screen The surfaces intersect to obtain intersection coordinates, and the arbitrary point coordinates intersect with the coordinates Point coordinates - mapping;  A first coordinate mapping relationship from coordinates of the display screen to image coordinates taken from the first angle is established according to each of the arbitrary point coordinates and the intersection point coordinates corresponding to the arbitrary point coordinates.  8. The method of claim 7 wherein:  If the display screen is a vertical extruded surface, restoring the surface of the display screen according to the position parameter of the display screen, including:  Arranging an arbitrary point on the upper contour curve with an optical center of the camera to obtain a second straight line, the second straight line intersecting a plane where the three-dimensional upper contour curve is located, and the intersection point is a three-dimensional upper contour point, according to the The set of contour points on the three-dimensional shape determines a three-dimensional upper contour curve;  Translating the three-dimensional upper contour curve downward by a distance equal to the height of the projection screen to obtain a three-dimensional lower contour curve;  Determining a curved surface of the display screen by the three-dimensional upper contour curve and the three-dimensional lower contour curve;  If the display screen is an irregular plane, the surface of the display screen is restored according to the position parameter of the display screen, including:  Forming a curved surface of the display screen using a triangulation technique based on stereo image matching point extraction according to a position parameter of the display screen, the position parameter of the display screen being a parameter calibrated using a three-dimensional calibration template;  If the display screen is a pure plane, the surface of the display screen is restored according to the position parameter of the display screen, including:  And obtaining a vertex three-dimensional coordinate of the four corners of the display screen according to the position parameter of the display screen, and determining a curved surface of the display screen by three-dimensional coordinates of the vertex of the four corners.  9. The method according to claim 1, wherein the image coordinates captured from the first angle are set to the captured image of the second angle according to the first image and the second image The second coordinate mapping relationship of the coordinates, including: Extracting a first feature point and a second feature point of the first image and the second image, where the first feature point and the second feature point are respectively used to represent location information of the first image and the second image; Searching for the first feature point and the second feature point of the mapping using a feature point detection algorithm; establishing image coordinates captured from the first angle according to the first feature point and the second feature point of the mapping a second coordinate mapping relationship of the captured image coordinates to the second angle. 10. A brightness function acquiring device, comprising:  a first acquiring unit, configured to acquire a first image of a display screen photographed from a first angle, where the first angle is a photographing angle used for camera calibration;  a second acquiring unit, configured to acquire a second image of the display screen taken from the second angle and a brightness image, where the second angle is an arbitrary shooting angle specified by the user;  a first calculating unit, configured to calculate a camera parameter according to the first image;  a first establishing unit, configured to establish, according to the camera parameter and a position parameter of the display screen, a first coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the first angle;  a second establishing unit, configured to establish, according to the first image and the second image, a second coordinate mapping relationship of image coordinates captured from the first angle to captured image coordinates of the second angle;  a third establishing unit, configured to calculate, according to the first coordinate mapping relationship and the second coordinate mapping relationship, a third coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the second angle;  And a second calculating unit, configured to calculate a linearized brightness function of the display screen according to the third coordinate mapping relationship and the brightness image.  The apparatus according to claim 10, wherein the second calculating unit comprises: a first coordinate transformation module and a first linearization module, or a second coordinate transformation module and a second linearization module;  The first coordinate transformation module is configured to perform coordinate transformation on the brightness image according to the third coordinate mapping relationship, and if the brightness image captured from the second angle is nonlinear data, obtain the display screen a brightness function of the coordinates, and triggering the first linearization module; if the brightness image captured from the second angle is linear data, directly obtaining a linearized brightness function of the display screen coordinates;  The first linearization module is configured to linearize a brightness function of the display screen coordinates to obtain a linearized brightness function of the display screen; The second linearization module is configured to perform linearization processing on the brightness image to obtain a linearized brightness image captured from the second angle, and trigger the second coordinate transformation module; the second coordinate And a transform module, configured to perform coordinate transformation on the linearized luminance image according to the third coordinate mapping relationship to obtain a linearized luminance function of the display screen. 12. The apparatus according to claim 10, wherein the first calculating unit comprises:  a first extraction module, configured to extract contour coordinates of the display screen according to the first image; a first acquiring module, configured to acquire an upper contour curve and a lower contour curve of the display screen according to the contour coordinates;  An estimation module for estimating camera parameters based on the contour coordinates, the upper contour curve, and the lower contour curve using a nonlinear iterative optimization algorithm.  13. The apparatus according to claim 12, wherein the first establishing unit comprises:  a second acquiring module, configured to acquire an arbitrary point coordinate of the first image in an imaging plane of the camera;  a third acquiring module, configured to connect an arbitrary point in the imaging plane with an optical center of the camera to obtain a first straight line;  a fourth obtaining module, configured to restore a curved surface of the display screen according to a position parameter of the display screen, where the first straight line intersects a curved surface of the display screen to obtain intersection point coordinates, where the coordinates of the arbitrary point and the coordinates Description of intersection coordinates - mapping;  a first establishing module, configured to establish, according to each of the arbitrary point coordinates and the intersection point coordinates corresponding to the arbitrary point coordinates, a first coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the first angle .  14. The apparatus according to claim 10, wherein the second establishing unit comprises:  a second lifting block, configured to respectively extract a first feature point and a second feature point of the first image and the second image, where the first feature point and the second feature point are respectively used to represent the first feature Position information of an image and a second image;  a searching module, configured to search, by using a feature point detection algorithm, the first feature point and the second feature point of the mapping;  a second establishing module, configured to establish, according to the first feature point and the second feature point of the mapping, image coordinates captured from the first angle to a second image of the captured image coordinates of the second angle Coordinate mapping relationship.  15. A brightness function acquisition system, comprising: Camera device, display device, brightness function acquisition device; The camera device includes at least two lenses, respectively capturing a display screen of the display device from a first angle and a second angle, the first angle being a shooting angle for camera calibration, and the second angle being specified by a user Any angle of shooting;  The display device is configured to display an image in a display screen;  The brightness function acquiring means is configured to respectively acquire, from the camera device, a first image of a display screen photographed from a first angle, and a second image of a display screen photographed from a second angle, and a brightness image, according to the Calculating camera parameters according to an image; establishing a first coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the first angle according to the camera parameters and position parameters of the display screen; And the second image establishes a second coordinate mapping relationship of the image coordinates captured from the first angle to the captured image coordinates of the second angle; according to the first coordinate mapping relationship and the second coordinate The mapping relationship calculates a third coordinate mapping relationship from coordinates of the display screen to image coordinates captured from the second angle; calculating linearity of the display screen according to the third coordinate mapping relationship and the brightness image The brightness function.