CN114494443A - Automatic positioning method and device for sine wave star map, electronic equipment and storage medium - Google Patents
Automatic positioning method and device for sine wave star map, electronic equipment and storage medium Download PDFInfo
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Abstract
The invention discloses a sine wave star map automatic positioning method, a sine wave star map automatic positioning device, electronic equipment and a storage medium, which belong to the field of image processing, and comprise the steps of carrying out graying operation on a shot picture; identifying the central point of the photo, and constructing a plane coordinate system by taking the central point of the photo as a coordinate origin; identifying an MTF test area of the photo, and recording the MTF test area of the sine-wave star chart photo as a first position by using a plane coordinate system; the 16 gray scale blocks of the sinewave star map photograph are located according to the first position. The method preferentially identifies the position with obvious characteristics, low identification difficulty and high identification speed in the standard plate for positioning, determines the positions of other patterns based on the position relation between the positioned position and other patterns, reduces the positioning difficulty of the patterns with unobvious characteristics, does not need to manually repeatedly operate a direction key to move up, down, left and right to position a test image, can improve the test efficiency, and can also accurately identify and improve the test precision of the image with perspective deformation.
Description
Technical Field
The invention relates to a sine wave star map automatic positioning method and device, electronic equipment and a storage medium, and belongs to the field of image processing.
Background
The sine wave star map test target is an image test international standard ISO 12233 issued in 2014: 2014 ", which is the most widely used resolution test format published at present, for testing camera resolution and sharpness, the background transmittance is 18%. As shown in fig. 1, the star map is a sine-wave modulated starlight pattern, 4 corners are pure black rectangles, the center of each pure black rectangle is a pure white rectangle, each pure black rectangle extends 2 gray scale blocks towards each adjacent pure black rectangle, 4 pure black rectangles × each pure black rectangle has 2 adjacent pure black rectangles × extends 2 gray scale blocks =16 gray scale blocks, the 16 gray scale blocks are different, 16 gray scale blocks surround the periphery of a large circle, the large circle is an MTF test area, is an inscribed circle of a rectangle formed by connecting adjacent pure white rectangles, and is formed by a circular array of fan-shaped white stripes with extremely small central angles, the frequency is usually 144 cycles per circle, the center of the large circle is a circle divided into four parts and alternating black and white, and the circumscribed rectangle of the MTF test area passes through the central points of the 4 pure white rectangles. For lower resolution endoscope systems, a 72 cycle star or less may be used. The modulation of the test standard is known to be not less than 96%.
The sine-wave star test can test MTF (modulation transfer function) curves for various directions of a lens or a camera, compared to ISO 12233: 2000 ", the sine wave star map test can more finely and comprehensively reflect the resolution performance of the lens or the camera, but is not as convenient as the wedge line test, and is difficult to quantify the resolution by naked eyes, and the MTF (modulation transfer function) curve needs to be obtained by a specific algorithm with the help of computer software. The method comprises the specific steps of shooting a sine wave star map by using a camera (including a civil camera, an industrial camera, an endoscope and the like) to obtain a picture, transmitting the picture to a computer, and testing the resolution of the camera shooting the picture by using test software on the computer.
In the test software in the prior art, a tester needs to position a test image by moving a direction key up, down, left and right, one test usually needs dozens of clicks, the test time is long, and the test progress is influenced; in addition, perspective deformation always exists in shooting, and under the condition that corners of a shot test picture are stretched due to the perspective deformation, existing test software is often inaccurate in positioning, so that a test result is inaccurate.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a sine wave star map automatic positioning method, a sine wave star map automatic positioning device, an electronic device and a storage medium, so that manual operation is reduced, and positioning accuracy can be improved.
The technical scheme adopted by the invention for solving the technical problems is as follows:
in a first aspect, the present application provides a method for automatically positioning a sine wave star map, comprising the following steps:
carrying out gray level operation on the shot sine wave star map picture;
identifying the central point of the sine wave star atlas picture, and constructing a plane coordinate system by taking the central point of the sine wave star atlas picture as a coordinate origin;
identifying an MTF test area of the sine wave star atlas photo, and recording the MTF test area of the sine wave star atlas photo as a first position by using the plane coordinate system;
according to the first position, 16 gray blocks of the sine wave star map photo are located.
The automatic positioning method of the sine wave star map does not need manual positioning, can automatically position the test image, and is beneficial to improving the test efficiency.
Optionally, the identifying the center point of the sine wave star map photo further comprises:
acquiring a central area screenshot of a sine wave star chart test standard plate as a template;
the step of identifying the central point of the sine wave star map photo and constructing a plane coordinate system by taking the central point of the sine wave star map photo as a coordinate origin comprises the following steps of:
traversing the sine wave star map photo by using a template matching algorithm, and searching a photo center area matched with the template;
and constructing a plane coordinate system by taking the gravity center of the central area of the picture as a coordinate origin.
The template matching algorithm needs to carry out multiple operations on the template and the image to be detected, the larger the template is or the larger the image is, the larger the operation amount is, small circles at the center of the sine wave star map test standard plate, which are alternate in black and white, are selected as the template to carry out first-step positioning on the shot image, and other positions or a larger range of the sine wave star map test standard plate are not selected as the template, so that the obvious characteristics of the small circles are considered, the image size is small, the rapid positioning is facilitated, a plane coordinate system is rapidly established, and the operation amount is reduced.
Optionally, the template matching algorithm is an error method. The error method is one of template matching algorithms, has less calculation amount and is beneficial to improving the efficiency of the first-step positioning.
Optionally, the step of traversing the sine wave star atlas photo by using a template matching algorithm includes:
traversing the limited area of the sine wave star atlas picture by utilizing a template matching algorithm;
the step of delimiting the defined area comprises:
two longitudinal division lines are arranged at one quarter and three quarters of the width of the sine wave star atlas picture pixel, two transverse division lines are arranged at one quarter and three quarters of the height of the sine wave star atlas picture pixel, and the area enclosed by the longitudinal division lines and the transverse division lines is the limited area.
Even if the corners of the photo are distorted due to perspective deformation, the small black and white circles at the center of the sine wave star chart test standard plate cannot deviate from the central point of the photo too originally, a limited area is defined, the template matching range is narrowed, the operation amount is further reduced, and the recognition speed is improved.
Optionally, the step of identifying the MTF test area of the sinogram photograph and recording the MTF test area of the sinogram photograph as a first position in the planar coordinate system includes:
identifying an MTF test area of the sine wave star map photo as an ellipse;
recording each pixel constituting a boundary of the ellipse as the first position in the form of coordinates according to the planar coordinate system.
The MTF test area is identified as a second step of positioning, and the positions of 16 gray-scale blocks are identified as a third step of positioning based on the second step of positioning. Although the MTF test area in the sine wave star map test standard is a circle, the sine wave star map in the shot image is set to be an ellipse by considering that the shot image has perspective deformation, so that the second-step positioning is facilitated to be accurate, and the third-step positioning based on the second-step positioning is more accurate.
Optionally, the first location comprises a first coordinate of an upper vertex, a lower vertex, a left vertex, a right vertex of the ellipse in the planar coordinate system;
the step of locating the 16 gray blocks of the sinewave star map photo according to the first position comprises:
and positioning 16 gray scale blocks of the sine wave star atlas picture according to the first coordinate.
Optionally, the step of locating 16 gray-scale blocks of the sine wave star atlas picture according to the first coordinate comprises:
making an upper horizontal line through the upper vertex, making a lower horizontal line through the lower vertex, making a left vertical line through the left vertex, and making a right vertical line through the right vertex;
and calculating the central points of the 16 gray-scale blocks on the upper horizontal line, the lower horizontal line, the left vertical line and the right vertical line.
Optionally, the step of identifying the MTF test area of the sine wave star atlas photo as an ellipse includes:
calculating the pixel value variance of a first row of pixels, a last row of pixels, a first column of pixels or a last column of pixels of the sine wave star map photo as a background noise level;
calculating the pixel value variance of each line of pixels from top to bottom from the first line of pixels on the sine wave star map picture, recording one line when the pixel value variance is more than Q times of the background noise level as an upper mutation line, and calculating the distance from the upper mutation line to the coordinate origin as the upper half-axis length of an ellipse;
starting from the first row of pixels below the sine wave star atlas picture, calculating the pixel value variance of each row of pixels from bottom to top, recording one row when the pixel value variance is more than Q times of the background noise level as a lower mutation row, and calculating the distance from the lower mutation row to the coordinate origin as the length of a lower half shaft of an ellipse;
starting from the first row of pixels from the left of the sine wave star map picture, calculating the pixel value variance of each row of pixels from left to right, recording a row when the pixel value variance is more than Q times of the background noise level as a left mutation row, and calculating the distance from the left mutation row to the coordinate origin as the length of a left half shaft of an ellipse;
calculating the pixel value variance of each row of pixels from right to left from the first row of pixels on the right side of the sine wave star map picture, recording a row when the pixel value variance is more than Q times of the background noise level as a right abrupt change row, and calculating the distance from the right abrupt change row to the coordinate origin as the right semi-axis length of an ellipse;
establishing an elliptic standard equation according to the length of the upper half shaft, the length of the lower half shaft, the length of the left half shaft and the length of the right half shaft;
wherein the value range of Q is 8-12.
When the pixel value variance is calculated, no matter which direction the pixel value variance starts, the pixel value variance always meets a black rectangle on a background area and a corner of a sine wave star image test standard plate, and the black rectangle is used as a background noise level, for the up-down direction, the pixel value variance can be greatly changed after meeting an MTF test area, for the left-right direction, the pixel value variance can also be changed when meeting a gray block, therefore, the value of Q needs to be carefully determined, if the Q is too small, the Q can be mistakenly judged to enter the MTF test area when meeting the gray block, if the Q is too large, the Q can be insensitive to the pixel value variance after entering the MTF test area, namely, if the Q is too large or too small, the range of the MTF test area can not be accurately identified. The method and the device have the advantages that the next direction is calculated after the MTF test area is considered to enter the MTF test area in one direction, the characteristic that the MTF test area is close to the edge of a sine wave star map is adapted, the calculation amount is favorably reduced, and the second-step positioning of the shot image is favorably realized.
In a second aspect, the present application provides a device, in particular, a device for testing the resolution of a camera based on a sine wave star chart test target, comprising;
the graying module is used for performing graying operation on the shot sine wave star map picture;
the first identification module is used for identifying the central point of the sine wave star atlas picture and constructing a plane coordinate system by taking the central point of the sine wave star atlas picture as a coordinate origin;
the second identification module is used for identifying the MTF test area of the sine wave star atlas photo and recording the MTF test area of the sine wave star atlas photo as a first position by using the plane coordinate system;
and the third identification module is used for positioning 16 gray scale blocks of the sine wave star map photo according to the first position.
The device provided by the application can automatically position and shoot the sine wave star icon plate in the image, and is favorable for improving the resolution test efficiency.
In a third aspect, the present application provides an electronic device comprising a processor and a memory, wherein the memory stores computer readable instructions, and the computer readable instructions, when executed by the processor, perform the steps of the method according to the first aspect.
In a fourth aspect, the present application provides a storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of the method according to the second aspect.
The invention has the beneficial effects that: the automatic positioning method of the sine wave star map can quickly and automatically position the sine wave star map of the shot image, reduces the complexity degree in the resolution test operation, identifies the sine wave star map of the shot image in three steps from inside to outside on the whole, preferentially identifies the positions with obvious characteristics, low identification difficulty and high identification speed in the sine wave star map test standard plate for positioning, determines the positions of other patterns based on the position relation between the positioned positions and the other patterns, reduces the positioning difficulty of the patterns with or without obvious characteristics, does not need to manually repeatedly operate direction keys to move up, down, left and right to position the test image, can improve the test efficiency and the positioning precision, and is favorable for efficient positioning.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
Fig. 1 is ISO 12233: 2014 specified in the specification.
Fig. 2 is a flowchart of an automatic positioning method for a sine wave star map according to an embodiment of the present application.
Fig. 3 is a schematic view of a first structure of an apparatus according to an embodiment of the present disclosure.
Fig. 4 is a schematic structural diagram of an electronic device according to an embodiment of the present application.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
The following disclosure provides many different embodiments or examples for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Referring to fig. 2, an automatic positioning method for a sine wave star map includes the following steps:
s1: and carrying out graying operation on the shot sine wave star map picture.
The sine wave star map photo is obtained by shooting a sine wave star map test standard plate by using a camera with the resolution to be measured. The essence of the identification operation is that the pixel value is calculated, the sine wave star image test target version is black and white, and the condition that the red value, the green value and the blue value of some pixels are close but not equal can occur when some cameras with uncorrected color temperatures take pictures, so that the pictures are subjected to graying operation, the characteristics of the sine wave star image test target version are met, and the calculation amount of subsequent identification operation is reduced.
S2: and identifying the central point of the sine wave star atlas picture, and constructing a plane coordinate system by taking the central point of the sine wave star atlas picture as a coordinate origin.
This step is referred to herein as the first step of positioning. As shown in figure 1, the center of the sine wave star chart test standard is a small circle which is black and white and has obvious characteristics and is easy to identify. After the central point is positioned, a coordinate system can be constructed, and other positions can be conveniently positioned.
S3: and identifying the MTF test area of the sine-wave star atlas photo, and recording the MTF test area of the sine-wave star atlas photo as a first position by using a plane coordinate system.
This step is referred to herein as the second step positioning. The characteristics of the MTF test area are obvious, but the area of the area is large, and the range of the MTF test area is convenient to describe by means of a plane coordinate system provided by the first positioning step.
S4: from the first position, 16 gray scale blocks of the sinewave star map photograph are located.
This step is referred to as the third step positioning by the home position. The 16 gray-scale blocks have a position relation with the MTF test area, and the positions of the 16 gray-scale blocks can be deduced after the MTF test area is known.
Preferably, step S0 is further included before step S2.
S0: and acquiring a screenshot of the central area of the sine wave star chart test standard plate as a template.
Specifically, a sine wave star map test standard plate is downloaded or scanned to obtain an electronic version of the sine wave star map test standard plate, and small black and white circles in the center of the sine wave star map test standard plate are captured by screenshot software and stored as a template.
The detailed steps of step S2 include:
s21: and traversing the whole picture of the sine wave star map picture by utilizing a template matching algorithm, and searching a picture center area matched with the template.
S22: and constructing a plane coordinate system by taking the gravity center of the central area of the picture as a coordinate origin.
In some embodiments, step S21 may not traverse the full photo map, but only the restricted area. Wherein the step of defining the defined area comprises:
two longitudinal division lines are arranged at one quarter and three quarters of the width of the pixels of the sine wave star map photo, two transverse division lines are arranged at one quarter and three quarters of the height of the pixels of the sine wave star map photo, and the area enclosed by the longitudinal division lines and the transverse division lines is the limited area.
The template matching algorithm may be an error method, and the template T (M, N) is stacked on the searched image S (M, N) and translated, where M is the number of pixels per column, N is the number of pixels per row, M represents the pixel height of the searched image, and N represents the pixel width of the searched image. The template covers the region called subgraph S of the searched graphijThe search range is therefore: i is more than or equal to 1 and less than or equal to W-n, j is more than or equal to 1 and less than or equal to H-m, and the formula is 1.
in the formula, E (i, j) represents an error, the position where E (i, j) is the minimum value is the matched target, and the coordinate origin (x0, y0) of the plane coordinate system is formed, and (i, j) represents the coordinate of the lower left corner of the subgraph on the searched graph S (M, N).
The template matching algorithm needs to carry out multiple operations on the template and the image to be detected, the larger the template is or the larger the image is, the larger the operation amount is, small circles at the center of the sine wave star map test standard plate, which are alternate in black and white, are selected as the template to carry out first-step positioning on the shot image, and other positions or a larger range of the sine wave star map test standard plate are not selected as the template, so that the obvious characteristics of the small circles are considered, the image size is small, the rapid positioning is facilitated, a plane coordinate system is rapidly established, and the operation amount is reduced. In some embodiments, an error method with a slightly smaller operation amount is further selected, so that the test efficiency is further improved.
The specific steps of step S3 are:
s31: the MTF test area of the sine-wave star map photograph is identified as an ellipse.
S32: each pixel constituting the boundary of the ellipse is recorded as a first position in the form of coordinates according to a planar coordinate system.
According to the characteristics of the sine wave star atlas test standard plate, the center of the pure black rectangle at each corner is a white rectangle, the MTF test area is an inscribed circle of a rectangle formed by connecting lines of adjacent white rectangles, and the gray scale blocks extend out of each pure black rectangle to the adjacent pure black rectangles, so that the positions of the white rectangles can be found by finding the upper, lower, left and right vertexes of the MTF test area, the positions of the pure black rectangles can be found, and then 16 gray scale blocks can be found according to the position relation of the pure black rectangles and the gray scale blocks. In some embodiments, the first location comprises a first coordinate of an upper vertex, a lower vertex, a left vertex, and a right vertex of the ellipse in a planar coordinate system. From the first coordinates, 16 gray blocks of the sinewave star map photograph can be located.
In some embodiments, the step of locating the 16 gray tiles using the first coordinates is as follows:
s421: and drawing an upper horizontal line through the upper vertex, drawing a lower horizontal line through the lower vertex, drawing a left vertical line through the left vertex and drawing a right vertical line through the right vertex. The intersection point of the upper horizontal line, the lower horizontal line, the left vertical line and the right vertical line is the position of the pure white rectangle, namely the position of the pure black rectangle is obtained at the same time.
S422: according to the position relation between the pure white rectangle and the 16 gray-scale blocks, the central points of the 16 gray-scale blocks are calculated on the upper horizontal line, the lower horizontal line, the left vertical line and the right vertical line.
In the third step of positioning represented by this embodiment, the gray-scale blocks are not substantially positioned according to the graphic features of the 16 gray-scale blocks, because the graphic features of the 16 gray-scale blocks are less obvious and are distributed more dispersedly, and this embodiment uses the position relationship between the 16 gray-scale blocks and other positioned MTF test areas to deduce the positions of the 16 gray-scale blocks. Although the shot photo may have perspective deformation, the MTF test area occupies a larger area of the sine wave star map test standard and is located at a central position, after the MTF test area is accurately positioned, the perspective deformation of the MTF test area is corrected, and 16 gray-scale blocks which are relatively close to the boundary of the MTF test area are not obviously influenced by the perspective deformation.
In some embodiments, the specific step of step S31 includes:
s310: calculating the variance of pixel values of a first row of pixels, a last row of pixels, a first column of pixels, or a last column of pixels of a sine-wave asterogram
As a background noise level NL.
Specifically, the first row of pixels may be the first row of pixels from the top or the first row of pixels from the bottom, and when the first row of pixels from the top is the first row of pixels, the first row of pixels from the bottom is the last row of pixels. The last row of pixels, the first column of pixels and the last column of pixels are the same.
S311: calculating the variance of the pixel values of each row of pixels from top to bottom starting from the first row of pixels from the top of the sine wave star chart
When the d-th row is calculated, the variance of the pixel value
Greater than Q times the background noise level NL: (
>Q NL), recording the row as an upper mutation row, and calculating the distance from the mutation row to the origin of coordinates as the upper semi-axis length of the ellipse. The length of the upper half-axis of the ellipse b1= y 0-d, with the upper vertex coordinates (x0, d).
S312: calculating the pixel value variance of each line of pixels from bottom to top from the first line of pixels from the bottom of the sine wave star chart
When the u-th row is calculated, the variance of the pixel value
And recording the row as a lower mutation row when the background noise level is more than Q times, and calculating the distance from the lower mutation row to the coordinate origin as the length of a lower half shaft of the ellipse. The length of the lower half axis of the ellipse b2= M-y0-u, and the lower vertex coordinates are (x0, M-u), where M is the pixel height of the captured sine wave star map photograph.
S313: and calculating the pixel value variance of each column of pixels from left to right from the first column of pixels from the left of the sine wave star map picture, recording the column as a left abrupt change column when the pixel value variance is more than Q times of the background noise level when the k-th row is calculated, and calculating the distance from the left abrupt change column to the coordinate origin as the left half-axis length of the ellipse. The left half length of the ellipse a2= x 0-k, and the left vertex coordinates are (k, y 0).
S314: and calculating the pixel value variance of each column of pixels from right to left from the first column of pixels on the right side of the sine wave star map picture, recording the column as a right abrupt change column when the pixel value variance is more than Q times of the background noise level when the c-th row is calculated, and calculating the distance from the right abrupt change column to the coordinate origin as the right semi-axis length of the ellipse. The right major axis length of the ellipse, a1= N-x0-c, with the right vertex coordinates (N-c, y0), where N is the width of the captured sine wave star map picture pixels.
The steps S311, S312, S313 and S314 can be performed in any order, the value range of Q is 8-12, and the variance of the pixel values of each row is
The calculation formula of (c) is as shown in formula 2.
Wherein n is the number of pixels per line,
for the e-th pixel value in each row of pixels,
is the pixel average value of each row of pixels; when calculating the variance of the pixel values of each column, n in equation 2 is replaced with m, i.e., the number of pixels per column. No matter which direction the variance of the pixel values starts, the variance of the pixel values always meets a black rectangle on a background area and a corner of a sine wave star image test standard plate, the black rectangle is used as a background noise level, the variance of the pixel values can be greatly changed after meeting an MTF test area for the up-down direction, and the variance of the pixel values can also be changed when meeting a gray-scale block for the left-right directionThe variance of the pixel value changes, so that the value of Q needs to be carefully determined, when the Q is too small, the Q is wrongly judged to enter an MTF test area when the gray-scale block is encountered, and when the Q is too large, the Q is not sensitive to the variance of the pixel value after the Q enters the MTF test area, namely, the Q is too large or too small, which is not beneficial to accurately identifying the range of the MTF test area. Most preferably, Q = 10.
The boundary of the MTF test area is close to the boundary of the sine wave star chart test standard, and the steps from S31 to S34 are calculated from outside to inside, so that the vertices of the MTF test area in the up-down, left-right directions can be found quickly. Although the MTF test area is large in area, the calculation is actually carried out on the periphery of the area, so that the calculation amount is reduced, and the detection efficiency is improved.
Then, a standard equation of the ellipse can be established according to the length of the upper half shaft, the length of the lower half shaft, the length of the left half shaft and the length of the right half shaft:
wherein x is the abscissa and y is the ordinate, a = a1+ a2, b = b1+ b 2.
The specific step of step S32 includes:
s325: calculating the fourth MTF test zone in the first quadrant according to the right axis length a1 and the upper axis length b1
A boundary point (x 1)p，y1p) I.e., the positions of the pixels constituting the MTF test area boundary in the first quadrant in the captured image,
= 1,2,3……max1，max1=int((1/4)*(2
b1+4(a1-b 1)). Such as formula 4 and formula 5.
wherein
Representing the angle between the line connecting the point to the origin of coordinates and the horizontal axis of the planar coordinate system,
，
。
s326: calculating the second quadrant of the MTF test area according to the left semi-major axis length a2 and the upper semi-minor axis length b1
A boundary point (x 2)p，y2p) I.e., the positions of the pixels constituting the MTF test area boundary in the second quadrant in the captured image,
= 1,2,3……max2，max2= int((1/4)*(2
b1+4(a2-b 1)). The calculation formulas are as shown in formula 6 and formula 7.
wherein
Representing the angle between the line connecting the point to the origin of coordinates and the horizontal axis of the planar coordinate system,
，
。
s327: calculating the third MTF test area in the third quadrant according to the left semi-major axis length a2 and the lower semi-minor axis length b2
A boundary point (x 3)p，y3p) I.e., the position of the pixels constituting the MTF test area boundary in the third quadrant in the captured image,
= 1,2,3……max3，max3= int((1/4)*(2
b2+4(a2-b 2)). The calculation formula is as shown in formula 8 and formula 9.
wherein
Representing the angle between the connecting line of the point to the origin of coordinates and the horizontal axis of the plane coordinate system,
，
。
s328: calculating the fourth MTF test zone in the fourth quadrant according to the right semi-major axis length a1 and the lower semi-minor axis length b2
A boundary point (x 4)p，y4p) I.e., the positions of the pixels constituting the MTF test area boundary in the first quadrant in the captured image,
= 1,2,3……max4，max4= int((1/4)*(2
b2+4(a1-b 2)). The calculation formula is as shown in formula 10 and formula 11.
wherein
Representing the angle between the line connecting the point to the origin of coordinates and the horizontal axis of the planar coordinate system,
，
。
after the steps S310 to S328 are performed, each pixel constituting the ellipse is recorded as a position in the form of coordinates and is regarded as a first position, i.e., the MTF test area is completely located.
In the second positioning step represented by this embodiment, the MTF test area is found out substantially by the image characteristics of the MTF test area, but not by the positional relationship between the MTF test area and the black and white alternating small circles, because the MTF test area occupies a large area of the sine-wave star icon plate and is easily affected by the perspective deformation of the shot, the area is assumed to be an ellipse after the circle is stretched, and the MTF test area is found out according to the characteristics of the area, which has a large area occupation ratio and many pixel points, and is favorable for recording and positioning by using a plane coordinate system.
In some embodiments that are parallel to the above steps S421 to S422, the step S4 specifically includes the following steps:
s411: the coordinates P1 (k, d), P2 (N-c, d), P3 (k, M-u), P4 (N-c, M-u) of 4 pure white rectangles in the photograph are determined according to the 4 vertex coordinates of the ellipse.
S412: and determining the positions of the 16 gray blocks according to the relative position relationship between the 16 gray blocks and the pure white rectangles of the star map 4. The 16 gray-scale blocks are uniformly distributed at the connecting line of the 4 pure white rectangles P1, P2, P3 and P4, for example, the gray-scale block 1 is positioned at the connecting line of the pure white rectangles P1 and P2
1 pixel, the coordinate of gray block 1
，
) The calculation formula is as in formulas 12 to 14.
wherein (A), (B), (C), (D), (C), (B), (C)
，
) Is a pure white rectangle P1 coordinates, i.e. (k, d), (b), (c), (d)
，
) Is a pure white rectangle P2 with coordinates, i.e. (N-c, d),
the length of the connecting line of the pure white rectangles P1 and P2. The positions of the remaining 15 gray scale blocks can be obtained in the same way. And finally, taking the positions as centers, selecting a square area in each gray scale block, and completing the positioning of 16 gray scale blocks.
Referring to fig. 3, an embodiment of the present application provides a device, in particular, a device for testing a resolution of a camera based on a sine wave star chart test target, including;
the graying module 201 is used for performing graying operation on the shot sine wave star map picture;
the first identification module 202 is used for identifying the central point of the sine wave star atlas picture and constructing a plane coordinate system by taking the central point of the sine wave star atlas picture as a coordinate origin;
the second identification module 203 is used for identifying the MTF test area of the sine wave star atlas photo and recording the MTF test area of the sine wave star atlas photo as a first position by using a plane coordinate system;
the third identifying module 204 locates 16 gray blocks of the sinewave star map photo according to the first position.
The device positions sine wave star map pictures shot by the camera to be detected in three steps, and the positioning is accurate and efficient. Certainly, the device also comprises a receiving module for receiving the photos taken by the camera to be tested; the test module is used for testing the resolution of the camera based on the sine wave star chart test standard according to the method in the prior art; and the acquisition module is used for acquiring the screenshot of the central area of the sine wave star chart test standard plate as a template.
Referring to fig. 4, fig. 4 is a schematic structural diagram of an electronic device according to an embodiment of the present disclosure, where the present disclosure provides an electronic device, including: the processor 301 and the memory 302, the processor 301 and the memory 302 being interconnected and communicating with each other via a communication bus 303 and/or other form of connection mechanism (not shown), the memory 302 storing a computer program executable by the processor 301, the computer program being executable by the processor 301 when the computing device is running to perform the method in any of the alternative implementations of the above embodiments when the processor 301 executes the computer program to perform the following functions: carrying out gray level operation on the shot sine wave star map picture; identifying the central point of the sine wave star atlas picture, and constructing a plane coordinate system by taking the central point of the sine wave star atlas picture as a coordinate origin; identifying an MTF test area of the sine wave star atlas photo, and recording the MTF test area of the sine wave star atlas photo as a first position by using a plane coordinate system; from the first position, 16 gray scale blocks of the sinewave star map photograph are located.
The embodiment of the present application provides a storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the computer program executes the method in any optional implementation manner of the above embodiment to implement the following functions: carrying out gray level operation on the shot sine wave star map picture; identifying the central point of the sine wave star atlas picture, and constructing a plane coordinate system by taking the central point of the sine wave star atlas picture as a coordinate origin; identifying an MTF test area of the sine wave star atlas photo, and recording the MTF test area of the sine wave star atlas photo as a first position by using a plane coordinate system; from the first position, 16 gray scale blocks of the sinewave star map photograph are located.
The storage medium may be implemented by any type of volatile or nonvolatile storage device or combination thereof, such as a Static Random Access Memory (SRAM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), an Erasable Programmable Read-Only Memory (EPROM), a Programmable Read-Only Memory (PROM), a Read-Only Memory (ROM), a magnetic Memory, a flash Memory, a magnetic disk, or an optical disk.
The automatic positioning method of the sine wave star map can quickly and automatically position the sine wave star map of the shot image, reduces the complexity of the positioning process during the resolution test operation, positions the sine wave star map of the shot image by three steps of identification from inside to outside on the whole (from S311 to S314 in the steps to the outside actually), preferentially identifies the positions with obvious characteristics, low identification difficulty and high identification speed in the sine wave star map test standard plate, carries out first-step positioning and constructs a coordinate system, then identifying the area with obvious characteristics in the sine wave star chart test standard plate to carry out second part positioning, and the position is recorded by the formation of the coordinates, and finally the positions of other patterns are determined based on the position relation between the positioned position and other patterns, so that the positioning difficulty of the patterns with unobvious characteristics is reduced, the efficient positioning is facilitated, and the method can also accurately identify and improve the testing precision of the images with perspective deformation.
In the description of the present specification, reference to the terms "one embodiment," "certain embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (10)
1. An automatic positioning method of a sine wave star map is characterized by comprising the following steps:
carrying out gray level operation on the shot sine wave star map picture;
identifying the central point of the sine wave star atlas picture, and constructing a plane coordinate system by taking the central point of the sine wave star atlas picture as a coordinate origin;
identifying an MTF test area of the sine wave star atlas photo, and recording the MTF test area of the sine wave star atlas photo as a first position by using the plane coordinate system;
according to the first position, 16 gray blocks of the sine wave star map photo are located.
2. The method of claim 1, wherein the step of identifying the center point of the sinogram photograph further comprises the steps of:
acquiring a central area screenshot of a sine wave star chart test standard plate as a template;
the step of identifying the central point of the sine wave star map photo and constructing a plane coordinate system by taking the central point of the sine wave star map photo as a coordinate origin comprises the following steps of:
traversing the sine wave star map photo by using a template matching algorithm, and searching a photo center area matched with the template;
and constructing a plane coordinate system by taking the gravity center of the central area of the picture as a coordinate origin.
3. The method of claim 2, wherein the step of traversing the sinogram photograph using a template matching algorithm comprises:
traversing the limited area of the sine wave star atlas picture by utilizing a template matching algorithm;
the step of delimiting the defined area comprises:
two longitudinal division lines are arranged at one quarter and three quarters of the width of the sine wave star atlas picture pixel, two transverse division lines are arranged at one quarter and three quarters of the height of the sine wave star atlas picture pixel, and the area enclosed by the longitudinal division lines and the transverse division lines is the limited area.
4. The method of claim 1, wherein the step of identifying the MTF test area of the sinogram photograph and recording the MTF test area of the sinogram photograph as a first location in the planar coordinate system comprises:
identifying an MTF test area of the sine wave star map photo as an ellipse;
recording each pixel constituting a boundary of the ellipse as the first position in the form of coordinates according to the planar coordinate system.
5. The sinewave star map automatic location method of claim 4, wherein the first position comprises first coordinates of the upper vertex, the lower vertex, the left vertex, the right vertex of the ellipse in the planar coordinate system;
the step of locating the 16 gray blocks of the sinewave star map photo according to the first position comprises:
and positioning 16 gray scale blocks of the sine wave star atlas picture according to the first coordinate.
6. The method as claimed in claim 5, wherein the step of locating 16 gray blocks of the sine wave star atlas photograph according to the first coordinate comprises:
making an upper horizontal line through the upper vertex, making a lower horizontal line through the lower vertex, making a left vertical line through the left vertex, and making a right vertical line through the right vertex;
and calculating the central points of the 16 gray-scale blocks on the upper horizontal line, the lower horizontal line, the left vertical line and the right vertical line.
7. The method of claim 4, wherein the step of identifying the MTF test area of the sinogram photo as an ellipse comprises:
calculating the pixel value variance of a first row of pixels, a last row of pixels, a first column of pixels or a last column of pixels of the sine wave star map photo as a background noise level;
calculating the pixel value variance of each line of pixels from top to bottom from the first line of pixels on the sine wave star map picture, recording one line when the pixel value variance is more than Q times of the background noise level as an upper mutation line, and calculating the distance from the upper mutation line to the coordinate origin as the upper half-axis length of the ellipse;
calculating the pixel value variance of each line of pixels from bottom to top from the first line of pixels at the bottom of the sine wave star map photo, recording one line as a lower mutation line when the pixel value variance is more than Q times of the background noise level, and calculating the distance from the lower mutation line to the coordinate origin as the length of a lower half shaft of the ellipse;
starting from the first row of pixels from the left of the sine wave star map picture, calculating the pixel value variance of each row of pixels from left to right, recording a row when the pixel value variance is more than Q times of the background noise level as a left mutation row, and calculating the distance from the left mutation row to the coordinate origin as the length of a left half shaft of the ellipse;
calculating the pixel value variance of each row of pixels from right to left from the first row of pixels on the right side of the sine wave star map picture, recording a row when the pixel value variance is more than Q times of the background noise level as a right abrupt change row, and calculating the distance from the right abrupt change row to the coordinate origin as the right semi-axis length of an ellipse;
establishing a standard equation of the ellipse according to the length of the upper half shaft, the length of the lower half shaft, the length of the left half shaft and the length of the right half shaft;
wherein the value range of Q is 8-12.
8. A camera resolution testing device based on a sine wave star chart testing target is characterized by comprising a camera, a sine wave star chart testing target and a sine wave star chart testing target;
the graying module is used for performing graying operation on the shot sine wave star map picture;
the first identification module is used for identifying the central point of the sine wave star atlas picture and constructing a plane coordinate system by taking the central point of the sine wave star atlas picture as a coordinate origin;
the second identification module is used for identifying the MTF test area of the sine wave star atlas photo and recording the MTF test area of the sine wave star atlas photo as a first position by using the plane coordinate system;
and the third identification module is used for positioning 16 gray scale blocks of the sine wave star map photo according to the first position.
9. An electronic device comprising a processor and a memory, said memory storing computer readable instructions which, when executed by said processor, perform the steps of the method according to any one of claims 1 to 7.
10. A storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, performs the steps of the method according to any one of claims 1-7.
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