CN104459639B - Real-time display method of polar coordinate image - Google Patents
Real-time display method of polar coordinate image Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
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- Radar Systems Or Details Thereof (AREA)
Abstract
The invention relates to a real-time display method of a polar coordinate image. The method comprises the steps that the lengths of scanning lines in off-centered display are pre-calculated and stored as a data table; the pixel positions of the scanning lines with the coordinates converted into row and column coordinates are pre-calculated and stored as a data table; the data of the scanning lines are received in real time; the tables are queried to obtain the length information of the current scanning line; the tables are queried to obtain the coordinate conversion pixel position information of the current scanning line; scanning line image information is written into a video memory according to the length information and pixel position information of the current scanning line; the steps from receiving the scanning line information to writing the scanning line image information into the video memory are circularly executed to achieve real-time display of the polar coordinate image. By means of the method, the scanning line information of the polar coordinate image can be displayed in real time, complex emergencies or large maneuvers can be better monitored, requirements for hardware chips can be effectively lowered, chip heating can be reduced, and stability can be improved.
Description
Technical Field
The invention relates to the technical field of digital image processing, in particular to a polar coordinate image real-time display method.
Background
The radar image is composed of scanning lines acquired in a polar coordinate scanning mode. The traditional display method is to transfer the scanning lines obtained in real time into a cache stored according to a rectangular coordinate row and column form, and after the radar finishes scanning for 360 degrees in a week, the cached row and column form images are displayed. The traditional method has a long image display period, and has a great influence on the monitoring effect under the conditions of complex or emergency situations and great maneuverability; the radar scanning period is limited by various factors such as observation distance, pulse frequency, signal-to-noise ratio and the like, and the display period is accelerated by improving the scanning speed, so that the method is basically infeasible. In practical application, the radar often needs to perform eccentric display, a method of double caching and hardware mask trimming is generally adopted in the traditional method during the eccentric display, a display module of the system is required to have a hierarchical mask (Overlay) function, and the requirement on hardware is high. The Overlay function is generally realized in a chip model with an MMU function for realizing multimedia complex operation, and the hardware cost, the system heating and the power consumption are correspondingly increased.
Therefore, a real-time display method for monitoring images in a polar coordinate form is needed to better adapt to the application of the situations of complex emergency, heavy maneuvering and the like, reduce the performance index requirements on hardware, and realize low-cost, efficient and stable monitoring.
Disclosure of Invention
In order to overcome the defects of the conventional method, the invention aims to provide a polar coordinate image real-time display method, which improves the monitoring effect on the conditions of complex emergency, large maneuver and the like by synchronously displaying scanning lines acquired in real time. In order to more conveniently view the monitoring content in the designated direction, the radar image is often required to be eccentrically displayed, namely the position of the radar is not displayed in the center of a circular area displayed on a screen, but is biased to the opposite direction of the interested target area; the monitoring target of interest can be observed more completely and clearly through the magnification and the eccentric display. The method can efficiently realize the eccentric real-time display of the polar coordinate image scanning line, does not need hardware with a layered mask function, and does not need real-time floating point arithmetic capability.
The invention provides a polar coordinate image real-time display method, which comprises the following specific steps:
the polar coordinate image real-time display method is characterized by comprising the following specific steps:
(1) scanning an image by using a radar in a circumferential scanning mode, wherein when the position of the radar is displayed at the center of a circle, the lengths displayed by scanning lines in all directions are equal; when the radar image is displayed eccentrically, the eccentricity needs to be calculated in advance because the display lengths of the scanning lines in different directions are differentSeparation deviceScanning lines at all angles within the range from zero to the radius R of the circular area by the length required to be displayed, and storing the lengths as a data table L; the length of the display is obtained by equation (1):（1）
wherein,in order to be the azimuth angle of the scan line,is composed ofThe length of the directional scan line that needs to be displayed,in order to show the radius of the circular area,、is the eccentricity distance and azimuth; according to the symmetry of the circular scan, the azimuthAdopting 0-90 degrees; said eccentric distanceThe length of 0-512 scanning lines corresponding to 0-90 degrees in the range of 0-512 pixels; the length of each scanning line is stored as a 16-bit integer, and occupies 2 bytes;
(2) based on the symmetry of the circle, the conversion of 0-512 scanning lines corresponding to 0-90 degrees is calculatedThe scanning lines are in a polar coordinate form, converted into pixel positions of row-column rectangular coordinates according to a formula (2), and stored as a data table G;（2）
wherein,is the distance from the pixel point to the origin under the polar coordinate,in order to be the azimuth angle of the scan line,、x, Y coordinates showing the origin in rectangular coordinates respectively,、the coordinates of the pixel points under the rectangular coordinates;
in consideration of the extreme case of off-center display, each scanning line stores coordinates of 1024 pixel positions, which are twice the radius of a display area, and the distance between adjacent pixels on one scanning line in rectangular coordinates in the form of rows and columns is only 0 or plus or minus 1 in the row and column directions, so that each pixel only needs to occupy 4 bits; x, Y each has 2 bits, the high bit represents positive or negative, the low bit represents 0 or 1;
(3) receiving scanning line data in real time; receiving scanning line information in real time according to a scanning pulse frequency set by a radar; setting the coordinate of a current eccentric display center point O1 as an eccentric distance m pixels, wherein the eccentric angle is determined by n scanning lines;
(4) inquiring the data table L obtained in the step (1) according to the scanning line information obtained in the step (3) to obtain length information of the current scanning line, namely the length of the current scanning line to be displayed; if the current received scanning line is the kth scanning line, according to the difference between the current angle and the eccentricity angle, inquiring the length information of the kth-mth scanning line with the eccentricity distance of m pixels in the data table L;
(5) inquiring a data table G to obtain the position information of the coordinate conversion pixel of the current scanning line;
(6) directly writing the scanning line image information into a video memory according to the current scanning line length information obtained in the step (4) and the pixel position information obtained in the step (5);
(7) and (5) repeatedly and circularly executing the step (3) to the step (6), and displaying the received scanning line image information in real time.
The working principle of the invention is as follows:
(1) receiving scanning line image information in real time
The radar generally equally divides 360 degrees of a circle into 1024-4096 scanning lines based on a set scanning pulse frequency, and receives scanning line information in real time according to the scanning pulse frequency set by the radar;
(2) determining the length of the current scanning line to be displayed in the corresponding direction
The radar is in a circular scanning form, and when the position of the radar is displayed at the center of a circle, the lengths displayed by scanning lines in all directions are equal. In order to more conveniently view the monitored content in the designated direction, the radar image is often required to be displayed eccentrically, that is, the position of the radar is not displayed in the center of the circular area displayed on the screen, but is biased to the opposite direction of the target area of interest, as shown in fig. 2. The monitoring target of interest can be observed more completely and clearly through the magnification and the eccentric display.
When the radar displays off-center, the display lengths of the scan lines in different directions are different. The traditional method generally adopts double memory space and is realized by hierarchical mask (Overlay) function or software cutting of the display card hardware, but the method has higher requirement on the computing capacity of the display hardware or a processor and higher hardware cost.
The method does not cache the received scanning lines, calculates the length of each scanning line which needs to be displayed under the eccentric condition according to the formula (1), and then can directly display the scanning line image without a hardware mask function, thereby effectively reducing the hardware cost, reducing the power consumption and the heat of a chip and increasing the stability of long-term operation.
（1）
Wherein,in order to be the azimuth angle of the scan line,is composed ofThe length of the directional scan line that needs to be displayed,in order to show the radius of the circular area,、distance and azimuth of eccentricity.
Based on the symmetry of circular scanning, the display length of each scanning line within 0-90 degrees only needs to be calculated, and the rest directions can be subjected to mirror image mapping. Can be calculated in advanceFrom zeroAnd the display length values of the scanning lines within 0-90 degrees of each eccentric distance in the range of the radius R of the circular area coexist into a table, and only the length data of each scanning line corresponding to the current eccentric distance needs to be read and displayed according to the length data during real-time display, so that real-time floating point operation is not needed.
3) Determining scan line pixel conversion coordinates
The scanning line is in a polar coordinate form and can be converted into a row-column rectangular coordinate form according to the formula (2).
（2）
Wherein,is the distance from the pixel point to the origin under the polar coordinate,the angle of clockwise rotation of the scanning line from the positive direction to the upper direction under the polar coordinate,、x, Y coordinates showing the origin in rectangular coordinates respectively,、the coordinates of the pixel points under the rectangular coordinates.
The distance between its adjacent pixels in the rectangular coordinates in the form of rows and columns on a scan line may be 0 or plus or minus 1 in the row and column directions, respectively. When in storage, each pixel only needs to store the relative difference value with the previous pixel, and each pixel only needs 4 bits.
In order to reduce the cost and the power consumption of a hardware chip, the conversion positions of all the angle directions can be calculated in advance and stored as a data table, the table content only needs to be read during actual display, and no floating point operation is needed during real-time image display.
4) Real-time display of scan line image information
The method does not buffer the received scanning line information, and directly writes the scanning line length table and the scanning line pixel conversion coordinate position information which are stored in advance into the display memory address corresponding to the scanning line pixel to be displayed, thereby displaying the scanning line image information in real time.
Compared with the prior art, the invention has the following advantages:
1) the method can realize real-time display of the polar coordinate monitoring image scanning line, and has better monitoring effect on the emergency complex or large maneuver conditions.
2) The method only needs the hardware chip to have the basic display function, does not need the functions of floating point operation, hardware hierarchical mask and the like, and can adopt a low-cost chip.
3) The method realizes the real-time display of the scanning line by table lookup and direct-write caching, does not need floating point operation, image cutting mask operation and other operations, can effectively reduce the power consumption and the heating of a chip, and improves the stability of long-term operation.
Drawings
FIG. 1 is a process flow diagram of the method of the present invention.
FIG. 2 is a polar coordinate image display with eccentricity.
Detailed Description
The invention is further illustrated by the following examples.
Example 1:
the processing flow of the method of the invention is shown in the attached figure 1. The image off-center display is shown in figure 2. In the following embodiments, the radar image shows a circular area with a radius R of 512 pixels and a 360-degree circumference divided into 2048 scan lines. The specific implementation steps are as follows:
1) and (3) calculating the length of the eccentric display scanning line according to the formula (1).
Based on the symmetry of the circle, only the eccentric distance r needs to be calculated0Within the range of 0-512 pixels, the length of 0-512 scanning lines corresponding to 0-90 degrees can be obtained. The length of each scan line is stored as a 16-bit integer, taking 2 bytes. I.e. the data table L has a size of 512x512x2=512 KB.
2) And (3) calculating the pixel position of which the polar coordinate is converted into the rectangular row-column coordinate according to the formula (2).
Based on the symmetry of the circle, only the conversion pixel positions of 0-512 scanning lines corresponding to 0-90 degrees need to be calculated. Considering the extreme case of off-center display, each scan line stores coordinates of two times the radius of the display area, i.e., 1024 pixel locations. Because the difference between the rows and the columns of the adjacent pixels on the straight line is only 0 or plus or minus 1, each pixel only needs to occupy 4 bits, X, Y respectively occupies 2 bits, the high bit represents plus or minus, and the low bit represents 0 or 1. I.e. the data table G size is 512x1024x4/8=256 KB.
3) Receiving scan line data
The hardware receives the scanning line image data according to the set scanning frequency. Setting the center point O of the current eccentric display1The coordinates are the eccentricity distance 300 pixels, eccentricity angle 256 scan lines.
4) Query the current scan line display length table L
Assume that the 256 th scan line is currently received. The length information of the 0 th scan line with the eccentricity distance of 300 (the current angle-eccentricity angle = 256-. In order to improve the operation efficiency, 512 scan line length information corresponding to the eccentricity distance can be read into a 1KB buffer at one time after the eccentricity distance is set.
5) Inquiring the pixel position table G for converting the current scanning line into the row and column coordinates
The pixel position information of the 256 th scan line in the table G is looked up. Here, the X, Y information for each pixel is 01 and 01 (the 256 th scan line direction is a 45 degree direction). In order to improve the operation efficiency, 512 scan line pixel position information can be read into a 256KB buffer at a time.
6) Real-time display of scan line image data
From the current off-centre display centre point O1Firstly, according to the read pixel coordinate information and length information, directly writing l pixels into a video memory, and then displaying the scanning line image information in real time.
7) And continuously repeating the steps 3) to 6), and displaying the received scanning line image information in real time.
Claims (1)
1. A polar coordinate image real-time display method is characterized by comprising the following specific steps:
(1) scanning an image by using a radar in a circumferential scanning mode, wherein when the position of the radar is displayed at the center of a circle, the lengths displayed by scanning lines in all directions are equal; when the radar image is displayed eccentrically, the display length of the scanning line is different in different directions, so that the eccentric distance needs to be calculated in advanceScanning lines at all angles within the range from zero to the radius R of the circular area by the length required to be displayed, and storing the lengths as a data table L; the required length of each angle scanning line displayed is obtained through the formula (1):
（1）
wherein,in order to be the azimuth angle of the scan line,is composed ofThe length of the directional scan line that needs to be displayed,in order to show the radius of the circular area,is an eccentric distance,Is the azimuth of the eccentricity; azimuth of said eccentricity according to symmetry of circular scanAdopting 0-90 degrees; said eccentric distanceThe length of 0-512 scanning lines corresponding to 0-90 degrees in the range of 0-512 pixels; the length of each scanning line is stored as a 16-bit integer, and occupies 2 bytes;
(2) based on the symmetry of the circle, calculating the conversion pixel positions of 0-512 scanning lines corresponding to 0-90 degrees, wherein the scanning lines are in a polar coordinate form, converting the scanning lines into pixel positions of row-column rectangular coordinates according to a formula (2), and storing the pixel positions as a data table G;
（2）
wherein,is the distance from the pixel point to the origin under the polar coordinate,in order to be the azimuth angle of the scan line,、x, Y coordinates showing the origin in rectangular coordinates respectively,、the coordinates of the pixel points under the rectangular coordinates;
in consideration of the extreme case of off-center display, each scanning line stores coordinates of 1024 pixel positions, which are twice the radius of a display area, and the distance between adjacent pixels on one scanning line in rectangular coordinates in the form of rows and columns is only 0 or plus or minus 1 in the row and column directions, so that each pixel only needs to occupy 4 bits; x, Y each has 2 bits, the high bit represents positive or negative, the low bit represents 0 or 1;
(3) receiving scanning line data in real time; receiving scanning line information in real time according to a scanning pulse frequency set by a radar; setting the coordinate of a current eccentric display center point O1 as an eccentric distance m pixels, wherein the eccentric angle is determined by n scanning lines;
(4) inquiring the data table L obtained in the step (1) according to the scanning line information obtained in the step (3) to obtain length information of the current scanning line, namely the length of the current scanning line to be displayed; if the current received scanning line is the kth scanning line, according to the difference between the current angle and the eccentricity angle, inquiring the length information of the kth-mth scanning line with the eccentricity distance of m pixels in the data table L;
(5) inquiring a data table G to obtain the position information of the coordinate conversion pixel of the current scanning line;
(6) directly writing the scanning line image information into a video memory according to the current scanning line length information obtained in the step (4) and the pixel position information obtained in the step (5);
(7) and (5) repeatedly and circularly executing the step (3) to the step (6), and displaying the received scanning line image information in real time.
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| US5650787A (en) * | 1995-05-24 | 1997-07-22 | Hughes Electronics | Scanning antenna with solid rotating anisotropic core |
| JPH09304508A (en) * | 1996-05-10 | 1997-11-28 | Nec Corp | Ppi display device |
| US7646328B2 (en) * | 2005-03-10 | 2010-01-12 | Honeywell International Inc. | Versatile constant altitude plan position indicator for radars |
| JP5797920B2 (en) * | 2011-03-28 | 2015-10-21 | 日本無線株式会社 | Cache memory device and control method |
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