Method for judging and eliminating ground light in high-resolution image

Abstract

The application discloses a method for judging and eliminating ground light in high-resolution images, and belongs to the field of space visible light detection, and the steps are as follows: firstly, the input visible light image is evenly divided into four areas according to rows, and the brightness sum of each area is calculated; secondly, a ground light judging factor is calculated, and if the ground light judging factor is greater than 0, it is indicated that the ground light exists; and then, the brightness of the image with the ground light is balanced according to rows, so that the purpose of eliminating the ground light is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of space visible light detection, and particularly relates to a method for judging and eliminating ground light in high-resolution images. BACKGROUND

[0002] The space radiation energy received by the surface of a space target mainly comes from the direct radiation of the sun, the radiation of the earth's atmosphere and the reflection of the earth's surface, and in the visible light and near-infrared wave bands, the direct radiation of the sun and the reflection of the earth's surface are dominant. In the visible light wave band, the space target is a non-self-radiation object, and mainly generates brightness by reflecting sunlight. When sunlight irradiates the earth's surface, the energy is transmitted in three parts, namely absorption, specular reflection and diffuse reflection. The absorbed energy is re-radiated to space in the form of infrared waves, specular reflection occurs in places with reflective surfaces, and since the energy that can be received is very small, the two can be ignored, while the diffuse reflection energy is relatively large, resulting in uneven display of the light image. The influence of the above ground light diffusion is usually referred to as the influence of ground light.

[0003] When observing a space target, the current ground light influence is manifested as the influence of uneven illumination on the overall imaging, the gray value of the affected side image rises, and part of the image information is submerged in the ground light, which is very unfavorable for subsequent threshold segmentation and target extraction. Therefore, judging whether there is the influence of ground light and finding ways to eliminate it have become the focus of space visible light detection. The influence of ground light is actually a special case of the image non-uniform illumination problem, and belongs to the category of background suppression in image preprocessing. If it is in the field of conventional image segmentation, non-uniform illumination can easily bring very obvious background noise to the image, and at the same time, it can also combine with part of the interference signal, reduce the image contrast, and bring black spots, so that the image quality is obviously poor. This makes the image preprocessing have many uncertainties, so that there is no universal image background suppression method for any scene. At present, space visible light detection in China is in a vigorous development stage, and it is necessary to study the problem of ground light influence in space visible light detection.

[0004] At the present stage, there are relatively few studies on how to judge whether the ground light exists or not and how to eliminate the ground light. In high-resolution images, the conventional filtering method can achieve a weakening effect, but due to the limited resources of the application platform and the high real-time requirement, it is difficult to implement complex filtering in engineering and waste resources, so it is of great significance to study a simple and easy-to-implement method for judging and eliminating ground light for subsequent space visible light detection. SUMMARY

[0005] The present application aims at the problem that the research on how to judge and eliminate the ground light is relatively less, and the conventional filtering method is relatively resource-consuming in engineering implementation, and proposes a ground light judgment and elimination method based on image brightness, which has low processing and calculation complexity, simple method implementation and high engineering application value.

[0006] The technical solution of the present application is a high-resolution image ground light judgment and elimination method, comprising the following steps:

[0007] Step 1: The input visible light image is divided into four regions by rows, and the brightness sum of each region is calculated, and step 2 is entered.

[0008] Step 2: Calculate the ground light judgment factor k juge If greater than 0, it indicates that there is ground light, and step 3 is entered.

[0009] Step 3: For the image with ground light, the brightness is balanced according to the row divided in step 1, so as to eliminate the ground light.

[0010] Compared with the prior art, the present application has the following advantages: 1) it can quickly judge whether there is ground light under high-resolution image, and effectively eliminate it.

[0011] 2) The present application is a supplement to the existing ground light elimination method, which is simple to implement and beneficial to the implementation of FPGA and other hardware platforms, can effectively save resources, and has practical engineering application value in the direction of space visible light detection. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 The high-resolution image ground light judgment and elimination method of the present application.

[0013] Figure 2 The high-resolution original gray scale image with ground light of the present application.

[0014] Figure 3 The high-resolution gray scale image after eliminating the ground light of the present application. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0016] It should be noted that all the direction indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the direction indications will also change accordingly.

[0017] In addition, the descriptions such as "first", "second" and the like in the present application are only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can be explicitly or implicitly included at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically defined.

[0018] In the present application, unless otherwise specifically defined and limited, the terms "connection", "fixing" and the like should be understood in a broad sense, for example, "fixing" can be fixed connection, or detachable connection, or integral; "connection" can be mechanical connection, or electrical connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0019] In addition, the technical solutions of each embodiment of the present application can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope required by the present application.

[0020] The specific implementation, technical difficulties and inventive points of the present application will be further introduced below in combination with the design examples.

[0021] The high-resolution image ground light judgment and elimination method provided by the present application first proposes a ground light judgment factor k juge , and judges whether the ground light exists or not by means of k juge , and eliminates it by means of brightness equalization. The method flow is as shown in Figure 1 , including the following steps:

[0022] Step 1, the input visible light high-resolution image f is divided into f1, f2, f3, f4 four regions according to the rows, and the brightness sum of each region is calculated.

[0023] Further, the input visible light high-resolution image f is divided into f1, f2, f3, f4 four regions according to the rows, and the brightness sum of each region is calculated.

[0024] Go to step 2.

[0025] Step 2, calculate the ground light judgment factor k juge , k juge =k1*k2, if greater than 0, it indicates that there is ground light, as follows:

[0026] Step 21, according to the sum of image pixel brightness of two regions f1 and f4, and calculate the first ground light feature factor k1,

[0027]

[0028] Where f ij represents the image brightness value of the i-th row and j-th column, N represents the total number of rows, M represents the total number of columns, T1 is the first judgment threshold, T1=2.

[0029] Step 22, according to the sum of image pixel brightness of four regions f1, f2, f3, f4, and calculate the second ground light feature factor k2,

[0030]

[0031] Where f ij represents the image brightness value of the i-th row and j-th column, T2 is the second judgment threshold, T2=5.

[0032] Step 23, calculate the ground light judgment factor k juge =k1*k2, k juge greater than 0 indicates that there is ground light, go to step 3.

[0033] Step 3, for the image with ground light, according to the row division in step 1, the original image is brightness balanced to achieve the purpose of eliminating ground light.

[0034] Step 31, calculate the average brightness ave1, ave2, ave3, ave4 of the image of four regions f1, f2, f3, f4.

[0035] Step 32, if (ave1+ave2) is less than (ave3+ave4), then according to the row division in step 1, the brightness is balanced:

[0036] When divided by rows, calculate the average brightness ave k of each N rows of image, N is 4, each image pixel point f ij in each N rows is subtracted by ave k respectively until the brightness of all pixels is balanced, that is, f' ij =f ij -ave k , where f ij represents the image brightness value of the i-th row and j-th column.

[0037] Example 1

[0038] Combination Figure 1 , Figure 2 , Figure 3 The following specific examples illustrate the implementation of the present invention, such as... Figure 2 As shown, when inputting a visible light grayscale image with a resolution of 2048*2048, it can be seen that in addition to interference from stars and noise points, there is also the influence of ground-based light at the bottom of the image, causing some information to be submerged in ground-based light. The following section uses the proposed method of "a method for judging and eliminating ground-based light in high-resolution images" to judge... Figure 2 To determine whether there is ground-based light and to eliminate it, the specific steps are as follows:

[0039] Step 1: Divide the input visible light image into four regions, f1, f2, f3, and f4, according to rows, and calculate the total brightness of each region.

[0040] Step 2: Calculate the ground light judgment factor k juge k juge =k1·k2, based on the image pixel brightness of regions f1 and k4 and and Calculate the ground-based light eigenfactors k1 and k2.

[0041]

[0042] T1 = 2.

[0043]

[0044] T2 = 5.

[0045] Since (k1·k2) is greater than 0, the ground-based light judgment factor k juge The value is greater than 0, therefore ground-based light exists.

[0046] Step 3, for Figure 2 Brightness equalization is performed row by row to eliminate ground glare. The effect after elimination is as follows: Figure 3 As shown, ground-based light was eliminated and the image was enhanced without losing target information.

[0047] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for determining and eliminating ground lights in a high resolution image, characterized in that, Comprising the following steps: Step 1, the input visible light image is divided into four regions by rows and the brightness sum of each region is calculated: For the input visible light high-resolution image f, the image resolution is at least 1280x720, the image is divided into f1, f2, f3, f4 four regions by rows and the brightness sum of each region is calculated; Go to step 2; Step 2, calculating the ground light judgment factor k juge If greater than 0, it indicates that there is ground light, comprising the following steps: Step 21, according to the image pixel brightness sum of f1 and f4 two regions, the first ground light feature factor k1 is calculated, wherein f ij represents the image brightness value of the ith row and the jth column, N represents the total number of rows, M represents the total number of columns, T1 is a first judgment threshold, and T1 = 2. Step 22, according to the image pixel brightness sum of f1, f2, f3, f4 four regions, the second ground light feature factor k2 is calculated, wherein f ij represents the image brightness value of the ith row and jth column, T2 is a second judgment threshold, and T2 = 5. Step 23, calculate the ground light judgment factor k juge = k1-k2, if greater than 0, it indicates that there is ground light, go to step 3; In step 3, step 3, the brightness of the image with ground light is balanced according to the rows divided in step 1, so as to achieve the purpose of eliminating ground light, comprising the following steps: Step 31, the image brightness average ave1, ave2, ave3, ave4 corresponding to f1, f2, f3, f4 four regions is calculated respectively; Step 32, if (ave1+ave2) is less than (ave3+ave4), then the brightness of the image is equalized according to the row divided in step 1: calculate the average brightness ave of each N row of image k , N takes 4, each image pixel point f ij In each N row is subtracted ave k Until the brightness equalization of all pixels is completed, that is f' ij =f ij -ave k , where f ij Indicates the brightness value of the image in the i-th row and the j-th column.

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