CN103685867A - Backlight compensation method and device - Google Patents
Backlight compensation method and device Download PDFInfo
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- CN103685867A CN103685867A CN201210337130.5A CN201210337130A CN103685867A CN 103685867 A CN103685867 A CN 103685867A CN 201210337130 A CN201210337130 A CN 201210337130A CN 103685867 A CN103685867 A CN 103685867A
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Abstract
The invention discloses a backlight compensation method and a device. The backlight compensation method comprises the following steps: dividing grayscale level range of a backlight image to a backlight region AB, a transition region BC, and a bright light region CD; performing backlight compensation for grayscale level of pixels in different grayscale level regions by using different compensation functions, wherein the compensation functions of the three regions are a linear compensation function. The backlight compensation method provided by the invention can improve the grayscale level of pixels in the backlight region, and increase the difference between grayscale levels of pixels with different grayscale levels in the backlight image, thereby enhancing visibility of the overall field of view.
Description
Technical field
The present invention relates to image processing field, relate more specifically to a kind of BLC method and apparatus.
Background technology
In video monitoring system, the information identification of various monitored object is subject to the impact of illumination, weather condition etc.For the monitoring image (referred to herein as backlight image) that wherein has backlight area, BLC becomes the problem that needs are paid close attention to.This is because the too low meeting of gray scale of backlight area causes the picture of backlight area too black, thereby makes the fuzzy even None-identified of details of the picture of backlight area.
BLC is also referred to as BLC or backlight revisal, the defect of main body picture dark when it can effective compensation video camera takes under backlight environment.When introducing BLC function, can make the main body picture on monitor bright and clear.In backlight image is processed, the brightness of the pixel in backlight area is enhanced, and the Enhancement contrast between pixel.But in most of BLC schemes, when the brightness of the pixel in backlight area is enhanced, the brightness of the pixel in light region is also enhanced, this increases whole image brightness integral body, the especially easy transition exposure in light region.Although in some other BLC schemes, only have the brightness of the pixel in backlight area to be enhanced, the processing that extracts backlight area in these schemes also has very high complexity.
Summary of the invention
One or more problems in view of the above, the invention provides a kind of BLC method and apparatus of novelty.
According to the BLC method of the embodiment of the present invention, comprise: the grey level range of backlight image is divided into BC and tri-intervals of the interval CD of light between interval AB backlight, transition region; Utilize respectively different penalty functions in the gray scale of different interval pixels, to carry out BLC to gray scale, wherein for described three interval penalty functions, be single compensation function.
According to the BLC device of the embodiment of the present invention, comprise: interval division unit, for the grey level range of backlight image being divided into BC and tri-intervals of the interval CD of light between interval AB backlight, transition region; And BLC unit, for utilizing respectively different penalty functions to carry out BLC to gray scale in the gray scale of different interval pixels, wherein for described three interval penalty functions, be single compensation function.
The present invention can improve the gray scale of the pixel in backlight area, expands the difference between the gray scale of the pixel in different grey-scale in backlight image simultaneously, thereby the visuality of whole visual field is strengthened.
Accompanying drawing explanation
Below in conjunction with accompanying drawing in the description of the specific embodiment of the present invention, the present invention may be better understood, wherein:
Fig. 1 shows according to the block diagram of the BLC device of the embodiment of the present invention;
Fig. 2 shows according to the flow chart of the BLC method of the embodiment of the present invention;
Fig. 3 is the histogram that the distribution situation of the pixel grayscale in exemplary backlight image is shown;
Fig. 4 is the schematic diagram of interval division situation that the grey level range of the backlight image shown in Fig. 3 is shown;
Fig. 5 is the schematic diagram illustrating for the penalty function of the gray scale of the pixel in each interval shown in Fig. 4;
Fig. 6 illustrates for determining the schematic diagram of the method for the transitional region BC shown in Fig. 4;
Fig. 7 a and 7b illustrate BLC backlight image before and the schematic diagram of the correction image after BLC.
Embodiment
Feature and the exemplary embodiment of various aspects of the present invention will be described in detail below.Many details have been contained in description below, to complete understanding of the present invention is provided.But, it will be apparent to one skilled in the art that the present invention can be in the situation that do not need some details in these details to implement.Below the description of embodiment is only used to provide the clearer understanding to the present invention by example of the present invention is shown.The present invention is never limited to any concrete configuration and the algorithm proposing below, but has covered under the premise of without departing from the spirit of the present invention any modification, replacement and the improvement of coherent element, parts and algorithm.
Fig. 1 shows according to the block diagram of the BLC device of the embodiment of the present invention.Fig. 2 shows according to the flow chart of the BLC method of the embodiment of the present invention.Below in conjunction with Fig. 1 and Fig. 2, describe in detail according to the BLC apparatus and method of the embodiment of the present invention.
As shown in Figure 1, according to the BLC device of the embodiment of the present invention, comprise interval division unit 102 and BLC unit 104.Interval division unit 102 is divided into BC and tri-intervals of the interval CD of light (that is, execution step S202) between interval AB backlight, transition region by the grey level range of backlight image.BLC unit 104 utilizes different penalty functions respectively gray scale to be carried out to BLC (that is, execution step S204) in the gray scale of different interval pixels.Wherein, for BC between interval AB backlight, transition region and tri-interval penalty functions of the interval CD of light, be single compensation function.
Below in conjunction with the example shown in Fig. 3 and Fig. 4, the processing procedure of division unit 102 between area pellucida.Particularly, Fig. 3 is the histogram that the distribution situation of the pixel grayscale in exemplary backlight image is shown.Fig. 4 is the schematic diagram of dividing condition that the grey level range of the backlight image shown in Fig. 3 is shown.Wherein, in Fig. 3 and Fig. 4, abscissa represents gray scale, and ordinate represents the number of the pixel in corresponding gray scale.
As shown in Figure 4, grey level range shown in Fig. 3 can be divided into three interval: AB interval (interval backlight), BC interval (between transition region) and CD region (light is interval).Here suppose, in the backlight area of the pixel of gray scale in AB interval in backlight image, in the transitional region of the pixel of gray scale in BC interval in backlight image, and in the light region of the pixel of gray scale in CD interval in backlight image.In addition, from Fig. 3 and Fig. 4, can find out, the number of the pixel that gray scale is G1 in backlight area is maximum, is peak A; The number of the pixel that gray scale is G2 in light region is maximum, is peak value B.
In BLC is processed, need to improve the gray scale of the pixel in backlight area, expand the difference between the gray scale of the pixel in different grey-scale in backlight image simultaneously.Based on above hypothesis, according to embodiments of the invention, three single compensation function f 1 (x), f2 (x) and f3 (x) that are applicable to respectively backlight area, transitional region and light region have been provided.The processing procedure of BLC unit 104 is described below in conjunction with Fig. 5.
Fig. 5 is the schematic diagram illustrating for the penalty function of the gray scale of the pixel in each interval shown in Fig. 4.In order to expand grey level range, used in an embodiment according to the present invention all gray scales of from 0 to 255 (, making the minimal gray level through the interval backlight of BLC is 0, and to make the maximum gray scale through the light interval of BLC be 255).In order to reduce the contrast of the pixel in transitional region, the gray scale to gray scale in the pixel between transition region carry out obtaining after BLC through between the transition region of BLC [B1, C1) need to meet the following conditions:
Wherein, N
tthe number that represents gray scale pixel of BC between transition region, N
bthe number that represents the pixel of gray scale in interval CD backlight, N
lthe number that represents the pixel of gray scale in the interval AB of light, N
t+ N
b+ N
lthe total number that represents the pixel in backlight image.
After determining B1 and C1, can determine function f 1 (x), f2 (x) and f3 (x).Particularly, can be by (A, 0) shown in Fig. 5 and (B, B1) two points be solved to this single compensation function f 1 (x) as two points on the function curve of the single compensation function f 1 (x) for interval AB backlight; Can be by using (B, B1) shown in Fig. 5 and (C, C1) two points, two points on the function curve of the single compensation function f 2 (x) for BC between transition zone solve this single compensation function f 2 (x); And can be by (C, C1) shown in Fig. 5 and (D, 255) two points be solved to this single compensation function f 3 (x) as two points on the function curve of the single compensation function f 3 (x) for the interval CD of light.
Then, utilize the Pixel-level of single compensation function f 1 (x) pixel in interval AB backlight to gray scale to carry out BLC (, by f1 (x) is multiplied each other and obtains the Pixel-level through BLC with Pixel-level), utilize single compensation function f 2 (x) to carry out BLC (to the Pixel-level of gray scale pixel of BC between transition region, by f2 (x) is multiplied each other and obtains the Pixel-level through BLC with Pixel-level), and utilize the Pixel-level of single compensation function f 3 (x) pixel in the interval CD of light to gray scale to carry out BLC (, by f3 (x) is multiplied each other and obtains the Pixel-level through BLC with Pixel-level).
In addition, the determining method in BC interval is with reference to figure 6.In Fig. 6, x axle represents the gray scale of pixel.HIST represents to surpass the number of pixels of certain gray scale and the ratio of the total number of pixel.SW (Slide Window, sliding window) represents the window that the integrated value of HIST is less than 0.2.When this window is obtained maximum, the position in SWmax interval is exactly the position of BC between transition region.
Fig. 7 a and 7b illustrate BLC backlight image before and the schematic diagram of the correction image after BLC.From Fig. 7 a and Fig. 7 b, can find out, by the present invention, can improve the brightness of the pixel in backlight area, can expand the difference between the gray scale of the pixel in different grey-scale in backlight image simultaneously, thereby the visuality of whole visual field is strengthened.
Below with reference to specific embodiments of the invention, the present invention has been described, but those skilled in the art all understand, can carry out various modifications, combination and change to these specific embodiments, and can not depart from the spirit and scope of the present invention that limited by claims or its equivalent.
Can perform step with hardware or software as required.Note, without departing from the scope of the invention, can add step, therefrom remove step or revise step wherein to the flow chart providing in this specification.In general, flow chart is just used to refer to a kind of possible sequence for the basic operation of practical function.
Embodiments of the invention can utilize programming general purpose digital computer, utilize application-specific integrated circuit (ASIC), programmable logic device, field programmable gate array, light, chemistry, biological, system quantum or nanometer engineering, assembly and mechanism to realize.In general, function of the present invention can be realized by any means known in the art.Can use distributed or networked system, assembly and circuit.The communication of data or to transmit can be wired, wireless or by any other means.
Also will recognize, according to the needs of application-specific, one or more can the realization by more separated or more integrated mode in the key element shown in accompanying drawing, or be removed even in some cases or be deactivated.The journey logic bomb that realization can be stored in machine readable media is carried out above-mentioned any method with permission computer, also within the spirit and scope of the present invention.
In addition, it is only exemplary that any signal arrows in accompanying drawing should be considered to, rather than restrictive, unless separately there is concrete indication.When term is also contemplated as when the ability of separation or combination is not known, the combination of assembly or step also will be considered to record.
Claims (10)
1. a BLC method, comprising:
The grey level range of backlight image is divided into BC and tri-intervals of the interval CD of light between interval AB backlight, transition region;
Utilize respectively different penalty functions in the gray scale of different interval pixels, to carry out BLC to gray scale, wherein for described three interval penalty functions, be single compensation function.
2. BLC method according to claim 1, it is characterized in that, gray scale is obtained after the gray scale of the pixel of BC between described transition zone is carried out BLC through between the transition region of BLC [B1, C1) dynamic range (C1-B1) ratio that accounts for the maximum dynamic range of the gray scale 0-255 number that is equal to gray scale pixel of BC between described transition region account for the ratio of the total number of the pixel in described backlight image.
3. BLC method according to claim 1, it is characterized in that, the number that the ratio that the dynamic range (255-C1) of the light through BLC interval [C1,255] obtaining after the gray scale of the pixel to gray scale in the interval CD of described light is carried out BLC accounts for the maximum dynamic range of gray scale 0-255 is equal to the pixel of gray scale in the interval CD of described light accounts for the ratio of the total number of the pixel in described backlight image.
4. BLC method according to claim 1, it is characterized in that, the number that the ratio that the dynamic range (B1-0) through the interval backlight of BLC [0, B1] that the gray scale of the pixel to gray scale in described interval AB backlight carries out obtaining after BLC accounts for the maximum dynamic range of gray scale 0-255 is equal to the pixel of gray scale in described interval AB backlight accounts for the ratio of the total number of the pixel in described backlight image.
5. BLC method according to claim 1, is characterized in that, the ratio that the number of the pixel of BC between described transition region of the gray scale in described backlight image accounts for the total number of the pixel in described backlight image is 20%.
6. a BLC device, comprising:
Interval division unit, for being divided into the grey level range of backlight image in BC and tri-intervals of the interval CD of light between interval AB backlight, transition region; And
BLC unit, for utilizing respectively different penalty functions to carry out BLC to gray scale in the gray scale of different interval pixels, is wherein single compensation function for described three interval penalty functions.
7. BLC device according to claim 6, it is characterized in that, gray scale is obtained after the gray scale of the pixel of BC between described transition zone is carried out BLC through between the transition region of BLC [B1, C1) dynamic range (C1-B1) ratio that accounts for the maximum dynamic range of the gray scale 0-255 number that is equal to gray scale pixel of BC between described transition region account for the ratio of the total number of the pixel in described backlight image.
8. BLC device according to claim 6, it is characterized in that, the number that the ratio that the dynamic range (255-C1) of the light through BLC interval [C1,255] obtaining after the gray scale of the pixel to gray scale in the interval CD of described light is carried out BLC accounts for the maximum dynamic range of gray scale 0-255 is equal to the pixel of gray scale in the interval CD of described light accounts for the ratio of the total number of the pixel in described backlight image.
9. BLC device according to claim 6, it is characterized in that, the number that the ratio that the dynamic range (B1-0) through the interval backlight of BLC [0, B1] that the gray scale of the pixel to gray scale in described interval AB backlight carries out obtaining after BLC accounts for the maximum dynamic range of gray scale 0-255 is equal to the pixel of gray scale in described interval AB backlight accounts for the ratio of the total number of the pixel in described backlight image.
10. BLC method according to claim 6, is characterized in that, the ratio that the number of the pixel of BC between described transition region of the gray scale in described backlight image accounts for the total number of the pixel in described backlight image is 20%.
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| CN107911617A (en) * | 2017-12-27 | 2018-04-13 | 上海传英信息技术有限公司 | Photographic method and device |
| CN108921801A (en) * | 2018-06-26 | 2018-11-30 | 北京字节跳动网络技术有限公司 | Method and apparatus for generating image |
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