CN102957919A - Digital image brightness enhancement method - Google Patents
Digital image brightness enhancement method Download PDFInfo
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- CN102957919A CN102957919A CN2012104568344A CN201210456834A CN102957919A CN 102957919 A CN102957919 A CN 102957919A CN 2012104568344 A CN2012104568344 A CN 2012104568344A CN 201210456834 A CN201210456834 A CN 201210456834A CN 102957919 A CN102957919 A CN 102957919A
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Abstract
The invention discloses a digital image brightness enhancement method, comprising the following steps of uniformly transforming formats of an input image into a first image signal in a brightness and chromaticity separation format, extracting a brightness signal Y, and dividing the image into a dark area, a middle area and a light area according to the size of Y; transforming the brightness signal Y in the first image signal to generate a second image signal in a manner that the dark area adopts the logarithmic function transformation, the middle area adopts the direct proportion function transformation and the light area adopts the power function transformation; and outputting the image signal after recovering the format of the second image signal to be the format of the input image. The digital image brightness enhancement method is mainly used in the field of video image processing, and can evenly enhance the brightness of the image.
Description
Technical field
The invention belongs to the digital image processing techniques field, be specifically related to a kind of brightness enhancement of digital picture.
Background technology
At present image brightness enhancing is that the key step in the digital image processing field is poly-.For this reason, people have successively made up multiple corresponding algorithm from spatial domain and frequency domain, and typical algorithm has image equalization algorithm, Logarithmic Algorithm and straight segments to strengthen algorithm etc.But at present numerous image brightness strengthens algorithms and usually adopts single function, so, all exist some defectives, such as: in the dark space, clear zone and mesozone balance be bad.
Summary of the invention
Technical problem to be solved by this invention is: propose a kind of brightness enhancement of digital picture, can strengthen evenly the brightness of image, solve in the conventional art in the dark space, clear zone and the bad technological deficiency of mesozone balance.
The present invention solves the problems of the technologies described above the technical scheme that adopts:
A kind of luminance digital image Enhancement Method may further comprise the steps:
The uniform format standard of input picture is converted into the first picture signal of brightness and chrominance separation form, and isolates brightness signal Y;
To brightness signal Y subregion in such a way: Y value is less than the dark space parameter d
1Divide the dark space into, Y value is between the dark space parameter d
1With the clear zone parameter d
2Between divide the mesozone into, Y value is greater than the clear zone parameter d
2Divide the clear zone into;
Brightness signal Y in the first picture signal is generated the second picture signal after the conversion in such a way: the logarithmic function conversion is adopted in the dark space, and the direct proportion function conversion is adopted in the mesozone, and the power function conversion is adopted in the clear zone;
The form of the second picture signal is recovered to be converted into output image signal behind the form of input picture.
The invention has the beneficial effects as follows: because image has been carried out subregion, can utilize the characteristic of logarithmic function that brightness is suitably lightened for the dark space, can utilize the characteristic of power function that brightness is suitably dimmed for the clear zone, the mesozone then utilizes the characteristic of direct proportion function that brightness is remained unchanged substantially, therefore so that whole image-region after strengthening through brightness, has good balance.
Description of drawings
Fig. 1 is schematic diagram of the present invention.
Fig. 2 is flow chart of the present invention.
Embodiment
The invention will be further described below in conjunction with the drawings and specific embodiments.
Such as Fig. 1, the present invention is a kind of image brightness Enhancement Method that combines based on logarithmic function, direct proportion function and power function, and wherein the logarithmic function conversion is adopted in the dark space, and the direct proportion function conversion is adopted in the mesozone, and the power function conversion is adopted in the clear zone.Logarithmic function is y in the present embodiment
1=a*log
n(x+1), direct proportion function is y
2=k*x, power function is y
3=b*x
m+ c, a wherein, n, k, b, m, c are function parameters.
The flow process of taking is as follows:
Determine parameter: comprise the dark space parameter d
1, the clear zone parameter d
2With function parameter a, n, k, b, m, the value of c.For example: get d
1=50, d
2=200, n=2, k=1, m=1.2 then according to continuous and boundary condition, can correspondence arrange a=8.86, b=0.282, c=37.3 makes the separation brightness in dark space, mesozone, clear zone change maintenance continuously.
Color space positive-going transition: the first picture signal that the received image signal unified standard is converted into brightness and chrominance separation form, if input picture has been the picture signal of brightness and chrominance separation form, just met standard, namely the first picture signal is identical with received image signal.In the present embodiment, then take the picture signal of input picture as RGB chrominance space form, the picture signal form that standard transforms then is the brightness in YCbCr space and the picture signal of chrominance separation form, therefore need to be transformed into the brightness in YCbCr space and the picture signal of chrominance separation form to input picture from RGB chrominance space standard, and isolate brightness signal Y, in the present embodiment brightness Y value scope is in [0,255].
Brightness strengthen to be processed: from the first picture signal, isolate brightness signal Y, and to brightness signal Y subregion in such a way: Y value is less than the dark space parameter d
1Divide the dark space into, Y value is between the dark space parameter d
1With the clear zone parameter d
2Between divide the mesozone into, Y value is greater than the clear zone parameter d
2Divide the clear zone into; Then the brightness signal Y in the first picture signal is generated the second picture signal after the conversion in such a way: the logarithmic function conversion is adopted in the dark space, and the direct proportion function conversion is adopted in the mesozone, and the power function conversion is adopted in the clear zone;
Color space transformation by reciprocal direction: the picture signal of the second picture signal transformation by reciprocal direction being returned RGB chrominance space form.
Image output: will finish behind the color space transformation by reciprocal direction image signal output.
In order further to improve picture quality, can also account for according to dark space pixel in the image and clear zone pixel the percentage of the total pixel of image, select adaptively the corresponding parameter of logarithmic function and power function, be described as follows:
(1) dark space: input any piece image, suppose that its total pixel value is p, wherein at [0, d
1] zone is that the pixel value of dark space is q, then to account for the percentage of total pixel be t=(q/p) * 100% to the dark space pixel.If during t 〉=60%, assert that entire image is very dark, then need lifting amplitude in dark space is strengthened, this moment is by changing logarithmic function y
1=a*log
n(x+1) the parameter a in and n just can change y corresponding to x
1Value, namely brightness value is realized respectively the dark space of different images is strengthened processing.
(2) clear zone: input any piece image, suppose that its total pixel value is p, wherein at [d
2, 255] and the zone is that the pixel value in clear zone is r, then to account for the percentage of total pixel be s=(r/p) * 100% to the dark space pixel.If during s 〉=60%, assert that entire image is very bright, then need the brightness the clear zone is suitably reduced, be parameter b, m and c in y3=b*xm+c by the change power function this moment, just can change y corresponding to x
3Value, namely brightness value is realized respectively the clear zone brightness processed to different images.
Process if all images are all carried out identical enhancing, only need to get fixed one group of parameter value and get final product.For example: when x=40, if a=10, n=2, then y
1=54, if a=14, n=3, then y
1=47.
In order to keep brightness constant, the corresponding direct proportion function in mesozone is fixed as a function, need not change parameter wherein.
Can find out from the flow process that whole image is processed, just the luminance signal in the picture signal is processed, carrier chrominance signal in the picture signal is not processed, the second picture signal is just replaced the Y in YCbCr space than the first picture signal, therefore last image output has kept original chroma state, brightness then to seem more balance.
The present invention is mainly used in field of video image processing, and a main functional modules that can be used as the image quality improving chip is incorporated into wherein, also can be used for the processing of still image.
Claims (4)
1. luminance digital image Enhancement Method is characterized in that may further comprise the steps:
The uniform format standard of input picture is converted into the first picture signal of brightness and chrominance separation form, and isolates brightness signal Y;
To brightness signal Y subregion in such a way: Y value is less than the dark space parameter d
1Divide the dark space into, Y value is between the dark space parameter d
1With the clear zone parameter d
2Between divide the mesozone into, Y value is greater than the clear zone parameter d
2Divide the clear zone into;
Brightness signal Y in the first picture signal is generated the second picture signal after the conversion in such a way: the logarithmic function conversion is adopted in the dark space, and the direct proportion function conversion is adopted in the mesozone, and the power function conversion is adopted in the clear zone;
The form of the second picture signal is recovered to be converted into output image signal behind the form of input picture.
2. a kind of luminance digital image Enhancement Method according to claim 1 is characterized in that described logarithmic function is y
1=a*log
n(x+1), direct proportion function is y
2=k*x, power function is y
3=b*xm+c.
3. a kind of luminance digital image Enhancement Method according to claim 1 characterized by further comprising following steps:
Statistics dark space pixel quantity, clear zone pixel quantity, general area pixel quantity, wherein the general area pixel quantity is the summation of dark space pixel quantity, clear zone pixel quantity, mesozone pixel quantity;
The transformation parameter setting is arranged in logarithmic function, and this transformation parameter arranges and accounts for general area quantitative proportion size according to the dark space pixel quantity and arrange;
The transformation parameter setting is arranged in power function, and this transformation parameter arranges and accounts for general area quantitative proportion size according to the clear zone pixel quantity and arrange.
4. a kind of luminance digital image Enhancement Method according to claim 1, it is characterized in that described logarithmic function conversion, direct proportion function conversion, power function have transformation parameter setting separately, make the separation brightness in dark space, mesozone, clear zone change maintenance continuously.
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Cited By (5)
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| CN106897963A (en) * | 2017-01-04 | 2017-06-27 | 奇酷互联网络科技（深圳）有限公司 | Adjust method, device and the terminal device of brightness of image |
| CN108665428A (en) * | 2018-04-26 | 2018-10-16 | 青岛海信移动通信技术股份有限公司 | Image enchancing method, device, equipment and storage medium |
| WO2018188260A1 (en) * | 2017-04-14 | 2018-10-18 | 西安诺瓦电子科技有限公司 | Image display control method and device, and display screen control system |
| CN109167892A (en) * | 2018-08-22 | 2019-01-08 | 银河互联网电视有限公司 | A kind of video image detail enhancing method and system |
| CN111626993A (en) * | 2020-05-07 | 2020-09-04 | 武汉科技大学 | Image automatic detection counting method and system based on embedded FEFnet network |
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Application publication date: 20130306 |