CN104079909A - Automatic white balance method and device for image - Google Patents
Automatic white balance method and device for image Download PDFInfo
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Abstract
The invention discloses an automatic white balance method. The method comprises the following steps: obtaining the driving current value of an LED white-light lamp; judging whether the driving current value is larger than the preset threshold value or not, if the driving current value is larger than the preset threshold value, setting the environment color temperature value of the current image to be the preset color temperature value, and if the driving current value is less than the preset threshold value, calculating the environment color temperature value of the current image; performing color temperature gain calculation according to the environment color temperature value of the current image to obtain gain coefficients u and v; performing color temperature adjusting on a next image according to the gain coefficients u and v; repeating the steps until the color difference signals Cr and Cb are less than the preset threshold value. The invention further discloses an automatic white balance device. The automatic white balance method and device disclosed by the invention can effectively reduce the influences of a lighting supplementary lamp on white balance, and improves the white balance effect and imaging quality.
Description
Technical field
The present invention relates to digital imagery field, particularly relate to a kind of image auto white balance method and device.
Background technology
The basic conception of white balance is " no matter under any light source, white object can be reduced to white ".Automatic white balance and automatic exposure are all the necessary functions of front end digital imaging apparatus, and the quality of its realization directly affects the quality of video.
Natural colour temperature span is extremely wide, and we can be low to moderate 1800K by common high-pressure sodium light path lamp color temperature, and the sunny blue sky colour temperature in overhead, waters can reach 27000K, and Automatic white balance algorithm can be guaranteed the good color performance of imaging device in different-colour environment.
Because the sensor devices of headend equipment exists limitation, in the time that illumination condition is bad, can not present good video effect, be mainly manifested in that noise increases, details resolution capability declines, dark space object cannot identification etc. problem, safety-security area addresses the above problem by the scheme that increases secondary light source at present.The secondary light source of current industry mainly contains two kinds, be infrared LED lamp and white LED lamp, both main distinctions are light wavelength difference, infrared LED lamp can only be used for black and white video, for not only needing good low photograph effect but also needing the occasion of color video also inapplicable, owing to there is heating and life problems, infrared LED lamp is endured to the fullest extent and is denounced always simultaneously.And white LED lamp is the novel green lighting of energy-conserving and environment-protective, it is a kind of visible ray, belong to cold light source, so can not generate heat and the life-span long, be widely used in the floor light of safety monitoring, because imaging device night is in the floor light situation of white light, the image of picked-up is colored, and can meet special applications is colored requirement for image always.
Because LED white light has its specific wavelength and light characteristics, can be on white balance time, colour temperature be calculated and is produced certain impact, affects white balance effect and image quality.
Summary of the invention
Technical problem to be solved by this invention is: a kind of auto white balance method is provided, and the method can effectively reduce the impact of LED white light on white balance, improves image quality.
In order to solve the problems of the technologies described above, the technical solution used in the present invention is:
A kind of auto white balance method, comprises step: the driving current value of obtaining LED white light; Judge whether described driving current value exceedes default threshold value, if so, the environment colour temperature of present image is set to default color temperature value, if not, calculates the environment color temperature value of present image; Carry out colour temperature gain according to the environment color temperature value of present image and calculate, obtain gain coefficient u and v; According to described gain coefficient u and v, lower piece image is carried out to colour temperature adjusting; Repeat above-mentioned steps, until color difference signal Cr and Cb are less than default threshold value.
For solving the problems of the technologies described above, the present invention also provides a kind of another technical scheme:
A kind of Automatic white balance device, comprises electric current acquisition module, judge module, gain calculation module, colour temperature adjustment module and loop module; Described electric current acquisition module is for obtaining the driving current value of LED white light; Described judge module is for judging whether described driving current value exceedes default threshold value, and if so, the environment colour temperature of present image is set to default color temperature value, if not, calculates the environment color temperature value of present image; Described gain calculation module is calculated for carry out colour temperature gain according to the environment color temperature value of present image, obtains gain coefficient u and v; Described colour temperature adjustment module is for carrying out colour temperature adjusting according to described gain coefficient u and v to lower piece image; Described loop module is used for repeating to call above-mentioned module, until color difference signal Cr and Cb are less than default threshold value.
Beneficial effect of the present invention is: be different from the white balance effect and the not good problem of imaging effect that in prior art, exist, the present invention is by including the drive current of LED white light in the reference factor of white balance control, judge whether described driving current value exceedes default threshold value, if, the environment colour temperature of present image is set to default color temperature value, therefore, effectively reduce the impact of LED white light on white balance, thereby improve effect and the image quality of Automatic white balance.
Brief description of the drawings
Fig. 1 is the manner of execution flow chart of a kind of auto white balance method in an embodiment of the present invention;
Fig. 2 is the functional block diagram of a kind of Automatic white balance device in an embodiment of the present invention;
Main label declaration:
10-electric current acquisition module; 20-judge module; 30-gain calculation module; 40-colour temperature adjustment module; 50-loop module.
Embodiment
Explanation of nouns:
The vision signal in color difference signal Cr and Cb:YCbCr space represents, Cb is the difference of blue component and luminance signal, and Cr is the difference of red component and luminance signal;
Gain coefficient u and v: system custom parameter, u and v are respectively the gain correction factor of Cr and Cb
Constraints α, β and γ: system custom parameter, α, β and γ are default binding occurrence, are obtained by a large amount of scrnario testings and lamp box test statistics;
By describing technology contents of the present invention, structural feature in detail, being realized object and effect, below in conjunction with execution mode and coordinate accompanying drawing to be explained in detail.
The design of most critical of the present invention is: by judging that LED white light drive current sets the image-context colour temperature of Automatic white balance, effectively reduce the impact of LED white light on white balance, thereby improve effect and the image quality of Automatic white balance.
Refer to Fig. 1, a kind of auto white balance method, comprises step:
S1, obtain the driving current value of LED white light;
S2, judge whether described driving current value exceedes default threshold value, if so, the environment colour temperature of present image is set to default color temperature value, if not, calculates the environment color temperature value of present image;
S3, carry out colour temperature gain according to the environment color temperature value of present image and calculate, obtain gain coefficient u and v;
S4, according to described gain coefficient u and v, lower piece image is carried out to colour temperature adjusting;
S5, repeat above-mentioned steps, until color difference signal Cr and Cb are less than default threshold value.
The designed Automatic white balance of the present invention is carried out at yuv space, does not consider brightness signal Y, uses color difference signal Cr, Cb to carry out computing.First processor obtains color difference signal Cr, Cb, in the time that color difference signal Cr, Cb are greater than default colour temperature threshold value, the environment colour temperature of computed image, and according to the calculating that gains of environment colour temperature, obtain and adjust gain coefficient u and v, then u, v value return to lower piece image and do colour temperature adjusting, if next width color temp is estimated also not pass through, continue iteration, otherwise, finishing iteration process,, when Cr, Cb are less than default threshold value, has completed the computing of an Automatic white balance.
Wherein, it is a most important ring in three basic operations of video camera Automatic white balance algorithm that environment colour temperature is calculated, color temperature estimation must estimate correct aberration, the correctness of guarantee subsequent operation, particularly in the time that reference picture is full of large-area colour, algorithm must have certain robustness, to ensure the integrality of color.
The present invention is directed to colour temperature and calculate this link, be optimized processing, take into full account the impact that LED white light uses reality, therefore, as color difference signal Cr, when Cb is greater than default colour temperature threshold value, obtain the driving current value of LED white light, by described drive current and default current threshold are compared, judge the leading colour temperature of colour temperature of current environment, the colour temperature that LED white light is described in the time that drive current is greater than current threshold is the leading colour temperature of present image, the colour temperature of all the other light is less for the impact of imaging device, therefore the environment color temperature value of present image is determined to the colour temperature of LED white light, described colour temperature is set as 6000K to 7000K in the present embodiment, thereby the colour temperature while effectively reducing low photograph is calculated erroneous judgement.
From foregoing description, beneficial effect of the present invention is: by the collection of LED white light drive current and judgement being adjusted to the environment colour temperature of present image, the colour temperature while effectively reducing low photograph is calculated erroneous judgement, improves effect and the image quality of Automatic white balance.
Further, in order to calculate more accurately the environment color temperature value of present image, present embodiment is carried out color temperature estimation and obtains the environment color temperature value of present image under the constraints α default, β and γ to the environment colour temperature of present image, wherein, α, β and γ are default binding occurrence, α, β and γ obtain by a large amount of scrnario testings and lamp box test statistics the constraints of finally deciding, as shown in Equation 1:
Formula 1
Further, in the present embodiment, in the time that described driving current value exceedes default threshold value, the environment colour temperature of present image is set to 6500K.
Further, in the above-described embodiment, in the described step front step that also comprises of " obtaining the driving current value of LED white light ":
Obtain the brightness value of present image, adjust aperture size, shutter speed, automatic gain and LED white light drive current according to described brightness value and carry out automatic exposure.
Present embodiment is included LED white light drive current in the adjustment parameter of automatic exposure in, makes automatic exposure more accurate.
Because there is certain impact to the quality of image in automatic gain, therefore, in order to improve the quality of image, reduce the impact of automatic gain on image, in the time carrying out automatic exposure, preferential adjust aperture size and shutter speed is carried out automatic exposure, in the time that aperture size and shutter speed exceed default threshold value, then adjust automatic gain and LED white light drive current carries out automatic exposure.
In the prior art, when LED white light is used to light filling, only be provided with and open and close or high, medium and low some shelves, therefore, in the time opening LED white light or adjust LED white light, the light of environment and colour temperature have obvious saltus step, thereby Automatic white balance is produced to impact impact, reduce the effect of white balance.Therefore, in the above-described embodiment, adjust the drive current of LED white light by PWM voltage regulator, realize the wireless adjustment of LED white light drive current, and the drive current initial value of LED white light is set to minimum firing current.Thereby, realize LED white light and drive the linear adjustment of electric wire, further improve Automatic white balance effect.
Refer to Fig. 2, the present invention also provides a kind of Automatic white balance device, and this device comprises electric current acquisition module 10, judge module 20, gain calculation module 30, colour temperature adjustment module 40 and loop module 50;
Described electric current acquisition module 10 is for obtaining the driving current value of LED white light;
Described judge module 20 is for judging whether described driving current value exceedes default threshold value, and if so, the environment colour temperature of present image is set to default color temperature value, if not, calculates the environment color temperature value of present image;
Described gain calculation module 30 is calculated for carry out colour temperature gain according to the environment color temperature value of present image, obtains gain coefficient u and v;
Described colour temperature adjustment module 40 is for carrying out colour temperature adjusting according to described gain coefficient u and v to lower piece image;
Described loop module 50 is called above-mentioned module for repeating, until color difference signal Cr and Cb are less than default threshold value.
Further, described judge module 20 comprises color temperature estimation unit, and described color temperature estimation unit for carrying out color temperature estimation and obtain the environment color temperature value of present image under default constraints α, β and γ to the environment colour temperature of present image.
Further, described judge module 20 comprises colour temperature setting unit, and described colour temperature setting unit is in the time that described driving current value exceedes default threshold value, and the environment colour temperature of present image is set to 6500K.
Further, described Automatic white balance device also comprises automatic exposure module, described automatic exposure module, for obtaining the brightness value of present image, is adjusted aperture size, shutter speed, automatic gain and LED white light drive current according to described brightness value and is carried out automatic exposure.
Further, described automatic exposure module comprises parameter set unit, described parameter set unit is in the time carrying out automatic exposure, preferential adjustment aperture size and shutter speed are carried out automatic exposure, in the time that aperture size and shutter speed exceed default threshold value, then adjust automatic gain and LED white light drive current carries out automatic exposure.
In sum, auto white balance method provided by the invention and device can effectively reduce the impact of LED white light on Automatic white balance, improve effect and the image quality of Automatic white balance, simultaneously, environment colour temperature of the present invention is calculated accurately, can effectively prevent from, because of the impact that Automatic white balance is caused that suddenlys change of LED white light light, further improving image quality.
The foregoing is only embodiments of the invention; not thereby limit the scope of the claims of the present invention; every equivalent structure or conversion of equivalent flow process that utilizes specification of the present invention and accompanying drawing content to do; or be directly or indirectly used in other relevant technical fields, be all in like manner included in scope of patent protection of the present invention.
Claims (10)
1. an auto white balance method, is characterized in that, comprises step:
Obtain the driving current value of LED white light;
Judge whether described driving current value exceedes default threshold value, if so, the environment colour temperature of present image is set to default color temperature value, if not, calculates the environment color temperature value of present image;
Carry out colour temperature gain according to the environment color temperature value of present image and calculate, obtain gain coefficient u and v;
According to described gain coefficient u and v, lower piece image is carried out to colour temperature adjusting;
Repeat above-mentioned steps, until color difference signal Cr and Cb are less than default threshold value.
2. auto white balance method according to claim 1, it is characterized in that, the method for described the environment color temperature value of present image " calculate " is: the environment color temperature value that the environment colour temperature of present image is carried out color temperature estimation and obtained present image under default constraints.
3. auto white balance method according to claim 1, is characterized in that, in the time that described driving current value exceedes default threshold value, the environment colour temperature of present image is set to 6500K.
4. auto white balance method according to claim 1, is characterized in that, in the described step front step that also comprises of " obtaining the driving current value of LED white light ":
Obtain the brightness value of present image, adjust aperture size, shutter speed, automatic gain and LED white light drive current according to described brightness value and carry out automatic exposure.
5. auto white balance method according to claim 4, it is characterized in that, in the time carrying out automatic exposure, preferential adjustment aperture size and shutter speed are carried out automatic exposure, in the time that aperture size and shutter speed exceed default threshold value, then adjust automatic gain and LED white light drive current carries out automatic exposure.
6. an Automatic white balance device, is characterized in that, comprises electric current acquisition module, judge module, gain calculation module, colour temperature adjustment module and loop module;
Described electric current acquisition module is for obtaining the driving current value of LED white light;
Described judge module is for judging whether described driving current value exceedes default threshold value, and if so, the environment colour temperature of present image is set to default color temperature value, if not, calculates the environment color temperature value of present image;
Described gain calculation module is calculated for carry out colour temperature gain according to the environment color temperature value of present image, obtains gain coefficient u and v;
Described colour temperature adjustment module is for carrying out colour temperature adjusting according to described gain coefficient u and v to lower piece image;
Described loop module is used for repeating to call above-mentioned module, until color difference signal Cr and Cb are less than default threshold value.
7. Automatic white balance device according to claim 6, it is characterized in that, described judge module comprises color temperature estimation unit, and described color temperature estimation unit for carrying out color temperature estimation and obtain the environment color temperature value of present image under default constraints to the environment colour temperature of present image.
8. Automatic white balance device according to claim 6, it is characterized in that, described judge module comprises colour temperature setting unit, and described colour temperature setting unit is in the time that described driving current value exceedes default threshold value, and the environment colour temperature of present image is set to 6500K.
9. Automatic white balance device according to claim 6, it is characterized in that, also comprise automatic exposure module, described automatic exposure module, for obtaining the brightness value of present image, is adjusted aperture size, shutter speed, automatic gain and LED white light drive current according to described brightness value and is carried out automatic exposure.
10. Automatic white balance device according to claim 9, it is characterized in that, described automatic exposure module comprises parameter set unit, described parameter set unit is in the time carrying out automatic exposure, preferential adjustment aperture size and shutter speed are carried out automatic exposure, in the time that aperture size and shutter speed exceed default threshold value, then adjust automatic gain and LED white light drive current carries out automatic exposure.
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