CN101873429B - Processing method and device of image contrast - Google Patents

Abstract

The embodiment of the invention discloses a processing method and a device of image contrast, which is used for processing image contrast in digital camera equipment. The method comprises the following steps: acquiring a frame image to be processed; carrying out histogram statistics for each channel corresponding to the color space of the frame image so as to acquire histogram statistical information; adjusting the pixel gray level distribution of the image according to the histogram statistical information, and outputting the mapping relation between the unadjusted pixel gray level and the adjusted pixel gray level; and remapping the pixel gray value of the image according to the mapping relation to acquire the image with processed contrast. The embodiment of the invention realizes the enhancement of the image contrast before the image is compressed or transferred, thereby avoiding the problem that the noise or the interference of the image is further expanded caused by carrying out contrast enhancement for the image with quality reduction after the image is compressed or transferred; and front-end optimization of the contrast is carried out in the digital camera equipment, thereby enhancing the display effect of video images.

Description

The processing method of picture contrast and device

Technical field

The application relates to technical field of image processing, relates in particular to a kind of processing method and device of picture contrast.

Background technology

Video camera is the electronic equipment that obtains image, and it can change optical image signal into the signal of telecommunication, thereby realizes the storage to image.Along with the development of camcorder technology, adopt the digital camera of resolution height, interface flexible to obtain image now usually, when obtaining video image; May be owing to the weather reason, the distinct inadequately image of output contrast under the situation of insufficient light, such picture quality is not high; Especially in the security monitoring field; If the picture quality of output is undesirable, will be difficult to the important information in the recognisable image, reduce the accuracy rate of monitoring.

Referring to Fig. 1, for a kind of in the prior art LCD is shown the structural representation of the device that contrast is optimized, this device comprises image signal amplifier, peak detector and valley value detector.Wherein, Peak detector is used for the peak value of gradation of image signal is detected; The peak value of this gradation of image signal outputs to peak A GC (automatic gain control) control end of gradation of image signal amplifier after treatment; Be used for the amplitude of described gradation of image signal being controlled, and make picture signal according to specific response curve amplification according to detected gradation of image signal peak; Valley value detector is used for the valley of gradation of image signal is detected; And the valley of this gradation of image signal outputed to the black level control end of described gradation of image signal amplifier, be used for making the level of the dark-part of image reach black level through the bias voltage of gradation of image signal amplifier.

The inventor finds in the research process to above-mentioned prior art; The above-mentioned method that the contrast of image is optimized is accomplished at display terminal; But along with the development of digitlization with networking; Particularly digital camera is universal day by day, and the vision signal of digital camera output is that image has been carried out the vision signal after certain compression, strengthens if the vision signal after these compressions is outputed to display terminal degree of comparing; Can make that for example the granular sensation of picture noise and color sensation can increase the weight of in enhancing contrast ratio because the image information loss that image compression causes is more obvious when contrast is optimized.Hence one can see that, in the prior art at display terminal to the optimization of digital video image degree of comparing, with the display effect that reduces video image.

Summary of the invention

The purpose of the application embodiment provides the processing method and the device of picture contrast, and optimization will reduce the problem of its display effect to digital video image degree of comparing at display terminal to solve in the prior art.

For solving the problems of the technologies described above, the application embodiment provides following technical scheme:

A kind of processing method of picture contrast is used in digital photographing apparatus, image degree of comparing being handled, and comprising:

Obtain a pending two field picture;

Pairing each passage of the color space of a said two field picture is carried out statistics with histogram, obtain statistics with histogram information, comprising: calculate the corresponding number of pixels of each grey level in each corresponding passage of the color space of a said two field picture; The probability that occurs according to each grey level in each passage after the said number of pixels output normalization, the probability that said each grey level is occurred is as the statistics with histogram information of said each passage;

The pixel grey scale of adjusting said image according to said statistics with histogram information distributes; And pixel grey scale rank before the output adjustment and the mapping relations between the adjusted pixel grey scale rank; Comprise: the probability to each grey level in each passage occurs carry out local averageization, obtains the local average histogram information of each passage; Said local average histogram can obtain through following formula:

$p_c\left(i\right)=\left\{\begin{array}{c}\frac{\underset{j=i}{\overset{i+k}{\mathrm{\Σ}}}{h}_c\left(j\right)}{k},i\∈[l_{\min },l_{\max }-k]\\ \frac{\underset{j=i}{\overset{l_{\max }}{\mathrm{\Σ}}}{h}_c\left(j\right)+(i+k-l_{\max })*h_c\left(l_{\max }\right)}{k},i\∈(l_{\max }-k,l_{\max }]\end{array}\right.$

Wherein, i is certain grey level of selected channel components c, h _c(j) be the statistics with histogram information of channel components c, k is the smoothing factor of local averageization, l _MinBe the minimal gray rank of original image, l _MaxFor the maximum gray scale of original image other;

Target histogram according to preset travels through said local average histogram, and the minimal gray rank and the maximum gray scale that obtain to satisfy the specify arithmetic relation are other;

Other according to said minimal gray rank and the maximum gray scale that satisfies specify arithmetic relation, obtain preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank, said mapping relations can obtain through following formula: $T_c\left(i\right)=\frac{i-l_{\mathrm{Min}}^{\′}}{l_{\mathrm{Max}}^{\′}-l_{\mathrm{Min}}^{\′}}*\mathrm{\ζ}\left(i\right)*(l_{\mathrm{Max}}-l_{\mathrm{Min}})+l_{\mathrm{Min}}$

Wherein, l ' _MinFor from i=l _MinBeginning increases progressively the i value gradually, and local equalization histogram is traveled through, and is detecting certain p _c(i)＞G _cThe time, the value of i, l ' _MaxFor from i=l _MaxBegin to successively decrease gradually the i value, local equalization histogram is traveled through, detecting certain p _c(i)＞G _cThe time, the value of i, G _cBe a preset threshold value, this threshold value is used to control the histogram enhanced strength; l _Min, l _MaxThe minimal gray rank and the maximum gray scale that are respectively original image are other;

Remap according to the grey scale pixel value of said mapping relations, obtain the image after contrast is handled said image.

Said obtaining before the pending two field picture also comprises: the frame period threshold value of obtaining a two field picture is set in advance;

Saidly obtain a pending two field picture and be specially: obtain satisfy said frame period threshold value a two field picture as a said pending two field picture.

Said obtaining after the pending two field picture, also comprise: the color space to a said two field picture is changed;

Pairing each passage of said color space to a two field picture carries out statistics with histogram and is specially: pairing each passage of the color space after the conversion of a said two field picture is carried out statistics with histogram.

Saidly adjust said image pixel intensity profile according to statistics with histogram information and comprise:

The probability that each grey level in each passage is occurred adds up, and obtains the accumulative histogram of each passage;

Obtain preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank according to accumulative histogram.

Saidly remap according to the grey scale pixel value of mapping relations to image, the image that obtains after contrast is handled comprises:

Obtain said each pixel of image each passage grey scale pixel value as the adjustment before grey scale pixel value;

Mate said mapping relations according to the grey scale pixel value before the said adjustment, obtain the corresponding adjusted grey scale pixel value of each pixel;

According to said adjusted grey scale pixel value said each pixel is carried out the gray scale adjustment;

Adjusted said each passage is synthesized the contrast of accomplishing said image to be handled.

A kind of processing unit of picture contrast is used in picture pick-up device, image degree of comparing being handled, and comprising:

Acquiring unit is used to obtain a pending two field picture;

Statistic unit is used for pairing each passage of the color space of a said two field picture is carried out statistics with histogram, obtains statistics with histogram information; Said statistic unit comprises:

The number of pixels computation subunit is used for calculating the corresponding number of pixels of each grey level of each corresponding passage of the color space of a said two field picture;

Gray probability normalization subelement is used for the probability that each grey level according to each passage after the said number of pixels output normalization occurs, and the probability that said each grey level is occurred is as the statistics with histogram information of said each passage;

Adjustment unit is used for adjusting according to said statistics with histogram information the pixel grey scale distribution of said image, and pixel grey scale rank before the output adjustment and the mapping relations between the adjusted pixel grey scale rank; Said adjustment unit comprises:

Histogram local average beggar unit is used for the probability that each grey level to each passage occurs and carry out local averageization, obtains the local average histogram information of each passage; The local average histogram can obtain through following formula:

$p_c\left(i\right)=\left\{\begin{array}{c}\frac{\underset{j=i}{\overset{i+k}{\mathrm{\Σ}}}{h}_c\left(j\right)}{k},i\∈[l_{\min },l_{\max }-k]\\ \frac{\underset{j=i}{\overset{l_{\max }}{\mathrm{\Σ}}}{h}_c\left(j\right)+(i+k-l_{\max })*h_c\left(l_{\max }\right)}{k},i\∈(l_{\max }-k,l_{\max }]\end{array}\right.$

Wherein, i is certain grey level of selected channel components c, h _c(j) be the statistics with histogram information of channel components c, k is the smoothing factor of local averageization, l _MinBe the minimal gray rank of original image, l _MaxFor the maximum gray scale of original image other;

Histogram traversal subelement is used for according to preset target histogram said local average histogram being traveled through, and the minimal gray rank and the maximum gray scale that obtain to satisfy the specify arithmetic relation are other;

Mapping relations are obtained subelement; Be used for according to the minimal gray rank and the maximum gray scale of said specify arithmetic relation other; Obtain preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank, said mapping relations can obtain through following formula:

$T_c\left(i\right)=\frac{i-l_{\min }^{\′}}{l_{\max }^{\′}-l_{\min }^{\′}}*\mathrm{\ζ}\left(i\right)*(l_{\max }-l_{\min })+l_{\min }$

Wherein, l _MinFor from i=l _MinBeginning increases progressively the i value gradually, and local equalization histogram is traveled through, and is detecting certain p _c(i)＞G _cThe time, the value of i, l _MaxFor from i=l _MaxBegin to successively decrease gradually the i value, local equalization histogram is traveled through, detecting certain p _c(i)＞G _cThe time, the value of i, G _cBe a preset threshold value, this threshold value is used to control the histogram enhanced strength; l _Min, l _MaxThe minimal gray rank and the maximum gray scale that are respectively original image are other;

Map unit is used for remapping according to the grey scale pixel value of said mapping relations to said image, obtains the image after contrast is handled.

Also comprise: preset unit is used for being provided with in advance the frame period threshold value of obtaining a two field picture;

Said acquiring unit, specifically be used to obtain satisfy said frame period threshold value a two field picture as a said pending two field picture.

Also comprise: converting unit is used for the color space of a said two field picture is changed;

Said statistic unit specifically is used for pairing each passage of the color space after the conversion of a said two field picture is carried out statistics with histogram.

Said adjustment unit comprises:

Histogram accumulative total subelement is used for the probability that each grey level to each passage occurs and adds up, and obtains the accumulative histogram of each passage;

Mapping relations are obtained subelement, are used for obtaining preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank according to accumulative histogram.

Said map unit comprises:

The source pixel gray scale is obtained subelement, the grey scale pixel value of the grey scale pixel value of each pixel that is used to obtain said each passage of image before as adjustment;

Object pixel gray scale coupling subelement is used for mating said mapping relations according to the grey scale pixel value before the said adjustment, obtains the corresponding adjusted grey scale pixel value of each pixel;

Pixel grey scale adjustment subelement is used for according to said adjusted grey scale pixel value said each pixel being carried out the gray scale adjustment;

Passage synthon unit is used for that adjusted said each passage is synthesized the contrast of accomplishing said image and handles.

It is thus clear that; The application embodiment is applied in the picture pick-up device image degree of comparing is handled; After obtaining a pending two field picture, pairing each passage of the color space of this two field picture is carried out statistics with histogram, obtain statistics with histogram information; Pixel grey scale according to this image of statistics with histogram information adjustment distributes; And pixel grey scale rank before the output adjustment and the mapping relations between the adjusted pixel grey scale rank, remap according to the grey scale pixel value of mapping relations to this image, obtain the image after contrast is handled.It is that the contrast of in picture pick-up device, carrying out is handled that the contrast that application the application embodiment carries out image is handled; Promptly, realizes image the contrast of image is strengthened before compressing or transmit; Avoided image degree of comparing enhancement process to compression or the quality decline of transmission back; Cause the noise of image or disturb the problem that further enlarges,, strengthened the display effect of digital video image thus through in the optimization process of picture pick-up device degree of comparing front end.

Description of drawings

In order to be illustrated more clearly in the application embodiment or technical scheme of the prior art; To do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below; Obviously, the accompanying drawing in describing below only is some embodiment that put down in writing among the application, for those of ordinary skills; Under the prerequisite of not paying creative work property, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is a kind of structural representation that LCD is shown the device that contrast is optimized in the prior art;

Fig. 2 is the first embodiment flow chart of the processing method of the application's picture contrast;

Fig. 3 is the second embodiment flow chart of the processing method of the application's picture contrast;

Fig. 4 A is the structural representation of the applied a kind of picture pick-up device of the application embodiment;

Fig. 4 B is the sketch map of the histogram optimal curve among the application embodiment;

Fig. 5 is the first embodiment block diagram of the processing unit of the application's picture contrast;

Fig. 6 is the second embodiment block diagram of the processing unit of the application's picture contrast;

Fig. 7 A is the embodiment block diagram of the statistic unit that installs shown in Fig. 6;

Fig. 7 B is the embodiment block diagram of a kind of adjustment unit of installing shown in Fig. 6;

Fig. 7 C is the embodiment block diagram of the another kind of adjustment unit that installs shown in Fig. 6;

Fig. 7 D is the embodiment block diagram of the map unit of installing shown in Fig. 6.

Embodiment

The application embodiment provides a kind of processing method and device of picture contrast, and the application embodiment is applied in the digital photographing apparatus (for example, digital camera), is used for that image is carried out the front end contrast and handles.

In order to make those skilled in the art person understand the technical scheme among the application embodiment better; And make the above-mentioned purpose of the application embodiment, feature and advantage can be more obviously understandable, below in conjunction with accompanying drawing technical scheme among the application embodiment done further detailed explanation.

Referring to Fig. 2, be the first embodiment flow chart of the processing method of the application's picture contrast:

Step 201: obtain a pending two field picture.

Step 202: pairing each passage of the color space of a two field picture is carried out statistics with histogram, obtain statistics with histogram information.

Concrete; Calculate the corresponding number of pixels of each grey level in each corresponding passage of the color space of a two field picture; The probability that occurs according to each grey level in each passage after the number of pixels output normalization, the probability that each grey level is occurred is as the statistics with histogram information of each passage.

Step 203: the pixel grey scale according to statistics with histogram information adjustment image distributes, and pixel grey scale rank before the output adjustment and the mapping relations between the adjusted pixel grey scale rank.

Concrete, the probability that can occur each grey level in each passage adds up, and obtains the accumulative histogram of each passage, obtains preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank according to accumulative histogram; Perhaps; The probability that also can occur each grey level in each passage carry out local averageization; Obtain the local average histogram information of each passage, according to preset target histogram local equalization histogram is traveled through, the minimal gray rank and the maximum gray scale that obtain to satisfy specified requirements are other; Other according to minimal gray rank that satisfies specified requirements and maximum gray scale, obtain preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank.

Step 204: remap according to the grey scale pixel value of mapping relations, obtain the image after contrast is handled to image.

Concrete; Obtain each passage of image each pixel grey scale pixel value as the adjustment before grey scale pixel value; According to the coupling of the pixel grey scale rank before adjustment mapping relations; Obtain the corresponding adjusted grey scale pixel value of each pixel, each pixel is carried out the gray scale adjustment, adjusted each passage is synthesized the contrast of accomplishing image handle according to adjusted grey scale pixel value.

Referring to Fig. 3, be the second embodiment flow chart of the processing method of the application's picture contrast, this embodiment shows in detail in video camera image is carried out the detailed process that the front end contrast is handled:

Step 301: the frame period threshold value of obtaining a two field picture is set in advance.

Video camera is when obtaining video image; The video image of consecutive frame has continuity and similitude in certain time period; In order to improve the image processing speed of video camera; Can only handle and obtain other mapping relations of pixel grayscale, and utilize other mapping relations of this pixel grayscale that other two field picture in this time period is carried out getting final product with the same contrast processing of this image, for example the two field picture degree of comparing in certain period; Can be provided with in advance and whenever obtain a frame video image at a distance from ten frames, then other nine two field picture all adopts the mapping relations of this two field picture to shine upon.

Step 302: judge whether a two field picture that receives satisfies the frame period threshold value, if then execution in step 303; Otherwise, execution in step 308.

Step 303: a two field picture that will receive is changed the color space of this two field picture as a pending two field picture.

Among the application embodiment, it is optional step that two field picture is carried out color space conversion.When needs are used a plurality of color space information, when particularly color video frequency image being handled, can utilize the combination of a plurality of color spaces, guarantee that thus the video image contrast strengthens front and back, bigger distortion can not take place in the color of image; When the image pickup mode of video camera is grayscale mode, perhaps when video camera is less demanding to color assurance degree, can two field picture not carried out color space conversion.

When two field picture is carried out color space conversion, with the video image of input from a color space conversion to another one or the several objects color space, and the data of each passage of export target color space.

Step 304: calculate the corresponding number of pixels of each grey level in each corresponding passage of the color space of a two field picture.

Step 305: the probability that occurs according to each grey level in each passage after the number of pixels output normalization, the probability that each grey level is occurred is as the statistics with histogram information of each passage.

Step 306: the probability that each grey level in each passage is occurred adds up, and obtains the accumulative histogram of each passage.

Step 307: obtain preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank according to accumulative histogram.

Need to prove that above-mentioned steps 306 obtains mapping relations with the mode that step 307 illustrates through accumulative histogram; In addition, the application embodiment also can adopt the histogrammic mode of local averageization to obtain mapping relations, and perhaps, the mode that accumulative histogram and local equalization histogram are combined obtains mapping relations, and this application embodiment is not limited.

The mapping relations that obtained are exactly to be used for mapping relations that statistics with histogram information is strengthened; These mapping relations can be adjusted histogrammic shape; Make the ground that distributes in its tonal range (0 to 255) more even, thereby strengthen the contrast of image at image.

Step 308: obtain each passage of image each pixel grey scale pixel value as the adjustment before grey scale pixel value.

Two field picture for not satisfying the frame period threshold value in the step 302 is directly carried out this step, and promptly the contrast mapping relations of the two field picture through satisfying frame period are to other two field picture degree of the comparing adjustment in this frame period.

Step 309:, obtain the corresponding adjusted grey scale pixel value of each pixel according to the coupling of the pixel grey scale rank before adjustment mapping relations.

Step 310: each pixel is carried out the gray scale adjustment according to adjusted grey scale pixel value.

Step 311: adjusted each passage is synthesized the contrast of accomplishing image handle.

Referring to Fig. 4 A; Be the structural representation of the applied a kind of picture pick-up device of the application embodiment, complete showing in this picture pick-up device: image processing module 450, contrast processing module 460 and coding modules 470 such as camera lens module 410, image sensor module 420, color interpolation module 430, exposure control module 440, white balance like lower module.Wherein, contrast processing module 460 among the application embodiment in picture pick-up device, carrying out the module that the front end contrast is handled to be increased, the function of other module is consistent with prior art.Contrast processing module 460 can further be subdivided into color space conversion submodule 461, statistics with histogram submodule 462, histogram enhancer module 463 and pixel and remap submodule 464.

In conjunction with Fig. 4 A; Outside scenery is through the optical path of camera lens module 410; On image sensor module 420, form real image, become the view data of Bayer form, carry out color interpolation through 430 pairs of Bayer data of color interpolation module again via imageing sensor; And be transformed into specific color space; View data after will handling then outputs to exposure control module 440, and exposure control module 440 is exported the control signal that camera lens, shutter are controlled on the one hand, on the one hand picture signal is outputed to image processing modules 450 such as white balance; Picture signal is carried out output to contrast processing module 460 after the processing such as AWB; Carry out outputing to coding module 470 after the auto contrast strengthens via 460 pairs of view data of contrast processing module, show or handle through outputing to rear end (for example, PC etc.) after coding module 470 coding again.

460 pairs of view data of contrast processing module are carried out the auto contrast when strengthening; At first; Optional, the picture signal of image processing modules such as white balance 450 being imported through color space conversion submodule 461 is transformed into another one or other several color space from a color space, after the execution color space transforms needed calculating; The video data of each passage of export target color space, and statistics and storage are used for the follow-up color data that histogram strengthens of carrying out; Each passage in 462 pairs of primitive color spaces of statistics with histogram submodule; Perhaps each passage in the color space conversion submodule 461 color of object space of being exported carries out statistics with histogram; Number of pixels to each grey level is corresponding in each passage carries out stored counts; And be normalized to the probability that each grey level occurs in this channel image, export the statistics with histogram information of each passage then; The probability that histogram enhancer module 463 occurs according to each grey level in the statistics with histogram information; The histogrammic shape of adaptive adjustment; Histogram is more evenly distributed in whole tonal range; Thereby realize the contrast of video image is strengthened, what histogram enhancer module 463 was exported mainly is the mapping relations between the pixel grey scale rank before and after histogram strengthens; Pixel remaps the pixel grey scale rank mapping relations before and after the enhancing that submodule 464 exported according to histogram enhancer module 463; Each pixel to video image remaps; Give its new grey scale pixel value; After the gray value of all pixels of entire image shone upon, the gray value of pixel by reasonable distribution to whole tonal range, thereby improved the contrast of entire image.In addition; Need to prove, consider the continuity and the similitude of video image adjacent several frames in the special time scope, in order to improve the speed of service of picture pick-up device; Also can whenever just carry out a histogram at a distance from some two field pictures strengthens; For other consecutive frame image in this time range, can remap submodule 464 by pixel and other consecutive frame image remapped correspondence according to the mapping relations that a histogram enhancing obtains, other consecutive frame image is after 450 outputs of image processing modules such as white balance; Can be directly inputted to pixel and remap submodule 464 and remap, handle laggard line output through coding module 470 then.

Below in conjunction with Fig. 4 A, an application example that utilizes the application embodiment that the contrast of one two field picture is handled is described.

The first, obtain a two field picture as key frame.Key frame refers to the contrast of video image is carried out when frame is handled; A two field picture that is received is for recomputating a two field picture of pixel grey scale rank mapping relations, and other two field picture can be through pixel grey scale rank mapping relations degree of the comparing adjustment of key frame;

The second, the key frame that obtains is carried out color space conversion as original image frame to it.When carrying out color space conversion, can colored original image frame be handled to obtain the better contrast effect through combining the information of a plurality of color spaces.For example; If the color space of original image frame is a rgb format; Then can rgb format be transformed into the color space of yuv format,, then can it be transformed into the color space of rgb format if the color space of original image frame is a yuv format; If the color space of original image frame is yuv format or rgb format; Then also can its color space that is transformed into the form such as color space or CMY of HSI form perhaps also can be transformed into a kind of color space of form the color space of multiple form, this application embodiment is not limited.When carrying out color space conversion, can carry out, repeat no more at this according to existing color space conversion mode;

The 3rd, carry out statistics with histogram.No matter whether original image frame is carried out the conversion of color space; The color space of pending original image frame is all corresponding a plurality of passages when each passage to these selected color spaces carries out statistics with histogram, supposes that c is certain channel components in the picture frame of selecting; I is certain grey level of this selected channel components c; Then when carrying out statistics with histogram, need add up, obtain the statistic histogram h of channel components c the value of each pixel among the channel components c _c(i), the abscissa of this statistic histogram has been represented different grey levels, and ordinate has been represented the number of pixels that each grey level comprised in the image, obtains statistics with histogram information h _c(i) time, can adopt following formula:

$h_c\left(i\right)=\frac{n_i}{n},i\∈[l_{\min },l_{\max }]$

In the following formula, n representes the number of pixels of a two field picture, n _iThe expression grey level is the number of times that the pixel of i occurs, and grey level i span is [l _Min, l _Max], wherein, l _MinBe the minimal gray rank of image, l _MaxFor the maximum gray scale of image other;

The 4th, carry out histogram and strengthen.It mainly is the adjustment of histogram being carried out shape that histogram strengthens, and it is reasonable more, even that it is distributed in tonal range, thereby strengthens the contrast of original image frame indirectly.When carrying out the histogram enhancing, can adopt several different methods as follows:

Method 1:

To aforementioned statistics with histogram information h _c(i), it is added up, obtain the accumulative histogram of passage c, accumulative histogram can be obtained by following formula:

$s_c\left(i\right)=\underset{j=0}{\overset{i}{\mathrm{\Σ}}}{h}_c\left(j\right),i\∈[l_{\min },l_{\max }]$

Can know the histogram h after the normalization by following formula _c(i) also be the probability density function of each gray scale of passage c simultaneously, and s _c(i) be h _c(i) accumulated probability density.

Before and after histogram strengthens any pixel grayscale of passage c other remap and concern T _c(i) can obtain through following formula:

T _c(i)＝[k ₁*s _c(i)+k ₂*ζ(i)]*(l _max-l _min)+l _min

In the following formula, ζ (i) is a pre-set histogram optimal curve, and its typical shape can be shown in Fig. 4 B, s _c(i) be the histogram equalization curve, k ₁, k ₂Be the weight coefficient of equalization curve and preset histogram optimal curve, generally can be with k ₁, k ₂All be set at 0.5, distinguishingly, also can be with k ₂Be made as 0.

Method 2:

For aforementioned statistics with histogram information h _c(i), it carry out local averageization, obtain the local average histogram of passage c, the local average histogram can obtain through following formula:

$p_c\left(i\right)=\left\{\begin{array}{c}\frac{\underset{j=i}{\overset{i+k}{\mathrm{\Σ}}}{h}_c\left(j\right)}{k},i\∈[l_{\min },l_{\max }-k]\\ \frac{\underset{j=i}{\overset{l_{\max }}{\mathrm{\Σ}}}{h}_c\left(j\right)+(i+k-l_{\max })*h_c\left(l_{\max }\right)}{k},i\∈(l_{\max }-k,l_{\max }]\end{array}\right.$

In the following formula, k is the smoothing factor of local averageization, but general value is (l _Max-l _MinThe local average histogram is asked for mainly in order to make histogram more level and smooth in)/32, is keeping removing the little spike in the histogram under the immovable prerequisite of histogram global shape.

After having obtained the local average histogram, can be from i=l _MinBeginning increases progressively the i value gradually, local equalization histogram is traveled through, if detect certain p _c(i)＞G _c, then i value at this moment is designated as l ' _MinSame, from i=l _MaxBegin to successively decrease gradually the i value, local equalization histogram is traveled through, if detect certain p _c(i)＞G _c, then i value at this moment is designated as l ' _MaxWherein, G _cBe a preset threshold value, this threshold value is used to control the histogram enhanced strength.

After above-mentioned traversal is accomplished, before and after can strengthening with the computes histogram any pixel grayscale of passage c other remap and concern T _c(i):

$T_c\left(i\right)=\frac{i-l_{\min }^{\′}}{l_{\max }^{\′}-l_{\min }^{\′}}*\mathrm{\ζ}\left(i\right)*(l_{\max }-l_{\min })+l_{\min }$

In the following formula, ζ (i) is a pre-set histogram optimal curve equally, and its meaning is with identical shown in shape and the method 1.

Method 3:

For aforementioned statistics with histogram information h _c(i), asking for its accumulative histogram s _c(i) time, can adopt following formula:

$s_c\left(i\right)=\underset{j=0}{\overset{i}{\mathrm{\Σ}}}{h}_c\left(j\right),i\∈[l_{\min },l_{\max }]$

Asking its local average histogram p _c(i) time, can adopt following formula:

$p_c\left(i\right)=\left\{\begin{array}{c}\frac{\underset{j=i}{\overset{i+k}{\mathrm{\Σ}}}{h}_c\left(j\right)}{k},i\∈[l_{\min },l_{\max }-k]\\ \frac{\underset{j=i}{\overset{l_{\max }}{\mathrm{\Σ}}}{h}_c\left(j\right)+(i+k-l_{\max })*h_c\left(l_{\max }\right)}{k},i\∈(l_{\max }-k,l_{\max }]\end{array}\right.$

The traversal that in the local average histogram, increases progressively and successively decrease then increases progressively and detects certain p _c(i)＞G _cThe time, then i at this moment is designated as l ' _MinSuccessively decrease and detect certain p _c(i)＞G _c, then i at this moment is designated as l ' _MaxG _cIt is a preset threshold value.

Before and after histogram strengthens any pixel grayscale of passage c other remap and concern T _c(i) can obtain by following mode:

Wherein, s _c(i) be the histogram equalization curve,

Be histogram shape curve, k ₁, k ₂Be the weight coefficient of equalization curve and pattern curve, generally can all get 0.5.

can be obtained by following formula:

Need to prove, more than three kinds of methods only be that several kinds that histogram among the application embodiment is strengthened possibly implementations describe, be not limited to the concrete scope of application and the method for using of the application embodiment.

The 5th, according to the pixel mapping relation original image frame is remapped.The enhancing of aforementioned process histogram can obtain remapping of any pixel grey scale rank of passage c i and concern T _c(i), therefore, according to T _c(i) can recomputate the channel components c ' after promptly being enhanced after the calculating to the gray value of all pixels of passage c.After each passage to original image frame carries out above-mentioned processing, each passage is synthesized, promptly obtain the result images after the auto contrast handles.

Different and according to selected color space to the requirement of amount of calculation, can carry out flexibly the processing of each passage.For example, for the RGB passage, synthetic again after can respectively three passages of RGB being handled; Perhaps also can use the mapping relations of this passage directly all passages to be remapped processing to after wherein certain passage is handled; Perhaps also can calculate mapping relations, then all passages remapped processing with the mean value of RGB passage; Perhaps also can combine other color space, ask for mapping relations, then to the processing of remapping of all passages such as Y passage with the YUV color space.

In the foregoing description; The contrast processing that image is carried out is that the contrast of in digital photographing apparatus, carrying out is handled; Promptly before image compresses or transmits, realize the contrast of image is strengthened, avoided, cause the noise of image or disturb the further problem that enlarges image degree of the comparing enhancement process of compressing or transmission back quality descends; Through in the optimization process of digital photographing apparatus degree of comparing front end, strengthened the display effect of video image thus; The not enough problem of contrast that the application embodiment can solve because the image that a variety of causes such as illumination condition causes is gloomy etc. increases the clear sense of video image, thus the visual effect of the video image that the lifting picture pick-up device is exported.

Corresponding with the embodiment of the processing method of the application's picture contrast, the application also provides the embodiment of the processing unit of picture contrast.

Referring to Fig. 5, be the first embodiment block diagram of the processing unit of the application's picture contrast.

This device comprises: acquiring unit 510, statistic unit 520, adjustment unit 530 and map unit 540.

Wherein, acquiring unit 510 is used to obtain a pending two field picture;

Statistic unit 520 is used for pairing each passage of the color space of a two field picture is carried out statistics with histogram, obtains statistics with histogram information;

Adjustment unit 530 is used for distributing according to the pixel grey scale of statistics with histogram information adjustment image, and pixel grey scale rank before the output adjustment and the mapping relations between the adjusted pixel grey scale rank;

Map unit 540 is used for remapping according to the grey scale pixel value of mapping relations to image, obtains the image after contrast is handled.

Referring to Fig. 6, be the second embodiment block diagram of the processing unit of the application's picture contrast.

This device comprises: preset unit 610, acquiring unit 620, converting unit 630, statistic unit 640, adjustment unit 650 and map unit 660.

Wherein, preset unit 610 is used for being provided with in advance the frame period threshold value of obtaining a two field picture;

Acquiring unit 620, be used to obtain satisfy the frame period threshold value a two field picture as a pending two field picture;

Converting unit 630 is used for the color space of the two field picture that obtains is changed;

Statistic unit 640 is used for pairing each passage of the color space after the conversion of a two field picture is carried out statistics with histogram;

Adjustment unit 650 is used for distributing according to the pixel grey scale of statistics with histogram information adjustment image, and pixel grey scale rank before the output adjustment and the mapping relations between the adjusted pixel grey scale rank;

Map unit 660 is used for remapping according to the grey scale pixel value of mapping relations to image, obtains the image after contrast is handled.

Referring to Fig. 7 A, be the embodiment block diagram of the statistic unit that installs shown in Fig. 6.

This statistic unit 640 comprises: number of pixels computation subunit 641 and gray probability normalization subelement 642.

Wherein, number of pixels computation subunit 641 is used for calculating the corresponding number of pixels of each grey level of each corresponding passage of the color space of a said two field picture;

Gray probability normalization subelement 642 is used for the probability that each grey level according to each passage after the said number of pixels output normalization occurs, and the probability that said each grey level is occurred is as the statistics with histogram information of said each passage.

Referring to Fig. 7 B, be the embodiment block diagram of a kind of adjustment unit of installing shown in Fig. 6.

This adjustment unit 650 comprises: histogram accumulative total subelement 651 obtains subelement 652 with mapping relations.

Wherein, histogram accumulative total subelement 651 is used for the probability that each grey level to each passage occurs and adds up, and obtains the accumulative histogram of each passage;

Mapping relations are obtained subelement 652, are used for obtaining preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank according to accumulative histogram.

Referring to Fig. 7 C, be the embodiment block diagram of the another kind of adjustment unit that installs shown in Fig. 6.

This adjustment unit 650 comprises: histogram local average beggar unit 653, histogram traversal subelement 654 and mapping relations are obtained subelement 655.

Wherein, histogram local average beggar unit 653 is used for the probability that each grey level to each passage occurs and carry out local averageization, obtains the local average histogram information of each passage;

Histogram traversal subelement 654 is used for according to preset target histogram said local average histogram being traveled through, and the minimal gray rank and the maximum gray scale that obtain to satisfy the specify arithmetic relation are other;

Mapping relations are obtained subelement 655, are used for according to minimal gray rank and the maximum gray scale of said specify arithmetic relation, obtain preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank.

Referring to Fig. 7 D, be the embodiment block diagram of the map unit of installing shown in Fig. 6.

This map unit 660 comprises: the source pixel gray scale is obtained subelement 661, object pixel gray scale coupling subelement 662, pixel grey scale adjustment subelement 663 and passage synthon unit 664.

Wherein, the source pixel gray scale is obtained subelement 661, the grey scale pixel value of the grey scale pixel value of each passage that is used to obtain said each pixel of image before as adjustment;

Object pixel gray scale coupling subelement 662 is used for mating said mapping relations according to the grey scale pixel value before the said adjustment, obtains the adjusted grey scale pixel value of each pixel in the correspondence of said each passage;

Pixel grey scale adjustment subelement 663 is used for according to said adjusted grey scale pixel value said each pixel being carried out the grey level adjustment at each passage;

Passage synthon unit 664 is used for that adjusted each passage is synthesized the contrast of accomplishing image and handles.

Description through above execution mode can be known; The application embodiment is applied in the picture pick-up device image degree of comparing is handled; After obtaining a pending two field picture, pairing each passage of the color space of this two field picture is carried out statistics with histogram, obtain statistics with histogram information; Pixel grey scale according to this image of statistics with histogram information adjustment distributes; And pixel grey scale rank before the output adjustment and the mapping relations between the adjusted pixel grey scale rank, remap according to the grey scale pixel value of mapping relations to this image, obtain the image after contrast is handled.It is that the contrast of in picture pick-up device, carrying out is handled that the contrast that application the application embodiment carries out image is handled; Promptly, realizes image the contrast of image is strengthened before compressing or transmit; Avoided image degree of comparing enhancement process to compression or the quality decline of transmission back; Cause the noise of image or disturb the problem that further enlarges,, strengthened the display effect of video image thus through in the optimization process of digital photographing apparatus degree of comparing front end.

Description through above execution mode can know, those skilled in the art can be well understood to the application and can realize by the mode that software adds essential general hardware platform.Based on such understanding; The part that the application's technical scheme contributes to prior art in essence in other words can be come out with the embodied of software product; This computer software product can be stored in the storage medium, like ROM/RAM, magnetic disc, CD etc., comprises that some instructions are with so that a computer equipment (can be a personal computer; Server, the perhaps network equipment etc.) carry out the described method of some part of each embodiment of the application or embodiment.

Each embodiment in this specification all adopts the mode of going forward one by one to describe, and identical similar part is mutually referring to getting final product between each embodiment, and each embodiment stresses all is the difference with other embodiment.Especially, for system embodiment, because it is basically similar in appearance to method embodiment, so description is fairly simple, relevant part gets final product referring to the part explanation of method embodiment.

The application can describe in the general context of the computer executable instructions of being carried out by computer, for example program module.Usually, program module comprises the routine carrying out particular task or realize particular abstract, program, object, assembly, data structure or the like.Also can in DCE, put into practice the application, in these DCEs, by through communication network connected teleprocessing equipment execute the task.In DCE, program module can be arranged in this locality and the remote computer storage medium that comprises memory device.

Though described the application through embodiment, those of ordinary skills know, the application has many distortion and variation and the spirit that do not break away from the application, hope that appended claim comprises these distortion and variation and the spirit that do not break away from the application.

Claims (10)

1. the processing method of a picture contrast is characterized in that, is used in digital photographing apparatus, image degree of comparing being handled, and comprising:

Obtain a pending two field picture;

Pairing each passage of the color space of a said two field picture is carried out statistics with histogram, obtain statistics with histogram information, comprising: calculate the corresponding number of pixels of each grey level in each corresponding passage of the color space of a said two field picture; The probability that occurs according to each grey level in each passage after the said number of pixels output normalization, the probability that said each grey level is occurred is as the statistics with histogram information of said each passage;

The pixel grey scale of adjusting said image according to said statistics with histogram information distributes; And pixel grey scale rank before the output adjustment and the mapping relations between the adjusted pixel grey scale rank; Comprise: the probability to each grey level in each passage occurs carry out local averageization, obtains the local average histogram information of each passage; Said local average histogram can obtain through following formula:

$p_c\left(i\right)=\left\{\begin{array}{c}\frac{\underset{j=i}{\overset{i+k}{\mathrm{\Σ}}}{h}_c\left(j\right)}{k},i\∈[l_{\min },l_{\max }-k]\\ \frac{\underset{j=i}{\overset{l_{\max }}{\mathrm{\Σ}}}{h}_c\left(j\right)+(i+k-l_{\max })*h_c\left(l_{\max }\right)}{k},i\∈(l_{\max }-k,l_{\max }]\end{array}\right.$

Wherein, i is certain grey level of selected channel components c, h _c(j) be the statistics with histogram information of channel components c, k is the smoothing factor of local averageization, l _MinBe the minimal gray rank of original image, l _MaxFor the maximum gray scale of original image other;

Target histogram according to preset travels through said local average histogram, and the minimal gray rank and the maximum gray scale that obtain to satisfy the specify arithmetic relation are other;

Other according to said minimal gray rank and the maximum gray scale that satisfies specify arithmetic relation, obtain preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank, said mapping relations can obtain through following formula:

$T_c\left(i\right)=\frac{i-l_{\min }^{\′}}{l_{\max }^{\′}-l_{\min }^{\′}}*\mathrm{\ζ}\left(i\right)*(l_{\max }-l_{\min })+l_{\min }$

Wherein, l ' _MinFor from i=l _MinBeginning increases progressively the i value gradually, and local equalization histogram is traveled through, and is detecting certain p _c(i)＞G _cThe time, the value of i, l ' _MaxFor from i=l _MaxBegin to successively decrease gradually the i value, local equalization histogram is traveled through, detecting certain p _c(i)＞G _cThe time, the value of i, G _cBe a preset threshold value, this threshold value is used to control the histogram enhanced strength; l _Min, l _MaxThe minimal gray rank and the maximum gray scale that are respectively original image are other;

Remap according to the grey scale pixel value of said mapping relations, obtain the image after contrast is handled said image.

2. method according to claim 1 is characterized in that, said obtaining before the pending two field picture also comprises: the frame period threshold value of obtaining a two field picture is set in advance;

Saidly obtain a pending two field picture and be specially: obtain satisfy said frame period threshold value a two field picture as a said pending two field picture.

3. method according to claim 1 is characterized in that, said obtaining after the pending two field picture, and also comprise: the color space to a said two field picture is changed;

Pairing each passage of said color space to a two field picture carries out statistics with histogram and is specially: pairing each passage of the color space after the conversion of a said two field picture is carried out statistics with histogram.

4. method according to claim 1 is characterized in that, saidly adjusts said image pixel intensity profile according to statistics with histogram information and comprises:

The probability that each grey level in each passage is occurred adds up, and obtains the accumulative histogram of each passage;

Obtain preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank according to accumulative histogram.

5. method according to claim 1 is characterized in that, saidly remaps according to the grey scale pixel value of mapping relations to image, and the image that obtains after contrast is handled comprises:

Obtain said each pixel of image each passage grey scale pixel value as the adjustment before grey scale pixel value;

Mate said mapping relations according to the grey scale pixel value before the said adjustment, obtain the adjusted grey scale pixel value of each pixel in the correspondence of said each passage;

According to said adjusted grey scale pixel value said each pixel is carried out the grey level adjustment at each passage;

Adjusted said each passage is synthesized the contrast of accomplishing said image to be handled.

6. the processing unit of a picture contrast is characterized in that, is used in digital photographing apparatus, image degree of comparing being handled, and comprising:

Acquiring unit is used to obtain a pending two field picture;

Statistic unit is used for pairing each passage of the color space of a said two field picture is carried out statistics with histogram, obtains statistics with histogram information; Said statistic unit comprises:

The number of pixels computation subunit is used for calculating the corresponding number of pixels of each grey level of each corresponding passage of the color space of a said two field picture;

Gray probability normalization subelement is used for the probability that each grey level according to each passage after the said number of pixels output normalization occurs, and the probability that said each grey level is occurred is as the statistics with histogram information of said each passage;

Adjustment unit is used for adjusting according to said statistics with histogram information the pixel grey scale distribution of said image, and pixel grey scale rank before the output adjustment and the mapping relations between the adjusted pixel grey scale rank; Said adjustment unit comprises:

Histogram local average beggar unit is used for the probability that each grey level to each passage occurs and carry out local averageization, obtains the local average histogram information of each passage; The local average histogram can obtain through following formula:

$p_c\left(i\right)=\left\{\begin{array}{c}\frac{\underset{j=i}{\overset{i+k}{\mathrm{\Σ}}}{h}_c\left(j\right)}{k},i\∈[l_{\min },l_{\max }-k]\\ \frac{\underset{j=i}{\overset{l_{\max }}{\mathrm{\Σ}}}{h}_c\left(j\right)+(i+k-l_{\max })*h_c\left(l_{\max }\right)}{k},i\∈(l_{\max }-k,l_{\max }]\end{array}\right.$

Wherein, i is certain grey level of selected channel components c, h _c(j) be the statistics with histogram information of channel components c, k is the smoothing factor of local averageization, l _MinBe the minimal gray rank of original image, l _MaxFor the maximum gray scale of original image other;

Histogram traversal subelement is used for according to preset target histogram said local average histogram being traveled through, and the minimal gray rank and the maximum gray scale that obtain to satisfy the specify arithmetic relation are other;

Mapping relations are obtained subelement; Be used for according to the minimal gray rank and the maximum gray scale of said specify arithmetic relation other; Obtain preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank, said mapping relations can obtain through following formula:

$T_c\left(i\right)=\frac{i-l_{\min }^{\′}}{l_{\max }^{\′}-l_{\min }^{\′}}*\mathrm{\ζ}\left(i\right)*(l_{\max }-l_{\min })+l_{\min }$

Wherein, l _MinFor from i=l _MinBeginning increases progressively the i value gradually, and local equalization histogram is traveled through, and is detecting certain p _c(i)＞G _cThe time, the value of i, l _MaxFor from i=l _MaxBegin to successively decrease gradually the i value, local equalization histogram is traveled through, detecting certain p _c(i)＞G _cThe time, the value of i, G _cBe a preset threshold value, this threshold value is used to control the histogram enhanced strength; l _Min, l _MaxThe minimal gray rank and the maximum gray scale that are respectively original image are other;

Map unit is used for remapping according to the grey scale pixel value of said mapping relations to said image, obtains the image after contrast is handled.

7. device according to claim 6 is characterized in that, also comprises: preset unit is used for being provided with in advance the frame period threshold value of obtaining a two field picture;

Said acquiring unit, specifically be used to obtain satisfy said frame period threshold value a two field picture as a said pending two field picture.

8. device according to claim 6 is characterized in that, also comprises: converting unit is used for the color space of a said two field picture is changed;

Said statistic unit specifically is used for pairing each passage of the color space after the conversion of a said two field picture is carried out statistics with histogram.

9. device according to claim 6 is characterized in that, said adjustment unit comprises:

Histogram accumulative total subelement is used for the probability that each grey level to each passage occurs and adds up, and obtains the accumulative histogram of each passage;

Mapping relations are obtained subelement, are used for obtaining preceding pixel grey scale rank of adjustment and the mapping relations between the adjusted pixel grey scale rank according to accumulative histogram.

10. device according to claim 6 is characterized in that, said map unit comprises:

The source pixel gray scale is obtained subelement, the grey scale pixel value of the grey scale pixel value of each passage that is used to obtain said each pixel of image before as adjustment;

Object pixel gray scale coupling subelement is used for mating said mapping relations according to the grey scale pixel value before the said adjustment, obtains the adjusted grey scale pixel value of each pixel in the correspondence of said each passage;

Pixel grey scale adjustment subelement is used for according to said adjusted grey scale pixel value said each pixel being carried out the grey level adjustment at each passage;

Passage synthon unit is used for that adjusted said each passage is synthesized the contrast of accomplishing said image and handles.

Images