CN103745438A - Haze removing method for large-area background light haze-containing image - Google Patents

Abstract

The invention discloses a haze removing method for a large-area background light haze-containing image. The haze removing method comprises the steps of 1) obtaining an intensity histogram A of a haze-containing image, judging whether the histogram A meets the requirement of having large-area background light or not and calculating the horizontal coordinate xA of partial peak values of the background light; 2) haze removing the image by using a dark channel prior algorithm, calculating a histogram B of a haze-removed picture and determining the coordinate (xB, hB) on which burr occurs; 3) reestablishing the histogram B: reserving the part with intensity which is smaller than xB, reestablishing the part with intensity which is larger than xB and performing reestablishment by adopting a monotonic increasing convex function; 4) performing histogram specification to the reestablished histogram and the haze-removed picture to obtain an improved haze-removed picture. The haze removing method for the large-area background light haze-containing image has the advantages that since the dark channel prior algorithm is post-processed through the histogram, the method is simple and flexible to operate; since different parameters are set according to different specific images, the situation that the result of dark channel prior processing is difficult to fine tune is avoided; the algorithm efficiency is higher, the quality of the obtained haze-removed picture is higher and the picture is more close to an actual haze-free picture.

Description

Extended background light is containing the defogging method capable of mist image

Technical field

The present invention relates to and image processing techniques, be specifically related to the defogging method capable of a kind of extended background light containing mist image.

Background technology

When camera is found a view out of doors, phase tablet quality conventionally can cause impact in various degree because of the absorption of the particle suspending in atmosphere on object light or scattering, and in foggy weather, above-mentioned phenomenon becomes particularly evident.When the weather that has mist is found a view, due to the interference of a large amount of water droplets of air, when on the one hand the reflected light of object arrives camera lens after the absorption of water droplet and refraction, can produce decay, on the other hand due to the diffuse reflection of water droplet to atmosphere light, have more atmosphere light and enter camera lens simultaneously; Cause on the one hand the colour brightness of object in picture comparatively dim, a large amount of atmosphere light also makes integral image seem greyish white on the other hand, has lost this due color of object.When the scenery obtaining when needs contains a large amount of bias lights, it is particularly evident that distortion just seems.

At computer vision field, it is generally acknowledged the brightness of image, the object features of contrast reaction, due to containing mist image with above-mentioned all factors, adopt general image processing techniques to process containing mist picture and inevitably there will be deviation, the result that impact is processed; The field that particularly need to use computer vision algorithms make solving practical problems in such as communications and transportation, outdoor supervision, landform detecting etc., the mist elimination of image has demand widely.

Summary of the invention

The technical problem to be solved in the present invention is extended background light to carry out mist elimination containing mist image, avoids that mist elimination result images contrast is on the low side, the dim unsharp problem of image.

Technical scheme of the present invention comprises the defogging method capable of a kind of extended background light containing mist image, comprises the following steps:

S1, obtaining the described intensity histogram A containing mist image, judge whether described histogram A meets and have larger area bias light, is the horizontal ordinate x that calculates bias light part peak value _a;

S2, utilization are helped first checking method secretly image are carried out to mist elimination, the histogram B of picture after calculating mist elimination, and determine the coordinate (x that occurs burr _b, h _b);

S3, reconstruction histogram B: strength retention is less than horizontal ordinate x _bpart, rebuild intensity be greater than horizontal ordinate x _bpart, and adopt single Convex Functions increasing to rebuild;

S4, to rebuild histogram B ' and mist elimination picture carry out histogram specification, the mist elimination picture after being improved.

Beneficial effect of the present invention comprises: by histogram, to helping first checking method secretly, carry out aftertreatment, simple to operate flexible, parameter that can be different according to different concrete image setting, has avoided helping secretly priori result and be difficult to fine setting; Efficiency of algorithm is higher, and the mist elimination picture quality of acquisition is higher, and more presses close to true in mist view.

Accompanying drawing explanation

Fig. 1 is that the defogging method capable of the embodiment of the present invention is realized design sketch.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail.

The invention provides the defogging method capable of a kind of extended background light containing mist image, comprise step:

S1, obtaining the described intensity histogram A containing mist image, judge whether described histogram A meets and have larger area bias light, is the horizontal ordinate x that calculates bias light part peak value _a;

S2, utilization are helped first checking method secretly image are carried out to mist elimination, the histogram B of picture after calculating mist elimination, and determine the coordinate (x that occurs burr _b, h _b);

S3, reconstruction histogram B: strength retention is less than horizontal ordinate x _bpart, rebuild intensity be greater than horizontal ordinate x _bpart, and adopt single Convex Functions increasing to rebuild;

S4, to rebuild histogram B ' and mist elimination picture carry out histogram specification, the mist elimination picture after being improved.

The embodiment of the present invention is carried out aftertreatment by histogram to helping first checking method secretly, simple to operate flexible, and parameter that can be different according to different concrete image setting, has avoided helping secretly priori result and be difficult to fine setting; Efficiency of algorithm is higher, and the mist elimination picture quality of acquisition is higher, and more presses close to true in mist view.

One embodiment of the invention provides the defogging method capable of a kind of extended background light containing mist image, comprises,

S1, obtaining the described intensity histogram A containing mist image, judge whether described histogram A meets and have larger area bias light, is the horizontal ordinate x that calculates bias light part peak value _a;

The above-mentioned larger area bias light of stating is that the intensity histogram of image has a peak in low-intensity part and high strength part, and has separatrix between described two peaks; In histogram, can significantly see the Luminance Distribution that contribute in foreground area and bias light region.

As shown in Figure 1, in figure, a is original in mist image, and b is the mist elimination result through helping first checking method secretly, and c is the improvement result of algorithm of the present invention, and d, e, g are respectively three's histograms, and f is the reconstruction of algorithm of the present invention to e.

S2, utilization are helped first checking method secretly image are carried out to mist elimination, the histogram B of picture after calculating mist elimination, and determine the coordinate (x that occurs burr _b, h _b);

S3, reconstruction histogram B: strength retention is less than horizontal ordinate x _bpart, rebuild intensity be greater than horizontal ordinate x _bpart, for strengthening the contrast of whole image and the brightness of bias light, adopt single Convex Functions increasing to rebuild;

Single Convex Functions increasing is that its increase slope along with horizontal ordinate is also increasing, and can promote on the one hand the ratio of histogram high strength part, simultaneously also can be because the narrower bias light that makes of the larger local width of density becomes too bright.

Above-mentioned single Convex Functions increasing is quadratic function, and quadratic function parameter is:

Starting point coordinate is (x _b, h _b), the point that occurs noise is the separatrix of prospect light and bias light just;

Terminal horizontal ordinate is x _a, for the brightness and the atmosphere light that make bias light approach, terminal ordinate is α h _max, wherein, h _maxfor the peak of histogram B;

Thirdly coordinate is

Wherein, α scope is 0.8-0.9, and β scope is 0.2-0.3.

S4, to rebuild histogram B ' and mist elimination picture carry out histogram specification, the mist elimination picture after being improved.

The value that promotes the density function of a part of intensity is just equivalent to the value of the density function that reduces another part, and therefore changing merely bias light is also the contrast that has strengthened prospect light; Histogram specification is applicable to the change image of dirigibility among a small circle, if changed, too much can cause larger distortion, thereby reduces the quality of image.

Wherein, above-mentionedly help first checking method secretly and be,

Have the figure of mist to be:

I(x)=J(x)t(x)+Y[1-t(x)] (1)

Wherein, I is the image intensity observing, and J is the light intensity of scenery under without mist condition, and Y is surround lighting composition, and t is for propagating parameter;

Help priori rule secretly: in the regional area of non-sky, certain some pixel always has at least one Color Channel and has very low value, in other words, the minimum value of this area light intensity is a very little number, and it is expressed as:

J ^dark(x)=min _c∈{R,G,B}(min _y∈Ω(x)J ^C(y) (2)

Wherein, J ^cfor some Color Channels of J, Ω (x) is the square region centered by x; For the image without mist, gone out the region of sky, J ^darkalways very low and region zero of intensity.

Priori is helped in utilization secretly, obtains propagating parameter

$\tilde{t}\left(x\right)=1-\mathrm{\ω}\underset{c\∈\{R,G,B\}}{\min }\left(\underset{y\∈\mathrm{\Ω}\left(x\right)}{\min }\frac{I^C\left(y\right)}{Y^C}\right)---\left(3\right)$

Wherein, parameter ω retains a part of mist information;

To described propagation parameter

become more meticulous, obtain propagating parameter t, by formula (1), obtain mist elimination image: $J\left(x\right)=\frac{I\left(x\right)-A}{\max (t\left(x\right),t0)}+A---\left(4\right),$

Wherein, t0 is the restriction in order to prevent that t (x) in denominator is too small and carry out.

For RGB image, due to each pixel three in Color Channel brightness and inconsistent therefore respectively to RGB tri-chrominance channels ask histogram process and then merging be inapplicable.Histogram is, rgb matrix is converted to HSI matrix, colourity (hue), saturation degree (saturation) and brightness (intensity) the description one secondary coloured image of image for HSI space, and strength component I is done to histogram analysis,

$H=\left\{\begin{array}{cc}\mathrm{\θ}& B\≤G\\ 360-\mathrm{\θ}& B>G\end{array}\right.$

$S=1-\frac{3}{(R+G+B)}\left[\min (R,G,B)\right]$

$I=\frac{1}{3}(R+G+B),$

Wherein, $\mathrm{\θ}=\arccos \left\{\frac{\frac{1}{2}[(R-G)+(R-B)]}{{[{(R-G)}^2+(R-B)(G-B)]}^{1/2}}\right\}.$

Before conversion, can from histogram, see significantly the interval between the distribution of object and the distribution of bias light, have an obvious minimum point; After conversion, bias light and and the distribution of object between boundary thicken unclearly, also after i.e. conversion, the contrast between object and bias light diminishes;

Utilize the appearance one line bad point in histogram to tell object and bias light, and histogram is processed respectively, obtain reasonable distribution.

The embodiment of the present invention, solve utilize the single image mist elimination algorithm of helping priori secretly to contain extended background light containing mist image, carry out mist elimination time, avoid causing that mist elimination result images contrast is on the low side, image is dim unintelligible; Solve utilize the single image mist elimination algorithm of helping priori secretly to contain extended background light containing mist image, carry out mist elimination time, the bias light part causing occurs that burr, noise etc. cause image quality decrease; Utilize the dirigibility of histogram specification among a small circle picture quality being made to further processing, increase the dirigibility of result, improve the quality that solves mist elimination image.

The above the specific embodiment of the present invention, does not form limiting the scope of the present invention.Various other corresponding changes and distortion that any technical conceive according to the present invention has been done, all should be included in the protection domain of the claims in the present invention.

Claims (7)

1. extended background light, containing a defogging method capable for mist image, is characterized in that, comprises the following steps:

S1, obtaining the described intensity histogram A containing mist image, judge whether described histogram A meets and have larger area bias light, is the horizontal ordinate x that calculates bias light part peak value _a;

S2, utilization are helped first checking method secretly image are carried out to mist elimination, the histogram B of picture after calculating mist elimination, and determine the coordinate (x that occurs burr _b, h _b);

S3, reconstruction histogram B: strength retention is less than horizontal ordinate x _bpart, rebuild intensity be greater than horizontal ordinate x _bpart, and adopt single Convex Functions increasing to rebuild;

S4, to rebuild histogram B ' and mist elimination picture carry out histogram specification, the mist elimination picture after being improved.

2. extended background light according to claim 1 is containing the defogging method capable of mist image, it is characterized in that, described to have larger area bias light be that the intensity histogram of image has a peak in low-intensity part and high strength part, and have separatrix between described two peaks.

3. extended background light according to claim 1, containing the defogging method capable of mist image, is characterized in that, described single Convex Functions increasing is quadratic function.

4. extended background light according to claim 3, containing the defogging method capable of mist image, is characterized in that, described quadratic function parameter is:

Starting point coordinate is (x _b, h _b);

Terminal horizontal ordinate is x _a, terminal ordinate is α h _max, wherein, h _maxfor the peak of histogram B;

Thirdly coordinate is

5. extended background light according to claim 4, containing the defogging method capable of mist image, is characterized in that, described α scope is 0.8-0.9, and described β scope is 0.2-0.3.

6. extended background light according to claim 1, containing the defogging method capable of mist image, is characterized in that, described in help first checking method secretly and be,

Have the figure of mist to be:

I(x)=J(x)t(x)+Y[1-t(x)] (1)

Wherein, I is the image intensity observing, and J is the light intensity of scenery under without mist condition, and Y is surround lighting composition, and t is for propagating parameter;

Help priori rule secretly: in the regional area of non-sky, certain some pixel always has at least one Color Channel and has very low value, and it is expressed as:

J ^dark(x)=min _c∈{R,G,B}(min _y∈Ω(x)J ^C(y) (2)

Wherein, J ^cfor some Color Channels of J, Ω (x) is the square region centered by x;

Priori is helped in utilization secretly, obtains propagating parameter

$\tilde{t}\left(x\right)=1-\mathrm{\ω}\underset{c\∈\{R,G,B\}}{\min }\left(\underset{y\∈\mathrm{\Ω}\left(x\right)}{\min }\frac{I^C\left(y\right)}{Y^C}\right)---\left(3\right)$

Wherein, parameter ω retains a part of mist information;

To described propagation parameter become more meticulous, obtain propagating parameter t, by formula (1), obtain mist elimination image: $J\left(x\right)=\frac{I\left(x\right)-A}{\max (t\left(x\right),t0)}---\left(4\right).$

7. extended background light according to claim 1, containing the defogging method capable of mist image, is characterized in that, described histogram is, rgb matrix is converted to HSI matrix, and strength component I is done to histogram analysis,

$H=\left\{\begin{array}{cc}\mathrm{\θ}& B\≤G\\ 360-\mathrm{\θ}& B>G\end{array}\right.$

$S=1-\frac{3}{(R+G+B)}\left[\min (R,G,B)\right]$

$I=\frac{1}{3}(R+G+B),$ Wherein, $\mathrm{\θ}=\arccos \left\{\frac{\frac{1}{2}[(R-G)+(R-B)]}{{[{(R-G)}^2+(R-B)(G-B)]}^{1/2}}\right\}.$

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