CN105869112B - A kind of edge keeps the high dynamic range image tone mapping method of minimum - Google Patents
A kind of edge keeps the high dynamic range image tone mapping method of minimum Download PDFInfo
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Abstract
The high dynamic range image tone mapping method minimized is kept the invention discloses a kind of edge, is specifically implemented according to the following steps: step 1: obtaining the luminance picture L (x, y) of high dynamic range images；Step 2: Steerable filter is carried out to L (x, y) using Steerable filter device；Step 3: according to the photography tone mapping transformation for mula simplified, the luminance picture L (x, y) of high dynamic range images being converted；Step 4: calculating Z with the method for iterationn+1(x,y)；Step 5: luminance picture Z (x, y)=Zn+1(x, y) calculates error e if e > T, T are threshold value and is transferred to step 4, otherwise, be transferred to step 6；Step 6: completing high dynamic range image tone mapping.A kind of edge of the present invention keeps the high dynamic range image tone mapping method minimized high dynamic range images can be carried out display output in low-dynamic range equipment, both it has taken into account and original image has been approached, the marginal information of original image can be preferably kept again, and the image of display has the characteristics that contrast is high, detail rendition effect is good.
Description
Technical field
The invention belongs to digital image processing techniques fields, and in particular to a kind of edge keeps the high dynamic range of minimum
Image tone mapping method.
Background technique
Dynamic range in natural scene will usually cross over 1014The order of magnitude, with the development of imaging technique, high dynamic range
The acquisition of image is more and more convenient, is widely used in the fields such as video display, game, military affairs, astronomy and medicine detection.It is same with this
When, the display equipment development of high dynamic range images is also relatively slower and price is more expensive.In order in the display of low-dynamic range
The detailed information that high dynamic range images are preferably reproduced in equipment is often needed using certain method compression high dynamic range figure
The dynamic range of picture, the display equipment of low-dynamic range can be matched by being allowed to dynamic range, this process is known as tone mapping
(tone mapping)。
The tone mapping method of mainstream can be divided into two classes at present: (1) global (Global) operator；(2) part (Local)
Operator.Global operator applies same transformation to the pixel in image with same pixel value, does not consider its surrounding pixel；Part
For mapping algorithm when carrying out tone mapping, the neighborhood information of reference pixel converts it, it is contemplated that the Local Phase of image
Guan Xing, thus preferable mapping effect can be obtained, become the emphasis paid close attention at present.Although there is more local tone mapping at present
Method, but it is still not good enough to the reservation of details.
Summary of the invention
The high dynamic range image tone mapping method minimized is kept the object of the present invention is to provide a kind of edge, is solved
Not not clear enough the problem of image detail existing for existing local tone mapping method.
The technical scheme adopted by the invention is that a kind of edge keeps the high dynamic range image tone mapping side minimized
Method is specifically implemented according to the following steps:
Step 1: obtaining the luminance picture L (x, y) of high dynamic range images；
Step 2: Steerable filter being carried out to L (x, y) using Steerable filter device, obtaining filtered result is b (x, y)；
Step 3: according to the photography tone mapping transformation for mula simplified, to the luminance picture L of high dynamic range images (x,
Y) it is converted, transformation results are a (x, y)；
Step 4: calculating Z with the method for iterationn+1(x, y), n indicate the number of iteration；
Step 5: luminance picture Z (x, y)=Zn+1(x, y) calculates error e if e > T, T are threshold value and is transferred to step 4,
Otherwise, it is transferred to step 6；
Step 6: completing high dynamic range image tone mapping.
The features of the present invention also characterized in that
The luminance picture L (x, y) of step 1 acquisition high dynamic range images are as follows:
L (x, y)=0.2126R+0.7152G+0.0722B (1)
Wherein, R, G, B are respectively red, green, blue color value of the high dynamic range images at pixel (x, y).
Need to be arranged two parameters: windows radius r and regularization factors when carrying out Steerable filter to L (x, y) in step 2
ε。
Step 3 is added lustre to principle according to shading-, photography tone mapping transformation for mula is simplified, to high dynamic range
The luminance picture L (x, y) of image is converted, transformation results a (x, y) are as follows:
Step 4 specifically: compressed luminance picture Z (x, y) is acquired by the minimum of following formula:
Wherein, λ is regularization parameter；
The calculation formula of iteration are as follows:
Wherein n indicates the number of iteration；
Initial value Z is taken when iteration0(x, y)=L (x, y).
Regularization parameter λ value range is 1~2.
Step 5 specifically:
Luminance picture Z (x, y)=Zn+1(x, y), error e are as follows:
If e > T, T are threshold value, it is transferred to step 4, otherwise, is transferred to step 6.
Step 6 specifically:
In conjunction with tri- color values of luminance picture L (x, y) and R, G, B of former high dynamic range images, utilize what is finally obtained
Low dynamic brightness image Z (x, y) completes high dynamic range image tone mapping:
Wherein Ro、Go、BoRespectively indicate at each pixel of the low dynamic range echograms obtained after tone mapping it is red, green,
Blue color value, γ indicate the parameter of Gamma transformation.
The beneficial effects of the present invention are: a kind of edge of the present invention keeps the high dynamic range image tone mapping side minimized
High dynamic range images can be carried out display output, to high dynamic range images brightness by method in low-dynamic range equipment
When information is compressed, both takes into account and original image has been approached, it is contemplated that the marginal information of original image is kept, thus show
Image has the characteristics that contrast is high, detail rendition effect is good.
Detailed description of the invention
Fig. 1 is the flow chart of high dynamic range image tone mapping method of the present invention；
Fig. 2 is the high dynamic range images shown after high dynamic range image tone mapping method of the present invention is handled；
Fig. 3 is using treated the high dynamic range images of the tone mapping method based on bilateral filtering.
Specific embodiment
The following describes the present invention in detail with reference to the accompanying drawings and specific embodiments.
A kind of edge of the present invention keeps the high dynamic range image tone mapping method minimized, flow chart as shown in Figure 1,
It is specifically implemented according to the following steps:
Step 1: then reading high dynamic range images first obtain the luminance picture L (x, y) of high dynamic range images:
L (x, y)=0.2126R+0.7152G+0.0722B (1)
Wherein, R, G, B are respectively red, green, blue color value of the high dynamic range images at pixel (x, y)；
Step 2: Steerable filter being carried out to L (x, y) using Steerable filter device, guidance figure when filtering is just selected as L (x, y)
Itself, obtaining filtered result is b (x, y).Need to be arranged two parameters: window half when carrying out Steerable filter to L (x, y)
Diameter r and regularization factors ε.Windows radius r determines the size of window in filtering, is related to the more of the pixel for participating in operation
Few, to pixel, finally filtered numerical value has an impact.Regularization factors ε determines the division of edge and smooth region, the numerical value
Choice relation edge and smooth region into image judgement.
Step 3: added lustre to principle according to the shading-used in photography, photography tone mapping transformation for mula is simplified,
The luminance picture L (x, y) of high dynamic range images is converted, transformation results a (x, y) are as follows:
Step 4: compressed luminance picture Z (x, y) is acquired by the minimum of following formula:
Wherein λ is regularization parameter, the degree that value is kept between 1 to 2, to determine luminance picture edge.
Formula above minimizes solving the result is that luminance picture Z (x, y), Z (x, y) are a functions, therefore are one
A variational problem can solve it using the method for iteration.Initial value Z is taken when iteration0(x, y)=L (x, y), the meter of iteration
Calculate formula are as follows:
Wherein n indicates the number of iteration.
Step 5: setting Z (x, y)=Zn+1(x, y) calculates error e:
A threshold value T is set, if e > T, is unsatisfactory for the termination condition of iteration, is transferred to step 4；Otherwise, iteration terminates
It is transferred to step 6.
Step 6: in conjunction with the brightness and color of former high dynamic range images, utilizing the low dynamic brightness image Z finally obtained
(x, y) completes high dynamic range image tone mapping:
Wherein Ro、Go、BoRespectively indicate at each pixel of the low dynamic range echograms obtained after tone mapping it is red, green,
Blue color value, γ indicate the parameter of Gamma transformation, and value is between 1.8 to 2.5.
The high dynamic range image tone mapping method minimized is kept using a kind of edge of the present invention, takes windows radius r
=8, regularization factors ε=0.01, regularization parameter λ=1.5, parameter γ=2.2 of threshold value T=100, Gamma transformation, processing
The high dynamic range images that show afterwards are as shown in Fig. 2, Fig. 3 is that treated is high using the tone mapping method based on bilateral filtering
Dynamic image, by comparison as can be seen that high dynamic range images show using the method for the present invention have contrast height,
The good feature of details display effect.
Claims (5)
1. a kind of edge keeps the high dynamic range image tone mapping method minimized, which is characterized in that specifically according to following
Step is implemented:
Step 1: obtain the luminance picture L (x, y) of high dynamic range images, obtain high dynamic range images luminance picture L (x,
Y) are as follows:
L (x, y)=0.2126R+0.7152G+0.0722B (1)
Wherein, R, G, B are respectively red, green, blue color value of the high dynamic range images at pixel (x, y)；
Step 2: Steerable filter being carried out to L (x, y) using Steerable filter device, obtaining filtered result is b (x, y)；
Step 3: according to the photography tone mapping transformation for mula simplified, to the luminance picture L (x, y) of high dynamic range images into
Row transformation, transformation results are a (x, y)；
Step 4: calculating Z with the method for iterationn+1(x, y), n indicate the number of iteration, specifically: it is asked by the minimum of following formula
Obtain compressed luminance picture Z (x, y):
Wherein, λ is regularization parameter；
The calculation formula of iteration are as follows:
Wherein n indicates the number of iteration；
Initial value Z is taken when iteration0(x, y)=L (x, y)；
Step 5: luminance picture Z (x, y)=Zn+1(x, y) calculates error e if e > T, T are threshold value and is transferred to step 4, otherwise,
It is transferred to step 6；
Step 6: high dynamic range image tone mapping is completed, specifically: in conjunction with the luminance picture L of former high dynamic range images
Tri- color values of (x, y) and R, G, B complete high dynamic range images using the low dynamic brightness image Z (x, y) finally obtained
Tone mapping:
Wherein Ro、Go、BoRespectively indicate the red, green, blue face at each pixel of the low dynamic range echograms obtained after tone mapping
Color value, γ indicate the parameter of Gamma transformation.
2. a kind of edge according to claim 1 keeps the high dynamic range image tone mapping method minimized, special
Sign is, needs to be arranged two parameters: windows radius r and regularization when carrying out Steerable filter to L (x, y) in the step 2
Factor ε.
3. a kind of edge according to claim 1 keeps the high dynamic range image tone mapping method minimized, special
Sign is, the step 3 is added lustre to principle according to shading-, photography tone mapping transformation for mula is simplified, to high dynamic range
The luminance picture L (x, y) for enclosing image is converted, transformation results a (x, y) are as follows:
4. a kind of edge according to claim 1 keeps the high dynamic range image tone mapping method minimized, special
Sign is that the regularization parameter λ value range is 1~2.
5. a kind of edge according to claim 1 keeps the high dynamic range image tone mapping method minimized, special
Sign is, the step 5 specifically:
Luminance picture Z (x, y)=Zn+1(x, y), error e are as follows:
If e > T, T are threshold value, it is transferred to step 4, otherwise, is transferred to step 6.
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| CN106847149B (en) * | 2016-12-29 | 2020-11-13 | 武汉华星光电技术有限公司 | Tone mapping and displaying method for high dynamic contrast image |
| CN107895350B (en) * | 2017-10-27 | 2020-01-03 | 天津大学 | HDR image generation method based on self-adaptive double gamma transformation |
| CN108053381B (en) * | 2017-12-22 | 2022-04-22 | 深圳创维－Rgb电子有限公司 | Dynamic tone mapping method, mobile terminal and computer-readable storage medium |
| CN108510557B (en) * | 2018-04-09 | 2020-09-11 | 湖南国科微电子股份有限公司 | Image tone mapping method and device |
| CN109919841B (en) * | 2019-01-24 | 2022-12-27 | 重庆邮电大学 | Synthesis method of guide graph for high dynamic range image joint up-sampling |
| CN110415188B (en) * | 2019-07-10 | 2021-08-20 | 首都师范大学 | HDR image tone mapping method based on multi-scale morphology |
| CN112689138B (en) * | 2019-10-18 | 2022-08-26 | 华为技术有限公司 | Image signal conversion processing method and device and terminal equipment |
| CN111970564B (en) * | 2020-08-26 | 2023-03-24 | 展讯通信（上海）有限公司 | Optimization method and device for HDR video display processing, storage medium and terminal |
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| US20120041722A1 (en) * | 2009-02-06 | 2012-02-16 | The Hong Kong University Of Science And Technology | Generating three-dimensional models from images |
| CN102722868A (en) * | 2012-05-23 | 2012-10-10 | 西安理工大学 | Tone mapping method for high dynamic range image |
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