CN102567966A - Small error lookup method for non-linear image enhancement - Google Patents
Small error lookup method for non-linear image enhancement Download PDFInfo
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- CN102567966A CN102567966A CN201110427081XA CN201110427081A CN102567966A CN 102567966 A CN102567966 A CN 102567966A CN 201110427081X A CN201110427081X A CN 201110427081XA CN 201110427081 A CN201110427081 A CN 201110427081A CN 102567966 A CN102567966 A CN 102567966A
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Abstract
The invention provides a quick small error lookup method for non-linear image enhancement. According to the method, by enhancing the relationship between function input and output, a mapping table of the input and the output is constructed so as to fulfill the aim of quick calculation. By adopting the method, a contrast ratio of the image is enhanced; details of the image are maintained; the computing complexity is reduced; and the computing amount is reduced.
Description
Technical field
The present invention is a kind of technology that image non-linear strengthens calculating real-time property that solves, and promptly utilizes the relation that strengthens the function input and output, and the mapping table between the structure input and output satisfies the certain precision requirement, reaches quick computation purpose.
Background technology
Contrast is to weigh an important indicator of image.In order to improve the quality of image, it is normally indispensable to strengthen its contrast.At present, algorithm for image enhancement mainly contains following three kinds: frequency field algorithm for image enhancement, spatial domain algorithm for image enhancement and non-linear enhancement algorithms.The frequency field enhancement algorithms need be carried out the space-frequency conversion, and the time complexity of fast discrete Fourier conversion is O (N*log (N)); To each pixel, the spatial domain enhancement algorithms all need be calculated corresponding whole masterplate, calculates loaded down with trivial details; In non-linear enhancement algorithms, logarithm or exponent arithmetic in the non-linear stretching function greatly influence algorithm speed.Data volume after the image digitazation is very big, and image pixel is usually in 1,000,000, and above-mentioned enhancement algorithms is difficult to satisfy real-time requirement.
In the prior art, look-up table can greatly improve arithmetic speed, but can sacrifice certain precision simultaneously, reduces the quality of algorithm.The corresponding image pixel intensity value of handling front and back of non-linear stretching function input and output, and pixel brightness value is discrete and limited.The little error look-up method that a kind of image non-linear fast strengthens is proposed in view of the above.
Summary of the invention
The present invention proposes a kind of real-time nonlinear images enhancement techniques.This techniques make use strengthen function input with
The relation of output, the mapping table between the structure input and output reaches quick computation purpose.Use the invention has the advantages that:
(1) the present invention adopts a kind of nonlinear images enhancement techniques, can significantly promote picture contrast, can keep image detail again;
(2) the present invention is based on the algorithm real-time that mapping table proposes, satisfy the certain precision requirement, avoided influencing the logarithm or the exponent arithmetic of arithmetic speed simultaneously, reach quick computation purpose.
Description of drawings
The non-linear enhancing function curve of Fig. 1.
Embodiment
Following below in conjunction with detailed description of the drawings:
Human eye has the characteristic to the image local information sensing, strengthens image information and improves picture contrast exactly.We adopt the image local Enhancement Method of window mode to improve picture contrast, make human eye to the information sensing in the image.Window is more little, and detailed information is abundant more, so we are set to a pixel with minimum window.Monochrome information is nighttime image key character place, so we only handle brightness of image, strengthens image with this.
At first we need become luminance picture with the three spectrum RGB image transitions that imaging device obtains.Adopt following formula:
For the ease of the computing of back, we change brightness value normalization between [0,1] with its value.
According to local adaptation's property of human eye, we will strengthen the local contrast of image, need obtain the local environment value of each pixel.In order to improve operation efficiency, adopt mean filter.
Wherein, H is a mean filter.
Night scene is incandescent and the simultaneous situation of utmost point dark areas normally, generally uses nonlinear algorithm to strengthen image, can reduce the brightness of luminance area, can strengthen dark areas brightness again, increases the contrast of scenery simultaneously.Nonlinear function is following:
Wherein q obtains according to top Imean:
（5）
This is equivalent to image pixel value has been done non-linear adjustment as shown in Figure 1.
Non-linear enhancing function (4) has two input values: image pixel value I ', the value q relevant with the local environment value.Output valve is the image pixel value after strengthening.Make up interpolation table through following steps:
(1) 100 column indexes of structure, its value represent pixel value I ' amplifies 10
2Value doubly;
(2) 1000 line index of structure, on behalf of q, its value amplify 10
3Value doubly;
(3) each row and column that calculate are corresponding output valve is inserted in the table.
Construct the bivariate table of what a respective function input, output valve in this way in advance.During calculating, only need table look-up, can draw through the adjusted output valve of nonlinear function at pixel value and the corresponding position of environment value.Computation complexity is O (n).
Claims (3)
1. a method is used for strengthening fast picture contrast, and it comprises:
Adopt a kind of nonlinear images enhancement techniques, can significantly promote picture contrast, can keep image detail again;
Utilize mapping table, reach computing real-time, satisfy the certain precision requirement, avoided influencing the logarithm or the exponent arithmetic of arithmetic speed simultaneously.
2. the method for claim 1, it comprises sets up an Image Intensified System, and this system features is: can significantly promote picture contrast, can keep image detail again.
3. the method for claim 1, it comprises the mapping table of setting up a function input and output value, satisfies the certain precision requirement, can reach real-time computation purpose.
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| CN201110427081XA CN102567966A (en) | 2011-12-20 | 2011-12-20 | Small error lookup method for non-linear image enhancement |
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| CN201110427081XA CN102567966A (en) | 2011-12-20 | 2011-12-20 | Small error lookup method for non-linear image enhancement |
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Citations (4)
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|---|---|---|---|---|
| WO2004051569A1 (en) * | 2002-11-29 | 2004-06-17 | Uea Enterprises Limited | Image signal processing |
| CN1892697A (en) * | 2005-07-08 | 2007-01-10 | 杭州波导软件有限公司 | Colour-image reinforcing method |
| CN101303766A (en) * | 2008-07-09 | 2008-11-12 | 北京航空航天大学 | Method for rapidly reinforcing color image based on Retinex theory |
| CN101340510A (en) * | 2008-08-07 | 2009-01-07 | 中兴通讯股份有限公司 | Method for video enhancement and apparatus thereof |
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2011
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004051569A1 (en) * | 2002-11-29 | 2004-06-17 | Uea Enterprises Limited | Image signal processing |
| CN1892697A (en) * | 2005-07-08 | 2007-01-10 | 杭州波导软件有限公司 | Colour-image reinforcing method |
| CN101303766A (en) * | 2008-07-09 | 2008-11-12 | 北京航空航天大学 | Method for rapidly reinforcing color image based on Retinex theory |
| CN101340510A (en) * | 2008-08-07 | 2009-01-07 | 中兴通讯股份有限公司 | Method for video enhancement and apparatus thereof |
Non-Patent Citations (1)
| Title |
|---|
| 文迪等: "基于DSP的Retinex实时视频图像处理系统设计", 《计算机与现代化》 * |
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Application publication date: 20120711 |