Rapid low-illumination image enhancing method based on improved dark channel prior

A dark channel prior and dark channel image technology, applied in the field of fast low-light image enhancement, can solve the problems of poor processing effect, poor real-time performance, and inapplicability of light-colored areas, so as to enhance brightness and contrast, and improve image and video quality Effect

Active Publication Date: 2013-10-09
HARBIN INST OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] The present invention aims to solve the problems of large amount of calculation, poor real-time performance, easy blurring of edge information, dark channel prior method is not applicable to light-colored areas, and the original low-illuminan

Method used

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  • Rapid low-illumination image enhancing method based on improved dark channel prior
  • Rapid low-illumination image enhancing method based on improved dark channel prior
  • Rapid low-illumination image enhancing method based on improved dark channel prior

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Example Embodiment

[0030] Specific implementation manner 1: The fast low-illumination image enhancement method with improved dark channel prior of this embodiment includes the following steps:

[0031] Step 1: Input image I(i,j), get the size of image I(i,j) as w*h, and the RGB three-channel image IR(i,j), IG(i) of image I(i,j) ,j), IB(i,j), where w is the width of the image, h is the height of the image, IR(i,j), IG(i,j), IB(i,j) are the red and green of the image respectively Blue three-channel image;

[0032] Step 2: For each pixel of the image I(i,j), find the minimum value of the grayscale of the RGB three-channel image IR(i,j), IG(i,j), IB(i,j), Recorded as Imin (i, j), the calculation formula is as follows:

[0033] I min ( i , j ) = min c A { R , G , B , } ( I c ( x , y ) )

[0034] For each pixel in the image Imin(i,j), the minimum filtering process is performed, and the calculation formula of D(i,j) is obtained as foll...

Example Embodiment

[0089] Specific implementation manner 2: This implementation manner is different from the specific implementation manner in that the method for judging light-colored areas in an image in step four is:

[0090] A. The absolute value of the difference between the gray levels of the RGB three channels is less than 5;

[0091] B. The dark channel gray value corresponding to the pixel is greater than the mean dark channel gray value meangray;

[0092] C. The gray value of the dark channel corresponding to the pixel is less than half maxgray / 2 of the maximum dark channel gray value. Other steps and parameters are the same as in the first embodiment.

Example Embodiment

[0093] Specific embodiment three: This embodiment is different from specific embodiment one or two in that the steps of performing linear smoothing on the modified dark channel image in step five are:

[0094] a. Determine the size of the window used to smooth the dark channel image according to the size of the image I(i, j);

[0095] b. Calculate linear approximation parameters for each window a k And b k ;

[0096] c. Approximate parameters a for all windows containing each pixel k And b k Perform averaging to obtain approximate parameters after averaging;

[0097] d. Linearly approximate the image with the averaged approximate parameters;

[0098] Among them, the linear smoothing formula for the modified dark channel image is: for the window W centered at point k and the size is M*M k All pixels in x: E x =a k D x +b k , M=N-2, N is the size of the window used when obtaining the dark channel image, where D x Is the modified dark channel image, E x Is the smoothed result, a k And b k ...

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Abstract

The invention discloses a rapid low-illumination image enhancing method based on improved dark channel prior, which relates to a rapid low-illumination image enhancing method, and is used for solving the problems of a conventional low-illumination image enhancing method that the calculation amount is large, that the real-time performance is poor, that boundary information is easy to be fuzzed, that a dark channel prior method is not applicable to light color areas, and that an original low illumination enhancing method based on dark channel prior has a poor processing effect on light reflecting and non-uniform illumination areas. The method comprises the following steps of: firstly, inputting an image I (i, j); secondly, calculating an initial dark channel image D (i, j) of the image I (i, j); thirdly, calculating an average pixel dark channel gray value and a maximum dark channel gray value of the D (i, j); fourthly, judging the light color area of the image I (i, j); fifthly, carrying out linear smoothing on the modified dark channel image; sixthly, acquiring a histogram of the smoothed illumination intensity image, and confirming standard illumination intensity; and seventhly, recovering the image. The method belongs to the field of image and video processing.

Description

technical field [0001] The invention relates to a fast low-illuminance image enhancement method, which belongs to the field of image and video processing. Background technique [0002] Under cloudy and rainy days and low light conditions at night, the overall gray value and image contrast of the obtained image are reduced due to the poor lighting conditions of the surrounding environment when collecting images and videos and the low illuminance, which leads to the aggravation of the noise of the image or video equipment. Image quality and visibility are severely degraded, making it difficult to identify regions of interest. In addition, some areas in the target image are difficult to extract the information of this part of the image due to the lack of illumination or the fusion of the shadow area and the background. Therefore, to enhance the image brightness and contrast under low illumination and improve the overall image quality, it can be used in civilian intelligent vid...

Claims

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Application Information

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IPC IPC(8): G06T5/00G06T5/40
Inventor 遆晓光曲悠杨张彬彬
Owner HARBIN INST OF TECH
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