Brighten low-light image
[___] = imlocalbrighten(___,'AlphaBlend',TF)
brightens low-light areas in
specifies whether you want to preserve content of the input image in the output image.
imlocalbrighten alpha blends the
input image with the enhanced image to preserve brighter areas of the input image.
imlocalbrighten uses the estimate of darkness matrix,
D, to preserve content of the input image proportional to the amount
of light in each pixel. The parameter name can be abbreviated, and case does not
Brighten a low-light image using default parameters. View the original image and the lightened version of the image.
A = imread('lowlight_2.jpg'); B = imlocalbrighten(A); figure, imshowpair(A,B,'montage')
Brighten the low-light image again, this time specifying the amount of lightening to apply to the image. View the original image and this lightened version of the image.
A = imread('lowlight_2.jpg'); B2 = imlocalbrighten(A,0.8); figure, imshowpair(A,B2,'montage')
AlphaBlend option to preserve content from the original image in the lightened image. This time, view the lightened output image from the first example with the alpha blended output image. Compare the detail shown in the wall above arched entryway near the center of the image in the alpha-blended version with the original lightened image.
A = imread('lowlight_2.jpg'); Bblend = imlocalbrighten(A,'AlphaBlend',true); figure, imshowpair(B,Bblend,'montage')
Get the estimated darkness-per-pixel matrix return value. View the original image and the darkness estimate matrix.
A = imread('lowlight_2.jpg'); [~,D] = imlocalbrighten(A); figure, imshowpair(A,D,'montage')
A— Image to be brightened
Image to be brightened, specified as a real, nonsparse, grayscale image (M-by-N) or RGB image (M-by-N-by-3).
amount— How much to brighten the image
How much to brighten the image, specified as a numeric scalar in the range
[0 1]. When the value is
1 (the default),
imlocalbrighten brightens the low-light areas of
A as much as possible. When the value is
imlocalbrighten returns the input image unmodified.
B— Brightened image
Brightened image, returned as a grayscale or an RGB image, the same size and class
as the input image
D— Estimate of darkness of each pixel
Estimate of darkness of each pixel in the input image, returned as a numeric matrix.
D is the same size as the first two dimensions of the input image
and is of class
 Dong, X., G. Wang, Y. Pang, W. Li, J. Wen, W. Meng, and Y. Lu. "Fast efficient algorithm for enhancement of low lighting video." Proceedings of IEEE® International Conference on Multimedia and Expo (ICME). 2011, pp. 1–6.
 He, Kaiming. "Single Image Haze Removal Using Dark Channel Prior." Thesis, The Chinese University of Hong Kong, 2011.
 Dubok Park; Hyungjo Park; David K. Han; Hanseok Ko "Single Image Dehazing with Image Entropy and Information Fidelity." ICIP, 2014.