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Low-Light Image Enhancement

This example shows how to brighten dark regions of an image while preventing oversaturation of bright regions.

Images can be highly degraded due to poor lighting conditions. These images can have low dynamic ranges with high noise levels that affect the overall performance of computer vision algorithms. To make computer vision algorithms robust in low-light conditions, use low-light image enhancement to improve the visibility of an image.

Read and display an RGB image captured in low light.

A = imread("lowlight_1.jpg");
title("Original Image")

Localized Brightening

Brighten the low-light image in proportion to the darkness of the local region, then display the brightened image. Dark regions brighten significantly. Bright regions also have a small increase in brightness, causing oversaturation. The image looks somewhat unnatural and is perhaps brightened too much.

B = imlocalbrighten(A);

Display a histogram of the pixel values for the original image and the brightened image. For the original image, the histogram is skewed towards darker pixel values. For the brightened image, the pixel values are more evenly distributed throughout the full range of pixel values.

title("Original Image")
title("Brightened Image")

Brighten the original low-light image again and specify a smaller brightening amount.

amt = 0.5;
B2 = imlocalbrighten(A,amt);

Display the brightened image. The image looks more natural. The dark regions of the image are enhanced, but the bright regions by the windows are still oversaturated.

title("Image with Less Brightening")

To reduce oversaturation of bright regions, apply alpha blending when brightening the image. The dark regions are brighter, and the bright pixels retain their original pixel values.

B3 = imlocalbrighten(A,amt,AlphaBlend=true);
title("Image with Alpha Blending")

For comparison, display the three enhanced images in a montage.

montage({B,B2,B3},Size=[1 3],BorderSize=5,BackgroundColor="w")


[1] 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.

See Also