Readability Enhancement of Low Light Videos Based on Discrete Wavelet Transform

In this paper, we propose readability enhancement of low light videos based on discrete wavelet transform (DWT). Captured videos under the low light condition have a narrow dynamic range (low contrast) with a dark tone as well as are highly corrupted by noise. We achieve both contrast enhancement and noise reduction in low light videos using wavelet coefficients. First, we perform normalization to stretch a dynamic range of an image. Then, we decompose the image into high-pass and low-pass sub-bands using DWT. Next, we perform de-noising and weak edge enhancement in the high-pass sub-bands (LH, HL, HH) and contrast enhancement in the low-pass sub-band (LL). Finally, we conduct color correction to compensate for color distortions caused by contrast enhancement. Experimental results demonstrate that the proposed method outperforms state-of-the-art ones in contrast enhancement, noise reduction, and color reproduction in terms of both subjective and objective evaluations.