Extracting Noise and Darkness: Low-Light Image Enhancement via Dual Prior Guidance

The complex entanglement between darkness and noise hinders the advance of low-light image enhancement. Most existing methods adopted lightening-then-denoising or embedded a special denoising module into enhancement network without specific noise knowledge as supervision to restore low-light images. However, they either fail to remove the amplified noise or blur the detail information. Against above drawbacks, we propose a novel dual prior guidance method for low-light image enhancement that relights darkness and suppresses noise simultaneously. Concretely, the main novelties of our proposed method are three-fold. Firstly, our formulation originates from a statistic observation that darkness can be disentangled into luminance channel, yet noise still exists each channel when low-light images are transformed from RGB space to YCbCr space. It inspires us to design an ingenious method, extracting noise and darkness, termed END, to enhance low-light images. Secondly, we propose a prior extraction network with prior composition module to extract luminance and noise priors from different channels. Thirdly, an image enhancement network deployed with prior guidance module is proposed to progressively lighten the darkness and remove noise. Extensive experiments on multiple benchmarks demonstrate that our proposed method achieves remarkable performance compared to other state-of-the-art low-light image enhancement methods. The source code and trained model can be found in https://github.com/WHK-Huake/END.