HVI: A New Color Space for Low-light Image Enhancement
Qingsen YanYixu FengCheng ZhangGuansong PangKangbiao ShiPeng WuWei DongJinqiu SunYanning Zhang
Proposes a dedicated Horizontal/Vertical-Intensity color space alongside a lightweight decoupling network to eliminate red and black noise artifacts commonly found in low-light image enhancement.
Capturing visual data in low-light environments often yields severe noise, poor brightness, and color distortion. While traditional computer vision methods operate in standard red-green-blue (sRGB) color spaces, they frequently suffer from color bias because luminance and chrominance are tightly coupled. Alternative approaches that decouple brightness by converting images to hue-saturation-value (HSV) color spaces resolve illumination problems but introduce severe red color discontinuities and dark region artifacts. The article introduces a novel color space termed Horizontal/Vertical-Intensity (HVI) alongside a dedicated dual-branch neural network, the Color and Intensity Decoupling Network (CIDNet), to deliver robust, artifact-free low-light image enhancement.
The research demonstrates how the proposed HVI representation overcomes HSV's limitations by applying polarization to the hue axis to eliminate red discontinuities and introducing an adaptive intensity collapse function to cluster and suppress noise in near-black regions. The paired CIDNet architecture independently processes chromatic information and scene brightness across dual branches, utilizing cross-attention mechanisms to exchange guidance between features. Evaluated across 10 benchmark datasets, CIDNet achieved top-tier visual and quantitative performance, achieving an optimal balance between quality and computational efficiency with only 1.88 million parameters and 7.57 GFLOPs of computational load. Furthermore, applying the HVI transformation as a plug-and-play pre-processing module to six external state-of-the-art models consistently improved their enhancement quality, increasing peak signal-to-noise ratios by up to 3.56 decibels.
These results indicate that adopting the HVI color space substantially reduces computational overhead and operational risk for real-world computer vision deployments in low-light scenarios, outperforming heavier diffusion-based models while running at a fraction of the processing time. Organizations building computer vision pipelines should consider integrating the HVI transform and CIDNet framework to improve low-light image quality efficiently. Future efforts should focus on deploying these lightweight models in live edge environments and conducting pilot tests across specialized sensor hardware.
- Paper: Deep Retinex Decomposition for Low-Light Enhancement, Chen Wei et al. (2018). This paper establishes the foundational LOL benchmark dataset and introduces deep Retinex decomposition for decoupling illumination and reflectance in low-light image enhancement.
- Paper: Zero-Reference Deep Curve Estimation for Low-Light Image Enhancement, Chunle Guo et al. (2020). This work demonstrates non-reference curve estimation and photometric adjustment across color channels, framing essential principles of dynamic range adjustment and color preservation.
- Paper: EnlightenGAN: Deep Light Enhancement Without Paired Supervision, Yifan Jiang et al. (2019). This study introduces illumination-guided attention mechanisms to handle uneven lighting and avoid over-enhancement in unpaired low-light restoration.
- Paper: Learning to See in the Dark, Chen Chen et al. (2018). This seminal paper characterizes extreme low-light sensor degradation and demonstrates the necessity of handling severe noise and color distortion during brightness amplification.
- Paper: SNR-Aware Low-light Image Enhancement, Xiaogang Xu et al. (2022). This paper addresses spatial noise and color fidelity challenges in low-light imaging through adaptive signal-to-noise ratio guidance.
- Paper: Degrade Is Upgrade: Learning Degradation for Low-Light Image Enhancement, Kui Jiang et al. (2022). This work formulates low-light relighting and color refinement as decoupled degradation estimation and content restoration steps.
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