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  ---
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  language:
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  - en
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- license: mit
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  library_name: pytorch
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  pipeline_tag: image-to-image
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  tags:
@@ -45,104 +44,83 @@ model-index:
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  # Multinex: Lightweight Low-Light Image Enhancement via Multi-prior Retinex
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- **Multinex** is a lightweight **low-light image enhancement (LLIE)** model based on a **multi-prior Retinex** formulation. It is designed to improve **brightness, color fidelity, and structural detail** in dark images while remaining extremely compact and efficient.
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- Multinex combines:
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- - a **Retinex-guided residual enhancement formulation**
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- - **analytic luminance and reflectance prior stacks**
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- - a **dual-branch lightweight fusion network**
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-
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- This design allows the model to achieve strong perceptual enhancement quality and competitive paired-image restoration performance at a tiny parameter budget, including a lightweight version around **45K parameters** and an even smaller nano variant around **0.7K parameters**. The paper reports strong results on both enhancement and downstream detection benchmarks.
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-
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- **Keywords:** low-light image enhancement, LLIE, Retinex, image restoration, lightweight neural network, edge deployment, exposure correction, color correction, perceptual image enhancement, real-time enhancement.
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  ## Model Description
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- Many low-light image enhancement methods either:
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- - use large neural networks that are hard to deploy on-device, or
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- - operate in a single color space where illumination and color remain partially entangled.
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-
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- Multinex addresses this with a structured and lightweight design. Instead of learning a full reconstruction in a standard Retinex manner, it predicts an **enhancement delta** added to the input image. The correction is factorized into:
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- - a **luminance correction**
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- - a **reflectance correction**
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- The model also uses **analytic representation priors** to reduce the burden on the network. In particular:
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- - the **luminance guidance stack** provides illumination-oriented cues
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- - the **reflectance guidance stack** provides chromatic and color-structure cues
 
 
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- This makes the model especially attractive for:
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- - mobile or embedded deployment
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- - lightweight computer vision pipelines
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- - preprocessing for downstream tasks such as object detection in dark scenes
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  ## Why Multinex?
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- Multinex is useful when you need a **small and efficient low-light enhancement model** without giving up physical interpretability.
 
 
 
 
 
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  ### Main advantages
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- - **Lightweight**: designed for very low parameter counts
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- - **Retinex-inspired**: uses luminance/reflectance structure as a prior
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- - **Analytic priors**: leverages hand-crafted luminance and chrominance descriptors
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- - **Strong perceptual quality**: especially strong on no-reference perceptual metrics
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- - **Practical utility**: enhancement can improve downstream visual tasks in low light
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- ## Architecture Overview
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- Multinex enhances an RGB input image through a residual Retinex-based formulation:
 
 
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- \[
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- \hat{\mathbf{I}} = \mathbf{I} + \Delta_{\mathbf{I}} = \mathbf{I} + \Delta_L \odot \Delta_R
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- \]
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- where:
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- - \(\mathbf{I}\) is the low-light input image
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- - \(\hat{\mathbf{I}}\) is the enhanced image
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- - \(\Delta_L\) is the learned luminance correction
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- - \(\Delta_R\) is the learned reflectance correction
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- Instead of learning directly from raw RGB alone, Multinex constructs two analytic prior stacks:
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- - **Luminance stack** for brightness-related structure
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- - **Reflectance stack** for color and chromatic structure
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-
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- These stacks are processed by lightweight fusion modules to produce the correction terms.
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  ## Prior Stacks
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- A key idea in Multinex is that **the network should not need to rediscover useful image priors from scratch**.
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  ### Luminance guidance stack
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- The paper uses a luminance stack built from multiple analytic luminance descriptors, including variants such as:
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- - Rec.709 luminance
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- - max-based luminance
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- - lightness-based luminance
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- - L2-based luminance
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  ### Reflectance guidance stack
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- The reflectance stack uses complementary chromatic descriptors, including:
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- - \(C_b, C_r\)
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- - normalized chromaticities \(r, g\)
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- - saturation \(S\)
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- The supplementary further motivates these choices with **Linear Reconstruction Analysis (LRA)** and descriptor-complementarity analysis.
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  ## Intended Uses
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  ### Direct use
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  - Enhance dark photos
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- - Improve brightness and color visibility in low-light scenes
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- - Preprocess images before downstream computer vision tasks
 
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  ### Downstream use
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- - Machine Vision
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  - Low-light object detection
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- - Surveillance and nighttime vision preprocessing
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- - Embedded or edge imaging systems
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  - Mobile photography enhancement
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- - Robotics and autonomous perception in dim environments
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- ## Training Data
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- The paper evaluates on common low-light image enhancement benchmarks, including:
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  - **LOL-v1**
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  - **LOL-v2-real**
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  - **LOL-v2-syn**
@@ -152,18 +130,17 @@ The paper evaluates on common low-light image enhancement benchmarks, including:
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  - **NPE**
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  - **ExDark** for downstream detection evaluation
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- Please check the paper and codebase for the exact training split, preprocessing, and evaluation protocol used for each released checkpoint.
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  ## Performance
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  The paper reports that Multinex:
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- - outperforms prior lightweight and micro models in several settings
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- - achieves strong no-reference perceptual performance
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- - remains competitive relative to much larger methods
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- - improves downstream object detection performance in low-light conditions
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- ### Example reported paired restoration results
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- For the lightweight Multinex model, the paper reports:
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  | Dataset | PSNR | SSIM | LPIPS |
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  |---|---:|---:|---:|
@@ -171,14 +148,29 @@ For the lightweight Multinex model, the paper reports:
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  | LOL-v2-real | 23.04 | 0.860 | 0.178 |
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  | LOL-v2-syn | 25.04 | 0.930 | 0.068 |
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- ### Example reported no-reference results
 
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  | Metric | Mean |
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  |---|---:|
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  | NIQE ↓ | 3.64 |
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  | BRISQUE ↓ | 15.89 |
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  ### Efficiency
 
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  | Variant | Parameters | GFLOPs |
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  |---|---:|---:|
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  | Multinex | 0.0447M | 2.50 |
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  | Multinex-Nano | 0.0007M | very low |
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
  ---
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  language:
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  - en
 
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  library_name: pytorch
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  pipeline_tag: image-to-image
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  tags:
 
44
 
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  # Multinex: Lightweight Low-Light Image Enhancement via Multi-prior Retinex
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+ **Multinex** is a lightweight model for **low-light image enhancement**. It is designed to brighten dark images, recover clearer colors, and improve visible detail while staying very small and efficient.
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+ Multinex is built around a simple idea: instead of relying only on raw RGB input, it uses multiple useful image cues related to brightness and color, then combines them through a compact network. This helps it perform strongly even at a very small model size.
 
 
 
 
 
 
 
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  ## Model Description
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+ Many low-light enhancement methods are either large and expensive to run, or they struggle to separate brightness changes from color correction cleanly.
 
 
 
 
 
 
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+ Multinex addresses this with a lightweight and structured design. It uses:
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+ - a brightness-oriented branch
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+ - a color-oriented branch
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+ - compact fusion modules
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+ - carefully chosen analytic image priors
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+ These priors give the model a stronger starting point, so it does not need to learn everything from scratch.
 
 
 
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  ## Why Multinex?
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+ Multinex is useful when you want:
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+ - strong low-light enhancement
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+ - a small and efficient model
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+ - better brightness and color recovery
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+ - a method suitable for edge or real-time use
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+ - a practical preprocessing step for downstream vision tasks
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  ### Main advantages
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+ - **Lightweight**: very small compared to many recent methods
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+ - **Efficient**: suitable for resource-constrained settings
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+ - **Structured**: uses separate cues for brightness and color
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+ - **Practical**: useful both for visual enhancement and downstream tasks
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+ - **Robust**: performs well across both reference and no-reference benchmarks
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+ ## How It Works
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+ Multinex takes a dark RGB image and improves it using two types of guidance:
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+ - **luminance guidance**, which helps with brightness
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+ - **reflectance guidance**, which helps with color and appearance
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+ These two forms of guidance are processed by a lightweight network and combined into the final enhanced image.
 
 
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+ In simple terms, Multinex tries to answer two questions:
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+ - how should this image be brightened?
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+ - how should its colors and details be corrected?
 
 
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+ By handling these separately, the model can enhance low-light images more effectively.
 
 
 
 
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  ## Prior Stacks
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+ A key part of Multinex is its use of **prior stacks**.
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  ### Luminance guidance stack
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+ This stack provides different views of image brightness. It helps the model understand where the image is dark, how light is distributed, and how brightness should be adjusted.
 
 
 
 
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  ### Reflectance guidance stack
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+ This stack provides different views of image color and chromatic structure. It helps the model better recover color, preserve regions, and reduce unwanted artifacts.
 
 
 
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+ Together, these stacks give the model a richer and more stable representation of the image.
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  ## Intended Uses
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  ### Direct use
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  - Enhance dark photos
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+ - Improve brightness and color visibility
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+ - Recover clearer low-light images
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+ - Preprocess images before other vision tasks
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  ### Downstream use
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+ - Machine vision
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  - Low-light object detection
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+ - Surveillance and nighttime imaging
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+ - Embedded and edge systems
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  - Mobile photography enhancement
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+ - Robotics in dim environments
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+ ## Training and Evaluation Data
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+ Multinex is evaluated on common low-light image enhancement benchmarks, including:
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  - **LOL-v1**
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  - **LOL-v2-real**
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  - **LOL-v2-syn**
 
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  - **NPE**
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  - **ExDark** for downstream detection evaluation
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+ Please refer to the paper and code for exact training details and evaluation settings.
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  ## Performance
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  The paper reports that Multinex:
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+ - outperforms earlier lightweight and micro models in several settings
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+ - achieves strong no-reference perceptual quality
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+ - remains competitive with much larger methods
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+ - improves downstream object detection performance in low-light scenes
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+ ### Example paired restoration results
 
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  | Dataset | PSNR | SSIM | LPIPS |
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  |---|---:|---:|---:|
 
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  | LOL-v2-real | 23.04 | 0.860 | 0.178 |
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  | LOL-v2-syn | 25.04 | 0.930 | 0.068 |
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+ ### Example no-reference results
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+
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  | Metric | Mean |
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  |---|---:|
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  | NIQE ↓ | 3.64 |
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  | BRISQUE ↓ | 15.89 |
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  ### Efficiency
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+
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  | Variant | Parameters | GFLOPs |
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  |---|---:|---:|
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  | Multinex | 0.0447M | 2.50 |
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  | Multinex-Nano | 0.0007M | very low |
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+
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+
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+ ## Citation
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+
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+ If you use Multinex in your work, please cite the paper.
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+
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+ ```bibtex
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+ @inproceedings{multinex2026,
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+ title = {Multinex: Lightweight Low-light Image Enhancement via Multi-prior Retinex},
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+ author = {Alexandru Brateanu and Tingting Mu and Codruta O. Ancuti and Cosmin Ancuti},
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+ booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
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+ year = {2026}
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+ }