WDnCNN: ENHANCEMENT OF A CNN-BASED DENOISER BASED ON SPATIAL AND SPECTRAL ANALYSIS

This is the implementation of the following paper:

ENHANCEMENT OF A CNN-BASED DENOISER BASED ON SPATIAL AND SPECTRAL ANALYSIS

Rui Zhao, Daniel P.K. Lun and Kin-Man Lam

Abstract: Convolutional neural network (CNN)-based image denoising methods have been widely studied recently, because of their high-speed processing capability and good visual quality. However, most of the existing CNN-based denoisers learn the image prior from the spatial domain, and suffer from the problem of spatially variant noise, which limits their performance in real-world image denoising tasks. In this paper, we propose a discrete wavelet denoising CNN (WDnCNN), which restores images corrupted by various noise with a single model. Since most of the content or energy of natural images resides in the low-frequency spectrum, their transformed coefficients in the frequency domain are highly imbalanced. To address this issue, we present a band normalization module (BNM) to normalize the coefficients from different parts of the frequency spectrum. Moreover, we employ a band discriminative training (BDT) criterion to enhance the model regression. We evaluate the proposed WDnCNN, and compare it with other state-of-the-art denoisers. Experimental results show that WDnCNN achieves promising performance in both synthetic and real noise reduction, making it a potential solution to many practical image denoising applications.

arXiv: https://arxiv.org/abs/2006.15517

Dependencies

Python >= 3.6.5, Pytorch >= 0.4.1, and cuda-9.2.

Pretrained Models

Two pretrained WDnCNN models, WDnCNN_model_gray and WDnCNN_model_color, are used for evaluating the denoising performance on grayscale images and color images, respectively. Run demo.py to test the WDnCNN for both synthetic and real-world noise removal.

Network Architecture

Band Discriminative Training(BDT)

Please refer to the paper and the README.txt file.

Results

Grayscale AWGN Removal

Color AWGN Removal

Visual Results on Real-world Noisy Images

Noisy	CBM3D
FFDNet	Ours

Real-world Denoising Benchmark

We also evaluate our method on the 1,000 cropped real-world noisy images from Darmstadt Noise Dataset. You can find this benchmark at DND. For denoising the real-world noisy images in DND, we further fine tune our model on PolyU-Real-World-Noisy-Images-Dataset PRWNID. In the fine tuning, we adopt the sub-network for noisy level estimation in CBDNet, and jointly fine tune the sub-network with our WDnCNN.

You can find our results as WDnCNN+ on the DND official website. We achieve 38.87dB on sRGB images.

One PyTorch Implementation of CBDNet can be found at CBDNet_PyTorch.

Contact

If you have questions, problems with the code, or find a bug, please let us know. Contact Rui Zhao at rui.zhao16@alumni.imperial.ac.uk
Thank you!

Citation

@INPROCEEDINGS{8804295, 
    author={R. {Zhao} and K. {Lam} and D. P. K. {Lun}}, 
    booktitle={2019 IEEE International Conference on Image Processing (ICIP)}, 
    title={Enhancement of a CNN-Based Denoiser Based on Spatial and Spectral Analysis}, 
    year={2019}, 
    volume={}, 
    number={}, 
    pages={1124-1128}, 
    keywords={Image denoising;convolutional neural networks;spatial-spectral analysis;discrete wavelet transform}, 
    doi={10.1109/ICIP.2019.8804295}, 
    ISSN={2381-8549}, 
    month={Sep.},}