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CycleISP: Real Image Restoration via Improved Data Synthesis (CVPR 2020 -- Oral)

Syed Waqas Zamir, Aditya Arora, Salman Khan, Munawar Hayat, Fahad Shahbaz Khan, Ming-Hsuan Yang, and Ling Shao


Supplementary: pdf

Video Presentation:

Abstract: The availability of large-scale datasets has helped unleash the true potential of deep convolutional neural networks (CNNs). However, for the single-image denoising problem, capturing a real dataset is an unacceptably expensive and cumbersome procedure. Consequently, image denoising algorithms are mostly developed and evaluated on synthetic data that is usually generated with a widespread assumption of additive white Gaussian noise (AWGN). While the CNNs achieve impressive results on these synthetic datasets, they do not perform well when applied on real camera images, as reported in recent benchmark datasets. This is mainly because the AWGN is not adequate for modeling the real camera noise which is signal-dependent and heavily transformed by the camera imaging pipeline. In this paper, we present a framework that models camera imaging pipeline in forward and reverse directions. It allows us to produce any number of realistic image pairs for denoising both in RAW and sRGB spaces. By training a new image denoising network on realistic synthetic data, we achieve the state-of-the-art performance on real camera benchmark datasets. The parameters in our model are ~5 times lesser than the previous best method for RAW denoising. Furthermore, we demonstrate that the proposed framework generalizes beyond image denoising problem e.g., for color matching in stereoscopic cinema.

CycleISP for Synthesizing Data for Image Denoising

The proposed CycleISP framework allows converting sRGB images to RAW data, and then back to sRGB images. It has (a) RGB2RAW network branch, and (b) RAW2RGB network branch.

Overall Framework of CycleISP

Recursive Residual Group (RRG)

Proposed Denoising Network


The model is built in PyTorch 1.1.0 and tested on Ubuntu 16.04 environment (Python3.7, CUDA9.0, cuDNN7.5).

For installing, follow these intructions

sudo apt-get install cmake build-essential libjpeg-dev libpng-dev
conda create -n pytorch1 python=3.7
conda activate pytorch1
conda install pytorch=1.1 torchvision=0.3 cudatoolkit=9.0 -c pytorch
pip install matplotlib scikit-image yacs lycon natsort h5py tqdm

Data Synthesis using CycleISP

  • Download all the models and place them in ./pretrained_models/isp/
  • Download some sample images from the MIR-Flickr dataset and place them in ./datasets/some_sample_images/

Generating Data for RAW Denoising

The RGB2RAW network branch takes as input a clean sRGB image and converts it to a clean RAW image. The noise injection module adds shot and read noise of different levels to the (RAW) output of RGB2RAW network branch. Thereby, we can generate clean and its corresponding noisy image pairs {RAW_clean, RAW_noisy} from any sRGB image.

  • Run Demo

Generating Data for sRGB Denoising

Given a synthetic RAW noisy image as input, the RAW2RGB network branch maps it to a noisy sRGB image; hence we are able to generate an image pair {sRGB_clean, sRGB_noisy} for the sRGB denoising problem.

  • Run Demo


You can download, at once, the complete repository of CycleISP (including pre-trained models, datasets, results, etc) from this Google Drive link, or evaluate individual tasks with the following instructions:

Denoising RAW images of DND

  • Download the model and place it in ./pretrained_models/denoising/
  • Download RAW images of DND and place them in ./datasets/dnd/dnd_raw/
  • Run
python --save_images

Denoising RAW images of SIDD

  • Download the model and place it in ./pretrained_models/denoising/
  • Download RAW images of SIDD and place them in ./datasets/sidd/sidd_raw/
  • Run
python --save_images

Denoising sRGB images of DND

  • Download the model and place it in ./pretrained_models/denoising/
  • Download sRGB images of DND and place them in ./datasets/dnd/dnd_rgb/noisy/
  • Run
python --save_images

Denoising sRGB images of SIDD

  • Download the model and place it in ./pretrained_models/denoising/
  • Download sRGB images of SIDD and place them in ./datasets/sidd/sidd_rgb/
  • Run
python --save_images

Results on Real Image Datasets

Experiments are performed for denoising images in RAW and sRGB spaces. Results produced by CycleISP can be downloaded from Google Drive link.

Results for RAW Denoising

Results for sRGB Denoising


If you use CycleISP, please consider citing:

    title={CycleISP: Real Image Restoration via Improved Data Synthesis},
    author={Syed Waqas Zamir and Aditya Arora and Salman Khan and Munawar Hayat
            and Fahad Shahbaz Khan and Ming-Hsuan Yang and Ling Shao},


Should you have any question, please contact


Official repository for "CycleISP: Real Image Restoration via Improved Data Synthesis" (CVPR 2020--Oral)



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