Abstract

BackgroundDigital images are captured using sensors during the data acquisition phase, where they are often contaminated by noise (an undesired random signal). Such noise can also be produced during transmission or by poor-quality lossy image compression. Reducing the noise and enhancing the images are considered the central process to all other digital image processing tasks. The improvement in the performance of image denoising methods would contribute greatly on the results of other image processing techniques. Patch-based denoising methods recently have merged as the state-of-the-art denoising approaches for various additive noise levels. In this work, the use of the state-of-the-art patch-based denoising methods for additive noise reduction is investigated. Various types of image datasets are addressed to conduct this study.MethodsWe first explain the type of noise in digital images and discuss various image denoising approaches, with a focus on patch-based denoising methods. Then, we experimentally evaluate both quantitatively and qualitatively the patch-based denoising methods. The patch-based image denoising methods are analyzed in terms of quality and computational time.ResultsDespite the sophistication of patch-based image denoising approaches, most patch-based image denoising methods outperform the rest. Fast patch similarity measurements produce fast patch-based image denoising methods.ConclusionPatch-based image denoising approaches can effectively reduce noise and enhance images. Patch-based image denoising approach is the state-of-the-art image denoising approach.

Highlights

  • The noise level in digital images may vary from being almost imperceptible to being very noticeable

  • Xu et al [64] adapted the idea of patching from the NL-Means for filtering polarimetric synthetic aperture radar (POL-SAR) images; they use simultaneous sparse coding for transferring the patches into the frequency domain before assigning the weights

  • The weighted average is used for the Gaussian noise distribution in the NL-Means, but the probabilistic patch-based (PPB) filter applies smoothing based on the maximum likelihood estimator (MLE)

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Summary

Methods

We first explain the type of noise in digital images and discuss various image denoising approaches, with a focus on patch-based denoising methods. We experimentally evaluate both quantitatively and qualitatively the patch-based denoising methods. The patch-based image denoising methods are analyzed in terms of quality and computational time

Conclusion
Review
Algorithm used in the case of Gaussian noise
Dictionary learning
Sparse coding step:
Patch construction step:
Step 1: thresholding Grouping
Step two: Wiener filter coefficients Grouping
Results and discussions
Conclusions
Full Text
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