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Data-Driven Image Restoration

Anwar, Saeed

Description

Every day many images are taken by digital cameras, and people are demanding visually accurate and pleasing result. Noise and blur degrade images captured by modern cameras, and high-level vision tasks (such as segmentation, recognition, and tracking) require high-quality images. Therefore, image restoration specifically, image deblurring and image denoising is a critical preprocessing step. A fundamental problem in image deblurring is to recover...[Show more]

dc.contributor.authorAnwar, Saeed
dc.date.accessioned2018-10-24T23:34:09Z
dc.date.available2018-10-24T23:34:09Z
dc.identifier.otherb58076633
dc.identifier.urihttp://hdl.handle.net/1885/148622
dc.description.abstractEvery day many images are taken by digital cameras, and people are demanding visually accurate and pleasing result. Noise and blur degrade images captured by modern cameras, and high-level vision tasks (such as segmentation, recognition, and tracking) require high-quality images. Therefore, image restoration specifically, image deblurring and image denoising is a critical preprocessing step. A fundamental problem in image deblurring is to recover reliably distinct spatial frequencies that have been suppressed by the blur kernel. Existing image deblurring techniques often rely on generic image priors that only help recover part of the frequency spectrum, such as the frequencies near the high-end. To this end, we pose the following specific questions: (i) Does class-specific information offer an advantage over existing generic priors for image quality restoration? (ii) If a class-specific prior exists, how should it be encoded into a deblurring framework to recover attenuated image frequencies? Throughout this work, we devise a class-specific prior based on the band-pass filter responses and incorporate it into a deblurring strategy. Specifically, we show that the subspace of band-pass filtered images and their intensity distributions serve as useful priors for recovering image frequencies. Next, we present a novel image denoising algorithm that uses external, category specific image database. In contrast to existing noisy image restoration algorithms, our method selects clean image “support patches” similar to the noisy patch from an external database. We employ a content adaptive distribution model for each patch where we derive the parameters of the distribution from the support patches. Our objective function composed of a Gaussian fidelity term that imposes category specific information, and a low-rank term that encourages the similarity between the noisy and the support patches in a robust manner. Finally, we propose to learn a fully-convolutional network model that consists of a Chain of Identity Mapping Modules (CIMM) for image denoising. The CIMM structure possesses two distinctive features that are important for the noise removal task. Firstly, each residual unit employs identity mappings as the skip connections and receives pre-activated input to preserve the gradient magnitude propagated in both the forward and backward directions. Secondly, by utilizing dilated kernels for the convolution layers in the residual branch, each neuron in the last convolution layer of each module can observe the full receptive field of the first layer.
dc.language.isoen_AU
dc.subjectDeblurring
dc.subjectDenoising
dc.subjectClass-Specific
dc.subjectCategory-Specific
dc.subjectCNNs
dc.subjectConvolutional Neural Networks
dc.subjectObject Specific
dc.subjectObject deblurring
dc.subjectObject Denoising
dc.subjectPatch Similarity
dc.subjectFrequency bands
dc.titleData-Driven Image Restoration
dc.typeThesis (PhD)
local.contributor.supervisorPorikli, Fatih
local.contributor.supervisorcontactfatih.porikli@anu.edu.au
dcterms.valid2018
local.description.notesthe author deposited 25/10/2018
local.type.degreeDoctor of Philosophy (PhD)
dc.date.issued2018
local.contributor.affiliationCollege of Engineering and Computer Science, The Australian National University
local.identifier.doi10.25911/5d611ffe7c86e
local.identifier.proquestYes
local.mintdoimint
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