http://www.dagstuhl.de/16462

November 13 – 18 , 2016, Dagstuhl Seminar 16462

Inpainting-Based Image Compression

Organizers

Christine Guillemot (INRIA – Rennes, FR)
Gerlind Plonka-Hoch (Universität Göttingen, DE)
Thomas Pock (TU Graz, AT)
Joachim Weickert (Universität des Saarlandes, DE)

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Documents

Dagstuhl Report, Volume 6, Issue 11 Dagstuhl Report
Aims & Scope
List of Participants
Shared Documents

Summary

Since the amount of visual data is rapidly increasing, there is a high demand for powerful methods for compressing digital images. A well-known example is the lossy JPEG standard that is based on the discrete cosine transform. Unfortunately its quality deteriorates substantially for high compression rates, such that better alternatives are needed.

The goal of this seminar was to pursue a completely different strategy than traditional, transform-based codecs (coders and decoders): We studied approaches that rely on so-called inpainting methods. They store only a small, carefully selected subset of the image data. In the decoding phase, the missing data is reconstructed by interpolation with partial differential equations (PDEs) or by copying information from patches in other image regions. Such codecs allow a very intuitive interpretation, and first experiments show their advantages for high compression rates where they can beat even advanced transform-based methods.

However, inpainting-based codecs are still in an early stage and require to solve a number of challenging fundamental problems, in particular:

  • Which data gives the best reconstruction?
  • What are the optimal inpainting operators?
  • How should the selected data be encoded and decoded?
  • What are the most efficient algorithms for real-time applications?

These problems are highly interrelated. Moreover, they require interdisciplinary expertise from various fields such as image inpainting, data compression and coding, approximation theory, and optimisation. To design these codecs in an optimal way, one must also understand their connections to related areas such as sparsity and compressed sensing, harmonic analysis, scattered data approximation with radial basis functions, and subdivision strategies.

Our seminar constituted the first symposium on this topic. It brought together 29 researchers from 11 countries, covering a broad range of expertise in the different fields mentioned above. Many of them have met for the first time, which resulted in a very fruitful interaction.

In order to have a good basis for joint discussions, first all participants introduced themselves and briefly described their background and interests. Then the seminar proceeded with six tutorial talks (45 minutes plus 15 minutes discussion), given by the four organisers as well as by Simon Masnou and Nira Dyn. In this way all participants could acquire a general overview on the achievements and challenges of inpainting-based image compression and its various aspects such as coding, inpainting, convex optimisation, subdivision, and computational harmonic analysis.

Afterwards we decided to cluster the talks thematically into six sessions, each consisting of 3-4 talks (ca. 30 minutes plus 15 minutes discussion) and lasting half a day:

  1. Harmonic Analysis
    (talks by Gerlind Plonka-Hoch, Naoki Saito, and Hao-Min Zhou)
  2. Approximation Theory
    (talks by Martin Buhmann, Armin Iske, Nira Dyn, and Tomas Sauer)
  3. Inpainting
    (talks by Aurelien Bourquard, Carola-Bibiane Sch"onlieb, and Yann Gousseau)
  4. Compression
    (talks by Gene Cheung, Joan Serra Sagrista, and Claire Mantel)
  5. Optimisation of Data and Operators
    (talks by Zakaria Belhachmi, Laurent Hoeltgen, Peter Ochs, and Pascal Peter)
  6. Algorithms, Biological Vision, and Benchmarking
    (talks by Jalal Fadili, Johannes Ballé, and Sarah Andris)

These sessions triggered interesting discussions during the talks, in the breaks, and in the evening, and they allowed the different communities to learn many new things from each other.

Our program featured also an evening panel discussion on open research questions on the interface between image inpainting and image compression. It was a lively interaction between the five panel members and the audience, involving also controversial statements and views about the future of inpainting-based codecs.

The participants had a very positive impression of this seminar as an inspiring forum to bring together different fields. As a consequence, this symposium also created several new collaborations, e.g. regarding interpolation with radial basis functions, subdivision-based coding, and diffusion-based coding. There was a general consensus that it would be desirable to have another seminar on this topic in 2-3 years. Moreover, it is planned to compile a related monograph which will be the first in its field.

License
  Creative Commons BY 3.0 Unported license
  Joachim Weickert

Classification

  • Computer Graphics / Computer Vision
  • Multimedia
  • Optimization / Scheduling

Keywords

  • Inpainting
  • Lossy data compression
  • Image processing
  • Interpolation
  • Approximation
  • Partial differential equations (PDEs)
  • Optimisation
  • Sparsity
  • Radial basis functions

Book exhibition

Books from the participants of the current Seminar 

Book exhibition in the library, ground floor, during the seminar week.

Documentation

In the series Dagstuhl Reports each Dagstuhl Seminar and Dagstuhl Perspectives Workshop is documented. The seminar organizers, in cooperation with the collector, prepare a report that includes contributions from the participants' talks together with a summary of the seminar.

 

Download overview leaflet (PDF).

Publications

Furthermore, a comprehensive peer-reviewed collection of research papers can be published in the series Dagstuhl Follow-Ups.

Dagstuhl's Impact

Please inform us when a publication was published as a result from your seminar. These publications are listed in the category Dagstuhl's Impact and are presented on a special shelf on the ground floor of the library.

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