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ECE 533 Project. - Removing Blocking artifacts and Ringing artifacts in the Compressed Image Member : Park, Byung Kwan (single member). Ⅰ. Introduction …. Two Artifacts due to Transform-Based compression … - 1. Blocking Artifacts : direct result of block processing

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Ece 533 project

ECE 533 Project

- Removing Blocking artifacts and Ringing artifacts

in the Compressed Image

Member : Park, Byung Kwan (single member)


Introduction
Ⅰ. Introduction

  • Two Artifacts due to Transform-Based compression…

    - 1. Blocking Artifacts : direct result of block processing

    - 2. Ringing Artifacts : appearing along

    the edges like sharp oscillation or

    ghost shadows


  • How to solve these two artifacts

    - Using the theory of projections onto convex sets (POCS) method

    - Line processing along the horizontal, vertical, and two diagonal directions

    - Setting new smoothness constraint sets


Approach
Ⅱ. Approach

  • Constraint Sets (For blocking Artifacts)

    - Due to quantized block discrete-cosine transform (BDCT)

    - To suppress blocking artifacts along the vertical boundaries

    - Considering blocking artifacts severer along the edge


  • Constraint Sets ( For ringing artifacts )

    - Ringing artifacts occur around the edges, not the edge pixels

    - Leaving the edge and processing neighboring pixels

    - Arising the necessity of line processing to detect edges

    - Four directional (horizontal, vertical and two diagonal ) smoothness constraint sets based on each directional line processing


  • For horizontal direction

    Where lv(i,j) = 1 , if these exits an edge between the pixels (i,j) and (i,j+1)

    0 , otherwise

    - Making Vh(f) small enforce smoothness along the horizontal direction in an image

    - New constraint set

    - Other directions are also similar to horizontal direction


Methods
Ⅲ. Methods

  • Divide-And-Conquer method for smoothness constraint sets

    - Projections to four directional sets have numerical difficulty

    - Divide the image into blocks to calculate projections

    - Special attentions to window function in the smoothness sets also gives us the opportunity to remove the blocking artifacts




Implementation parameters
Ⅳ. Implementation… ( Parameters )

  • Line-Processing

    - Using statistical threshold

  • Visibility Weights

    - For removing blocking artifacts and ringing artifacts at the same time

  • Smoothness Bounds


Results

Original Image

Compress JPEG Image

Ⅴ. Results…




Discussion
Ⅵ. Discussion

  • One parameter ramda in projection Eq.

    • - It is the solution of non-linear Eq.

    • - I just input various values

  • Four directional Projections

    • - Just two directional projections implemented

  • Ringing artifacts

    • - The still image doesn’t show many ringing artifacts


References
Ⅶ. References

  • - Galatsanos,

    Removal of compression artifacts using projections onto convex sets and line process modeling

    IEEE Trans. Image Processing, vol. 6, pp. 1345-1357, 1997

  • - S. Yang, Y. H. Hu, D. L. Tull, and T. Q. Nguyen,

    Maximum likelihood parameter estimation for image ringing artifact removal

    IEEE Trans. Circuits and Systems for Video Technology, vol. 11, 2001.


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