Ece 533 project
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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

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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


Ece 533 project

  • 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


Ece 533 project

  • 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


Ece 533 project

  • 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


Ece 533 project

  • For Projection onto Horizontal Constraint sets

    1) For each i = 1,2,…,N and for each j = 8b with b = 0,1,…,Nk

    Whereif lv(I,j+k)=1

    Otherwise

    2) For the rest of the pixels

    - Vertical case is similar to this case


Ece 533 project

  • For Projection onto Diagonal Constraint sets

    1) For(i,j)∈Dd with d=1,2,5,6,9,10...

    Whereif lp(i,j)=1

    Otherwise

    2) The rest of the image pixels unchanged


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…


Ece 533 project

  • Line-Processing


Ece 533 project

  • Compressed Image and Recovered Image


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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