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New Appearance Models for Natural Image Matting

New Appearance Models for Natural Image Matting. Dheeraj Singaraju , Carsten Rother , Christoph Rhemann Johns Hopkins University, Microsoft Research, Vienna University of Technology 2009 Reporter: Chia Hao Hsieh Date: 20100615. Outline. Introduction Matting Laplacian

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New Appearance Models for Natural Image Matting

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  1. New Appearance Models for Natural Image Matting DheerajSingaraju, CarstenRother, ChristophRhemann Johns Hopkins University, Microsoft Research, Vienna University of Technology 2009 Reporter: ChiaHao Hsieh Date: 20100615

  2. Outline • Introduction • Matting Laplacian • Line-point color model • Results • Conclusions

  3. Introduction • Image matting • Estimate a fore- and back-ground layer from a single image Composite image Ground truth alpha

  4. Introduction • Assume • Intensities of the two layers vary linearly in small image patches  can estimate alpha mattes in a closed form fashion • Can be improved by additionally learning global color models • Matting Laplacian • A cost function for image matting in matrix form • Overfit, If the colors of either layer are locally constant

  5. Matting Laplacian [6] • For a small patch Wi centered around pixel i • Exist colors (Fi1, Fi2, Bi1, Bi2) such that foreground and background colors (Fj, Bj) of each pixel j ∈ Wi • Exist affine functions to the patch Wi, and [6] A. Levin, D. Lischinski, and Y. Weiss. A closed-form solution to natural image matting.

  6. Matting Laplacian [6] • depends only on alpha mattes a and the affine functions v • The cost function can be reduced to dependent on the alpha mattes only • L: Matting Laplacian [6] A. Levin, D. Lischinski, and Y. Weiss. A closed-form solution to natural image matting.

  7. Limitation of the Matting Laplacian • Violation of the color-line model • For complex intensity variations, the color-line model is too simple • The Author is interested in • A much simpler case, such as being locally constant • Insufficient user interaction

  8. Line-Point Color Models • The colors of exactly one layer satisfy the color line model • The colors of the other layer are constant and satisfies a color point model

  9. Line-Point Color Models • No constant term for the alpha mattes • If the alpha mattes of the pixels in the patch are known, vi can be estimated • Apply the substitution

  10. Results • Rank-adaptive • Construct the cost function by analyzing the rank of each image patch • Rank-adaptive-mod • Treat all rank 2 patches as rank 3 • Levin • Algorithm of [6] • Levin-mod • Biasing the mattes towards 0 for those connected regions in the trimap which have only 1 as boundary conditions

  11. Results

  12. Results

  13. Conclusions • New appearance models for the problem of image matting • More compact • Outperform the traditional color line model • No need additional user interaction • Future work • Images that have complex intensity variation

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