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Xiaopeng Zhang, Terence Sim , Xiaoping Miao School of Computing National University of Singapore

Enhancing Photographs with Near Infrared Images. Xiaopeng Zhang, Terence Sim , Xiaoping Miao School of Computing National University of Singapore. CVPR 2008 Speaker ： PoHan Lee. Introduction NIR images Approach Experiments Conclusions. Outline. Introduction. Dual-camera system

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Xiaopeng Zhang, Terence Sim , Xiaoping Miao School of Computing National University of Singapore

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  1. Enhancing Photographs with Near Infrared Images Xiaopeng Zhang, Terence Sim, Xiaoping MiaoSchool of ComputingNational University of Singapore CVPR 2008 Speaker：PoHan Lee

  2. Introduction • NIR images • Approach • Experiments • Conclusions Outline

  3. Introduction

  4. Dual-camera system • converting to HSV color space and using V channel. NIR images

  5. Statistics of NIR images • Gradient magnitude (logarithm and normalized) • Haar wavelet coefficients in horizontal (H), vertical (V) and diagonal (D) directions. NIR images

  6. Computing the weighted region mask • 2. Transferring contrast • 3. Transferring texture Approach

  7. Approach

  8. 1. Computing the weighted region mask • -saturation and brightness Approach

  9. high brightness and low saturation, have higher weights

  10. 1. Computing the weighted region mask Approach

  11. 2. Transferring contrast • -three methods Approach

  12. 2. Transferring contrast • -based on histogram matching and gradient • Histogram matching: • 把某圖的 accumulated histogram變成 • 和目標圖形的accumulated histogram一樣 • -cumulative distribution function(CDF) Approach

  13. 2. Transferring contrast • -three methods • Method 1: Histogram Matching • [2] S. Bae, S. Paris, and F. Durand. Two-scale tone management • for photographic look. In SIGGRAPH, 2006. 2, 4, 5 • Method 2: Histogram Matching • with Gradient Constraint • Method 3: Gradient Magnitude Matching Approach

  14. Method 1: Histogram Matching Approach Problem : destroy illumination consistency

  15. Method 2: Histogram Matching • with Gradient Constraint Approach

  16. banding-effect

  17. Q:How to smooth brightness map of V and N ?

  18. Q:How to smooth brightness map of V and N ? • A:bilateral filtering :decompose images to • large-scale layer and detail layer

  19. Method 3: Gradient Magnitude Matching use Laplacian Curve to transfer Approach

  20. Method 3: Gradient Magnitude Matching Using improved Poisson solver reconstruct Approach

  21. 2. Transferring contrast Approach

  22. 3. Transferring texture horizontal (H), vertical (V) and diagonal (D) V V ′ and V D′ are obtained similarly Approach

  23. 3. Transferring texture Approach

  24. Approach

  25. Experiments

  26. Experiments

  27. Experiments

  28. 1.Uses NIR information to adjust the contrast of photographs adaptively, and to enrich texture details automatically with one single shot. 2. A threshold-free method to detect regions that require enhancement. 3. A study of the statistical properties of NIR images of natural scenes. Conclusions

  29. 1. First to make use of NIR information for photograph enhancement 2. Better perceptual quality on brightness contrast than tone-mapped Conclusions

  30. Thank you !!

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