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Real-Time Artifact-Free Image Upscaling

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Presentation on theme: "Real-Time Artifact-Free Image Upscaling"— Presentation transcript:

1 Real-Time Artifact-Free Image Upscaling
IEEE Transactions on image processing Vol. 20, No.10, October 2011 by Andrea Giachetti and Nicola Asuni Speaker : 吳惠仙 首頁須把論文出處,含發表期刊,發表年與作者清楚標示出來

2 Outline Introduction Related Works Proposed Scheme Experiment Results
What’s the problem about image upscaling? Related Works Polynomial interpolation Statistical Methods Edge-directed interpolation Proposed Scheme ICBI(Iterative Curvature Based Interpolation) CUDA Experiment Results Objective test and Subjective test Conclusions 論文報告大綱需有這幾個項目

3 What’s the problem about image upscaling?
Introduction What’s the problem about image upscaling? 一開始先把論文要解決的問題說清楚,盡可能用圖來解說 Sometimes we need to obtain a digital image to be represented on a large bitmap from original data, it should look like it had acquired with a sensor having the resolution of the upscaled image or at least, present a “natural” texture.

4 What’s the problem about image upscaling?
Introduction What’s the problem about image upscaling? 緊接著請把這個題目的挑戰性做個說明,盡可能用圖來解說 But we have a problem is, how to insert these unknown values to the high resolution image? The solution to the problem is often referred to also as “single image super-resolution” that allows to obtain an High Resolution image from its Low Resolution counterpart.

5 Polynomial interpolation
Related works 在Related Works簡要介紹解決此問題的相關研究,把其概念想法,優點與缺點說清楚 Polynomial interpolation The simplest interpolation based on linear filtering. Methods like: Nearest Neighbor interpolation, Bilinear, Bicubic… adv. : computationally efficient(Bicubic is not.) dis. : blur and jagged contours

6 Related works Statistical Methods 讓投影片有高可讀性, 盡可能用完整英文句子。 重點可以特別標示出來。 Some authors have tried to exploit pixel or texture statistics or database of example images to obtain good high resolution images. Methods like : Example-based learning single-image for super-resolution[2008] adv. : variety of natural textures and scales makes. dis. : need a sufficiently representative set of examples.

7 Edge-directed Interpolation
Related works Edge-directed Interpolation These methods try to improve the accuracy of the interpolation characterizing the edge features in a larger region. They aims at interpolating along edges rather than across them to prevent blurring. Methods like: NEDI(New Edge-Directed Interpolation)[2001] iNEDI(improved NEDI)[2008] adv. : have good results for natural images. dis.: NEDI and iNEDI have high computationally. 介紹相關研究時,盡可能按照其發表時間依序介紹

8 Edge-directed Interpolation
Related works Edge-directed Interpolation 藉由相關研究的探討,來點出所提演算法想要真正解決的問題點 NEDI estimates local covariance coefficients from a low-resolution image Use these covariance estimates to adapt the interpolation at a higher resolution based on the geometric duality between the low-resolution covariance and the high-resolution covariance. Note:NEDI and iNEDI still create evident artifacts due to the effect of edge discontinuities. vs.

9 two-step hole filling from NEDI
Proposed Scheme-ICBI two-step hole filling from NEDI 介紹所提演算法時,應先描述其主要想法,盡可能用圖來解說 in the first one, pixels indexed (Fig1.A) are computed as a weighted average of the four diagonal neighbors . in the second the remaining holes(Fig1.B) are filled with the same rule(in horizontal and vertical directions).

10 FBCI(Fast Curvature-Based Interpolation)
Proposed Scheme-ICBI FBCI(Fast Curvature-Based Interpolation) average of the two neighbors in the direction of lowest second order derivative using 8 valued neighboring pixels, then assigning to the point(2i+1, 2j+1) in the direction where the derivative is lower.

11 Proposed Scheme-ICBI Energy Function Define an energy component at each new pixel location that is locally minimized when the second order derivative are constant. Then modified the interpolated pixel values in an iterative greedy procedure trying to minimize the global energy. U(2i+1,2j+1) : final value Uc(2i+1,2j+1) : curvature smoothing Ue(2i+1,2j+1) : curvature enhancement Ui(2i+1,2j+1) : isophote smoothing a, b, c, T : chosen by trial and error in order to maximize the perceived and measured image quality. 數學式要簡單扼要,符號要定義清楚,數學式的物理意義要解說清楚

12 Proposed Scheme-ICBI Energy Function

13 .. Contributions 實驗結果前可以先總結一下論文的主要貢獻 A review of constant covariance constraint used in the NEDI method with the proof of the relationship of that constraint with the second order derivatives smoothness used in our algorithm. ICBI based on the iterative smoothing of second order derivatives. The algorithm is initialized using a simple filling rule based on second order derivatives(FCBI) that can be considered an edge directed interpolation algorithm too. ICBI method demonstrated to be an improvement over previous ones, providing a reasonable reconstruction of the missing information and requiring considerably less computational power than other methods achieving good scores. A GPU implementation of the ICBI method able to enlarge images at interactive frame rates.

14 Experiment Results Objective Test 可以把實驗結果中要注意的地方清楚標示出來

15 Experiment Results Objective Test Dell XPS M1210 laptop with Intel Core2 Duo T GHz CPU. PSNR Computation Times 把實驗條件與目的,評量結果的量化指標等說明清楚

16 Experiment Results Subjective Test There are12 people to compare images, in order to select the best average “perceived quality”.

17 CUDA implementation for real-time
Experiment Results CUDA implementation for real-time GPUCard : nVidia GeForce GTX280 Language : Matlab and C 4x enlargement of 128x128 images in 16.2ms on average, corresponding to a ideal frame rate of 62 frames per second.  2x enlargement of 256x256 images in 12.3ms on average. CUDA is a parallel computing architecture developed by Nvidia. Nvidia GPUs that is accessible to software developers through variants of industry standard programming languages.  最好讓大家可以由所提演算法的主要想法,就能理解推論實驗結果的正確必然性

18 Conclusion Conclusion ICBI based on a greedy minimization of an energy function defined at the interpolated pixel locations. ICBI is not computationally expensive like example-based methods or NEDI and is easily parallelizable. Noise image? 最後為論文做個總結,簡述其所解決的問題與主要貢獻。最好能提一下所提方法的限制與可能的問題

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