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Final Project. 601410058 黃啟承. High Dynamic Range. 使 真實世界場景的亮暗對比,正確呈現在影像上。 現今多使用不同曝光度 的影像來產生 HDR image 。. approach.

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Final project

Final Project

601410058

黃啟承


High dynamic range
High Dynamic Range

  • 使真實世界場景的亮暗對比,正確呈現在影像上。

  • 現今多使用不同曝光度的影像來產生HDRimage。


Approach
approach

  • Reference : Paul E. Debevec , Jitendra Malik, Recovering high dynamic range radiance maps from photographs, Proceedings of the 24th annual conference on Computer graphics and interactive techniques, p.369-378, August 1997

  • 這篇使用不同曝光量照片來恢復成像過程的response function,從已知response function可以將多張影像合成單一影像。


F ilm response recovery
film response recovery

  • film reciprocity equation

  • Zij where i is a spatial index over pixels and j indexes over exposure times ∆tj, E is the irradiance.

  • Assume ∫ is invertible, and taking the natural logarithm

  • ;

  • Define , so


Final project

  • recovering g only requires recovering the finite number of values that g(z) can take since the domain of Z.

  • minimize the following quadratic objective function

  • Zmin and Zmax be the least and greatest pixel values (integers), N be the number of pixel locations and P be the number of photographs

  • use


Final project

  • introduce the additional values that g(z) can take since the domain of constraint

  • introduce a weighting function w(z) to emphasize the smoothness and fitting terms toward the middle of the curve.

  • Now,


Final project

  • We obtain values that g(z) can take since the domain of

  • we reuse the weighting function in Equation 4 to give higher weight to exposures in which the pixel’s value is closer to the middle of the response function

  • Equation 4 :


Result
result values that g(z) can take since the domain of

  • Source exposure times (32, 16, 8, 4)


Final project

  • Source values that g(z) can take since the domain of exposure times (2, 1, 1/2, 1/4)


Final project

  • Source values that g(z) can take since the domain of exposure times (1/8, 1/16, 1/32, 1/64)


Final project

  • Source values that g(z) can take since the domain of exposure times (1/128, 1/256, 1/512, 1/1024)


Final project

  • Output values that g(z) can take since the domain of

  • 藍色的部分為原本影像既有


Programs
programs values that g(z) can take since the domain of

  • UI load(讀取資料夾內的所有影像檔) start(顯示結果)


Final project
demo values that g(z) can take since the domain of

連結

  • http://www.youtube.com/watch?v=UGI6sVl9F68&feature=youtu.be