Final Project601410058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

• 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。

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

• 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

• introduce the additional constraint

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

• Now,

• We obtain

• 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

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

• Source exposure times (2, 1, 1/2, 1/4)

• Source exposure times (1/8, 1/16, 1/32, 1/64)

• Source exposure times (1/128, 1/256, 1/512, 1/1024)

• Output •藍色的部分為原本影像既有

programs

• UI load(讀取資料夾內的所有影像檔 ) start(顯示結果 )

demo

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