HDR圖像增強算法：PQ Curve &ReinHard

流程如下：

1. FFMPEG 提取16bit圖像
2. 運用EOTF將16bit圖像進行變換
3. 色調映射，imgTMO = ReinhardTMO(out);
4. 色彩校正，imgColor = ColorCorrection(imgTMO,1.2);
5. gamma校正，imgOut = GammaTMO(imgColor, 2.2, 0, 1);

%% EOTF linearization 
function C = transformEOTF(CV_full, isQuantify, nb)
% CV_full is the component¡¯s full range digital code value
% N: nonlinear Img
% L: linear img
% C: luminance cd/m2
if strcmp(isQuantify, 'Quantify')
    bits= nb;
    maxV = 2^ bits;
    N = CV_full ./ (maxV-1);
else 
    N = CV_full;
end
 
m1 = 2610/4096* 1/4; %0.1593017578125
m2 = 2523/4096*128;  %78.84375
c1 = 3424/4096;     %0.8359375=c3-c2+1
c2 = 2413/4096*32;  %18.851625
c3 = 2392/4096*32;  %18.6875
inv_m2 = 1/m2;
inv_m1 = 1/m1;
Npower = N.^ inv_m2;
tmp = 0*Npower;
numerator = max((Npower - c1), tmp);
denominator = c2 - c3 .* (Npower);
L = (numerator ./ denominator) .^ inv_m1;
 
C = 10000 * L;
% plot(N,L);
end

function imgOut = ColorCorrection(img, cc_s)
% 色彩校正
if(cc_s < 0.0)
    cc_s = 0.5;
end
L = lum(img);
imgOut = zeros(size(img));
 
for i=1:size(img, 3)
    imgOut(:,:,i) = ((img(:,:,i) ./ L).^cc_s) .* L;
end

function imgOut = GammaTMO(img, TMO_gamma, TMO_fstop, TMO_view)
% gamma 校正
% TMO_gamma = 2.2;
% TMO_fstop = 0.0;
invGamma = 1.0 / TMO_gamma;
exposure = 2.^TMO_fstop;
%clamping values out of the range [0.0,1.0]
imgOut = ClampImg((exposure .* img).^invGamma, 0, 1);

if(TMO_view)
    imshow(imgOut);
end

原始圖像

處理後圖像