demo_single_image.m

%% demo -- processing a single image
% Author: Mahmoud Afifi
% Copyright (c) 2020 Samsung Electronics Co., Ltd. All Rights Reserved
% Please cite our paper:
% Mahmoud Afifi,  Konstantinos G. Derpanis, Björn Ommer, and Michael S
% Brown. Learning Multi-Scale Photo Exposure Correction, In CVPR 2021.
%%

clear;
clc
close all;
addpath('bgu'); % for guided upsampling 
addpath('exFusion'); % for fusion post-processing (optional) -- this part was not used in our paper
modelName = fullfile('models','model.mat'); % model full file name
base_dir = 'example_images/'; % input image directory 
base_dir_out = 'results'; % output directory 
imageName = 'Floris van Lint-CC BY-NC 2.0.jpg';
vis = 1; % visualize input/result
device = 'gpu'; % use gpu? options are: 'gpu' or 'cpu'
pp = 0; % post-processing contrast adjustment -- this part was not included in our experiments in the paper
fusion = 0; % post-processing fusion between input and generated image -- this part was not included in our expereiments in the paper
L = 4; % number of sub-networks
if exist(base_dir_out,'dir') == 0
    mkdir(base_dir_out);
end
load(modelName);

disp('---------------------------------------------');
fprintf('processing image %s...\n',imageName);
disp('---------------------------------------------');
try
    I = im2double(imread(fullfile(base_dir,imageName)));
catch
    fprintf('Cannot read image %s!\n',imageName);
    return;
end

%% check image size
sz = size(I);
mxdim = max(sz);
inSz = 512;
if (mxdim > inSz) == 1
    S = [1.5, 1.5, 1.5, 1.05]; % scale vector -- tunable hyper-parameter
else
    S = [1,1,1,1];
end
I_ = I;
I = imresize(I,inSz/max(sz));
pad_factor = [inSz-size(I,1) inSz-size(I,2)];
I = padarray(I, pad_factor,'replicate','pre');
IMAGE = pre_process_img(I,L,S);
disp('Exposure correction...');
tic
if strcmpi(device,'gpu') == 1
    output = gather(extractdata(predict(net,gpuArray(dlarray(IMAGE,...
        'SSCB')))))/255;
else
    output = extractdata(predict(net,dlarray(IMAGE,'SSCB')))/255;
end
fprintf('Network processing time is %d seconds.\n',toc);

output = output(pad_factor(1)+1:end,pad_factor(2)+1:end,1:3);
I = I(pad_factor(1)+1:end,pad_factor(2)+1:end,:);


if (max(sz) > inSz) == 1
    disp('Upsampling...');
    tic
    output_s = double(imresize(output,[200,200]));
    I = double(imresize(I,[200,200]));
    results = computeBGU(I, rgb2luminance(I), output_s, [], ...
        I_, rgb2luminance(I_));
    output = results.result_fs;
    fprintf('Upsampling time: %f seconds.\n',toc);
else
    output = imresize(output,[sz(1) sz(2)]);
end


if fusion == 1
    disp('Fusion...');
    tic
    Out = zeros(size(output,1),size(output,2),size(output,3),2);
    Out(:,:,:,1) = I_;
    Out(:,:,:,2) = output;
    output = exposure_fusion(Out,[1 1 1]);
    fprintf('Fusion time: %f seconds.\n',toc);
end

if pp == 1
    output = histAdjust(output);
end
if vis == 1
    figure;
    subplot(1,2,1);imshow(I_);title('Input image');
    subplot(1,2,2);imshow(output);title('Result');
    linkaxes;
end

[~,name,ext] = fileparts(imageName);
imwrite(output,fullfile(base_dir_out,[name ext]));
fprintf('\n\n');