PS 图像调整— — gain and bias

clc;
clear all;
close all;

addpath('E:\PhotoShop Algortihm\Image Processing\PS Algorithm');

Image=imread('4.jpg');
Image=double(Image)/255;

% imshow(Image)
% set the gain value 0-1
% set the bias value 0-1

gain=0.5;
bias=0.25;

% adjust the gain
p=log(1-gain)/log(0.5);

sz=size(Image);

T1=Image(:);

T1(T1<0.001)=0;
T1(T1>0.999)=1.0;

ind_1=find(T1>0.001);
ind_2=ind_1(find(T1(ind_1)<0.5));
ind_3=find(T1>0.5);
ind_4=ind_3(find(T1(ind_3)<0.999));

T1(ind_2)=(2*T1(ind_2)).^p/2;
T1(ind_4)=1-(2*(1-T1(ind_4))).^p/2;

cc=(1.0/gain-2)*(1.0-2*T1);

ind_5=find(T1<0.5);
ind_6=find(T1>0.5);

T1(ind_5)=T1(ind_5)./(cc(ind_5)+1);
T1(ind_6)=(cc(ind_6)-T1(ind_6))./(cc(ind_6)-1.0);

% adjust the bias

T1=T1.^(log(bias)/log(0.5));
T1=T1./((1.0/bias-2)*(1.0-T1)+1);

Image_new=reshape(T1, [sz(1) sz(2) sz(3)]);

figure;
imshow(Image_new);
imwrite(Image_new, 'out.jpg');