Opencv— — Bias and Gain

// define head function
#ifndef PS_ALGORITHM_H_INCLUDED
#define PS_ALGORITHM_H_INCLUDED

#include <iostream>
#include <string>
#include "cv.h"
#include "highgui.h"
#include "cxmat.hpp"
#include "cxcore.hpp"
#include "math.h"

using namespace std;
using namespace cv;

void Show_Image(Mat&, const string &);

#endif // PS_ALGORITHM_H_INCLUDED

/*
Adjust bias and gain.
*/

#include "PS_Algorithm.h"

float Bias(float a, float b);
float Gain(float a, float b);

int main()
{
string  Image_name("4.jpg");
Mat Img=imread(Image_name.c_str());
Mat Img_out(Img.size(), CV_32FC3);

float gain_val = 0.75;   // 0-1
float bias_val = 0.25;   // 0-1

int width=Img.cols;
int height=Img.rows;

float val;

for (int y=0; y<height; y++)
{
for (int x=0; x<width; x++)
{

for (int k=0; k<3; k++)
{

val=(float)Img.at<Vec3b>(y, x)[k]/255;

val=Gain(val, gain_val);

Img_out.at<Vec3f>(y, x)[k]=Bias(val, bias_val);

}

}

}

Show_Image(Img_out, "New_img");

cout<<"All is well."<<endl;

waitKey();
}

float Bias(float a, float b)
{
float y;

a=pow(a, log(b)/log(0.5));

y=a/((1.0f/b-2)*(1.0f-a)+1);

return y;

}

float Gain(float a, float b)
{
/*
float p = log(1.0 - b) / log(0.5);

if (a < .001)
return 0.0f;
else if (a > .999)
return 1.0f;
if (a < 0.5)
return pow(2 * a, p) / 2;
else
return 1.0f - pow(2 * (1. - a), p) / 2;
*/

float c = (1.0f/b-2.0f) * (1.0f-2.0f*a);
if (a < 0.5)
return a/(c+1.0f);
else
return (c-a)/(c-1.0f);

}

// define the show image
#include "PS_Algorithm.h"
#include <iostream>
#include <string>

using namespace std;
using namespace cv;

void Show_Image(Mat& Image, const string& str)
{
namedWindow(str.c_str(),CV_WINDOW_AUTOSIZE);
imshow(str.c_str(), Image);

}