1

I would like to weigh values of luminance.

Example: I have a vector of luminance values:

vector <int> lum {50,100,150,200,250);

I have a vector of coefficients:

vector <float> coef {5.1 , 2.55 , 1.7 , 1.275, 1.02 }

I create an empty image:

Mat1 m(15):

So, my first value of luminance is 50 (lum[0]=50) and I want it to be applied on the 5.1 (coef[0]=5.1) first pixel of my matrix. To do that, I need to weight the 6th pixel with the first and the second value of luminance. In my case, the luminance of my 6th pixel will be 95 because (0.1*50)+ (0.9*100)=95

At the moment, for the second coefficient (coef[1]=2.55), I have used 0.9 on 2.55 for the previous calcul. It remains 1,65 on this coefficient so the 7th pixel will have 100 of luminance and the 8th will have (0.65*100)+ (0.35*150) = 117,5.

And so on...

Actually I have this:

//Blibliothèque Opencv
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui/highgui.hpp"
// cpp include
#include <iostream>
#include <cmath>
#include <math.h>
#include <string.h>
#include <vector>
#include <opencv2/opencv.hpp>

#define MPI 3.14159265358979323846264338327950288419716939937510
#define RAD2DEG (180./MPI)

using namespace cv;
using namespace std;


vector <int> lum{ 50, 100, 150, 200, 250 };
vector <float> coef (5,0);
vector <int> newv(15, 0);
float pixelRef = 255, angle = 0, coeff = 0;


int main()
{


    for (int n = 0; n < lum.size(); ++n)
    {
        //get angle
        angle = ((acos(lum[n] / pixelRef)));
        cout << "angle :" << angle*RAD2DEG << endl;
        // get coefficient
        coef [n] = (1 / (cos(angle)));
        cout << "coeff :" << coef [n] << endl;
        // try to weighted my pixels
        newv[n] = (coef*lum[n]) + ((1 - coeff)*lum[n + 1]);
    }
    return 0;
}
double-beep
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Guillaume Andreani
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  • Have you tried anything so far? Why the image has exactly 15 elements? – Miki Jan 09 '16 at 16:33
  • Not really, I have type some code but it does not work. 15 is just an example, maybe I should have use a vector. – Guillaume Andreani Jan 09 '16 at 16:39
  • Please put your code into the question. While we are here to help, it's nice to see that you actually tried something instead of just requiring others to write code for you. – Miki Jan 09 '16 at 16:40
  • Is this the sequence you're looking for? `50, 50, 50, 50, 50, 95, 100, 117.5, 150, 182.5, 218.75` – Miki Jan 09 '16 at 16:57

1 Answers1

0

I modified the last element of coef to 3.02f to show that this code handles well also the last element. The result sequence is:

50, 50, 50, 50, 50, 95, 100, 117.5, 150, 182.5, 218.75, 250, 250,

enter image description here

The code could be probably re-written better, but I'll leave this to you:

#include <opencv2/opencv.hpp>
#include <vector>
#include <iostream>
using namespace cv;
using namespace std;

int main()
{
    vector <int> lum{ 50, 100, 150, 200, 250 };
    vector <float> coef{ 5.1f, 2.55f, 1.7f, 1.275f, 3.02f };

    vector<float> v;

    int idx_lum = 0;
    int idx_coef = 0;

    while (true)
    {
        int c = int(coef[idx_coef]);
        for (int i = 0; i < c; ++i)
        {
            v.push_back(float(lum[idx_lum]));
        }

        float alpha = fmod(coef[idx_coef], 1.f);
        float beta = 1.f - alpha;

        v.push_back(alpha * lum[idx_lum] + beta * lum[idx_lum + 1]);

        idx_lum++;
        idx_coef++;
        coef[idx_coef] = coef[idx_coef] - beta;

        if (idx_lum >= lum.size() - 1 || idx_coef >= coef.size() - 1)
        {
            int cc = int(coef[idx_coef]);
            for (int i = 0; i < cc; ++i)
            {
                v.push_back(float(lum[idx_lum]));
            }

            // Only if the last remainder is needed
            //float alpha = fmod(coef[idx_coef], 1.f);
            //v.push_back(alpha * lum[idx_lum]);
            break;
        }
    }

    // Print out the values
    copy(v.begin(), v.end(), ostream_iterator<float>(cout, ", "));

    // Get a cv::Mat from the std::vector
    Mat1f m = Mat1f(v).t();

    return 0;
}
Miki
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