#pragma once
#include <memory>
#include <vector>
#include <opencv2/opencv.hpp>

std::vector<double> caculate_abcd(std::vector<std::pair<double, double>> point)
{
    int MaxElement = point.size() - 1;
    //计算常数f
    double f = point[0].second;
    //求解
    int n, m;

    std::vector<std::vector<double>> a;

    for (int i = 0; i < MaxElement; i++)
    {
        std::vector<double> b;
        b.resize(MaxElement + 1);
        a.push_back(b);
    }

    for (int i = 0; i < MaxElement; i++)
    {
        for (int j = 0; j < MaxElement; j++)
            a[i][j] = pow(point[i + 1].first, MaxElement - j);
        a[i][MaxElement] = point[i + 1].second - f;
    }

    int i, j;
    n = MaxElement;

    for (j = 0; j < n; j++)
    {
        double max = 0;
        double imax = 0;
        for (i = j; i < n; i++)
        {
            if (imax < fabs(a[i][j])) {
                imax = fabs(a[i][j]);
                max = a[i][j];//得到各行中所在列最大元素
                m = i;
            }
        }
        if (fabs(a[j][j]) != max)
        {
            double b = 0;
            for (int k = j; k < n + 1; k++) {
                b = a[j][k];
                a[j][k] = a[m][k];
                a[m][k] = b;
            }
        }

        for (int r = j; r < n + 1; r++)
        {
            a[j][r] = a[j][r] / max;//让该行的所在列除以所在列的第一个元素，目的是让首元素为1
        }

        for (i = j + 1; i < n; i++)
        {
            double c = a[i][j];
            if (c == 0.0) continue;
            for (int s = j; s < n + 1; s++) {
                a[i][s] = a[i][s] - a[j][s] * c;//前后行数相减，使下一行或者上一行的首元素为0
            }
        }
    }
    for (i = n - 2; i >= 0; i--)
    {
        for (j = i + 1; j < n; j++)
        {
            a[i][n] = a[i][n] - a[j][n] * a[i][j];
        }
    }

    std::vector<double> result;
    for (int k = 0; k < n; k++)
        result.push_back(a[k][n]);
    result.push_back(f);
    return result;
}

double caculate_value(const std::vector<double>& abcd, double x)
{
    return abcd[0] * x * x * x + abcd[1] * x * x + abcd[2] * x + abcd[3];
}

void brightness(cv::Mat& lut, int alpha = 170)
{
  std::vector<std::pair<double, double>> pos;
    pos.push_back(std::pair<double, double>(0, 0));
    pos.push_back(std::pair<double, double>(64, 64));
    pos.push_back(std::pair<double, double>(alpha, 255));
    pos.push_back(std::pair<double, double>(255, 255));
    std::vector<double> abcd = caculate_abcd(pos);
  
  uchar table[256];
  for (int i = 0; i < 256; i++)
    table[i] = static_cast<uchar>(caculate_value(abcd, i));
  
  uchar* ptr = lut.data;
  for (int i = 0, length = lut.total() * lut.channels(); i < length; i++)
    ptr[i] = table[ptr[i]];
}