remove white reflection from image

edit

One way would be to alter the saturation.

In C++:

#include <opencv2/opencv.hpp>
using namespace cv;
#pragma comment(lib, "opencv_world340.lib")

#include <iostream>
using namespace std;

int main(void)
{
    Mat frame = imread("rainbow.jpg");

    if (frame.empty())
    {
        cout << "Could not read image file." << endl;
        return 1;
    }

    Mat hsv;
    cvtColor(frame, hsv, CV_BGR2HSV);

    for (int j = 0; j < frame.rows; j++)
        for (int i = 0; i < frame.cols; i++)
            hsv.at<Vec3b>(j, i)[1] = 255;

    cvtColor(hsv, frame, CV_HSV2BGR);

    imshow("frame", frame);
    waitKey(0);

    return 0;
}

In Python:

import cv2
import numpy

frame = cv2.imread('rainbow.jpg')

if frame is None:
    print('Error loading image')
    exit()    

rows = frame.shape[0]
cols = frame.shape[1]

hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV);

for i in range(0, cols):
    for j in range(0, rows):
        hsv[j, i][1] = 255;

frame = cv2.cvtColor(hsv, cv2.COLOR_HSV2BGR);

cv2.imshow("Frame", frame)
cv2.waitKey(0)