Merging two images showing brightness - c++

Question

I am trying to blend two image or you can say put one image on other image , when i apply blending overlay on the image or simple merge two image it show me brightness in it.
here are my two images (first vignette is empty from inside , its not containing brightness in the centre )
and the other is
The code which i did is
int main( int argc, char** argv )
{
Mat img=imread("E:\\vig.png",-1);
Mat ch[4];
split(img,ch);
Mat im2 = ch[3]; // here's the vignette
im2 = 255 - im2; // eventually cure the inversion
Mat img2 = imread("E:\\ew.jpg");
Mat out2;
blending_overlay3(img2 , im2 , out2);
imshow("image",out2);
imwrite("E:\\image.jpg",out2);
waitKey();}
It show me the result like
but i require result like
EDIT
The first image is hollow/empty from center (the vignette one) , but when i read the image (vignette one) with my program then it become solid(bright) from the center , the history behind its implementation is here
There is the only problem and its with first (vignette) image reading , if it read as it is , like hollow/empty from the center , so that the other image with which we merge/blend/weight whatever apply it didn't effect the center part of the image , not even show brightness etc , that's what i want to do

Answer 1

it's me again :) It seems you are writing new photoshop.
The result I've got:
The code:
#include <iostream>
#include <vector>
#include <stdio.h>
#include <functional>
#include <algorithm>
#include <numeric>
#include <cstddef>
#include "opencv2/opencv.hpp"
#include <iostream>
#include <fstream>
using namespace std;
using namespace cv;
int main( int argc, char** argv )
{
namedWindow("Image");
Mat Img1=imread("Img1.png",-1);
Mat Img2=imread("Img2.png");
cv::resize(Img1,Img1,Img2.size());
Img1.convertTo(Img1,CV_32FC4,1.0/255.0);
Img2.convertTo(Img2,CV_32FC3,1.0/255.0);
vector<Mat> ch;
split(Img1,ch);
Mat mask = ch[3].clone(); // here's the vignette
ch.resize(3);
Mat I1,I2,result;
cv::multiply(mask,ch[0],ch[0]);
cv::multiply(mask,ch[1],ch[1]);
cv::multiply(mask,ch[2],ch[2]);
merge(ch,I1);
vector<Mat> ch2(3);
split(Img2,ch2);
cv::multiply(1.0-mask,ch2[0],ch2[0]);
cv::multiply(1.0-mask,ch2[1],ch2[1]);
cv::multiply(1.0-mask,ch2[2],ch2[2]);
merge(ch2,I2);
result=I1+I2;
imshow("Image",result);
waitKey(0);
}