how to calculate the mean value of multiple pictures

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Hi !

I'm trying to get the mean value of multiple pictures with opencv, here is my code :

 #include <opencv2\core\core.hpp>
 #include <opencv2\highgui\highgui.hpp>
 #include <opencv2\opencv.hpp>

  using namespace std;
  using namespace cv;

int main(){
cv::Mat frame,frame32f;
char filename[40];
cv::Mat mean;
const int count =10;
const int width  = 1920;
const int height = 1080;
cv::Mat resultframe = cv::Mat::zeros(height,width,CV_32FC3);
for(int i = 1 ; i<= count; i++){
sprintf(filename,"d:\\BMdvideos\\images\\image%d.tiff",i);
frame = imread(filename,CV_LOAD_IMAGE_COLOR);
frame.convertTo(frame32f,CV_32FC3);
resultframe +=frame32f;
    cout << " i = " << i<<endl;
//frame.release();
}
resultframe *= (1.0/count);

imshow("",resultframe);
waitKey(0);
return 0;
  }

I get a always a white frame in imshow, any idea why do I get this. thanks in advance for your help !