opencv/samples/cpp/tutorial_code/ImgProc/AddingImages.cpp

/**
 * @file AddingImages.cpp
 * @brief Simple linear blender ( dst = alpha*src1 + beta*src2 )
 * @author OpenCV team
 */

#include <cv.h>
#include <highgui.h>
#include <iostream>

using namespace cv;

/**
 * @function main
 * @brief Main function 
 */
int main( int argc, char** argv )
{

   double alpha = 0.5; double beta; double input; 

   Mat src1, src2, dst;

   /// Ask the user enter alpha
   std::cout<<" Simple Linear Blender "<<std::endl;
   std::cout<<"-----------------------"<<std::endl;
   std::cout<<"* Enter alpha [0-1]: ";
   std::cin>>input;

   // We use the alpha provided by the user iff it is between 0 and 1
   if( alpha >= 0 && alpha <= 1 )
     { alpha = input; }

   /// Read image ( same size, same type )
   src1 = imread("../images/LinuxLogo.jpg");
   src2 = imread("../images/WindowsLogo.jpg");

   if( !src1.data ) { printf("Error loading src1 \n"); return -1; }
   if( !src2.data ) { printf("Error loading src2 \n"); return -1; }

   /// Create Windows
   namedWindow("Linear Blend", 1);

   beta = ( 1.0 - alpha );
   addWeighted( src1, alpha, src2, beta, 0.0, dst);
  
   imshow( "Linear Blend", dst );


   waitKey(0);
   return 0;
}