example_05-01.cpp

// Example 5-1. Complete program to alpha-blend the ROI starting at (0,0) in src2 with the ROI starting at (x,y) in src1
// alphablend <imageA> <image B> <x> <y> <<alpha> <beta>
//
#include <opencv2/opencv.hpp>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>

using namespace cv;
using namespace std;

void help(const char **argv) {
  cout << "\n\n"
   << "This program alpha blends the first image onto the other \n"
   << "alpha is the blending of the first image and beta onto the second\n"
   << "Call:\n"
   << argv[0] << " <path/blend_this_img> <path/onto_this_img> <where_to_blend_x> <where_to_blend_y> <alpha> <beta>\n\n"
   << "Example:\n"
   << " ./example_05-01 ../faceTemplate.jpg ../faces.png 230 155 0.8 0.2\n"
   << endl;
}



int main( int argc, const char** argv )
{
	help(argv);
	if(argc != 7) {
		cout << "ERROR: Wrong # of parameters (7), you had " << argc  << "\n" << endl;
		return -1;
	}


  // Using the first two arguments, open up the image to be copied onto
  // (src1), and the image that will be copied from (src2).
  //
  cv::Mat src1 = cv::imread(argv[1],1);
  cv::Mat src2 = cv::imread(argv[2],1);

	int from_w = src1.size().width;
	int from_h = src1.size().height;
	int to_w = src2.size().width;
	int to_h = src2.size().height;


  if( argc==7 && !src1.empty() && !src2.empty() ) {

    // Four more arguments tell where in src1 to paste the chunk taken from
    // src2. Note that the width and height also specify what portion of
    // src2 to actually use.
    //
    int x = atoi(argv[3]);
    int y = atoi(argv[4]);

	// Make sure we don't exceed bounds:
	if((x < 0) || (y < 0) || (x > to_w - 1) || (y > to_h - 1) || (x+from_w > to_w - 1) || (y+from_h > to_h)) {
		cout << "\nError, at (x,y) (" << x << ", " << y <<"), your input image [w,h] [" << from_w << ", " 
		<< from_h << "] doesn't fit within the blend to image [w,h] [" << to_w << ", " << to_h  <<"]\n" << endl;
		return -1;
	}

    // Two more arguments set the blending coefficients.
    //
    double alpha = (double)atof(argv[5]);
    double beta  = (double)atof(argv[6]);

    cv::Mat roi1( src1, cv::Rect(0,0,from_w - 1,from_h - 1) ); //Just take the whole thing
    cv::Mat roi2( src2, cv::Rect(x,y,from_w - 1, from_h - 1) );

    // Blend together the image src2 onto the image src1
    // at the specified location.
    //
    cv::addWeighted( roi1, alpha, roi2, beta, 0.0, roi2 );

    // Create a window to shoow the result and show it.
    //
    cv::namedWindow( "Alpha Blend", 1 );
    cv::imshow( "Alpha Blend", src2 );

    // Leave the window up and runnnig until the user hits a key
    //
    cv::waitKey( 0 );

  }

  return 0;

}