opencv/samples/cpp/tutorial_code/ImgProc/Pyramids.cpp

/**
 * @file Pyramids.cpp
 * @brief Sample code of image pyramids (pyrDown and pyrUp)
 * @author OpenCV team
 */

#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"

using namespace cv;

/// Global variables
Mat src, dst, tmp;

const char* window_name = "Pyramids Demo";


/**
 * @function main
 */
int main( void )
{
  /// General instructions
  printf( "\n Zoom In-Out demo  \n " );
  printf( "------------------ \n" );
  printf( " * [u] -> Zoom in  \n" );
  printf( " * [d] -> Zoom out \n" );
  printf( " * [ESC] -> Close program \n \n" );

  /// Test image - Make sure it s divisible by 2^{n}
  src = imread( "../data/chicky_512.png" );
  if( src.empty() )
    { printf(" No data! -- Exiting the program \n");
      return -1; }

  tmp = src;
  dst = tmp;

  /// Create window
  namedWindow( window_name, WINDOW_AUTOSIZE );
  imshow( window_name, dst );

  /// Loop
  for(;;)
  {
    int c;
    c = waitKey(10);

    if( (char)c == 27 )
      { break; }
    if( (char)c == 'u' )
      { pyrUp( tmp, dst, Size( tmp.cols*2, tmp.rows*2 ) );
        printf( "** Zoom In: Image x 2 \n" );
      }
    else if( (char)c == 'd' )
      { pyrDown( tmp, dst, Size( tmp.cols/2, tmp.rows/2 ) );
        printf( "** Zoom Out: Image / 2 \n" );
      }

    imshow( window_name, dst );
    tmp = dst;
   }

   return 0;
}