Display the images in multiple scales

This program can be very good demo, which show us how to display the image in different scales.

/** * @file Pyramids.cpp * @brief Sample code of image pyramids (pyrDown and pyrUp) * @author OpenCV team */#include "opencv2/imgproc/imgproc.hpp"#include "opencv2/highgui/highgui.hpp"#include <math.h>#include <stdlib.h>#include <stdio.h>using namespace cv;/// Global variablesMat 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( "road.jpg" );  if( !src.data )    { printf(" No data! -- Exiting the program \n");      return -1; }  tmp = src;  dst = tmp;  /// Create window  namedWindow( window_name, CV_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;}

Result:

Scale up:

Scale down: