OpenCV  3.1.0
Open Source Computer Vision
Image Pyramids

Goal

In this tutorial you will learn how to:

Theory

Note
The explanation below belongs to the book Learning OpenCV by Bradski and Kaehler.

Image Pyramid

Gaussian Pyramid

Note
When we reduce the size of an image, we are actually losing information of the image.

Code

This tutorial code's is shown lines below. You can also download it from here

#include <math.h>
#include <stdlib.h>
#include <stdio.h>
using namespace cv;
Mat src, dst, tmp;
const char* window_name = "Pyramids Demo";
int main( void )
{
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" );
src = imread( "../data/chicky_512.png" );
if( src.empty() )
{ printf(" No data! -- Exiting the program \n");
return -1; }
tmp = src;
dst = tmp;
namedWindow( window_name, WINDOW_AUTOSIZE );
imshow( window_name, dst );
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;
}

Explanation

Let's check the general structure of the program:

Results