#include "cv.h"
#include "highgui.h"
IplImage* doCanny(
    IplImage* in,
    double    lowThresh,
    double    highThresh,
    double    aperture)
{
    IplImage* out = cvCreateImage(
        cvGetSize( in ),
        in->depth, //IPL_DEPTH_8U,
        1);
    cvCanny( in, out, lowThresh, highThresh, aperture );
    return( out );
}
IplImage* doPyrDown(
  IplImage* in,
  int       filter = IPL_GAUSSIAN_5x5)
{
    // Best to make sure input image is divisible by two.
    //
    assert( in->width%2 == 0 && in->height%2 == 0 );
    IplImage* out = cvCreateImage(
        cvSize( in->width/2, in->height/2 ),
        in->depth,
        in->nChannels
    );
    cvPyrDown( in, out );
    return( out );
};
int main( int argc, char** argv )
{
  cvNamedWindow("Example Gray", CV_WINDOW_AUTOSIZE );
  cvNamedWindow("Example Pyr", CV_WINDOW_AUTOSIZE );
  cvNamedWindow("Example Canny", CV_WINDOW_AUTOSIZE );
  IplImage* img_rgb = cvLoadImage("building.jpg" );
  IplImage* out;
  out = cvCreateImage( cvSize( img_rgb->width,img_rgb->height ), img_rgb->depth, 1);
  cvCvtColor(img_rgb, out ,CV_BGR2GRAY);
  cvShowImage("Example Gray", out );
  out = doPyrDown( out );
  out = doPyrDown( out );
  cvShowImage("Example Pyr", out );
  out = doCanny( out, 10, 100, 3 );
  cvShowImage("Example Canny", out );
  cvWaitKey(0);
  cvReleaseImage( &out);
  cvDestroyWindow("Example Gray");
  cvDestroyWindow("Example Pyr");
  cvDestroyWindow("Example Canny");
}  cvShowImage("Example Pyr", out );
  out = doCanny( out, 10, 100, 3 );
  cvShowImage("Example Canny", out );
  cvWaitKey(0);
  cvReleaseImage( &out);
  cvDestroyWindow("Example Gray");
  cvDestroyWindow("Example Pyr");
  cvDestroyWindow("Example Canny");
}