samples/cpp/laplace.cpp

An example using Laplace transformations for edge detection

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

#include <ctype.h>
#include <stdio.h>
#include <iostream>

using namespace cv;
using namespace std;

static void help()
{
    cout <<
            "\nThis program demonstrates Laplace point/edge detection using OpenCV function Laplacian()\n"
            "It captures from the camera of your choice: 0, 1, ... default 0\n"
            "Call:\n"
            "./laplace -c=<camera #, default 0> -p=<index of the frame to be decoded/captured next>\n" << endl;
}

enum {GAUSSIAN, BLUR, MEDIAN};

int sigma = 3;
int smoothType = GAUSSIAN;

int main( int argc, char** argv )
{
    VideoCapture cap;
    cv::CommandLineParser parser(argc, argv, "{ c | 0 | }{ p | | }");
    help();

    if( parser.get<string>("c").size() == 1 && isdigit(parser.get<string>("c")[0]) )
        cap.open(parser.get<int>("c"));
    else
        cap.open(parser.get<string>("c"));
    if( cap.isOpened() )
        cout << "Video " << parser.get<string>("c") <<
            ": width=" << cap.get(CAP_PROP_FRAME_WIDTH) <<
            ", height=" << cap.get(CAP_PROP_FRAME_HEIGHT) <<
            ", nframes=" << cap.get(CAP_PROP_FRAME_COUNT) << endl;
    if( parser.has("p") )
    {
        int pos = parser.get<int>("p");
        if (!parser.check())
        {
            parser.printErrors();
            return -1;
        }
        cout << "seeking to frame #" << pos << endl;
        cap.set(CAP_PROP_POS_FRAMES, pos);
    }

    if( !cap.isOpened() )
    {
        cout << "Could not initialize capturing...\n";
        return -1;
    }

    namedWindow( "Laplacian", 0 );
    createTrackbar( "Sigma", "Laplacian", &sigma, 15, 0 );

    Mat smoothed, laplace, result;

    for(;;)
    {
        Mat frame;
        cap >> frame;
        if( frame.empty() )
            break;

        int ksize = (sigma*5)|1;
        if(smoothType == GAUSSIAN)
            GaussianBlur(frame, smoothed, Size(ksize, ksize), sigma, sigma);
        else if(smoothType == BLUR)
            blur(frame, smoothed, Size(ksize, ksize));
        else
            medianBlur(frame, smoothed, ksize);

        Laplacian(smoothed, laplace, CV_16S, 5);
        convertScaleAbs(laplace, result, (sigma+1)*0.25);
        imshow("Laplacian", result);

        char c = (char)waitKey(30);
        if( c == ' ' )
            smoothType = smoothType == GAUSSIAN ? BLUR : smoothType == BLUR ? MEDIAN : GAUSSIAN;
        if( c == 'q' || c == 'Q' || c == 27 )
            break;
    }

    return 0;
}