This example was based on the filtroespacial.cpp algorithm and answers to the proposed exercises at agostinhobritojr.github.io.

This program adds one more function to the provided example. Through this new function, the laplacian of the gaussian of a captured image can be calculated by pressing the key "z" and the filtered image is displayed.

Comparing both laplacian and laplacion of gauss filters results, it is possible to conclude that the second filter returns a better filtering, as we can observe more easily the borders and cornes of the image.

#include <iostream>
#include <opencv2/opencv.hpp>

using namespace cv;
using namespace std;

void printmask(Mat &m){
  for(int i=0; i<m.size().height; i++){
    for(int j=0; j<m.size().width; j++){
      cout << m.at<float>(i,j) << ",";
    }
    cout << endl;
  }
}

void menu(){
  cout << "\npressione a tecla para ativar o filtro: \n"
    "a - calcular modulo\n"
    "m - media\n"
    "g - gauss\n"
    "v - vertical\n"
    "h - horizontal\n"
    "l - laplaciano\n"
    "z - laplaciano do gaussiano\n"
    "esc - sair\n";
}

int main(int argvc, char** argv){
  VideoCapture video;
  float media[] = {1,1,1,
                   1,1,1,
                   1,1,1};
  float gauss[] = {1,2,1,
                   2,4,2,
                   1,2,1};
  float horizontal[]={-1,0,1,
                      -2,0,2,
                      -1,0,1};
  float vertical[]={-1,-2,-1,
                    0,0,0,
                    1,2,1};
  float laplacian[]={0,-1,0,
                     -1,4,-1,
                     0,-1,0};
  float lapgauss[]={0,0,1,0,0,
                    0,1,2,1,0,
                    1,2,-16,2,1,
                    0,1,2,1,0,
                    0,0,1,0,0};


  Mat cap, frame, frame32f, frameFiltered;
  Mat mask(3,3,CV_32F), mask1;
  Mat result, result1;
  double width, height, min, max;
  int absolut;
  char key;

  video.open(0);
  if(!video.isOpened())
    return -1;
  width=video.get(CV_CAP_PROP_FRAME_WIDTH);
  height=video.get(CV_CAP_PROP_FRAME_HEIGHT);
  std::cout << "largura=" << width << "\n";;
  std::cout << "altura =" << height<< "\n";;

  namedWindow("filtroespacial",1);

  mask = Mat(3, 3, CV_32F, media);
  scaleAdd(mask, 1/9.0, Mat::zeros(3,3,CV_32F), mask1);
  swap(mask, mask1);
  absolut=1; // calcs abs of the image

  menu();
  for(;;){
    video >> cap;
    cvtColor(cap, frame, CV_BGR2GRAY);
    flip(frame, frame, 1);
    imshow("original", frame);
    frame.convertTo(frame32f, CV_32F);
    filter2D(frame32f, frameFiltered, frame32f.depth(), mask, Point(1,1), 0);
    if(absolut){
      frameFiltered=abs(frameFiltered);
    }
    frameFiltered.convertTo(result, CV_8U);
    imshow("filtroespacial", result);
    key = (char) waitKey(10);
    if( key == 27 ) break; // esc pressed!
    switch(key){
    case 'a':
      menu();
      absolut=!absolut;
      break;
    case 'm':
      menu();
      mask = Mat(3, 3, CV_32F, media);
      scaleAdd(mask, 1/9.0, Mat::zeros(3,3,CV_32F), mask1);
      mask = mask1;
      printmask(mask);
      break;
    case 'g':
      menu();
      mask = Mat(3, 3, CV_32F, gauss);
      scaleAdd(mask, 1/16.0, Mat::zeros(3,3,CV_32F), mask1);
      mask = mask1;
      printmask(mask);
      break;
    case 'h':
      menu();
      mask = Mat(3, 3, CV_32F, horizontal);
      printmask(mask);
      break;
    case 'v':
      menu();
      mask = Mat(3, 3, CV_32F, vertical);
      printmask(mask);
      break;
    case 'l':
      menu();
      mask = Mat(3, 3, CV_32F, laplacian);
      printmask(mask);
      break;
    case 'z':
      menu();
      mask = Mat(5, 5, CV_32F, lapgauss);
      printmask(mask);
    default:
      break;
    }
  }
  return 0;
}