modules/shape/samples/shape_example.cpp

An example using shape distance algorithm

/*
 * shape_context.cpp -- Shape context demo for shape matching
 */
 
#include "opencv2/shape.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <opencv2/core/utility.hpp>
#include <iostream>
#include <string>
 
using namespace std;
using namespace cv;
 
static void help()
{
 printf("\n"
 "This program demonstrates a method for shape comparison based on Shape Context\n"
 "You should run the program providing a number between 1 and 20 for selecting an image in the folder ../data/shape_sample.\n"
 "Call\n"
 "./shape_example [number between 1 and 20, 1 default]\n\n");
}
 
static vector<Point> simpleContour( const Mat& currentQuery, int n=300 )
{
 vector<vector<Point> > _contoursQuery;
 vector <Point> contoursQuery;
 findContours(currentQuery, _contoursQuery, RETR_LIST, CHAIN_APPROX_NONE);
 for (size_t border=0; border<_contoursQuery.size(); border++)
 {
 for (size_t p=0; p<_contoursQuery[border].size(); p++)
 {
 contoursQuery.push_back( _contoursQuery[border][p] );
 }
 }
 
 // In case actual number of points is less than n
 int dummy=0;
 for (int add=(int)contoursQuery.size()-1; add<n; add++)
 {
 contoursQuery.push_back(contoursQuery[dummy++]); //adding dummy values
 }
 
 // Uniformly sampling
 cv::randShuffle(contoursQuery);
 vector<Point> cont;
 for (int i=0; i<n; i++)
 {
 cont.push_back(contoursQuery[i]);
 }
 return cont;
}
 
int main(int argc, char** argv)
{
 string path = "data/shape_sample/";
 cv::CommandLineParser parser(argc, argv, "{help h||}{@input|1|}");
 if (parser.has("help"))
 {
 help();
 return 0;
 }
 int indexQuery = parser.get<int>("@input");
 if (!parser.check())
 {
 parser.printErrors();
 help();
 return 1;
 }
 if (indexQuery < 1 || indexQuery > 20)
 {
 help();
 return 1;
 }
 cv::Ptr <cv::ShapeContextDistanceExtractor> mysc = cv::createShapeContextDistanceExtractor();
 
 Size sz2Sh(300,300);
 stringstream queryName;
 queryName<<path<<indexQuery<<".png";
 Mat query=imread(queryName.str(), IMREAD_GRAYSCALE);
 Mat queryToShow;
 resize(query, queryToShow, sz2Sh, 0, 0, INTER_LINEAR_EXACT);
 imshow("QUERY", queryToShow);
 moveWindow("TEST", 0,0);
 vector<Point> contQuery = simpleContour(query);
 int bestMatch = 0;
 float bestDis=FLT_MAX;
 for ( int ii=1; ii<=20; ii++ )
 {
 if (ii==indexQuery) continue;
 waitKey(30);
 stringstream iiname;
 iiname<<path<<ii<<".png";
 cout<<"name: "<<iiname.str()<<endl;
 Mat iiIm=imread(iiname.str(), 0);
 Mat iiToShow;
 resize(iiIm, iiToShow, sz2Sh, 0, 0, INTER_LINEAR_EXACT);
 imshow("TEST", iiToShow);
 moveWindow("TEST", sz2Sh.width+50,0);
 vector<Point> contii = simpleContour(iiIm);
 float dis = mysc->computeDistance( contQuery, contii );
 if ( dis<bestDis )
 {
 bestMatch = ii;
 bestDis = dis;
 }
 std::cout<<" distance between "<<queryName.str()<<" and "<<iiname.str()<<" is: "<<dis<<std::endl;
 }
 destroyWindow("TEST");
 stringstream bestname;
 bestname<<path<<bestMatch<<".png";
 Mat iiIm=imread(bestname.str(), 0);
 Mat bestToShow;
 resize(iiIm, bestToShow, sz2Sh, 0, 0, INTER_LINEAR_EXACT);
 imshow("BEST MATCH", bestToShow);
 moveWindow("BEST MATCH", sz2Sh.width+50,0);
 waitKey();
 
 return 0;
}