OpenCV/opencv_contrib/modules/xfeatures2d/samples/pct_signatures.cpp

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/*
Contributed by Gregor Kovalcik <gregor dot kovalcik at gmail dot com>
    based on code provided by Martin Krulis, Jakub Lokoc and Tomas Skopal.

References:
    Martin Krulis, Jakub Lokoc, Tomas Skopal.
    Efficient Extraction of Clustering-Based Feature Signatures Using GPU Architectures.
    Multimedia tools and applications, 75(13), pp.: 8071–8103, Springer, ISSN: 1380-7501, 2016

    Christian Beecks, Merih Seran Uysal, Thomas Seidl.
    Signature quadratic form distance.
    In Proceedings of the ACM International Conference on Image and Video Retrieval, pages 438-445.
    ACM, 2010.
*/

#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/xfeatures2d.hpp>

#include <iostream>
#include <string>

using namespace std;
using namespace cv;
using namespace xfeatures2d;


void printHelpMessage(void);
void printHelpMessage(void)
{
    cout << "Example of the PCTSignatures algorithm computing and visualizing\n"
        "image signature for one image, or comparing multiple images with the first\n"
        "image using the signature quadratic form distance.\n\n"
        "Usage: pct_signatures ImageToProcessAndDisplay\n"
        "or:    pct_signatures ReferenceImage [ImagesToCompareWithTheReferenceImage]\n\n"
        "The program has 2 modes:\n"
        "- single argument: program computes and visualizes the image signature\n"
        "- multiple arguments: program compares the first image to the others\n"
        "  using pct signatures and signature quadratic form distance (SQFD)";
}

/** @brief

Example of the PCTSignatures algorithm.

The program has 2 modes:
- single argument mode, where the program computes and visualizes the image signature
- multiple argument mode, where the program compares the first image to the others
using signatures and signature quadratic form distance (SQFD)

*/
int main(int argc, char** argv)
{
    if (argc < 2)                               // Check arguments
    {
        printHelpMessage();
        return 1;
    }

    Mat source;
    source = imread(argv[1]);                   // Read the file

    if (!source.data)                           // Check for invalid input
    {
        cerr << "Could not open or find the image: " << argv[1];
        return -1;
    }

    Mat signature, result;                      // define variables
    int initSampleCount = 2000;
    int initSeedCount = 400;
    int grayscaleBitsPerPixel = 4;
    vector<Point2f> initPoints;

    namedWindow("Source", WINDOW_AUTOSIZE);     // Create windows for display.
    namedWindow("Result", WINDOW_AUTOSIZE);

                                                // create the algorithm
    PCTSignatures::generateInitPoints(initPoints, initSampleCount, PCTSignatures::UNIFORM);
    Ptr<PCTSignatures> pctSignatures = PCTSignatures::create(initPoints, initSeedCount);
    pctSignatures->setGrayscaleBits(grayscaleBitsPerPixel);

                                                // compute and visualize the first image
    double start = (double)getTickCount();
    pctSignatures->computeSignature(source, signature);
    double end = (double)getTickCount();
    cout << "Signature of the reference image computed in " << (end - start) / (getTickFrequency() * 1.0f) << " seconds." << endl;
    PCTSignatures::drawSignature(source, signature, result);

    imshow("Source", source);                   // show the result
    imshow("Result", result);

    if (argc == 2)          // single image -> finish right after the visualization
    {
        waitKey(0);         // Wait for user input
        return 0;
    }
    // multiple images -> compare to the first one
    else
    {
        vector<Mat> images;
        vector<Mat> signatures;
        vector<float> distances;

        for (int i = 2; i < argc; i++)
        {
            Mat image = imread(argv[i]);
            if (!source.data)                               // Check for invalid input
            {
                cerr << "Could not open or find the image: " << argv[i] << std::endl;
                return 1;
            }
            images.push_back(image);
        }

        pctSignatures->computeSignatures(images, signatures);
        Ptr<PCTSignaturesSQFD> pctSQFD = PCTSignaturesSQFD::create();
        pctSQFD->computeQuadraticFormDistances(signature, signatures, distances);

        for (int i = 0; i < (int)(distances.size()); i++)
        {
            cout << "Image: " << argv[i + 2] << ", similarity: " << distances[i] << endl;
        }
        waitKey(0); // Wait for user input
    }

    return 0;
}