OpenCV_4.2.0/opencv_contrib-4.2.0/modules/ximgproc/samples/graphsegmentation_demo.cpp

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#include "opencv2/ximgproc/segmentation.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/core.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>

using namespace cv;
using namespace cv::ximgproc::segmentation;

Scalar hsv_to_rgb(Scalar);
Scalar color_mapping(int);

static void help() {
    std::cout << std::endl <<
    "A program demonstrating the use and capabilities of a particular graph based image" << std::endl <<
    "segmentation algorithm described in P. Felzenszwalb, D. Huttenlocher," << std::endl <<
    "             \"Efficient Graph-Based Image Segmentation\"" << std::endl <<
    "International Journal of Computer Vision, Vol. 59, No. 2, September 2004" << std::endl << std::endl <<
    "Usage:" << std::endl <<
    "./graphsegmentation_demo input_image output_image [simga=0.5] [k=300] [min_size=100]" << std::endl;
}

Scalar hsv_to_rgb(Scalar c) {
    Mat in(1, 1, CV_32FC3);
    Mat out(1, 1, CV_32FC3);

    float * p = in.ptr<float>(0);

    p[0] = (float)c[0] * 360.0f;
    p[1] = (float)c[1];
    p[2] = (float)c[2];

    cvtColor(in, out, COLOR_HSV2RGB);

    Scalar t;

    Vec3f p2 = out.at<Vec3f>(0, 0);

    t[0] = (int)(p2[0] * 255);
    t[1] = (int)(p2[1] * 255);
    t[2] = (int)(p2[2] * 255);

    return t;

}

Scalar color_mapping(int segment_id) {

    double base = (double)(segment_id) * 0.618033988749895 + 0.24443434;

    return hsv_to_rgb(Scalar(fmod(base, 1.2), 0.95, 0.80));

}

int main(int argc, char** argv) {

    if (argc < 2 || argc > 6) {
        help();
        return -1;
    }

    Ptr<GraphSegmentation> gs = createGraphSegmentation();

    if (argc > 3)
        gs->setSigma(atof(argv[3]));

    if (argc > 4)
        gs->setK((float)atoi(argv[4]));

    if (argc > 5)
        gs->setMinSize(atoi(argv[5]));

    if (!gs) {
        std::cerr << "Failed to create GraphSegmentation Algorithm." << std::endl;
        return -2;
    }

    Mat input, output, output_image;

    input = imread(argv[1]);

    if (!input.data) {
        std::cerr << "Failed to load input image" << std::endl;
        return -3;
    }

    gs->processImage(input, output);

    double min, max;
    minMaxLoc(output, &min, &max);

    int nb_segs = (int)max + 1;

    std::cout << nb_segs << " segments" << std::endl;

    output_image = Mat::zeros(output.rows, output.cols, CV_8UC3);

    uint* p;
    uchar* p2;

    for (int i = 0; i < output.rows; i++) {

        p = output.ptr<uint>(i);
        p2 = output_image.ptr<uchar>(i);

        for (int j = 0; j < output.cols; j++) {
            Scalar color = color_mapping(p[j]);
            p2[j*3] = (uchar)color[0];
            p2[j*3 + 1] = (uchar)color[1];
            p2[j*3 + 2] = (uchar)color[2];
        }
    }

    imwrite(argv[2], output_image);

    std::cout << "Image written to " << argv[2] << std::endl;

    return 0;
}