Pixels and contours

contours.cpp

#include <iostream>

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

using namespace cv;
using namespace std;

int main()
{
    const uchar B = 0x00;
    const uchar F = 0xFF;
    uchar data[] = {
    B, B, B, B, B, B,
    B, B, F, F, F, B,
    B, F, F, F, F, B,
    B, F, F, F, B, B,
    B, F, F, F, B, B,
    B, B, B, B, B, B,
    };
    Mat img(Size(6, 6), CV_8UC1, data);
    vector<Mat> cont;
    findContours(img, cont, RETR_LIST, CHAIN_APPROX_NONE);
    for (Mat& c : cont)
        cout << c.t() << endl << "Area: " << contourArea(c) << endl;

    cvtColor(img, img, COLOR_GRAY2BGR);
    drawContours(img, cont, 0, Scalar(200, 200, 200), 1);

    double scale = 64;
    Mat viz;
    resize(img, viz, Size(), scale, scale, INTER_AREA);

    for (Mat& c : cont)
        c *= scale;
    drawContours(viz, cont, 0, Scalar(0, 255, 0), 3);
    for (Mat& c : cont)
        for (int i = 0; i < c.rows; ++i)
        {
            const Point p = c.at<Point>(i, 0);
            drawMarker(viz, p, Scalar(200, 0, 200), MARKER_DIAMOND, 10, 3);
            stringstream out;
            out << "(" << p.x / scale << ", " << p.y / scale << ")";
            putText(viz, out.str(), p + Point(5, 15), FONT_HERSHEY_PLAIN, 1, Scalar(0, 0, 240), 1, LINE_AA);
        }

    imshow("Image", viz);
    waitKey(0);

    return 0;
}