/**

 * @function findContours_Demo.cpp

 * @brief Demo code to find contours in an image

 * @author OpenCV team

 */

#include "opencv2/imgcodecs.hpp"

#include "opencv2/highgui.hpp"

#include "opencv2/imgproc.hpp"

#include <iostream>

using namespace cv;

using namespace std;

Mat src_gray;

int thresh = 100;

RNG rng(12345);

/// Function header

void thresh_callback(int, void* );

/**

 * @function main

 */

int main( int argc, char** argv )

{

    /// Load source image

    CommandLineParser parser( argc, argv, "{@input | ../data/HappyFish.jpg | input image}" );

    Mat src = imread( parser.get<String>( "@input" ) );

    if( src.empty() )

    {

      cout << "Could not open or find the image!\n" << endl;

      cout << "Usage: " << argv[0] << " <Input image>" << endl;

      return -1;

    }

    /// Convert image to gray and blur it

    cvtColor( src, src_gray, COLOR_BGR2GRAY );

    blur( src_gray, src_gray, Size(3,3) );

    /// Create Window

    const char* source_window = "Source";

    namedWindow( source_window );

    imshow( source_window, src );

    const int max_thresh = 255;

    createTrackbar( "Canny thresh:", source_window, &thresh, max_thresh, thresh_callback );

    thresh_callback( 0, 0 );

    waitKey();

    return 0;

}

/**

 * @function thresh_callback

 */

void thresh_callback(int, void* )

{

    /// Detect edges using Canny

    Mat canny_output;

    Canny( src_gray, canny_output, thresh, thresh*2 );

    /// Find contours

    vector<vector<Point> > contours;

    vector<Vec4i> hierarchy;

    findContours( canny_output, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE );

    /// Draw contours

    Mat drawing = Mat::zeros( canny_output.size(), CV_8UC3 );

    for( size_t i = 0; i< contours.size(); i++ )

    {

        Scalar color = Scalar( rng.uniform(0, 256), rng.uniform(0,256), rng.uniform(0,256) );

        drawContours( drawing, contours, (int)i, color, 2, LINE_8, hierarchy, 0 );

    }

    /// Show in a window

    imshow( "Contours", drawing );

}

// The "Square Detector" program.

// It loads several images sequentially and tries to find squares in

// each image

#include "opencv2/core.hpp"

#include "opencv2/imgproc.hpp"

#include "opencv2/imgcodecs.hpp"

#include "opencv2/highgui.hpp"

#include "opencv2/core/utils/filesystem.hpp"

#include <iostream>

using namespace cv;

using namespace std;

static void help(const char* programName)

{

    cout <<

    "\nA program using pyramid scaling, Canny, contours and contour simplification\n"

    "to find squares in a list of images (pic1-6.png)\n"

    "Returns sequence of squares detected on the image.\n"

    "Call:\n"

    "./" << programName << " [file_name (optional)]\n"

    "Using OpenCV version " << CV_VERSION << "\n" << endl;

}

int thresh = 50, N = 11;

const char* wndname = "Square Detection Demo";

// helper function:

// finds a cosine of angle between vectors

// from pt0->pt1 and from pt0->pt2

static double angle( Point pt1, Point pt2, Point pt0 )

{

    double dx1 = pt1.x - pt0.x;

    double dy1 = pt1.y - pt0.y;

    double dx2 = pt2.x - pt0.x;

    double dy2 = pt2.y - pt0.y;

    return (dx1*dx2 + dy1*dy2)/sqrt((dx1*dx1 + dy1*dy1)*(dx2*dx2 + dy2*dy2) + 1e-10);

}

// returns sequence of squares detected on the image.

static void findSquares( const Mat& image, vector<vector<Point> >& squares )

{

    squares.clear();

    Mat pyr, timg, gray0(image.size(), CV_8U), gray;

    // down-scale and upscale the image to filter out the noise

    pyrDown(image, pyr, Size(image.cols/2, image.rows/2));

    pyrUp(pyr, timg, image.size());

    vector<vector<Point> > contours;

    // find squares in every color plane of the image

    for( int c = 0; c < 3; c++ )

    {

        int ch[] = {c, 0};

        mixChannels(&timg, 1, &gray0, 1, ch, 1);

        // try several threshold levels

        for( int l = 0; l < N; l++ )

        {

            // hack: use Canny instead of zero threshold level.

            // Canny helps to catch squares with gradient shading

            if( l == 0 )

            {

                // apply Canny. Take the upper threshold from slider

                // and set the lower to 0 (which forces edges merging)

                Canny(gray0, gray, 0, thresh, 5);

                // dilate canny output to remove potential

                // holes between edge segments

                dilate(gray, gray, Mat(), Point(-1,-1));

            }

            else

            {

                // apply threshold if l!=0:

                //     tgray(x,y) = gray(x,y) < (l+1)*255/N ? 255 : 0

                gray = gray0 >= (l+1)*255/N;

            }

            // find contours and store them all as a list

            findContours(gray, contours, RETR_LIST, CHAIN_APPROX_SIMPLE);

            vector<Point> approx;

            // test each contour

            for( size_t i = 0; i < contours.size(); i++ )

            {

                // approximate contour with accuracy proportional

                // to the contour perimeter

                approxPolyDP(contours[i], approx, arcLength(contours[i], true)*0.02, true);

                // square contours should have 4 vertices after approximation

                // relatively large area (to filter out noisy contours)

                // and be convex.

                // Note: absolute value of an area is used because

                // area may be positive or negative - in accordance with the

                // contour orientation

                if( approx.size() == 4 &&

                    fabs(contourArea(approx)) > 1000 &&

                    isContourConvex(approx) )

                {

                    double maxCosine = 0;

                    for( int j = 2; j < 5; j++ )

                    {

                        // find the maximum cosine of the angle between joint edges

                        double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));

                        maxCosine = MAX(maxCosine, cosine);

                    }

                    // if cosines of all angles are small

                    // (all angles are ~90 degree) then write quandrange

                    // vertices to resultant sequence

                    if( maxCosine < 0.3 )

                        squares.push_back(approx);

                }

            }

        }

    }

}

// the function draws all the squares in the image

static void drawSquares( Mat& image, const vector<vector<Point> >& squares )

{

    for( size_t i = 0; i < squares.size(); i++ )

    {

        const Point* p = &squares[i][0];

        int n = (int)squares[i].size();

        polylines(image, &p, &n, 1, true, Scalar(0,255,0), 3, LINE_AA);

    }

    imshow(wndname, image);

}

String absoluteFilePath(const String& relative_path) {

    String root_path = "F:/opencv/build/bin/sample-data/";

    String path = utils::fs::join(root_path, relative_path);

    return path;

}

int main(int argc, char** argv)

{

    static const char* names[] = { "pic1.png", "pic2.png", "pic3.png",

        "pic4.png", "pic5.png", "pic6.png", 0 };

    help(names[0]);

    vector<vector<Point> > squares;

    for( int i = 0; names[i] != 0; i++ )

    {

        string filename = absoluteFilePath(names[i]);

        Mat image = imread(filename, IMREAD_COLOR);

        if( image.empty() )

        {

            cout << "Couldn't load " << filename << endl;

            continue;

        }

        findSquares(image, squares);

        drawSquares(image, squares);

        int c = waitKey();

        if( c == 27 )

            break;

    }

    return 0;

}