1// The "Square Detector" program.
2// It loads several images sequentially and tries to find squares in
3// each image
4
5#include "opencv2/core.hpp"
6#include "opencv2/core/ocl.hpp"
7#include "opencv2/core/utility.hpp"
8#include "opencv2/imgproc/imgproc.hpp"
9#include "opencv2/imgcodecs.hpp"
10#include "opencv2/highgui/highgui.hpp"
11#include <iostream>
12#include <string.h>
13
14using namespace cv;
15using namespace std;
16
17int thresh = 50, N = 11;
18const char* wndname = "Square Detection Demo";
19
20// helper function:
21// finds a cosine of angle between vectors
22// from pt0->pt1 and from pt0->pt2
23static double angle( Point pt1, Point pt2, Point pt0 )
24{
25    double dx1 = pt1.x - pt0.x;
26    double dy1 = pt1.y - pt0.y;
27    double dx2 = pt2.x - pt0.x;
28    double dy2 = pt2.y - pt0.y;
29    return (dx1*dx2 + dy1*dy2)/sqrt((dx1*dx1 + dy1*dy1)*(dx2*dx2 + dy2*dy2) + 1e-10);
30}
31
32
33// returns sequence of squares detected on the image.
34// the sequence is stored in the specified memory storage
35static void findSquares( const UMat& image, vector<vector<Point> >& squares )
36{
37    squares.clear();
38    UMat pyr, timg, gray0(image.size(), CV_8U), gray;
39
40    // down-scale and upscale the image to filter out the noise
41    pyrDown(image, pyr, Size(image.cols/2, image.rows/2));
42    pyrUp(pyr, timg, image.size());
43    vector<vector<Point> > contours;
44
45    // find squares in every color plane of the image
46    for( int c = 0; c < 3; c++ )
47    {
48        int ch[] = {c, 0};
49        mixChannels(timg, gray0, ch, 1);
50
51        // try several threshold levels
52        for( int l = 0; l < N; l++ )
53        {
54            // hack: use Canny instead of zero threshold level.
55            // Canny helps to catch squares with gradient shading
56            if( l == 0 )
57            {
58                // apply Canny. Take the upper threshold from slider
59                // and set the lower to 0 (which forces edges merging)
60                Canny(gray0, gray, 0, thresh, 5);
61                // dilate canny output to remove potential
62                // holes between edge segments
63                dilate(gray, gray, UMat(), Point(-1,-1));
64            }
65            else
66            {
67                // apply threshold if l!=0:
68                //     tgray(x,y) = gray(x,y) < (l+1)*255/N ? 255 : 0
69                cv::threshold(gray0, gray, (l+1)*255/N, 255, THRESH_BINARY);
70            }
71
72            // find contours and store them all as a list
73            findContours(gray, contours, RETR_LIST, CHAIN_APPROX_SIMPLE);
74
75            vector<Point> approx;
76
77            // test each contour
78            for( size_t i = 0; i < contours.size(); i++ )
79            {
80                // approximate contour with accuracy proportional
81                // to the contour perimeter
82
83                approxPolyDP(Mat(contours[i]), approx, arcLength(Mat(contours[i]), true)*0.02, true);
84
85                // square contours should have 4 vertices after approximation
86                // relatively large area (to filter out noisy contours)
87                // and be convex.
88                // Note: absolute value of an area is used because
89                // area may be positive or negative - in accordance with the
90                // contour orientation
91                if( approx.size() == 4 &&
92                        fabs(contourArea(Mat(approx))) > 1000 &&
93                        isContourConvex(Mat(approx)) )
94                {
95                    double maxCosine = 0;
96
97                    for( int j = 2; j < 5; j++ )
98                    {
99                        // find the maximum cosine of the angle between joint edges
100                        double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
101                        maxCosine = MAX(maxCosine, cosine);
102                    }
103
104                    // if cosines of all angles are small
105                    // (all angles are ~90 degree) then write quandrange
106                    // vertices to resultant sequence
107                    if( maxCosine < 0.3 )
108                        squares.push_back(approx);
109                }
110            }
111        }
112    }
113}
114
115// the function draws all the squares in the image
116static void drawSquares( UMat& _image, const vector<vector<Point> >& squares )
117{
118    Mat image = _image.getMat(ACCESS_WRITE);
119    for( size_t i = 0; i < squares.size(); i++ )
120    {
121        const Point* p = &squares[i][0];
122        int n = (int)squares[i].size();
123        polylines(image, &p, &n, 1, true, Scalar(0,255,0), 3, LINE_AA);
124    }
125}
126
127
128// draw both pure-C++ and ocl square results onto a single image
129static UMat drawSquaresBoth( const UMat& image,
130                            const vector<vector<Point> >& sqs)
131{
132    UMat imgToShow(Size(image.cols, image.rows), image.type());
133    image.copyTo(imgToShow);
134
135    drawSquares(imgToShow, sqs);
136
137    return imgToShow;
138}
139
140
141int main(int argc, char** argv)
142{
143    const char* keys =
144        "{ i input    | ../data/pic1.png   | specify input image }"
145        "{ o output   | squares_output.jpg | specify output save path}"
146        "{ h help     | false              | print help message }"
147        "{ m cpu_mode | false              | run without OpenCL }";
148
149    CommandLineParser cmd(argc, argv, keys);
150
151    if(cmd.has("help"))
152    {
153        cout << "Usage : squares [options]" << endl;
154        cout << "Available options:" << endl;
155        cmd.printMessage();
156        return EXIT_SUCCESS;
157    }
158    if (cmd.has("cpu_mode"))
159    {
160        ocl::setUseOpenCL(false);
161        std::cout << "OpenCL was disabled" << std::endl;
162    }
163
164    string inputName = cmd.get<string>("i");
165    string outfile = cmd.get<string>("o");
166
167    int iterations = 10;
168    namedWindow( wndname, WINDOW_AUTOSIZE );
169    vector<vector<Point> > squares;
170
171    UMat image;
172    imread(inputName, 1).copyTo(image);
173    if( image.empty() )
174    {
175        cout << "Couldn't load " << inputName << endl;
176        cmd.printMessage();
177        return EXIT_FAILURE;
178    }
179
180    int j = iterations;
181    int64 t_cpp = 0;
182    //warm-ups
183    cout << "warming up ..." << endl;
184    findSquares(image, squares);
185
186    do
187    {
188        int64 t_start = cv::getTickCount();
189        findSquares(image, squares);
190        t_cpp += cv::getTickCount() - t_start;
191
192        t_start  = cv::getTickCount();
193
194        cout << "run loop: " << j << endl;
195    }
196    while(--j);
197    cout << "average time: " << 1000.0f * (double)t_cpp / getTickFrequency() / iterations << "ms" << endl;
198
199    UMat result = drawSquaresBoth(image, squares);
200    imshow(wndname, result);
201    imwrite(outfile, result);
202    waitKey(0);
203
204    return EXIT_SUCCESS;
205}
206