1/**
2 * @file HoughLines_Demo.cpp
3 * @brief Demo code for Hough Transform
4 * @author OpenCV team
5 */
6
7#include "opencv2/imgcodecs.hpp"
8#include "opencv2/highgui/highgui.hpp"
9#include "opencv2/imgproc/imgproc.hpp"
10#include <iostream>
11#include <stdio.h>
12
13using namespace cv;
14using namespace std;
15
16/// Global variables
17
18/** General variables */
19Mat src, edges;
20Mat src_gray;
21Mat standard_hough, probabilistic_hough;
22int min_threshold = 50;
23int max_trackbar = 150;
24
25const char* standard_name = "Standard Hough Lines Demo";
26const char* probabilistic_name = "Probabilistic Hough Lines Demo";
27
28int s_trackbar = max_trackbar;
29int p_trackbar = max_trackbar;
30
31/// Function Headers
32void help();
33void Standard_Hough( int, void* );
34void Probabilistic_Hough( int, void* );
35
36/**
37 * @function main
38 */
39int main( int, char** argv )
40{
41   /// Read the image
42   src = imread( argv[1], 1 );
43
44   if( src.empty() )
45     { help();
46       return -1;
47     }
48
49   /// Pass the image to gray
50   cvtColor( src, src_gray, COLOR_RGB2GRAY );
51
52   /// Apply Canny edge detector
53   Canny( src_gray, edges, 50, 200, 3 );
54
55   /// Create Trackbars for Thresholds
56   char thresh_label[50];
57   sprintf( thresh_label, "Thres: %d + input", min_threshold );
58
59   namedWindow( standard_name, WINDOW_AUTOSIZE );
60   createTrackbar( thresh_label, standard_name, &s_trackbar, max_trackbar, Standard_Hough);
61
62   namedWindow( probabilistic_name, WINDOW_AUTOSIZE );
63   createTrackbar( thresh_label, probabilistic_name, &p_trackbar, max_trackbar, Probabilistic_Hough);
64
65   /// Initialize
66   Standard_Hough(0, 0);
67   Probabilistic_Hough(0, 0);
68   waitKey(0);
69   return 0;
70}
71
72/**
73 * @function help
74 * @brief Indications of how to run this program and why is it for
75 */
76void help()
77{
78  printf("\t Hough Transform to detect lines \n ");
79  printf("\t---------------------------------\n ");
80  printf(" Usage: ./HoughLines_Demo <image_name> \n");
81}
82
83/**
84 * @function Standard_Hough
85 */
86void Standard_Hough( int, void* )
87{
88  vector<Vec2f> s_lines;
89  cvtColor( edges, standard_hough, COLOR_GRAY2BGR );
90
91  /// 1. Use Standard Hough Transform
92  HoughLines( edges, s_lines, 1, CV_PI/180, min_threshold + s_trackbar, 0, 0 );
93
94  /// Show the result
95  for( size_t i = 0; i < s_lines.size(); i++ )
96     {
97      float r = s_lines[i][0], t = s_lines[i][1];
98      double cos_t = cos(t), sin_t = sin(t);
99      double x0 = r*cos_t, y0 = r*sin_t;
100      double alpha = 1000;
101
102       Point pt1( cvRound(x0 + alpha*(-sin_t)), cvRound(y0 + alpha*cos_t) );
103       Point pt2( cvRound(x0 - alpha*(-sin_t)), cvRound(y0 - alpha*cos_t) );
104       line( standard_hough, pt1, pt2, Scalar(255,0,0), 3, LINE_AA);
105     }
106
107   imshow( standard_name, standard_hough );
108}
109
110/**
111 * @function Probabilistic_Hough
112 */
113void Probabilistic_Hough( int, void* )
114{
115  vector<Vec4i> p_lines;
116  cvtColor( edges, probabilistic_hough, COLOR_GRAY2BGR );
117
118  /// 2. Use Probabilistic Hough Transform
119  HoughLinesP( edges, p_lines, 1, CV_PI/180, min_threshold + p_trackbar, 30, 10 );
120
121  /// Show the result
122  for( size_t i = 0; i < p_lines.size(); i++ )
123     {
124       Vec4i l = p_lines[i];
125       line( probabilistic_hough, Point(l[0], l[1]), Point(l[2], l[3]), Scalar(255,0,0), 3, LINE_AA);
126     }
127
128   imshow( probabilistic_name, probabilistic_hough );
129}
130