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
13 using namespace cv;
14 using namespace std;
15
16 /// Global variables
17
18 /** General variables */
19 Mat src, edges;
20 Mat src_gray;
21 Mat standard_hough, probabilistic_hough;
22 int min_threshold = 50;
23 int max_trackbar = 150;
24
25 const char* standard_name = "Standard Hough Lines Demo";
26 const char* probabilistic_name = "Probabilistic Hough Lines Demo";
27
28 int s_trackbar = max_trackbar;
29 int p_trackbar = max_trackbar;
30
31 /// Function Headers
32 void help();
33 void Standard_Hough( int, void* );
34 void Probabilistic_Hough( int, void* );
35
36 /**
37 * @function main
38 */
main(int,char ** argv)39 int 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 */
help()76 void 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 */
Standard_Hough(int,void *)86 void 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 */
Probabilistic_Hough(int,void *)113 void 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