Tutorial Hough Lines

samples/cpp/houghlines.cpp

@@ -1,77 +0,0 @@
-#include "opencv2/imgcodecs.hpp"
-#include "opencv2/highgui.hpp"
-#include "opencv2/imgproc.hpp"
-
-#include <iostream>
-
-using namespace cv;
-using namespace std;
-
-static void help()
-{
-    cout << "\nThis program demonstrates line finding with the Hough transform.\n"
-            "Usage:\n"
-            "./houghlines <image_name>, Default is ../data/pic1.png\n" << endl;
-}
-
-int main(int argc, char** argv)
-{
-    cv::CommandLineParser parser(argc, argv,
-        "{help h||}{@image|../data/pic1.png|}"
-    );
-    if (parser.has("help"))
-    {
-        help();
-        return 0;
-    }
-    string filename = parser.get<string>("@image");
-    if (filename.empty())
-    {
-        help();
-        cout << "no image_name provided" << endl;
-        return -1;
-    }
-    Mat src = imread(filename, 0);
-    if(src.empty())
-    {
-        help();
-        cout << "can not open " << filename << endl;
-        return -1;
-    }
-
-    Mat dst, cdst;
-    Canny(src, dst, 50, 200, 3);
-    cvtColor(dst, cdst, COLOR_GRAY2BGR);
-
-#if 0
-    vector<Vec2f> lines;
-    HoughLines(dst, lines, 1, CV_PI/180, 100, 0, 0 );
-
-    for( size_t i = 0; i < lines.size(); i++ )
-    {
-        float rho = lines[i][0], theta = lines[i][1];
-        Point pt1, pt2;
-        double a = cos(theta), b = sin(theta);
-        double x0 = a*rho, y0 = b*rho;
-        pt1.x = cvRound(x0 + 1000*(-b));
-        pt1.y = cvRound(y0 + 1000*(a));
-        pt2.x = cvRound(x0 - 1000*(-b));
-        pt2.y = cvRound(y0 - 1000*(a));
-        line( cdst, pt1, pt2, Scalar(0,0,255), 3, CV_AA);
-    }
-#else
-    vector<Vec4i> lines;
-    HoughLinesP(dst, lines, 1, CV_PI/180, 50, 50, 10 );
-    for( size_t i = 0; i < lines.size(); i++ )
-    {
-        Vec4i l = lines[i];
-        line( cdst, Point(l[0], l[1]), Point(l[2], l[3]), Scalar(0,0,255), 3, LINE_AA);
-    }
-#endif
-    imshow("source", src);
-    imshow("detected lines", cdst);
-
-    waitKey();
-
-    return 0;
-}

samples/cpp/tutorial_code/ImgTrans/houghlines.cpp

@@ -0,0 +1,89 @@
+/**
+ * @file houghclines.cpp
+ * @brief This program demonstrates line finding with the Hough transform
+ */
+
+#include "opencv2/imgcodecs.hpp"
+#include "opencv2/highgui.hpp"
+#include "opencv2/imgproc.hpp"
+
+using namespace cv;
+using namespace std;
+
+int main(int argc, char** argv)
+{
+    // Declare the output variables
+    Mat dst, cdst, cdstP;
+
+    //![load]
+    const char* default_file = "../../../data/sudoku.png";
+    const char* filename = argc >=2 ? argv[1] : default_file;
+
+    // Loads an image
+    Mat src = imread( filename, IMREAD_GRAYSCALE );
+
+    // Check if image is loaded fine
+    if(src.empty()){
+        printf(" Error opening image\n");
+        printf(" Program Arguments: [image_name -- default %s] \n", default_file);
+        return -1;
+    }
+    //![load]
+
+    //![edge_detection]
+    // Edge detection
+    Canny(src, dst, 50, 200, 3);
+    //![edge_detection]
+
+    // Copy edges to the images that will display the results in BGR
+    cvtColor(dst, cdst, COLOR_GRAY2BGR);
+    cdstP = cdst.clone();
+
+    //![hough_lines]
+    // Standard Hough Line Transform
+    vector<Vec2f> lines; // will hold the results of the detection
+    HoughLines(dst, lines, 1, CV_PI/180, 150, 0, 0 ); // runs the actual detection
+    //![hough_lines]
+    //![draw_lines]
+    // Draw the lines
+    for( size_t i = 0; i < lines.size(); i++ )
+    {
+        float rho = lines[i][0], theta = lines[i][1];
+        Point pt1, pt2;
+        double a = cos(theta), b = sin(theta);
+        double x0 = a*rho, y0 = b*rho;
+        pt1.x = cvRound(x0 + 1000*(-b));
+        pt1.y = cvRound(y0 + 1000*(a));
+        pt2.x = cvRound(x0 - 1000*(-b));
+        pt2.y = cvRound(y0 - 1000*(a));
+        line( cdst, pt1, pt2, Scalar(0,0,255), 3, CV_AA);
+    }
+    //![draw_lines]
+
+    //![hough_lines_p]
+    // Probabilistic Line Transform
+    vector<Vec4i> linesP; // will hold the results of the detection
+    HoughLinesP(dst, linesP, 1, CV_PI/180, 50, 50, 10 ); // runs the actual detection
+    //![hough_lines_p]
+    //![draw_lines_p]
+    // Draw the lines
+    for( size_t i = 0; i < linesP.size(); i++ )
+    {
+        Vec4i l = linesP[i];
+        line( cdstP, Point(l[0], l[1]), Point(l[2], l[3]), Scalar(0,0,255), 3, LINE_AA);
+    }
+    //![draw_lines_p]
+
+    //![imshow]
+    // Show results
+    imshow("Source", src);
+    imshow("Detected Lines (in red) - Standard Hough Line Transform", cdst);
+    imshow("Detected Lines (in red) - Probabilistic Line Transform", cdstP);
+    //![imshow]
+
+    //![exit]
+    // Wait and Exit
+    waitKey();
+    return 0;
+    //![exit]
+}