Morphology Lines Extraction Tutorial

samples/cpp/tutorial_code/ImgProc/Morphology_3.cpp

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+/**
+ * @file Morphology_3(Extract_Lines).cpp
+ * @brief Use morphology transformations for extracting horizontal and vertical lines sample code
+ * @author OpenCV team
+ */
+
+#include <iostream>
+#include <opencv2/opencv.hpp>
+
+using namespace std;
+using namespace cv;
+
+int main(int, char** argv)
+{
+//! [load_image]
+    // Load the image
+    Mat src = imread(argv[1]);
+
+    // Check if image is loaded fine
+    if(!src.data)
+        cerr << "Problem loading image!!!" << endl;
+
+    // Show source image
+    imshow("src", src);
+//! [load_image]
+
+//! [gray]
+    // Transform source image to gray if it is not
+    Mat gray;
+
+    if (src.channels() == 3)
+    {
+        cvtColor(src, gray, CV_BGR2GRAY);
+    }
+    else
+    {
+        gray = src;
+    }
+
+    // Show gray image
+    imshow("gray", gray);
+//! [gray]
+
+//! [bin]
+    // Apply adaptiveThreshold at the bitwise_not of gray, notice the ~ symbol
+    Mat bw;
+    adaptiveThreshold(~gray, bw, 255, CV_ADAPTIVE_THRESH_MEAN_C, THRESH_BINARY, 15, -2);
+
+    // Show binary image
+    imshow("binary", bw);
+//! [bin]
+
+//! [init]
+    // Create the images that will use to extract the horizontal and vertical lines
+    Mat horizontal = bw.clone();
+    Mat vertical = bw.clone();
+//! [init]
+
+//! [horiz]
+    // Specify size on horizontal axis
+    int horizontalsize = horizontal.cols / 30;
+
+    // Create structure element for extracting horizontal lines through morphology operations
+    Mat horizontalStructure = getStructuringElement(MORPH_RECT, Size(horizontalsize,1));
+
+    // Apply morphology operations
+    erode(horizontal, horizontal, horizontalStructure, Point(-1, -1));
+    dilate(horizontal, horizontal, horizontalStructure, Point(-1, -1));
+
+    // Show extracted horizontal lines
+    imshow("horizontal", horizontal);
+//! [horiz]
+
+//! [vert]
+    // Specify size on vertical axis
+    int verticalsize = vertical.rows / 30;
+
+    // Create structure element for extracting vertical lines through morphology operations
+    Mat verticalStructure = getStructuringElement(MORPH_RECT, Size( 1,verticalsize));
+
+    // Apply morphology operations
+    erode(vertical, vertical, verticalStructure, Point(-1, -1));
+    dilate(vertical, vertical, verticalStructure, Point(-1, -1));
+
+    // Show extracted vertical lines
+    imshow("vertical", vertical);
+//! [vert]
+
+//! [smooth]
+    // Inverse vertical image
+    bitwise_not(vertical, vertical);
+    imshow("vertical_bit", vertical);
+
+    // Extract edges and smooth image according to the logic
+    // 1. extract edges
+    // 2. dilate(edges)
+    // 3. src.copyTo(smooth)
+    // 4. blur smooth img
+    // 5. smooth.copyTo(src, edges)
+
+    // Step 1
+    Mat edges;
+    adaptiveThreshold(vertical, edges, 255, CV_ADAPTIVE_THRESH_MEAN_C, THRESH_BINARY, 3, -2);
+    imshow("edges", edges);
+
+    // Step 2
+    Mat kernel = Mat::ones(2, 2, CV_8UC1);
+    dilate(edges, edges, kernel);
+    imshow("dilate", edges);
+
+    // Step 3
+    Mat smooth;
+    vertical.copyTo(smooth);
+
+    // Step 4
+    blur(smooth, smooth, Size(2, 2));
+
+    // Step 5
+    smooth.copyTo(vertical, edges);
+
+    // Show final result
+    imshow("smooth", vertical);
+//! [smooth]
+
+    waitKey(0);
+    return 0;
+}