. Extract horizontal and vertical lines by using morphological operations

#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/highgui.hpp>
#include

void show_wait_destroy(const char* winname, cv::Mat img);

using namespace std;
using namespace cv;

int main(int argc, char** argv)
{
Mat src = imread( samples::findFile("/home/chang/projects/opencv_GPU_example/test.jpg"), IMREAD_COLOR);
if (src.empty())
{
cout << “Could not open or find the image!\n” << endl;
return -1;
}
// Show source image
imshow(“src”, src);

// Transform source image to gray if it is not already
Mat gray;
if (src.channels() == 3)
{
    cvtColor(src, gray, COLOR_BGR2GRAY);
}else{
    gray = src;
}
// Show gray image
show_wait_destroy("gray", gray);

// Apply adaptiveThreshold at the bitwise_not of gray, notice the ~ symbol
Mat bw;
adaptiveThreshold(~gray, bw, 255, ADAPTIVE_THRESH_MEAN_C, THRESH_BINARY, 15, -2);
// Show binary image
show_wait_destroy("binary", bw);

// Create the images that will use to extract the horizontal and vertical lines
Mat horizontal = bw.clone();
Mat vertical = bw.clone();

// Specify size on horizontal axis
int horizontal_size = horizontal.cols / 30;
// Create structure element for extracting horizontal lines through morphology operations
Mat horizontalStructure = getStructuringElement(MORPH_RECT, Size(horizontal_size, 1));
// Apply morphology operations
erode(horizontal, horizontal, horizontalStructure, Point(-1, -1));
dilate(horizontal, horizontal, horizontalStructure, Point(-1, -1));
// Show extracted horizontal lines
show_wait_destroy("horizontal", horizontal);

// Specify size on vertical axis
int vertical_size = vertical.rows / 30;
// Create structure element for extracting vertical lines through morphology operations
Mat verticalStructure = getStructuringElement(MORPH_RECT, Size(1, vertical_size));
// Apply morphology operations
erode(vertical, vertical, verticalStructure, Point(-1, -1));
dilate(vertical, vertical, verticalStructure, Point(-1, -1));
// Show extracted vertical lines
show_wait_destroy("vertical", vertical);

// Inverse vertical image
bitwise_not(vertical, vertical);
show_wait_destroy("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, ADAPTIVE_THRESH_MEAN_C, THRESH_BINARY, 3, -2);
show_wait_destroy("edges", edges);

// Step 2
Mat kernel = Mat::ones(2, 2, CV_8UC1);
dilate(edges, edges, kernel);
show_wait_destroy("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
show_wait_destroy("smooth - final", vertical);

return 0;

}

void show_wait_destroy(const char* winname, cv::Mat img) {
imshow(winname, img);
moveWindow(winname, 500, 0);
waitKey(0);
destroyWindow(winname);
}