I have several Images of shape H, F, I, L.. which have curved corners. How do I process them to give sharp right-angled corners? I tried approximating them with inner rectangles, but this takes a LOT of time.. How do I proceed with it?
This is the sample Image. I want to process it such that I get rid of rounded corneres.
here's how houghLinesP would look like. Not a solution yet, but maybe you can work with that:
int main()
{
cv::Mat image = cv::imread("SharpenCorners.jpg");
cv::imshow("image", image);
cv::Mat gray;
cv::cvtColor(image,gray,CV_BGR2GRAY);
cv::imshow("gray", gray);
cv::Mat output; image.copyTo(output);
// gradient:
cv::Mat gx, gy;
cv::Sobel(gray, gx, CV_32F, 1, 0, 3 );
cv::Sobel(gray, gy, CV_32F, 0, 1, 3 );
cv::Mat gm;
cv::magnitude(gx,gy,gm);
//cv::Mat g_thres = gray < 100;
cv::Mat g_thres = gm > 100;
//int lineThres = 5; // 1st image
//int lineThres = 10;// 2nd image
//int lineThres = 25;// 3rd image
int lineThres = 50;// 4th image
std::vector<cv::Vec4i> lines;
cv::HoughLinesP( g_thres, lines, 1, CV_PI/(4*180.0), lineThres, 10, 10 );
for( size_t i = 0; i < lines.size(); i++ )
{
cv::line( output, cv::Point(lines[i][0], lines[i][1]),
cv::Point(lines[i][2], lines[i][3]), cv::Scalar(155,255,155), 2, 8 );
}
cv::imwrite("houghpSharpen4.png", output);
cv::imshow("g thres", g_thres);
cv::namedWindow("output"); cv::imshow("output", output);
cv::waitKey(-1);
return 0;
}
with these results for given thresholds:
1st:
2nd:
3rd:
4th:
Additional idea:
Giving your own comment, that you might try to approximate each contour with rectangles, you could start with houghLinesP results (with a pretty high threshold to get at least all "long" line elements) and try to create the rectangles based on those lines
It is easy to find the contour for each character. You can analyze the contour to find the points at the corners. Using one line to connect two adjacent points can produce right angle corners.
