cv::gpu::HoughLines is not working properly - c++

Question

I am trying to detect some lines using Hough Transform on a cv::gpu::GpuMat structure. I have tried using both gpu::HoughLines and gpu::HoughLinesP but even with extremely low thresholds, I am not getting any results at all. During debugging, I see that the container which should contain the results (houghLines) has only zeros stored inside it. The code I have written is given below,
static cv::Mat drawHoughLinesOnMat (cv::gpu::GpuMat hough_Mat, cv::gpu::GpuMat houghLines)
{
cv::Mat output_Mat;
cv::cvtColor(cv::Mat(hough_Mat), output_Mat, CV_GRAY2BGR);
std::vector<cv::Vec4i> lines_vector;
if (!houghLines.empty())
{
lines_vector.resize(houghLines.cols);
cv::Mat temp_Mat (1, houghLines.cols, CV_8UC3, &lines_vector[0]);
houghLines.download (temp_Mat);
}
for (size_t i=0; i<lines_vector.size(); ++i)
{
cv::Vec4i l = lines_vector[i];
cv::line(output_Mat, cv::Point(l[0], l[1]), cv::Point(l[2], l[3]), cv::Scalar(0, 0, 255), 1, 8);
}
return output_Mat;
}
int main()
{
cv::Mat input = cv::imread(INPUT_DATA_1->c_str(), CV_LOAD_IMAGE_GRAYSCALE);
std::string imageType = getImgType(input.type());
cv::gpu::GpuMat mat_input(input), bil_out, mat_thresh, hough_lines;
cv::gpu::HoughLinesBuf hough_buffer;
int bilateral_thresh = 15; // 5 == 0.085s; 15 == 0.467s at run-time
cv::gpu::bilateralFilter(mat_input, bil_out, bilateral_thresh, bilateral_thresh*2, bilateral_thresh/2);
//cv::gpu::threshold(bil_out, mat_thresh, 10, 255, CV_THRESH_BINARY);
cv::gpu::Canny(bil_out, mat_thresh, 10, 60, 5);
cv::gpu::HoughLinesP(mat_thresh, hough_lines, hough_buffer, 1.0f, (float)(CV_PI/180.0f), 5, 1);
//cv::Mat test_hough(hough_lines);
cv::Mat hough_Mat = drawHoughLinesOnMat(mat_input, hough_lines);
cv::gpu::HoughLines(mat_thresh, hough_lines, 1.0f, (float)(CV_PI/180.0f), 1, true);
/*cv::Mat */hough_Mat = drawHoughLinesOnMat(mat_input, hough_lines);
return EXIT_SUCCESS
}
The image I am using is,
Could someone tell me what it is that I am doing wrong..? Thanks in advance.!
The output of the Canny filter is,
EDIT:
I have tested on the CPU version of HoughLines and it seems to work just fine.
EDIT_2:
The solution posted by #jet47 works perfectly.

Answer 1

You use incorrect code for downloading results from GPU back to CPU:
lines_vector.resize(houghLines.cols);
cv::Mat temp_Mat (1, houghLines.cols, CV_8UC3, &lines_vector[0]);
houghLines.download (temp_Mat);
You use incorrect type for temp_Mat - CV_8UC3, it must be CV_32SC4.
The correct code is:
lines_vector.resize(houghLines.cols);
cv::Mat temp_Mat(1, houghLines.cols, CV_32SC4, &lines_vector[0]);
houghLines.download(temp_Mat);

Answer 2

My guess is that the Method you are using is outdated (but im not entirely sure).
This is how i would do it(as demonstrated in this Example Code):
//d_src filled with your image somewhere
GpuMat d_lines;
{
Ptr<cuda::HoughSegmentDetector> hough = cuda::createHoughSegmentDetector(1.0f, (float) (CV_PI / 180.0f), 50, 5);
hough->detect(d_src, d_lines);
}
vector<Vec4i> lines_gpu;
if (!d_lines.empty())
{
lines_gpu.resize(d_lines.cols);
Mat h_lines(1, d_lines.cols, CV_32SC4, &lines_gpu[0]);
d_lines.download(h_lines);
}
for (size_t i = 0; i < lines_gpu.size(); ++i)
{
Vec4i l = lines_gpu[i];
line(dst_gpu, Point(l[0], l[1]), Point(l[2], l[3]), Scalar(0, 0, 255), 3, LINE_AA);
}
EDIT The above uses the OpenCv 3.0 Interface