added gpu::HoughLinesP function

samples/gpu/houghlines.cpp

@@ -0,0 +1,89 @@
+#include <cmath>
+#include <iostream>
+
+#include "opencv2/core/core.hpp"
+#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/imgproc/imgproc.hpp"
+#include "opencv2/gpu/gpu.hpp"
+
+using namespace std;
+using namespace cv;
+using namespace cv::gpu;
+
+static void help()
+{
+    cout << "This program demonstrates line finding with the Hough transform." << endl;
+    cout << "Usage:" << endl;
+    cout << "./gpu-example-houghlines <image_name>, Default is pic1.png\n" << endl;
+}
+
+int main(int argc, const char* argv[])
+{
+    const string filename = argc >= 2 ? argv[1] : "pic1.png";
+
+    Mat src = imread(filename, IMREAD_GRAYSCALE);
+    if (src.empty())
+    {
+        help();
+        cout << "can not open " << filename << endl;
+        return -1;
+    }
+
+    Mat mask;
+    Canny(src, mask, 100, 200, 3);
+
+    Mat dst_cpu;
+    cvtColor(mask, dst_cpu, CV_GRAY2BGR);
+    Mat dst_gpu = dst_cpu.clone();
+
+    vector<Vec4i> lines_cpu;
+    {
+        const int64 start = getTickCount();
+
+        HoughLinesP(mask, lines_cpu, 1, CV_PI / 180, 50, 60, 5);
+
+        const double timeSec = (getTickCount() - start) / getTickFrequency();
+        cout << "CPU Time : " << timeSec * 1000 << " ms" << endl;
+        cout << "CPU Found : " << lines_cpu.size() << endl;
+    }
+
+    for (size_t i = 0; i < lines_cpu.size(); ++i)
+    {
+        Vec4i l = lines_cpu[i];
+        line(dst_cpu, Point(l[0], l[1]), Point(l[2], l[3]), Scalar(0, 0, 255), 3, CV_AA);
+    }
+
+    GpuMat d_src(mask);
+    GpuMat d_lines;
+    HoughLinesBuf d_buf;
+    {
+        const int64 start = getTickCount();
+
+        gpu::HoughLinesP(d_src, d_lines, d_buf, 1.0f, (float) (CV_PI / 180.0f), 50, 5);
+
+        const double timeSec = (getTickCount() - start) / getTickFrequency();
+        cout << "GPU Time : " << timeSec * 1000 << " ms" << endl;
+        cout << "GPU Found : " << d_lines.cols << endl;
+    }
+    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, CV_AA);
+    }
+
+    imshow("source", src);
+    imshow("detected lines [CPU]", dst_cpu);
+    imshow("detected lines [GPU]", dst_gpu);
+    waitKey();
+
+    return 0;
+}
+