tracker/pt: try cache pixels slightly below `thres'

The logic is that each point has a halo around it. Catching the entire
halo will allow to have more stable centers. Larger points are more
stable as well.

1 files changed, 5 insertions, 1 deletions

diff --git a/tracker-pt/module/point_extractor.cpp b/tracker-pt/module/point_extractor.cpp
index fcf58c2d..f8c37351 100644
--- a/tracker-pt/module/point_extractor.cpp
+++ b/tracker-pt/module/point_extractor.cpp
@@ -190,7 +190,8 @@ void PointExtractor::threshold_image(const cv::Mat& frame_gray, cv::Mat1b& outpu
         float const* const __restrict ptr = hist.ptr<float>(0);
         const unsigned area = uround(3 * M_PI * radius*radius);
         const unsigned sz = unsigned(hist.cols * hist.rows);
-        unsigned thres = 32;
+        constexpr unsigned min_thres = 64;
+        unsigned thres = min_thres;
         for (unsigned i = sz-1, cnt = 0; i > 32; i--)
         {
             cnt += ptr[i];
@@ -199,6 +200,9 @@ void PointExtractor::threshold_image(const cv::Mat& frame_gray, cv::Mat1b& outpu
             thres = i;
         }
 
+        if (thres > min_thres)
+            thres *= .8;
+
         cv::threshold(frame_gray, output, thres, 255, cv::THRESH_BINARY);
     }
 }