pt, aruco: another take at focal length formula

Aspect ratio is meant to be viewport's ratio, not diagonal to axis.

2 files changed, 8 insertions, 6 deletions

diff --git a/ftnoir_tracker_aruco/ftnoir_tracker_aruco.cpp b/ftnoir_tracker_aruco/ftnoir_tracker_aruco.cpp
index 84f20a61..fa783fe9 100755
--- a/ftnoir_tracker_aruco/ftnoir_tracker_aruco.cpp
+++ b/ftnoir_tracker_aruco/ftnoir_tracker_aruco.cpp
@@ -154,10 +154,11 @@ void Tracker::run()
 
         static constexpr double pi = 3.1415926f;
         const int w = grayscale.cols, h = grayscale.rows;
-        const double diag = sqrt(w * w + h * h)/w, diag_fov = static_cast<int>(s.fov) * pi / 180.;
-        const double fov = 2.*atan(tan(diag_fov/2.)/sqrt(1. + diag*diag));
-        const float focal_length_w = .5 * w / tan(.5 * fov);
-        const float focal_length_h = focal_length_w;
+        const double diag_fov = static_cast<int>(s.fov) * pi / 180.;
+        const double fov_w = 2.*atan(tan(diag_fov/2.)/sqrt(1. + h/(double)w * h/(double)w));
+        const double fov_h = 2.*atan(tan(diag_fov/2.)/sqrt(1. + w/(double)h * w/(double)h));
+        const float focal_length_w = .5 * w / tan(.5 * fov_w);
+        const float focal_length_h = .5 * h / tan(.5 * fov_h);
 
         intrinsics.at<float> (0, 0) = focal_length_w;
         intrinsics.at<float> (1, 1) = focal_length_h;
diff --git a/ftnoir_tracker_pt/ftnoir_tracker_pt.cpp b/ftnoir_tracker_pt/ftnoir_tracker_pt.cpp
index e10cfea0..4fa70ccf 100644..100755
--- a/ftnoir_tracker_pt/ftnoir_tracker_pt.cpp
+++ b/ftnoir_tracker_pt/ftnoir_tracker_pt.cpp
@@ -57,8 +57,9 @@ bool Tracker_PT::get_focal_length(float& ret)
     {
         static constexpr double pi = 3.14159265359;
         const int w = info.res_x, h = info.res_y;
-        const double diag = sqrt(w * w + h * h)/w, diag_fov = static_cast<int>(s.fov) * pi / 180.;
-        const double fov = 2.*atan(tan(diag_fov/2.0)/sqrt(1. + diag*diag));
+        const double diag = sqrt(1. + h/(double)w * h/(double)w);
+        const double diag_fov = static_cast<int>(s.fov) * pi / 180.;
+        const double fov = 2.*atan(tan(diag_fov/2.0)/diag);
         ret = .5 / tan(.5 * fov);
         return true;
     }