Fixed division by zero case in SphericalProjector::mapForward

modules/stitching/include/opencv2/stitching/detail/warpers_inl.hpp

@@ -242,7 +242,8 @@ void SphericalProjector::mapForward(float x, float y, float &u, float &v)
     float z_ = r_kinv[6] * x + r_kinv[7] * y + r_kinv[8];
 
     u = scale * atan2f(x_, z_);
-    v = scale * (static_cast<float>(CV_PI) - acosf(y_ / sqrtf(x_ * x_ + y_ * y_ + z_ * z_)));
+    float w = y_ / sqrtf(x_ * x_ + y_ * y_ + z_ * z_);
+    v = scale * (static_cast<float>(CV_PI) - acosf(w == w ? w : 0));
 }