Merge remote-tracking branch 'upstream/3.4' into merge-3.4

modules/imgproc/include/opencv2/imgproc.hpp

@@ -1259,12 +1259,17 @@ protected:
 //! @addtogroup imgproc_feature
 //! @{
 
+/** @example samples/cpp/lsd_lines.cpp
+An example using the LineSegmentDetector
+\image html building_lsd.png "Sample output image" width=434 height=300
+*/
+
 /** @brief Line segment detector class
 
 following the algorithm described at @cite Rafael12 .
 
-@note Implementation has been removed due original code license conflict
-
+@note Implementation has been removed from OpenCV version 3.4.6 to 3.4.15 and version 4.1.0 to 4.5.3 due original code license conflict.
+restored again after [Computation of a NFA](https://github.com/rafael-grompone-von-gioi/binomial_nfa) code published under the MIT license.
 */
 class CV_EXPORTS_W LineSegmentDetector : public Algorithm
 {
@@ -1278,8 +1283,8 @@ public:
 
     @param image A grayscale (CV_8UC1) input image. If only a roi needs to be selected, use:
     `lsd_ptr-\>detect(image(roi), lines, ...); lines += Scalar(roi.x, roi.y, roi.x, roi.y);`
-    @param lines A vector of Vec4i or Vec4f elements specifying the beginning and ending point of a line. Where
-    Vec4i/Vec4f is (x1, y1, x2, y2), point 1 is the start, point 2 - end. Returned lines are strictly
+    @param lines A vector of Vec4f elements specifying the beginning and ending point of a line. Where
+    Vec4f is (x1, y1, x2, y2), point 1 is the start, point 2 - end. Returned lines are strictly
     oriented depending on the gradient.
     @param width Vector of widths of the regions, where the lines are found. E.g. Width of line.
     @param prec Vector of precisions with which the lines are found.
@@ -1327,8 +1332,6 @@ to edit those, as to tailor it for their own application.
 @param log_eps Detection threshold: -log10(NFA) \> log_eps. Used only when advance refinement is chosen.
 @param density_th Minimal density of aligned region points in the enclosing rectangle.
 @param n_bins Number of bins in pseudo-ordering of gradient modulus.
-
-@note Implementation has been removed due original code license conflict
  */
 CV_EXPORTS_W Ptr<LineSegmentDetector> createLineSegmentDetector(
     int refine = LSD_REFINE_STD, double scale = 0.8,