Fixed hough_transform::find_pixels_voting_for_lines(). It would sometimes

include a pixel multiple times in the output lists.

dlib/image_transforms/hough_transform.h

@@ -365,7 +365,11 @@ namespace dlib
             {
                 auto idx = hmap(hough_point.y(), hough_point.x());
                 if (idx < constituent_points.size())
-                    constituent_points[idx].push_back(img_point);
+                {
+                    // don't add img_point if it's already in the list.
+                    if (constituent_points[idx].size() == 0 || constituent_points[idx].back() != img_point)
+                        constituent_points[idx].push_back(img_point);
+                }
             };
 
             perform_generic_hough_transform(img, box, record_hit);

dlib/image_transforms/hough_transform_abstract.h

@@ -240,9 +240,9 @@ namespace dlib
                           that if angle_window_size or radius_window_size are made so large
                           that HP[i] overlaps HP[j] for i!=j then the overlapping regions
                           of Hough space are assigned to HP[i] or HP[j] arbitrarily.
-                          Therefore, all points in CONSTITUENT_POINTS are unique, that is,
-                          there is no overlap in points between any two elements of
-                          CONSTITUENT_POINTS.
+                          That is, we treat HP[i] and HP[j] as disjoint even if their boxes
+                          overlap.  In this case, the overlapping region is assigned to
+                          either HP[i] or HP[j] in an arbitrary manner.
         !*/
 
         template <