Added createWightMaps function into FeatherBlender (stitching)

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

@@ -72,6 +72,7 @@ class CV_EXPORTS FeatherBlender : public Blender
 {
 public:
     FeatherBlender(float sharpness = 0.02f) { setSharpness(sharpness); }
+
     float sharpness() const { return sharpness_; }
     void setSharpness(float val) { sharpness_ = val; }
 
@@ -79,6 +80,11 @@ public:
     void feed(const Mat &img, const Mat &mask, Point tl);
     void blend(Mat &dst, Mat &dst_mask);
 
+    // Creates weight maps for fixed set of source images by their masks and top-left corners.
+    // Final image can be obtained by simple weighting of the source images.
+    Rect createWeightMaps(const std::vector<Mat> &masks, const std::vector<Point> &corners,
+                          std::vector<Mat> &weight_maps);
+
 private:
     float sharpness_;
     Mat weight_map_;