added handling of camera parameters estimation errors (#3122)

modules/stitching/include/opencv2/stitching.hpp

@@ -59,7 +59,13 @@ class CV_EXPORTS Stitcher
 {
 public:
     enum { ORIG_RESOL = -1 };
-    enum Status { OK, ERR_NEED_MORE_IMGS };
+    enum Status
+    {
+        OK = 0,
+        ERR_NEED_MORE_IMGS = 1,
+        ERR_HOMOGRAPHY_EST_FAIL = 2,
+        ERR_CAMERA_PARAMS_ADJUST_FAIL = 3
+    };
 
     // Creates stitcher with default parameters
     static Stitcher createDefault(bool try_use_gpu = false);
@@ -138,7 +144,7 @@ private:
     Stitcher() {}
 
     Status matchImages();
-    void estimateCameraParams();
+    Status estimateCameraParams();
 
     double registr_resol_;
     double seam_est_resol_;