Merge pull request #13361 from okriof:brisk_getset

* Get/Set functions for BRISK parameters, issue #11527.

Allows setting threshold and octaves parameters after creating a brisk object. These parameters do not affect the initial pattern initialization and can be changed later without re-initialization.

* Fix doc parameter name.

* Brisk get/set functions tests. Check for correct value and make tests independent of default parameter values.

* Add dummy implementations for BRISK get/set functions not to break API in case someone has overloaded the Feature2d::BRISK interface. This makes BRISK different from the other detectors/descriptors on the other hand, where get/set functions are pure virtual in the interface.

modules/features2d/src/brisk.cpp

@@ -80,6 +80,26 @@ public:
         return NORM_HAMMING;
     }
 
+    virtual void setThreshold(int threshold_in) CV_OVERRIDE
+    {
+        threshold = threshold_in;
+    }
+
+    virtual int getThreshold() const CV_OVERRIDE
+    {
+        return threshold;
+    }
+
+    virtual void setOctaves(int octaves_in) CV_OVERRIDE
+    {
+        octaves = octaves_in;
+    }
+
+    virtual int getOctaves() const CV_OVERRIDE
+    {
+        return octaves;
+    }
+
     // call this to generate the kernel:
     // circle of radius r (pixels), with n points;
     // short pairings with dMax, long pairings with dMin