Fix a typo error

Fix a typo error
Conflicts:
	modules/features2d/include/opencv2/features2d.hpp

modules/features2d/include/opencv2/features2d/features2d.hpp

@@ -879,7 +879,7 @@ CV_EXPORTS Mat windowedMatchingMask( const vector<KeyPoint>& keypoints1, const v
 /*
  * OpponentColorDescriptorExtractor
  *
- * Adapts a descriptor extractor to compute descripors in Opponent Color Space
+ * Adapts a descriptor extractor to compute descriptors in Opponent Color Space
  * (refer to van de Sande et al., CGIV 2008 "Color Descriptors for Object Category Recognition").
  * Input RGB image is transformed in Opponent Color Space. Then unadapted descriptor extractor
  * (set in constructor) computes descriptors on each of the three channel and concatenate

samples/cpp/freak_demo.cpp

@@ -87,7 +87,7 @@ int main( int argc, char** argv ) {
 
     // DESCRIPTOR
     // Our proposed FREAK descriptor
-    // (roation invariance, scale invariance, pattern radius corresponding to SMALLEST_KP_SIZE,
+    // (rotation invariance, scale invariance, pattern radius corresponding to SMALLEST_KP_SIZE,
     // number of octaves, optional vector containing the selected pairs)
     // FREAK extractor(true, true, 22, 4, std::vector<int>());
     FREAK extractor;