Fix #750 making it compatible with Opencv4.4

Author: wandenberg

cc/xfeatures2d/SIFTDetector.h

@@ -6,7 +6,11 @@
 #ifndef __FF_SIFTDETECTOR_H__
 #define __FF_SIFTDETECTOR_H__
 
+#if CV_VERSION_GREATER_EQUAL(4, 4, 0)
+class SIFTDetector : public FeatureDetector, public FF::ObjectWrapTemplate<SIFTDetector, cv::Ptr<cv::SIFT>> {
+#else
 class SIFTDetector : public FeatureDetector, public FF::ObjectWrapTemplate<SIFTDetector, cv::Ptr<cv::xfeatures2d::SIFT>> {
+#endif
 public:
 	static Nan::Persistent<v8::FunctionTemplate> constructor;
 
@@ -47,7 +51,11 @@ class SIFTDetector : public FeatureDetector, public FF::ObjectWrapTemplate<SIFTD
 			auto sigma = opt<FF::DoubleConverter>("sigma", 1.6);
 
 			executeBinding = [=]() {
+			#if CV_VERSION_GREATER_EQUAL(4, 4, 0)
+				return cv::SIFT::create(
+			#else
 				return cv::xfeatures2d::SIFT::create(
+			#endif
 					nFeatures->ref(),
 					nOctaveLayers->ref(),
 					contrastThreshold->ref(),
@@ -67,4 +75,4 @@ class SIFTDetector : public FeatureDetector, public FF::ObjectWrapTemplate<SIFTD
 	};
 };
 
-#endif
+#endif