完全在C ++中使用的OpenCV Android

Question

I noticed that most of the Android examples in github uses the opencv in java. I have a working app in iOS right now and I tried my best to separate the opencv calls from the bridging header.

Is it possible in android to do the same? I noticed that the opencv detector like the CascadeClassifier here were all in java and not in c++.

Can I achieve the same thing in Android like iOS?

Answer 1

You can using entirely in C++, and you must using JNI to let java code call native code.

After you download the Opencv-android-sdk, you can only import header files and ".a" files which you needed. The java files is optional that is provided for those who don't know C++.
For example, the java class CascadeClassifier，finally called the native function, and you can also do that like this, in fact, it's JNI:

 // C++:   CascadeClassifier::CascadeClassifier()
private static native long CascadeClassifier_0();

// C++:   CascadeClassifier::CascadeClassifier(string filename)
private static native long CascadeClassifier_1(String filename);

// C++:  void CascadeClassifier::detectMultiScale(Mat image, vector_Rect& objects, double scaleFactor = 1.1, int minNeighbors = 3, int flags = 0, Size minSize = Size(), Size maxSize = Size())
private static native void detectMultiScale_0(long nativeObj, long image_nativeObj, long objects_mat_nativeObj, double scaleFactor, int minNeighbors, int flags, double minSize_width, double minSize_height, double maxSize_width, double maxSize_height);
private static native void detectMultiScale_1(long nativeObj, long image_nativeObj, long objects_mat_nativeObj);

// C++:  void CascadeClassifier::detectMultiScale(Mat image, vector_Rect& objects, vector_int rejectLevels, vector_double levelWeights, double scaleFactor = 1.1, int minNeighbors = 3, int flags = 0, Size minSize = Size(), Size maxSize = Size(), bool outputRejectLevels = false)
private static native void detectMultiScale_2(long nativeObj, long image_nativeObj, long objects_mat_nativeObj, long rejectLevels_mat_nativeObj, long levelWeights_mat_nativeObj, double scaleFactor, int minNeighbors, int flags, double minSize_width, double minSize_height, double maxSize_width, double maxSize_height, boolean outputRejectLevels);
private static native void detectMultiScale_3(long nativeObj, long image_nativeObj, long objects_mat_nativeObj, long rejectLevels_mat_nativeObj, long levelWeights_mat_nativeObj);

// C++:  bool CascadeClassifier::empty()
private static native boolean empty_0(long nativeObj);

// C++:  bool CascadeClassifier::load(string filename)
private static native boolean load_0(long nativeObj, String filename);

// native support for java finalize()
private static native void delete(long nativeObj);