Hi, I'm new to OpenCV and want to use SIFT and SURF features detector on Android Studio that is available on opencv_contrib. I'm using these tutorial (with modification) to build opencv 3.1.0 extra module https://github.com/tzutalin/build-opencv-for-android and this tutorial https://github.com/alexkarargyris/Caffe_OpenCV_Android_App but it shows the same error like this, eventhough I already declared it -DANDROID_NDK=/Documents/android-ndk-r8e
-- Caffe: NO -- Protobuf: NO -- Glog: NO
CMake Error at /Users/giovinnakhoharja/build-opencv-for-android/android-ndk-downloader/opencv/platforms/android/android.toolchain.cmake:447 (message): Could not find neither Android NDK nor Android standalone toolchain.
I can show you the ErrorLog if you want. And then I try to use CMake GUI with some modification of this tutorial https://zami0xzami.wordpress.com/2016/03/17/building-opencv-for-android-from-source/ but even when I already make new entry of ANDROID_NDK, after I press configure (using Unix Makefiles because Mac don't have MinGW) the variable ANDROID_NDK is missing.
I have El Captian 10.11.1, CMake.app 3.6.0, Android NDK r8e Darwin x86_64 (because CMakeList.txt says that it supports only r5-r10). I already install CMake on command line. Can someone tell me what is wrong?