Compiling Android JNI for OpenCV on Mac OSX

Question

Bear with me - this is a long description, but I wanted to include all details. I'm trying use android NDK and JNI for building OpenCV Android apps.

I'm following this tutorial to get everything installed: http://www.stanford.edu/class/ee368/Android/Tutorial-2-OpenCV-for-Android-Setup-Macintosh-API8.pdf

The following installed just fine:

/usr/bin/g++
/usr/local/bin/swig
/usr/bin/cmake
/usr/bin/make
/Developer/pcre-8.32/

Contents of my .bashrc file:

export  NDK=/Users/Me/Code/Android/android-ndk-r4-crystax
export  SDK=/Users/Me/Code/Android/adt-bundle-mac-x86_64-20130219/
export  OPCV=/Users/Me/Code/OpenCV/opencv
export  PATH=$NDK:$SDK/tools:$SDK/platform-tools:$PATH
export NDK_ROOT=$NDK

Making OpenCV libraries went just fine.

Due to complaint in using make, I had to make a small edit in /Users/Me/Code/OpenCV/opencv/android/android-jni/local.env.mk which looked like so:

#ANDROID_NDK_ROOT=$(HOME)/android-ndk-r4-crystax
ANDROID_NDK_ROOT=/Users/Me/Code/Android/android-ndk-r4-crystax

Then upon trying again to make in the android-jni, directory, disaster struck:

/Users/Me/Code/Android/android-ndk-r4-crystax/ndk-build OPENCV_CONFIG=../build/android-opencv.mk \
    PROJECT_PATH= ARM_TARGETS="armeabi armeabi-v7a" V= 
Gdbserver      : [arm-eabi-4.4.0] /Users/Me/Code/OpenCV/opencv/android/android-jni/libs/armeabi/gdbserver
Gdbsetup       : /Users/Me/Code/OpenCV/opencv/android/android-jni/libs/armeabi/gdb.setup
Gdbsetup       : + source directory /Users/Me/Code/OpenCV/opencv/android/android-jni/jni
Gdbserver      : [arm-eabi-4.4.0] /Users/Me/Code/OpenCV/opencv/android/android-jni/libs/armeabi-v7a/gdbserver
Gdbsetup       : /Users/Me/Code/OpenCV/opencv/android/android-jni/libs/armeabi-v7a/gdb.setup
Gdbsetup       : + source directory /Users/Me/Code/OpenCV/opencv/android/android-jni/jni
SharedLibrary  : libandroid-opencv.so
/Users/Me/Code/Android/android-ndk-r4-crystax/build/prebuilt/darwin-x86/arm-eabi-4.4.0/bin/../lib/gcc/arm-eabi/4.4.0/../../../../arm-eabi/bin/ld: cannot find -lopencv_calib3d
collect2: ld returned 1 exit status
make[1]: *** [/Users/Me/Code/OpenCV/opencv/android/android-jni/obj/local/armeabi/libandroid-opencv.so] Error 1
make: *** [libs/armeabi-v7a/libandroid-opencv.so] Error 2

I thought perhaps this was a pkg-config error, but that appears to be set up as well, though in my old install of OpenCV. Below is the output of pkg-config --cflags --libs opencv:

-I/usr/include/opencv  /usr/lib/libopencv_calib3d.dylib /usr/lib/libopencv_contrib.dylib /usr/lib/libopencv_core.dylib /usr/lib/libopencv_features2d.dylib /usr/lib/libopencv_flann.dylib /usr/lib/libopencv_gpu.dylib /usr/lib/libopencv_highgui.dylib /usr/lib/libopencv_imgproc.dylib /usr/lib/libopencv_legacy.dylib /usr/lib/libopencv_ml.dylib /usr/lib/libopencv_nonfree.dylib /usr/lib/libopencv_objdetect.dylib /usr/lib/libopencv_photo.dylib /usr/lib/libopencv_stitching.dylib /usr/lib/libopencv_ts.dylib /usr/lib/libopencv_video.dylib /usr/lib/libopencv_videostab.dylib 

The install built by this particular tutorial has placed an opencv.pc file at this location:

/Users/Me/Code/OpenCV/opencv/build/unix-install

BUT Running the below and trying make again doesn't fix the problem:

export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/Users/Me/Code/OpenCV/opencv/build/unix-install

I can't figure out what is wrong. I've been battling with this problem for about a month on and off, and finally needed some outside opinions. Any ideas?

Answer 1

Error message says

cannot find -lopencv_calib3d collect2: ld returned 1 exit status

It means linker can't find opencv_calib3d library. It may have name libopencv_calib3d.a or libopencv_calib3d.so. So you need find one of them and add path to this file to your LD_LIBRARY_PATH env variable.

I mean if let's say folder /Users/Me/Code/OpenCV/opencv/lib contains libopencv_calib3d.so then you need execute something like following before make:

export LD_LIBRARY_PATH=/Users/Me/Code/OpenCV/opencv/lib:$LD_LIBRARY_PATH