compile dlib and opencv with android ndk

bendaf 07/28/2017. 1 answers, 101 views
android android build android-ndk android-ndk dlib android-studio-2.3

I am an android developer, but I am new to Android NDK, please help, or tell me what else would you need/ how would you try to solve this type of problem.

I used this dlib for android example and the official opencv for android library and I would like to integrate the two in one application. When I trying to build the project I get the following error:

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':openCVSamplefacedetection:externalNativeBuildDebug'.
> Build command failed.
  Error while executing process /home/feli/Android/Sdk/ndk-bundle/ndk-build with arguments {NDK_PROJECT_PATH=null APP_BUILD_SCRIPT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/Android.mk NDK_APPLICATION_MK=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/Application.mk APP_ABI=mips64 NDK_ALL_ABIS=mips64 NDK_DEBUG=1 APP_PLATFORM=android-21 NDK_OUT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj NDK_LIBS_OUT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/lib /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/libdetection_based_tracker.so}
  [mips64] Compile++      : detection_based_tracker <= DetectionBasedTracker_jni.cpp
  [mips64] Prebuilt       : libopencv_java3.so <= /home/feli/Android/openCV/OpenCV-android-sdk/sdk/native/jni/../libs/mips64/
  [mips64] SharedLibrary  : libdetection_based_tracker.so
  /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/objs-debug/detection_based_tracker/DetectionBasedTracker_jni.o: In function `dlib_check_consistent_assert_usage':
  /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/threads/threads_kernel_shared.h:44: undefined reference to `USER_ERROR__missing_dlib_all_source_cpp_file__OR__inconsistent_use_of_DEBUG_or_ENABLE_ASSERTS_preprocessor_directives_'
  clang++: error: linker command failed with exit code 1 (use -v to see invocation)
  make: *** [/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/libdetection_based_tracker.so] Error 1


* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

My first guess were that I haven/t included the source.cpp in my Android.mk but placeing it to the src files didn't solve the porblem. Here is my Android.mk:

LOCAL_PATH := $(call my-dir)

## Build dlib to static library
include $(CLEAR_VARS)
LOCAL_MODULE := dlib
LOCAL_C_INCLUDES := $(LOCAL_PATH)/dlib

LOCAL_SRC_FILES += \
                $(LOCAL_PATH)/dlib/dlib/all/source.cpp \
                $(LOCAL_PATH)/dlib//dlib/threads/threads_kernel_shared.cpp \
                $(LOCAL_PATH)/dlib/dlib/entropy_decoder/entropy_decoder_kernel_2.cpp \
                $(LOCAL_PATH)/dlib/dlib/base64/base64_kernel_1.cpp \
                $(LOCAL_PATH)/dlib/dlib/threads/threads_kernel_1.cpp \
                $(LOCAL_PATH)/dlib/dlib/threads/threads_kernel_2.cpp

LOCAL_EXPORT_C_INCLUDES := $(LOCAL_C_INCLUDES)
include $(BUILD_STATIC_LIBRARY)

# Build opencv
include $(CLEAR_VARS)
OPENCVROOT := ~/Android/openCV/OpenCV-android-sdk
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on
OPENCV_LIB_TYPE := SHARED
include ${OPENCVROOT}/sdk/native/jni/OpenCV.mk

LOCAL_MODULE     := detection_based_tracker
LOCAL_C_INCLUDES += $(LOCAL_PATH)
LOCAL_SRC_FILES  := DetectionBasedTracker_jni.cpp

LOCAL_LDLIBS     += -lm -llog -ldl -lz -ljnigraphics
LOCAL_CPPFLAGS += -fexceptions -frtti -std=c++11

# LOCAL_STATIC_LIBRARIES += dlib

include $(BUILD_SHARED_LIBRARY)

Maybe the NDK_PROJECT_PATH=null is the problem? Than why the two libraries are building separately? Or what else can be the problem? I tried a lot modifying the Android.mk, but it's working is a mystery for me. Any help or opinion would be useful.

EDIT:

When I comment out the LOCAL_STATIC_LIBRARIES += dlib row, I got the following exception:

Build command failed.
  Error while executing process /home/feli/Android/Sdk/ndk-bundle/ndk-build with arguments {NDK_PROJECT_PATH=null APP_BUILD_SCRIPT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/Android.mk NDK_APPLICATION_MK=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/Application.mk APP_ABI=mips64 NDK_ALL_ABIS=mips64 NDK_DEBUG=1 APP_PLATFORM=android-21 NDK_OUT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj NDK_LIBS_OUT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/lib /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/libdetection_based_tracker.so}
  [mips64] Compile++      : detection_based_tracker <= DetectionBasedTracker_jni.cpp
  [mips64] Compile++      : dlib <= source.cpp
  In file included from /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/all/source.cpp:76:
  In file included from /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/all/../gui_widgets/fonts.cpp:14:
  /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/all/../gui_widgets/nativefont.h:27:10: fatal error: 'X11/Xlib.h' file not found
  #include <X11/Xlib.h>
           ^~~~~~~~~~~~
  1 error generated.
  make: *** [/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/objs-debug/dlib//home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/all/source.o] Error 1
5 Comments
Alex Cohn 07/28/2017
Do you really need MIPS build? If you intend to run your app on ARM devices, add abiFilters= "armeabi_v7a" to your build.gradle script.
bendaf 07/30/2017
I am running on abi arm64-v8a, but I am modifying the native c++ code also, so I suppose I need to build it also.
Alex Cohn 07/30/2017
You should not comment out LOCAL_STATIC_LIBRARIES += dlib
bendaf 07/31/2017
I have edited my question, please check it if you have time
1 Alex Cohn 07/31/2017
No, you should not worry about NDK_PROJECT_PATH, that's how Android Studio configures the native build via ndk-build. But dlib is structured around cmake, so should reproduce the build settings used there.

1 Answers


Alex Cohn 07/31/2017.

dlib uses cmake, and it is not a trivial setup. It may take a long time for an experience professional to prepare the ndk-build scripts for this library.

I suggest that you build your native library with cmake, instead of ndk-build. You can find an example of a native library that uses OpenCv on GitHub.

Also, I suggest that you start with abiFilters set to only one most relevant ABI, and only when you see that everything works for you, you can build your project for other ABIs. Remember that for some libraries porting to all ABIs may be tricky. And if you don't have a platform to perform at least a brief sanity check for some ABI, there is no sense in building for it.

1 comments
bendaf 07/31/2017
Thanks, I will try that!

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