I tried to compile a .so library using Visual Studio 2019 along with OpenCV Android in order to use this library in Unity.
There are some answers on how to configure Visual Studio to use OpenCV Android (here or here) but none of these work for me. Below you can see my configurations.
Visual Studio 2019 (running on Windows 10)
android-ndk-r21e // also tried with android-ndk-r15c android-ndk-r16b and android-ndk-r17c
OpenCV Android 4.5.2 // also tried with OpenCV Android 4.0.0, 4.0.1 and 4.1.0
My settings in Visual Studio 2019 look as follows:
Configuration Properties
- General
Platform Toolset Clang 5.0 (also tried Clang 3.8 or GCC 4.9)
Configuration Type Dynamic Library (.so)
Target API Level Nougat 7.0 (android-24) (also tried different versions)
Use STL LLVM libc++ static library (c++_static) (also tried "GNU STL static library (gnustl_static)")
C/C++
- General
Additional Include Directories "Path to OpenCV_4_5_2_Android\sdk\native\jni\include"
Code Generation Enable C++ Exceptions "Yes(-fexceptions)"
Language C++17(-std=c++1z)
Precompiled Headers Not using Precompiled Headers
Linker
- General
Additional Library Directories Path to OpenCV_4_5_2_Android\sdk\native\libs\armeabi-v7a
- Input
Additional Dependencies Path to OpenCV_4_5_2_Android\sdk\native\libs\armeabi-v7a\libopencv_java4.so
My Source.cpp I try to compile is just a single function for testing purposes
#include <opencv2/core.hpp>
extern "C" float test(float a, float b)
{float c = a * b; return c;}
Which gives me the following errors:
E0035 #error directive: This constructor has not been ported to this platform
E0020 identifier "__fp16" is undefined
use of undeclared identifier 'ANDROID_LOG_INFO'
The ANDROID_LOG_INFO error can be fixed when I add #include "android/log.h" at the top of the file that throws this error. But the other two errors still remain.
I had the exact same issue as you (though I used c++ 11) with the exact same setup, and struggled for days. I believe the errors you're seeing (like me) are from arm_neon.h. Very oddly, I was able to just build (not run) the .so successfully, even with those errors (I say "errors" because if you look at arm_neon.h, others pop up), so try it. Maybe it's some kind of IntelliJ/Intellisense mistake more than anything else where it's catching false negatives from some other toolchain setup.
At the same time, I'm not 100% sure I was always able to build with that issue, so try these steps as well if you can't:
use OpenCV 4.0.1 with Android NDK 16rb. The NDK matters when it comes to OpenCV builds, and this is the only supposed match that I know of.
follow this tutorial from scratch: https://amin-ahmadi.com/2019/06/03/how-to-use-opencv-in-unity-for-android/
if the downloaded OpenCV android SDK is still giving trouble, build OpenCV from the source using his other tutorial here: https://amin-ahmadi.com/2019/02/03/how-to-build-opencv-4-x-for-native-android-development/
and then repeat step 2.
MAJOR EDIT:
OpenCV 4.5.2 needs to be treated differently because it no longer uses toolchains with gnu c++.
-When you build OpenCV from CMake, build with Android NDK 21e, and do not use the toolchain in OpenCV 4.5.2. Use the one inside the Android NDK's build folder (android-ndk-r21e\build\cmake).
-When you build your .so from Visual Studio 2019, do not use the GNU STL, use the LLVM. GNU c++ is no longer part of Android NDKs, and you need to cut it out of the process entirely.
-In the Linker Input, put the names of your library files (or file, if it's just the world one) in the Library Dependencies field, not the Additional Dependencies field.
-Everything else is the same as in those common tutorials.
Related
I am very new to Android and I have to code an Android app with openCV.
I try to run the Use OpenCL in Android camera preview based CV application tutorial under Android studio.
I downloaded openCV 3.4 for android and imported the module into my project.
I used adb pull to get libOpenCL.so from my Samsung J5 (which I know supports openCL).
I downloaded OpenCL 1.1 header files and put them in /usr/include/CL
I integrated the java and cpp files from the tutorial samples repo and added the cpp into CMake
In my CMakeList.txt I have:
add_library( # Sets the name of the library.
native-lib
# Sets the library as a shared library.
SHARED
# Provides a relative path to your source file(s).
src/main/cpp/native-lib.cpp
src/main/cpp/jni.c
src/main/cpp/CLProcessor.cpp)
But I am getting TONS of error like
Error:(749, 23) error: use of undeclared identifier 'malloc'; did you mean 'alloca'?
or
Error:(36, 2) error: Bionic header ctype.h does not define either _U nor _CTYPE_U
Since this is my first ever Android project I am completly lost (I read a lot of papers/answers...).
Can anyone help me?
EDIT: I found why I had these particular compile error: I retrieved openCL 1.1 headers and changing them to 1.2 fixed compile error.
I managed to successfuly compile openCL with openCV (but even though my device has openCL with CL-GL interop, the platform has no openCL extensions at all).
(I have Android Studio 3.0.1 under Debian 9.3.)
This compile error is caused by use of openCL 1.1 headers. Use openCl 1.2 instead.
I have to compile a library (library BPG from Bellard.org) to create a .so or a dll that I can use with android/iOS.
I'm working with Visual Studio. With some researches, I found the project "Visual C++ -> Cross Platform -> Shared Library (Android, iOS)". But I am totally lost and can't do anything.
The downloaded library is organised with some folders but Visual don't allow to make tree, all files are sorted by filters (one for header and one for sources). So I can't build, I have more than 300 errors, "can't open source file", "undefined variable"...
Secondly, the README file from project says :
The following packages need to be installed: mingw64-gcc mingw64-libpng mingw64-libjpeg-turbo mingw64-SDL mingw64-SDL_image yasm
I found installed for mingw 32 bits but no 64 bits so I don't know if build can perform. I don't know how to find the libraries.
So my question is, what is the best way to compile a C/C++ library for android/iOS ? And where can I find a tutorial for beginners ?
Thank you
I have worked as cross compiling engineer for several years. The most suitable IDE for you I think, is the CLion with CMake inside.
CMake is a tool which can cross-compile the C/C++ library into ios\android\linux\etc.. using only one config file: "CMakeList.txt".
The main task of CMake is to translate CMakeList.txt to Makefile on every platform and provide you the .a and .so files.
CLion is very powerful IDE in code editing and debugging.
Furthermore, Android needs JNI (or JNA if performance is not concerned) to wrap your c++ interfaces to java classes. Here I would recommend SWIG. SWIG is a tool to wrap C++ interfaces to other languages, that means, not only java on android you can support , other days your lib can also support python\tcl\Go\etc.
Which os are u using to build the lib? macOS or win ?
For iOS : .a file
For Android: .so file
First you should check the README file
Edit the Makefile to change the compile options (the default
compile options should be OK). Type 'make' to compile and 'make
install' to install the compiled binaries.
Use 'make -j N' where N is the number of CPU cores to compile faster.
The following packages must be installed: SDL-devel
SDL_image-devel yasm. It is recommended to use yasm version >= 1.3.0
to have a faster compilation.
Only a 64 bit target is supported because x265 needs it for bit
depths > 8.
check this to install SDL packages
https://wiki.libsdl.org/Installation
I would like to download some working example of Android Studio NDK project with C or C++ which will be compiled to .so library (or APK from which I can extract .so).
I have tried ndkbuild with Android.mk build and also CMake with CMakeLists.txt, official and unofficial tutorials on Windows...
If I try them on android from same app (java), it is working but I want to use NDK in Unity3D on android and I keep getting DllNotFoundException.
I uploaded my Android and Unity projects to github.
First of all, here is a sample Android Project plugin you are looking for.
It's very important to know how to do this yourself.
This used to be hard to do before but the latest Android Studio made it easier to now use C/C++ or generate .so library easily. Update Android Studio to the latest version then follow steps below to create a C++ plugin.
1.Create a new Project in Android Studio
2.Check the Include C++ suport to enable C++.
3.On the Dropdown Menu, check C++ 11 on the C++ Standard drop-down menu. You will need C++ 11 to actually use most useful C++ features. Also, enable exception or frtti if you need them.
That's really it.
When you build the plugin:
The debug library is should be at:
\app\build\intermediates\cmake\debug\obj\
The release library is should be at:
\app\build\intermediates\cmake\debug\obj\
If you only see the debug but not the release version of the plugin, check here for how to make it appear.
Possible reasons you are getting DllNotFoundException on Android:
1.You did not wrap the C/C++ function around extern "C". You must do this for each function in the .cpp file or you do it in the function in the .h file.
2.You put the plugin in the wrong Unity folder.
The armeabi-v7a and x86 plugins generated at <ProjectDirectory>\app\build\intermediates\cmake\release\obj should be placed at Assets\Plugins\Android\libs\armeabi-v7a\ and Assets\Plugins\Android\libs\x86\ in the Unity project.
Make sure to spell these correctly. See this for more information about this.
3.You are loading it incorrectly from the C# side.
Let's say that the name of the plugin is libScreenshot.a, do not include the lib prefix, also do not add the .a when loading it.
[DllImport("Screenshot", CallingConvention = CallingConvention.Cdecl)]
public static extern void takeScreenshot();
I am trying to compile a C++ library to use it with an Android app. I am using CMake to generate the makefile, but when I configure the CMake script, the configuration takes "mips64el" as compilation reference (CMAKE_AR, CMAKE_ASM_COMPILER, CMAKE_C_COMPILER, etc.). This compiler is not compatible with the flags generated in the makefile, so the building process fails.
The most strange thing is that in a second PC, the same configuration defines "arm-linux" as compilation reference.
As additional note, I am using Ubuntu 14.04 in both pc's. I am defining "armeabi-v7a" as Android ABI, and Android API level as 9. Also, I have included the path to the NDK libraries (android-ndk-r10c) in the environment variables (as ANDROID_NDK and in the PATH variable).
Any sugestion?
The error was in the toolchain itself. It looks like the libraries in the first computer were ignored in the configuration step because those library versions where not listed in the toolchain, so the only available configurations was the mips64el.
I have updated the toolchain file from this github repository, and it is working properly now.
I've been working on an Android project which has several native C++ libraries. Compiling and debugging using Eclipse with ADT plugin works well. Obviously Android NDK uses arm-linux-gnueabi-gcc of some version to compile the native libraries.
Since I've been using NEON intrinsics heavily, I would like to try to compile the native libraries with ARM's official compiler armcc. I read everywhere that armcc is supposed to give better optimized code when using intrinsics. So I downloaded the trial version of DS-5 from ARM website, just to try and see whether there's really any speed difference.
The DS-5 seems to be just a modified version of Eclipse that uses the ARMCC toolchain, so I installed the ADT plugin. But when I compile using DS-5, it seems that the code is still generated using gcc rather than armcc.
Do you have any idea how to force DS-5 or Eclipse to build the Android native code using armcc? Or is it possible (and how) to build the static NDK libraries from command line and then replace the libraries in my project, so they get deployed to the testing phone?
ARM DS-5 Community Edition doesn't include ARM compiler (armcc).
If you could get hold of armcc best would be to separate your processing heavy algorithms to individual compilation units (separate C files), build them with armcc as you would do for any compilation unit. When you get the object files, convert them into an archive then use that in Android.mk as LOCAL_STATIC_LIBRARIES += <your_archive>.
You can't use armcc plainly to build Android compatible libraries mostly because of Bionic dependencies, I think.
You can use armcc to build Android compatible static libraries even though Android has a different C library (bionic). The key is the --library_interface flag for armcc. According to the documentation:
Use an option of the form --library_interface=aeabi_* when linking with an ABI-compliant C library. Options of the form --library_interface=aeabi_* ensure that the compiler does not generate calls to any optimized functions provided by the ARM C library.
In addition, there are a few more flags to ensure compatibility with the Android EABI resulting in the following command for an Android armeabi-v7a target:
armcc --library_interface=aeabi_clib --wchar32 --enum_is_int --no_hide_all --cpu=7-A --fpu=softvfp+vfpv3 -c -o libfunc.o libfunc.c
You can then use armar --create libfunc.a libfunc.o to create a static library that can be linked with the Android NDK as LOCAL_STATIC_LIBRARIES.
I have successfully tested this with Android NDK r10d on Android KitKat 4.4.2.