Generate custom opencv .so for Android [Windows 10] [Solved]

edit

Following mvuori's suggestion I checked the flags used in my compilation and could finally achieve after 4 days the result I wanted to, the step by step solution is as follows.

First, make sure you have the following software:

• Java JDK 8+ is required, you can use other versions but be careful and check compatibility with gradle since you will need it later (e. g. currently gradle 5 has no compatibilty with java 13 and it is expected to ship with gradle 6).

• Android SDK

• Android NDK (I used ver 20.0.5594570)

You can download both of them via the Android Studio SDK Manager, in the latest versions of AS (3.5+) it seems the ndk packaging changed so just check where it says NDK (Side by side)

• Apache ant 1.10.7

• MinGW Install and Make sure you have the following cheked:

• CMake The CMake GUI is really useful in windows so I higly recommend to use it (I used version 3.16.0-rc2)

• Python I used version 3.8.0 (Remember to check in the installer just before finishing to create the environment variables for you!)

Once you have all that installed remember to set up the environment variables for each one of those + your java configuration:

• Android:

• Ant:

• Java:

• Path:

Get the Open CV sources you want to build, I advise you to set them up like:

The build folder will be where the files for generation will be, so for now just create and empty folder.

You don't need to modify any file in the sources folder however, depending on you java version and the gradle version present in sources you might have to, for exampl, as I had Java 11 and fon OpenCV release 4.1.2 the gradle wrapper version is 4.6 you wil get an error when you try to get the folders to the install folder so just go to:

..\YOUR OPEN CV VERSION\source\platforms\android\gradle-wrapper\gradle\wrapper\gradle-wrapper.properties

And use a version compatible with your java set up, in my case I used 5.4.1 instead of 4.6

Now, open the CMake GUI and begin set up:

I recommend to check this, it will allow you to sort out the flags in a better way:

Add the following entries:

• ANDROID_NDK = The path to your NDK
• ANDROID_SDK_ROOT = The path to your SDK
• ANDROID_NATIVE_API_LEVEL = Whatever Min API you want, I used 17, but default is 21
• ANT_EXECUTABLE = Your path towards the ant.bat file located in the ../ant/bin/ folder
• ANDROID_STL = By default this value is c++_static however the default opencv android sdk ships with c++_shared so I use the same
• ANDROID_ABI = By default it will build armeabi-v7a, so you only need yo change it to repeat this process for arm64-v8a, x86 and x86-64 (Also you can use armeabi-v7a with NEON to improve FP performance)

Don't worry about the red here.

With all that done press configure, and select as follows ... (more)