Tutorial: Setting Up OpenCV for Android

Hey everyone,
Welcome!
My goal with this tutorial is to make it super easy for you to create an Android application using the OpenCV library.

Before we dive in, it's helpful to check the tool versions I used to avoid any compatibility issues.

Tools Version

Tool	Version
OpenCV Android SDK	openCV-3.2.0
Android Studio	v2.2.2
Android SDK Build-tools	v25
Android SDK Platform-tools	v25.0.3
Android Official NDK	android-ndk-r12b

OS: Windows 10

Getting Started

First things first—download these:

Extract the Files

Extract the NDK to a directory without spaces in the path, e.g. C:\work\android-ndk-r12b
Extract the OpenCV SDK to a location near the NDK (though its exact location doesn't really matter)

Setting Up Environment Variables (Java & NDK)

Right-click This PC → Properties → click Advanced system settings
In the window that appears, go to the Advanced tab and click Environment Variables
Under User variables, find the PATH variable and click Edit
Click New, then add the path to your Java bin folder
Example: C:\Program Files\Java\jdk1.8.0_40\bin\
Add the NDK root path in the same way
Example: C:\work\android-ndk-r12b
Done!

Installing CMake (Required for Native Code)

Open Android Studio and go to Settings
Navigate to Appearance & Behavior → System Settings → Android SDK
Go to the SDK Tools tab and make sure CMake is checked and installed
If it’s not, check it and click Apply

Creating Your Android Project

Let’s build your first project:

Open Android Studio → click New Project
Fill in the Application Name and Company Domain
Important: Check the box for Include C++ Support
Proceed with the default settings
On the final screen before clicking Finish, set the C++ standard. I recommend using Toolchain Default

Note:
If you encounter this error:
Error: NDK not configured. Download it with SDK manager.
Follow these steps:

Go to File → Project Structure
Set the correct NDK path under Android NDK location

Import the OpenCV Java Module

Go to File → New → Import Module
Navigate to {YOUR_OPENCV_SDK_DIR}\sdk\ and select the java folder
Click OK, then Next, then Finish
Open your app-level build.gradle file and add this under dependencies:

implementation project(':openCVLibrary320')

openCVLibrary320 is the default module name. Yours might differ depending on the SDK version.

Add `jniLibs` Folder

Right-click the app module → New → Folder → JNI Folder
Check Change Folder Location
Change the directory from src/main/jni/ to src/main/jniLibs/
Click Finish

Add Native Libraries

You’ll need native libraries for each processor architecture you want to support. Luckily, OpenCV provides them all!

They’re located in \sdk\native\libs inside the OpenCV SDK
Copy only the folders you need (or all of them) into your project’s jniLibs directory

Pro tip: Only include the architectures you plan to support to reduce app size.

Create and Configure `Android.mk`

Inside jniLibs, create a new file named Android.mk
Add the following content:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

OPENCV_LIB_TYPE := SHARED
OPENCV_CAMERA_MODULES := on
OPENCV_INSTALL_MODULES := on

include {OpenCV.mk_DIR}

LOCAL_SRC_FILES  := native-lib.cpp
LOCAL_C_INCLUDES += {INCLUDE_DIR}
LOCAL_LDLIBS     += -llog -ldl
LOCAL_CFLAGS     += -DOPENCV_OLDER_VERSION

LOCAL_CPP_FEATURES += exceptions
LOCAL_CPPFLAGS += -fexceptions

LOCAL_MODULE     := native-lib

include $(BUILD_SHARED_LIBRARY)

Notes:

{OpenCV.mk_DIR} → path to OpenCV.mk, usually:
\sdk\native\jni\OpenCV.mk
{INCLUDE_DIR} → path to OpenCV’s include directory:
\sdk\native\jni\include
LOCAL_MODULE → name of your native C++ source file (native-lib.cpp)

Optional Configs:

OPENCV_CAMERA_MODULES and OPENCV_INSTALL_MODULES:
Set to off if you want the app to require the OpenCV Manager app on the user's device

That’s It!

You’re now all set to start building your Android OpenCV app with native C++ support.

makbn/opencv_android_setup_tutorial

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