OpenCV For Android NDK

This is a showcase how to get OpenCV up and running with just the Android NDK

• This uses the NDK Camera2 API to get the image buffers
• It then uses OpenCV to processes the image buffer
• Lastly it gets the NDK ANativeWindow and displays the image for live previewing

Demo

Prerequisites

• Android API 24 (Nougat) or greater
• Android Studio 2.3+
• OpenCV-Android-SDK

How to setup

• Clone or download repo and open the OpenCV-NDK folder. (The 2nd one that is the child)
  • Click "Open project" in Android studio and find the folder saved in
• Change the OpenCV Android SDK library path in Android.mk file to your my/path/to/OpenCV-android-sdk/sdk/native/jni/OpenCV.mk
• Move all files in the Asset folder to your device
  • This is annoying af, but no good solution I could find easily fixed it since OpenCV requires a file string which the NDK only gives you a file descriptor.
  • Currently the folder location pointing to the asset files are listed in the CV_Main.h private values so make sure it matches
  • On your computer go to the ./OpenCV-NDK/app/src/main/assets folder and with your device plugged in run
    • adb push haarcascade_frontalface_alt.xml /sdcard/Download/opencv/haarcascade_frontalface_alt.xml
    • adb push haarcascade_eye_tree_eyeglasses.xml /sdcard/Download/opencv/haarcascade_eye_tree_eyeglasses.xml

How to run 32 bit (or x86)

To make compiling faster I only have it load and run ARM 64-bit (arm64-v8a). To add a different abi architecture:

• In the build.gradle file add , armeabi-v7a so gradle
• in the Application.mk file add armeabi-v7a