How to integrate OpenCV into Qt Creator Android project

Question

I use Qt Creator to compile an Android application. I needed to integrate OpenCV into it, and it took me half a day to configure it properly, so I want to document the steps

Answer 1

For OpenCV 4, sashoalm's approach did not work for me until I adapted it:

1. Download the Android-Pack and unzip it somewhere. We'll create a qmake-variable OPENCV_ANDROID which points to that directory later.

2. Add the following snippet to your *.pro-file:

   android {
       contains(ANDROID_TARGET_ARCH,arm64-v8a) {
           isEmpty(OPENCV_ANDROID) {
               error("Let OPENCV_ANDROID point to the opencv-android-sdk, recommended: v4.0")
           }
           INCLUDEPATH += "$$OPENCV_ANDROID/sdk/native/jni/include"
           LIBS += \
               -L"$$OPENCV_ANDROID/sdk/native/libs/arm64-v8a" \
               -L"$$OPENCV_ANDROID/sdk/native/3rdparty/libs/arm64-v8a" \
               -llibtiff \
               -llibjpeg-turbo \
               -llibjasper \
               -llibpng \
               -lIlmImf \
               -ltbb \
               -lopencv_java4 \
   
           ANDROID_EXTRA_LIBS = $$OPENCV_ANDROID/sdk/native/libs/arm64-v8a/libopencv_java4.so
       } else {
           error("Unsupported architecture: $$ANDROID_TARGET_ARCH")
       }
   }
   

   This will work for the arm64-v8a only. If you happen to build for another architecture (apparently 32-Bit is still the default for Qt@Android), you must change the .../libs/arm64-v8a part of the paths (occurs 3 times) and the same to match your actual target-architecture (the contains(...)-part in the second line of the snippet).

3. Tell qmake where to find the SDK. Add the following to qmake-call: "OPENCV_ANDROID=/path/to/OpenCV-android-sdk".
   • e.g., this looks like qmake example.pro "OPENCV_ANDROID=/home/user/OpenCV-android-sdk" from command line.
   • when you use QtCreator, add "OPENCV_ANDROID=..." to the "Additional arguments"-field. You can find it after enabling the Project-Mode in the Build-section of the android-kit. Expand the qmake-field under Build Steps