Install OpenCV

Master branch main algorothims of the Android App relies heavily on OpenCV 3.1. Indeed, a critical step is getting the data received in polar coordinates and we have to transform it in cartesian ones. OpenCV offers natively a routine to do that. Let's note that this piece of API knocks the JNI. That's the reason why in the preceding section, we invite the user to inform the ndk.dir in local.propeties file.

OpenCV 3.1 installation (by Greg Sadetsky)

Note: OpenCV versions 3 and later should be used as OpenCV 2.4.11 for Android lacks the polar interpolation functions.

The integration of OpenCV into the Android project (being developed in Android Studio) is a bit error-prone, and differs from one version of OpenCV and from one version of Android Studio to another. Here are the steps that worked for OpenCV 3.1 & Android Studio 1.5.1, based on these instructions (which seem to work for both OpenCV 2 & 3):

• Download the OpenCV 3.1 for Android from opencv.org
• Import the folder in Android Studio as an existing project
• Build everything in the project. Close the project.
• In the android-app project, choose Import Module, then select the <opencv directory>/sdk/java/sdk.iml file.
• Right-click the "app" in the project pane, choose "Open Module Settings"; under "Dependencies", click the "+" button, then choose "Module dependency", and then choose OpenCV
• from the OpenCV folder, copy the sdk/native/libs directory into your project's app/src/main, then rename it jniLibs