How do I send OpenCV Mat as a putExtra to Android Intent?

Question

I am trying to send either CvCameraViewFrame or Mat to another activity, but they don't implement Serializable or Parcelable and creating a wrapper class for them just to use it once seems like an overkill. How do I proceed?

Answer 1

I would have used fragments instead of activities and get/set common Mat present in container Activity from fragments.

If there is a need to stick with multiple activities, assuming it's within process, options are

1. Sharing - Use global Application subclass to get/set the Mat preferably in some thing like HashMap<String, WeakReference<Mat>> and passing HashMap's key string across activities(1). Make sure you stores a strong reference to the Mat before child activity completes onResume(), or else Mat could be garbage collected.

2. Copying - Using getNativeObjAddr(2) and pass the long address value as part of invoking Intent. Child activity would recreate the Mat with the native address(3). Cloning Mat in child is necessary since parent activity could be killed any time after onResume of child activity is completed.

Sample below.

// In parent activity
Mat img = ...;
long addr = img.getNativeObjAddr();
Intent intent = new Intent(this, B.class);
intent.putExtra( "myImg", addr );
startActivity( intent );

//In child activity
long addr = intent.getLongExtra("myImg", 0);
Mat tempImg = new Mat( addr );
Mat img = tempImg.clone();