如何将OpenCV Mat作为putExtra发送到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();  

Answer 2

@Kiran is right.

You should get instance of Matrix using its native address.

long frameAddress = intent.getLongExtra("extra_name", 0);
Mat m = new Mat(frameAddress);