Android: Custom NDK/C++ android.media.Image implementation backed by OpenGL texture/HardwareBuffer

Question

I'm working on a Camera2 app where I have a custom OpenGL pipeline set up for processing video frames.

In my pipeline, I use a couple of different third party frame-processing APIs that expect an android.media.Image as parameter (e.g. for detecting faces, or other models).

I have a OpenGL texture which I can use to create & fill a AHardwareBuffer. How do I now synchronously create android.media.Image instances which are backed by my OpenGL Texture/HardwareBuffer?

1. I understand that the android.media.Image class' implementation is pretty much entirely in NDK/C++, but AImage from mediandk also doesn't provide a constructor.
2. I say synchronously, because I am aware of creating an ImageReader and then streaming into it's Surface, but this is not what I want since those are not synchronously created, but instead only created in the setOnImageAvailableListener callback.

Answer 1

While an Android media.Image in fact is mostly a wrapper around a graphics buffer, and therefore at the low level can be treated as a AHardwareBuffer (plus metadata), there's unfortunately no public API to create a media.Image from a AHardwareBuffer (though the other way around is possible) since the media.Image also has ownership semantics related to ImageReaders and Writers.

I know you'd like a synchronous solution, but I don't believe there is one, in the public API. You basically have to use an ImageReader as the destination of your EGL rendering.