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I need help with an application I am working on. The application has to have a custom Camera interface to record a video with audio and have to add some objects in realtime on the TextureView canvas. Old Camera API is deprecated, so I have to use Camera2 API to render the live preview on TextureView. My goal is to draw some objects on top of the TextureView Canvas, could be some text/jpg/gif while the camera stream renders in the background and being able to record the video with my overlay canvas content and camera feed.

Problem is I can draw custom content in an transparent overlay view but that is is just for user's viewing purposes. I have tried researching this for a few days but I am not able to get the right approach to solve my purpose.

I tried the following code after calling the openCamera() method, but then I just see a rectangle drawn but not the camera preview:

Canvas canvas = mTextureView.lockCanvas();
Paint myPaint = new Paint();
myPaint.setColor(Color.WHITE);
myPaint.setStrokeWidth(10);
canvas.drawRect(100, 100, 300, 300, myPaint);
mTextureView.unlockCanvasAndPost(canvas);

I also tried a custom TextureView class and override thevonDrawForeground(Canvas canvas) method but it doesn't work.

The onDraw() method in TextureView class is final and thus, I am not able to do anything at this point except for just streaming the camera feed.

/**
 * Subclasses of TextureView cannot do their own rendering
 * with the {@link Canvas} object.
 *
 * @param canvas The Canvas to which the View is rendered.
 */
@Override
protected final void onDraw(Canvas canvas) {
}

In short, I want user to be able to record video through my camera app with some props here and there.

Rishabh Agrawal
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2 Answers2

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Modifying a video in real time is a high processor and hence, high battery overhead operation - I am sure you know this but its worth saying that if you can add your modifications on the server side, maybe by sending the stream along with a timestamped set of text overlays to the server, you should have more horsepower server side.

The following code will add text and an image to a still picture or frame captured by Camera2 on Android. I have not used it with video so can't comment on speed and whether it is practical to do this with a real time video stream - it wasn't optimised for this but it should be a starting point for you:

        //Copy the image to a BitBuffer
        ByteBuffer buffer = mCameraImage.getPlanes()[0].getBuffer();
        byte[] bytes = new byte[buffer.remaining()];
        Log.d(TAG,"ImageSaver bytes.length: " + bytes.length);
        buffer.get(bytes);
        BitmapFactory.Options opt = new BitmapFactory.Options();
        opt.inMutable = true;
        Bitmap cameraBitmap = BitmapFactory.decodeByteArray(bytes,0,bytes.length, opt);
        if (cameraBitmap == null) {
            Log.d(TAG,"ImageSaver cameraBitmap is null");
            return;
        } else {
            camImgBitmap = cameraBitmap;
        }

        //Modify captured picture by drawing on canvas
        Canvas camImgCanvas = new Canvas(camImgBitmap);

        //Draw an image in the middle
        Drawable d = ContextCompat.getDrawable(this, R.drawable.image_to_add);
        int bitMapWidthCenter = camImgBitmap.getWidth()/2;
        int bitMapheightCenter = camImgBitmap.getHeight()/2;
        int imageToDrawSize = camImgBitmap.getWidth()/10;
        int rTop = bitMapheightCenter - sightsSize;
        int rLeft = bitMapWidthCenter - sightsSize;
        int rRight = bitMapWidthCenter + sightsSize;
        int rBot = bitMapheightCenter + sightsSize;
        d.setBounds(rLeft, rTop, rRight, rBot);
        d.draw(camImgCanvas);

        //Now Draw in some text
        Paint paint = new Paint();
        paint.setColor(Color.GREEN);
        int textSize = camImgBitmap.getHeight()/20;
        int textPadding = 40;
        paint.setTextSize(textSize);
        camImgCanvas.drawText("Name: " + text1, textPadding, (camImgBitmap.getHeight() - (textSize * 2) ) - textPadding, paint);
        camImgCanvas.drawText("Time: " + text2 + " degrees", textPadding, (camImgBitmap.getHeight() - textSize) - textPadding, paint);
Mick
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Likely the most performant option is to pipe the camera feed straight into the GPU, draw on top of it there, and from there render to the display and a video encoder directly.

This is what many video chat apps do, for example, for any effects.

You can use a SurfaceTexture to connect camera2 to EGL, and then you can render the preview onto a quad, and then your additions on top.

Then you can render to a screen buffer (GLSurfaceView for example), and to a separate EGLImage from a MediaRecorder/MediaCodec Surface.

There's a lot of code involved there, and a lot of scaffolding for EGL setup, so it's hard to point to any simple examples.

Eddy Talvala
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