Getting smaller data from camera preview in Android

Question

Hi i am developing real time image processing application on android. I am using PreviewCallback to get image in every frame. When i get data in Tablet devices the data returns very big. So its too hard to work in large data in real time. My question is, is there any way to get smaller resolution data from camera preview.

CAMERA PREVIEW CODE:

public void onPreviewFrame(byte[] data, Camera camera) {
                        // TODO Auto-generated method stub
                        Camera.Parameters params = camera.getParameters();

                        Log.v("image format", Integer.toString(params.getPreviewFormat()));
                        //Frame captureing via frameManager
                        frameManager.initCamFrame(params.getPreviewSize().width, params.getPreviewSize().height,
                                data);
                    }
                });

score 0 · Answer 1 · answered Oct 15 '15 at 13:13

you can try this:

 @Override
        public void onPreviewFrame(byte[] data, Camera camera) {
        try {
            byte[] baos = convertYuvToJpeg(data, camera);
            StringBuilder dataBuilder = new StringBuilder();
            dataBuilder.append("data:image/jpeg;base64,").append(Base64.encodeToString(baos, Base64.DEFAULT));
            mSocket.emit("newFrame", dataBuilder.toString());
        } catch (Exception e) {
           Log.d("########", "ERROR");
        }
    }

};


public byte[] convertYuvToJpeg(byte[] data, Camera camera) {

    YuvImage image = new YuvImage(data, ImageFormat.NV21,
            camera.getParameters().getPreviewSize().width, camera.getParameters().getPreviewSize().height, null);

    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    int quality = 20; //set quality
    image.compressToJpeg(new Rect(0, 0, camera.getParameters().getPreviewSize().width, camera.getParameters().getPreviewSize().height), quality, baos);//this line decreases the image quality


    return baos.toByteArray();
}

score 0 · Answer 2 · answered Dec 04 '11 at 02:29

Are you aware you can get a list of supported preview sizes from the camera parameters by calling getSupportedPreviewSizes()? The devices I've tried this on all returned a sorted list, although sometimes in ascending and sometimes in descending order. You'll probably want to manually iterate the list to find the 'smallest' preview size, or sort it first and grab the first item.

score 0 · Accepted Answer · edited May 23 '17 at 11:58

You can call parameters.setPreviewSize(width, height), but you want to do it before camera preview starts. And you need to use supported value, viz previous answer.

And you also should not call camera.getParameters() every frame, just do that once and save the values to some variable. You have some limited time in onPreviewFrame, because byte[] data is overwritten on each frame, so try to do only the important stuff here.

And you should use setPreviewCallbackWithBuffer, it quite improves performance - check this post.

Getting smaller data from camera preview in Android

3 Answers3