How to create Bitmap from grayscaled byte buffer image?

Question

I am trying to get frame image to process while using new Android face detection mobile vision api.

So I have created Custom Detector to get Frame and tried to call getBitmap() method but it is null so I accessed grayscale data of frame. Is there a way to create bitmap from it or similiar image holder class?

public class CustomFaceDetector extends Detector<Face> {
private Detector<Face> mDelegate;

public CustomFaceDetector(Detector<Face> delegate) {
    mDelegate = delegate;
}

public SparseArray<Face> detect(Frame frame) {
    ByteBuffer byteBuffer = frame.getGrayscaleImageData();
    byte[] bytes = byteBuffer.array();
    int w = frame.getMetadata().getWidth();
    int h = frame.getMetadata().getHeight();
    // Byte array to Bitmap here
    return mDelegate.detect(frame);
}

public boolean isOperational() {
    return mDelegate.isOperational();
}

public boolean setFocus(int id) {
    return mDelegate.setFocus(id);
}}

Answer 1

You have probably sorted this out already, but in case someone stumbles upon this question in the future, here's how I solved it:

As @pm0733464 points out, the default image format coming out of android.hardware.Camera is NV21, and that is the one used by CameraSource.

This stackoverflow answer provides the answer:

YuvImage yuvimage=new YuvImage(byteBuffer, ImageFormat.NV21, w, h, null);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
yuvimage.compressToJpeg(new Rect(0, 0, w, h), 100, baos); // Where 100 is the quality of the generated jpeg
byte[] jpegArray = baos.toByteArray();
Bitmap bitmap = BitmapFactory.decodeByteArray(jpegArray, 0, jpegArray.length);

Although frame.getGrayscaleImageData() suggests bitmap will be a grayscale version of the original image, this is not the case, in my experience. In fact, the bitmap is identical to the one supplied to the SurfaceHolder natively.