저도 그게 필요해서 여기저기 찾다가 이런 소스를 발견했습니다. 적절히 수정해서 사용하시면 됩니다.

public class RoundedImageView extends ImageView {

    public RoundedImageView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
    }

    public RoundedImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public RoundedImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onDraw(Canvas canvas) {

        Drawable drawable = getDrawable();

        if (drawable == null) {
            return;
        }

        if (getWidth() == 0 || getHeight() == 0) {
            return; 
        }

        Bitmap b = null;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP 
            && drawable instanceof VectorDrawable) {
            ((VectorDrawable) drawable).draw(canvas);
            b = Bitmap.createBitmap(canvas.getWidth(), canvas.getHeight(), Bitmap.Config.ARGB_8888);
            Canvas c = new Canvas();
            c.setBitmap(b);
            drawable.draw(c);
        } 
        else {
            b = ((BitmapDrawable) drawable).getBitmap();
        }

        Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);

        int w = getWidth(), h = getHeight();

        Bitmap roundBitmap =  getCroppedBitmap(bitmap, w);
        canvas.drawBitmap(roundBitmap, 0,0, null);
    }

    public static Bitmap getCroppedBitmap(Bitmap bmp, int radius) {
        Bitmap sbmp;
        if(bmp.getWidth() != radius || bmp.getHeight() != radius)
            sbmp = Bitmap.createScaledBitmap(bmp, radius, radius, false);
        else
            sbmp = bmp;
        Bitmap output = Bitmap.createBitmap(sbmp.getWidth(),
                sbmp.getHeight(), Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        final int color = 0xffa19774;
        final Paint paint = new Paint();
        final Rect rect = new Rect(0, 0, sbmp.getWidth(), sbmp.getHeight());

        paint.setAntiAlias(true);
        paint.setFilterBitmap(true);
        paint.setDither(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(Color.parseColor("#BAB399"));
        canvas.drawCircle(sbmp.getWidth() / 2+0.7f, sbmp.getHeight() / 2+0.7f,
                sbmp.getWidth() / 2+0.1f, paint);
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        canvas.drawBitmap(sbmp, rect, rect, paint);


        return output;
    }
}