code: private static BitMatrix matrixFromString(String uri, int width, int height) {
          Writer qrWriter = new QRCodeWriter();
          BitMatrix matrix;
          try {
              matrix = qrWriter.encode(uri, BarcodeFormat.QR_CODE, width, height);
          } catch (WriterException e) {
              throw new RuntimeException(e);
          }
          return matrix;
      }
docs: Create a BitMatrix from a Bitcoin URI
  @param uri Bitcoin URI
  @return A BitMatrix for the QRCode for the URI