static BufferedImage byteArrayToGrayBufferedImage(byte[] pixels, int w, int h) {
  PixelInterleavedSampleModel sm = new(DataBuffer.TYPE_BYTE, w, h);
  DataBufferByte db = new(pixels, pixels.length);
  WritableRaster wr = Raster.createWritableRaster(sm, db, new Point);
  ret new BufferedImage(ColorModel.getRGBdefault(), wr, false, null);
}