Buffer result = new Buffer();
    result.writeAll(Okio.source(file));
    return result;
  }

  private String contentType(String path) {
    if (path.endsWith(".png")) return "image/png";
    if (path.endsWith(".jpg")) return "image/jpeg";
    if (path.endsWith(".jpeg")) return "image/jpeg";
    if (path.endsWith(".gif")) return "image/gif";