String[] imgs = new String[]{"1.jpg", "2.jpg", "3.jpg", "4.jpg", "5.jpg"};
 String path = Environment.getExternalStorageDirectory().getAbsolutePath() + "/Pictures/test/";
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
// test = Api.getBuilder().create(Test.class);
 String[] permissions = {Manifest.permission.WRITE_EXTERNAL_STORAGE
 , Manifest.permission.READ_PHONE_STATE
 , Manifest.permission.CAMERA};
 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
 requestPermissions(permissions, 0);
 }
 compress();
 }
 private void compress() {
 Observable.from(imgs)
 .subscribeOn(Schedulers.io())
 .doOnNext(new Action1<String>() {
  @Override
  public void call(String imgName) {
  compress(imgName);
  }
 })
 .subscribe();
 }
 private void compress(String imgName) {
 try {
 File file = new File(path, imgName);
 Log.i("compress", "jpg start");
 byte[] bytes = BitmapUtil.compressBitmapToBytes(file.getPath(), 600, 0, 60, Bitmap.CompressFormat.JPEG);
 File jpg = new File(path, imgName + "compress.jpg");
 FileUtils.writeByteArrayToFile(jpg, bytes);
 Log.i("compress", "jpg finish");
 Log.i("compress", "----------------------------------------------------");
 Log.i("compress", "webp start");
 byte[] bytes1 = BitmapUtil.compressBitmapToBytes(file.getPath(), 600, 0, 60, Bitmap.CompressFormat.WEBP);//分別是圖片路徑，寬度高度，質量，和圖片類型，重點在這里。
 File webp = new File(path, imgName + "compress.webp");
 FileUtils.writeByteArrayToFile(webp, bytes1);
 Log.i("compress", "webp finish");
 } catch (IOException e) {
 e.printStackTrace();
 }
 }

public static byte[] compressBitmapToBytes(String filePath, int reqWidth, int reqHeight, int quality, Bitmap.CompressFormat format) {
 Bitmap bitmap = getSmallBitmap(filePath, reqWidth, reqHeight);
 ByteArrayOutputStream baos = new ByteArrayOutputStream();
 bitmap.compress(format, quality, baos);
 byte[] bytes = baos.toByteArray();
 bitmap.recycle();
 Log.i(TAG, "Bitmap compressed success, size: " + bytes.length);
 return bytes;
 }
 public static Bitmap getSmallBitmap(String filePath, int reqWidth, int reqHeight) {
 BitmapFactory.Options options = new BitmapFactory.Options();
 options.inJustDecodeBounds = true;
 BitmapFactory.decodeFile(filePath, options);
 options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
 options.inJustDecodeBounds = false;
// options.inPreferQualityOverSpeed = true;
 return BitmapFactory.decodeFile(filePath, options);
 }
 public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
 int h = options.outHeight;
 int w = options.outWidth;
 int inSampleSize = 0;
 if (h > reqHeight || w > reqWidth) {
 float ratioW = (float) w / reqWidth;
 float ratioH = (float) h / reqHeight;
 inSampleSize = (int) Math.min(ratioH, ratioW);
 }
 inSampleSize = Math.max(1, inSampleSize);
 return inSampleSize;
 }

/** This interceptor compresses the HTTP request body. Many webservers can't handle this! */
final class GzipRequestInterceptor implements Interceptor {
 @Override public Response intercept(Interceptor.Chain chain) throws IOException {
 Request originalRequest = chain.request();
 if (originalRequest.body() == null || originalRequest.header("Content-Encoding") != null) {
 return chain.proceed(originalRequest);
 }
 Request compressedRequest = originalRequest.newBuilder()
 .header("Content-Encoding", "gzip")
 .method(originalRequest.method(), gzip(originalRequest.body()))
 .build();
 return chain.proceed(compressedRequest);
 }
 private RequestBody gzip(final RequestBody body) {
 return new RequestBody() {
 @Override public MediaType contentType() {
 return body.contentType();
 }
 @Override public long contentLength() {
 return -1; // We don't know the compressed length in advance!
 }
 @Override public void writeTo(BufferedSink sink) throws IOException {
 BufferedSink gzipSink = Okio.buffer(new GzipSink(sink));
 body.writeTo(gzipSink);
 gzipSink.close();
 }
 };
 }
}