GIf图像在android中转换为Base64，无需使用压缩

我的代码是，在这段代码中，所有图像都转换为base 64，但在gif图像中，也在png中，我希望转换后成为gif

ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, byteArrayOutputStream);
byte[] byteArray = byteArrayOutputStream.toByteArray();
return Base64.encodeToString(byteArray, Base64.NO_WRAP);

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=>此代码正在成功运行

 byte[] inputData = getBytes(iStream);

 Base64.encodeToString(inputData, Base64.NO_WRAP)

 public byte[] getBytes(InputStream inputStream) throws IOException {
    ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
    int bufferSize = 1024;
    byte[] buffer = new byte[bufferSize];

    int len = 0;
    while ((len = inputStream.read(buffer)) != -1) {
        byteBuffer.write(buffer, 0, len);
    }
    return byteBuffer.toByteArray();
}

public static String encodeToString(byte[] input, int flags) {
    try {
        return new String(encode(input, flags), "US-ASCII");
    } catch (UnsupportedEncodingException e) {
        // US-ASCII is guaranteed to be available.
        throw new AssertionError(e);
    }
}