Base64 编码省略最后 2 个字节

Question

此代码将位图编码为 Base64。出于调试目的，我还编写了几行代码将所有数据放入普通文件中。问题是文件不同：直接从位图保存的文件：

DB 5A C4 80 00 00

从解码的 b64 数据中保存的文件：

DB 5A C4 80

所以在 encode/decode 2 字节 MIA 之后正确的文件是第一个，因为它可以很容易地被 chrome、图像查看器等打开。我的代码：

Bitmap exportedBitmap = Bitmap.createBitmap(EXPORTED_IMAGE_SIZE, EXPORTED_IMAGE_SIZE, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(exportedBitmap);
float imageViewRatio = EXPORTED_IMAGE_SIZE / (float) getWidth();

canvas.save();
canvas.scale(imageViewRatio, imageViewRatio);
drawPhoto(canvas, mScale);
canvas.restore();



ByteArrayOutputStream outStream = new ByteArrayOutputStream(512000);
Base64OutputStream base64OutputStream = new Base64OutputStream(outStream, Base64.DEFAULT);

String timeString = new Date().toString();
File outputFile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "origin"+ timeString +".webp");
if (!outputFile.exists())
{
    outputFile.delete();
}
outputFile.createNewFile();
FileOutputStream fileOutputStream = new FileOutputStream(outputFile);
TeeOutputStream teeOutputStream = new TeeOutputStream(base64OutputStream, fileOutputStream);



exportedBitmap.compress(Bitmap.CompressFormat.WEBP, 85, teeOutputStream);

getContext().sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.fromFile(outputFile)));

exportedBitmap.recycle();
teeOutputStream.flush();
String outString = outStream.toString();
teeOutputStream.close();


decodeDataToFile(timeString, outString);

以及保存解码文件的方法（仅供参考-在不同平台后端服务上结果也是错误的）：

private void decodeDataToFile(String pTimeString, String pOutString) throws IOException
{
    File decodedFile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "processed" + pTimeString + ".webp");
    decodedFile.createNewFile();
    FileOutputStream decodedFileOutputStream = new FileOutputStream(decodedFile);
    decodedFileOutputStream.write(Base64.decode(pOutString, Base64.DEFAULT));

    decodedFileOutputStream.flush();
    decodedFileOutputStream.close();
    getContext().sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.fromFile(decodedFile)));
}

Answer 1

我找到了解决方案 - 这是答案：Android File To Base64 using streaming sometimes missed 2 bytes

简而言之 - 在使用编码 byte[] / String

做更多事情之前需要 base64OutputStream.close();

Base64 编码省略最后 2 个字节

Base64 encoding omits final 2 bytes

base64

android