Base64编码省略了最后2个字节(Base64 encoding omits final 2 bytes)

 此代码将位图编码为Base64。 出于调试目的，我还写了几行来将所有数据放入普通文件中。 问题是文件不同：文件直接从位图保存： 
 
DB 5A C4 80 00 00
 
 从解码的b64数据中保存的文件： 
 
DB 5A C4 80
 
 所以在编码/解码后2个字节MIA正确的文件是第一个，因为它可以通过chrome，图像查看器等轻松打开。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);
 
 并且保存解码文件方法（仅供参考 - 在不同平台后端服务上也是错误的结果）： 
 
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)));
}

This code is going to encode a bitmap to Base64. For debugging purposes I've written also few lines to put all the data into ordinary files. Problem is that files are different: File saved directly from bitmap:
 
DB 5A C4 80 00 00
 
file saved from decoded b64 data:
 
DB 5A C4 80
 
So after encode/decode 2 bytes MIA The right file is the first one as it can be easily opened by chrome, image viewers etc. My code:
 
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);
 
And the save decoded file method (just for reference - result of this is wrong also on different platform back end service):
 
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)));
}

原文：https://stackoverflow.com/questions/30444520