Android實戰技巧之三十七：圖片的Base64編解碼，

Android實戰技巧之三十七：圖片的Base64編解碼，

通常用Base64這種編解碼方式將位元據轉換成可見的字串格式，就是我們常說的大串，10塊錢一串的那種，^_^。

Android的android.util包下直接提供了一個功能十分完備的Base64類供我們使用，下面就示範一下如何將一張圖片進行Base64的編解碼。

1.找到那張圖片

public void onEncodeClicked(View view) {        //select picture        Intent intent = new Intent();        intent.setType("image/*");        intent.setAction(Intent.ACTION_GET_CONTENT);        startActivityForResult(intent, OPEN_PHOTO_FOLDER_REQUEST_CODE);    }    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        super.onActivityResult(requestCode, resultCode, data);        if(OPEN_PHOTO_FOLDER_REQUEST_CODE == requestCode && RESULT_OK == resultCode) {            //encode the image            Uri uri = data.getData();            try {                //get the image path                String[] projection = {MediaStore.Images.Media.DATA};                CursorLoader cursorLoader = new CursorLoader(this,uri,projection,null,null,null);                Cursor cursor = cursorLoader.loadInBackground();                int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);                cursor.moveToFirst();                String path = cursor.getString(column_index);                Log.d(TAG,"real path: "+path);                encode(path);            } catch (Exception ex) {                Log.e(TAG, "failed." + ex.getMessage());            }        }    }

2.將圖片轉換成bitmap並編碼

private void encode(String path) {                //decode to bitmap                Bitmap bitmap = BitmapFactory.decodeFile(path);                Log.d(TAG, "bitmap width: " + bitmap.getWidth() + " height: " + bitmap.getHeight());                //convert to byte array                ByteArrayOutputStream baos = new ByteArrayOutputStream();                bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);                byte[] bytes = baos.toByteArray();                //base64 encode                byte[] encode = Base64.encode(bytes,Base64.DEFAULT);                String encodeString = new String(encode);                mTvShow.setText(encodeString);}

3.將大串還原成圖片

    public void onDecodeClicked(View view) {        byte[] decode = Base64.decode(mTvShow.getText().toString(),Base64.DEFAULT);        Bitmap bitmap = BitmapFactory.decodeByteArray(decode, 0, decode.length);        //save to image on sdcard        saveBitmap(bitmap);    }    private void saveBitmap(Bitmap bitmap) {        try {            String path = Environment.getExternalStorageDirectory().getPath()                    +"/decodeImage.jpg";            Log.d("linc","path is "+path);            OutputStream stream = new FileOutputStream(path);            bitmap.compress(Bitmap.CompressFormat.JPEG, 90, stream);            stream.close();            Log.e("linc","jpg okay!");        } catch (IOException e) {            e.printStackTrace();            Log.e("linc","failed: "+e.getMessage());        }    }

需要注意的是，一張圖片的編碼速度會很慢，如果圖片很大就更慢了。畢竟手機的處理能力有限。不過decode的速度確實相當的快，超出你的想象。好了，就是這樣簡單，今天就到這裡了，晚安！