Android实战技巧之三十七：图片的Base64编解码

通常用Base64这种编解码方式将二进制数据转换成可见的字符串格式，就是我们常说的大串，10块钱一串的那种，^_^。

Android的android.util包下直接提供了一个功能十分完备的Base64类供我们使用，下面就演示一下如何将一张图片进行Base64的编解码。

1.找到那张图片

(View view) {//select pictureIntent intent = new Intent();intent.setType(“image/*”);intent.setAction(Intent.ACTION_GET_CONTENT);startActivityForResult(intent, OPEN_PHOTO_FOLDER_REQUEST_CODE);}(int requestCode, int resultCode, Intent data) {super.onActivityResult(requestCode, resultCode, data);if(OPEN_PHOTO_FOLDER_REQUEST_CODE == requestCode && RESULT_OK == resultCode) {//encode the imageUri uri = data.getData();try {//get the image pathString[] 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.将图片转换成bitmap并编码

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

3.将大串还原成图片

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 sdcardsaveBitmap(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，一张图片的编码速度会很慢，，如果图片很大就更慢了。毕竟手机的处理能力有限。不过decode的速度确实相当的快，超出你的想象。好了，就是这样简单，今天就到这里了，晚安！

值不值得，真是不足为外人道，自己心里有数就行。