Using Android Camera API, snapped photo's orie

问题:

I use the camera api and the photo taken is always rotated by 90 degree, and i would like to rotate it.

So first of all i would like to know the picture's orientation and this point im stuck. I always getting UNDEFINDED orientation in both ways.

Here is the code:

    @Override
        public void onPictureTaken(byte[] data, Camera camera) {


            //Bitmap Options for lowering quality the bitmap to save memory
            Options options = new BitmapFactory.Options();
            options.inSampleSize = 4;
            options.inPreferredConfig = Bitmap.Config.RGB_565;

            //Make the bitmap
            Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length, options);

            //Making the path, the root will be fine for tests
            String path = Environment.getExternalStorageDirectory().toString();

            //output stream
            OutputStream outputStream = null;
            //Making the file as a jpg
            File file = new File(path, "tmp_pic" + ".jpg"); // the File to save to
            try {

                //Writing the file
                outputStream = new FileOutputStream(file);
                outputStream.flush();
                outputStream.close(); // do not forget to close the stream


                //Getting the orientation in both possible ways
                int ori = getOrientationFromExif(file.getPath());
                int ori2 = getOrientationFromUri(Uri.fromFile(file));
            }
            catch (FileNotFoundException e) {
                e.printStackTrace();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            if (bitmap == null) {
                Toast.makeText(getApplicationContext(), "Error: Cant make photo.", Toast.LENGTH_SHORT).show();
            }
            else {
                PhotoTapView.photoViews.get(index).setPhotoImage(bitmap);
                finish();
            }
            cameraObject.release();
        }

The functions for orientation:

    //Getting orientation from file URI
    private int getOrientationFromUri(Uri imageUri) {
    String[] orientationColumn = { MediaStore.Images.Media.ORIENTATION };
    Cursor cur = getContentResolver().query(imageUri, orientationColumn, null, null, null);
    int orientation = -1;
    if (cur != null && cur.moveToFirst()) {
        orientation = cur.getInt(cur.getColumnIndex(orientationColumn[0]));
    }
    Log.i("Orientation from Uri", orientation + "");
    return orientation;
}

    //Getting orientation from ExifInterface  
    private static int getOrientationFromExif(String imagePath) {
    int orientation = -1;
    try {
        ExifInterface exif = new ExifInterface(imagePath);
        int exifOrientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
        Log.i("Orientation from Exif: ", exifOrientation + "");
        switch (exifOrientation) {
            case ExifInterface.ORIENTATION_ROTATE_270:
                orientation = 270;
                Log.i("Orientation from Exif", "270");
            break;
            case ExifInterface.ORIENTATION_ROTATE_180:
                orientation = 180;
                Log.i("Orientation from Exif", "180");
            break;
            case ExifInterface.ORIENTATION_ROTATE_90:
                Log.i("Orientation from Exif", "90");
                orientation = 90;
            break;
            case ExifInterface.ORIENTATION_NORMAL:
                orientation = 0;
                Log.i("Orientation from Exif", "0 - Normal");
            break;
            case ExifInterface.ORIENTATION_UNDEFINED:
                orientation = -1;
                Log.e("Orientation from Exif", "UNDEFINED");
        }
    }
    catch (IOException e) {}
    return orientation;
}

Log output:

01-14 19:46:09.468: E/Orientation from Exif(12411): UNDEFINED
01-14 19:46:09.468: I/Orientation from Uri(12411): -1

What could be the problem?

回答1:

I have been decoding/observing Android JPEG images since early 2011 because I published an image viewing application. In the 'early' days, the images were encoded in the sensor's native orientation and the actual orientation of the device was written into the EXIF metadata. Starting about 2 years ago, I noticed that the orientation was no longer being written into the EXIF data and instead, the camera app was rotating the image pixels before encoding the JPEG files. My guess is that this occurred because some photo viewers (* cough * Windows * cough *) ignore the EXIF orientation when displaying JPEG files and instead of waiting for Microsoft to fix it and blaming Android for doing something wrong, they decided to make use of the faster CPU/memory and just rotate the image.

The result is that without knowing the EXIF orientation, one can only determine that a photo was captured in landscape or portrait orientation. This bit of info is only an assumption because the majority of camera sensors are wider than they are tall.

回答2:

In this code

outputStream = new FileOutputStream(file);
bitmap.compress(Bitmap.CompressFormat.JPEG, 90, outputStream);  // Add this line
outputStream.flush();
outputStream.close(); // do not forget to close the stream

You forgot to actually write the bytes to the output stream. So, the file is 0 length and naturally doesn't contain any EXIF information.

Also be careful as you are calling decodeByteArray and then saving it out again, this will also lose the EXIF information! You need to parse the EXIF from the original image bytes.