使用 Android 相机 API，快照照片的方向始终未定义

Question

我用相机api拍出来的照片总是旋转90度，我想旋转一下。

所以首先我想知道图片的方向，这一点我卡住了。我总是在两种方式中都得到 UNDEFINDED orientation。

代码如下：

    @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();
        }

定位功能：

    //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;
}

日志输出：

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

可能是什么问题？

Answer 1

在此代码中

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

您忘记实际将字节写入输出流。所以，文件长度为0，自然不包含任何EXIF信息。

另外注意调用decodeByteArray然后再保存出来，这样也会丢失EXIF信息！您需要从原始图像字节中解析出 EXIF。

Answer 2

自 2011 年初以来，我一直是 decoding/observing Android JPEG 图片，因为我发布了一个图片查看应用程序。在 'early' 天里，图像以传感器的原始方向编码，设备的实际方向被写入 EXIF 元数据。大约从 2 年前开始，我注意到方向不再写入 EXIF 数据，取而代之的是，相机应用程序在编码 JPEG 文件之前旋转图像像素。我的猜测是，这是因为某些照片查看器 (* cough * Windows * cough *) 在显示 JPEG 文件时忽略了 EXIF 方向，而不是等待 Microsoft 修复它并指责 Android 做了某事错了，他们决定使用速度更快的 CPU/memory 并只旋转图像。

结果是，在不知道 EXIF 方向的情况下，只能确定照片是横向还是纵向拍摄的。这条信息只是一个假设，因为大多数相机传感器的宽度大于高度。

使用 Android 相机 API，快照照片的方向始终未定义

Using Android Camera API, snapped photo's orientation is always Undefined

camera

android

exif

orientation

android-camera