public int getRotationAngle() {
    parseMetadataIfNeeded();
    return mRotationAngle;
  }
@return the rotation angle if the rotation angle is known, else -1. The rotation angle may not
    be known if the image is incomplete (e.g. for progressive JPEGs).
imagepipeline-base/src/main/java/com/facebook/imagepipeline/image/EncodedImage.java