private float getValue(Matrix matrix, int whichValue) {
        matrix.getValues(mMatrixValues);
        return mMatrixValues[whichValue];
    }
Helper method that 'unpacks' a Matrix and returns the required value

@param matrix     Matrix to unpack
@param whichValue Which value from Matrix.M* to return
@return returned value
main/src/main/java/com/quxianggif/common/view/photoview/PhotoViewAttacher.java