Method rescale

include/singa/io/transformer.h:64–64

  int resize_height() const { return resize_height_; }
  int resize_width() const { return resize_width_; }
  float rescale() const { return rescale_; }
  const Shape crop_shape() const { return crop_shape_; }
  const string image_dim_order() const { return image_dim_order_; }