message: Make SubImage derive from Clone and Copy.
diff: @@ -1022,6 +1022,7 @@ pub trait GenericImage: GenericImageView {
  /// - [`GenericImage::sub_image`] to create a mutable view,
  /// - [`GenericImageView::view`] to create an immutable view,
  /// - [`SubImage::new`] to instantiate the struct directly.
  +#[derive(Copy, Clone)]
  pub struct SubImage<I> {
  image: I,
  xoffset: u32,
  @@ -1280,6 +1281,15 @@ mod tests {
  source.view(2, 2, 0, 0);
  }
  + #[test]
  + fn test_copy_sub_image() {
  + let source = ImageBuffer::from_pixel(3, 3, Rgba([255u8, 0, 0, 255]));
  + let view = source.view(0, 0, 3, 3);
  + let mut views = Vec::new();
  + views.push(view);
  + view.to_image();
  + }
  +
  #[test]
  fn test_load_rect() {
  struct MockDecoder {scanline_number: u64, scanline_bytes: u64}
  