message: imageops: Add `?Sized` bound to generic type `Map`.
  This allows unsized types like those returned by
  `Box<dyn ColorMap<_>>>.as_ref()` to be passed into these functions.
diff: @@ -318,7 +318,7 @@ macro_rules! do_dithering(
  /// Floyd-Steinberg dithering to improve the visual conception
  pub fn dither<Pix, Map>(image: &mut ImageBuffer<Pix, Vec<u8>>, color_map: &Map)
  where
  - Map: ColorMap<Color = Pix>,
  + Map: ColorMap<Color = Pix> + ?Sized,
  Pix: Pixel<Subpixel = u8> + 'static,
  {
  let (width, height) = image.dimensions();
  @@ -359,7 +359,7 @@ pub fn index_colors<Pix, Map>(
  color_map: &Map,
  ) -> ImageBuffer<Luma<u8>, Vec<u8>>
  where
  - Map: ColorMap<Color = Pix>,
  + Map: ColorMap<Color = Pix> + ?Sized,
  Pix: Pixel<Subpixel = u8> + 'static,
  {
  let mut indices = ImageBuffer::new(image.width(), image.height());
  