Convert DynamicImage to Image a in Pixel class?

[Zemyla]

I think the Pixel class should have a pair of functions to convert to and from a DynamicImage:

class (Storable (PixelBaseComponent a), Num (PixelBaseComponent a), Eq a) => Pixel a where
  ...

  toDynamicImage :: Image a -> DynamicImage

  fromDynamicImage :: DynamicImage -> Maybe (Image a)