Gets the largest reduction, as a power of two, that DecodeImage(ReadOnlyMemory<Byte>, ImageFilterContext) delivers when asked for it through Reduction: 0 (the default) for a codec that always decodes at full resolution, 3 for one that decodes at 1/2, 1/4 and 1/8.
public int MaxReduction { get; init; }
A display list keeps the encoded data of an image whose codec reduces, and decodes it when it is drawn, at the resolution it
is drawn at (see DisplayImage.GetSamplesAt); other images are decoded when the list is built.