Maps the raw values of a one-component Indexed image to table indices: rounded (half up) and clamped to 0 through highValue.
public void MapToIndices(ReadOnlySpan<ushort> raw, Span<byte> indices, int highValue)
Raw values.
At least as many bytes.
ISO 32000-2 §8.9.5.2 (the Decode mapping) and §8.6.6.3: "rounded to the nearest integer ... clipped to the range 0 to hival".