Evaluates the shading's function: the colour, in InterpolationColorSpace, for a parametric value.
public void EvaluateFunction(ReadOnlySpan<float> input, Span<float> color)
The function's input: (x, y) in the domain for a function-based shading (Type 1), t for the others.
Receives ColorComponentCount components, each clipped to its component's range.
ISO 32000-2 §8.7.4.5: "If the value returned by the function for a given colour component is out of range, it shall be adjusted to the nearest valid value." Thread-safe and allocation-free. A function that meets an error while evaluating records one diagnostic and yields its repaired outputs.