An axial shading (Type 2): colour varies along the axis between two points and is constant across it.
public sealed class PdfAxialShading : PdfShading
ISO 32000-2 §8.7.4.5.3, Table 79. For a point (x, y) the axis parameter is x′ = ((x₁ − x₀)(x − x₀) + (y₁ − y₀)(y − y₀)) / ((x₁ − x₀)² + (y₁ − y₀)²); t = t₀ + (t₁ − t₀)x′, and beyond the ends t₀ or t₁ when that end is extended, else nothing is painted. TryGetParameter(Double, Double, out Double) computes it; the colour is EvaluateFunction(ReadOnlySpan<Single>, Span<Single>) of t. Coincident end points paint nothing.
kind:method, kind:property, kind:ctor. Press Esc to clear.DomainGets [t₀ t₁], the parametric values at the start and end of the axis. Default [0 1].EndGets the ending point of the axis, (x₁, y₁), in the target space.ExtendEndGets a value indicating whether the shading extends beyond the ending point. Default false.ExtendStartGets a value indicating whether the shading extends beyond the starting point. Default false.StartGets the starting point of the axis, (x₀, y₀), in the target space.TryGetParameter(Double, Double, out Double)Returns the parametric value t of a point of the target space.