Returns the pattern a Pattern colour selected, such as FillColor when painting with a pattern.
public PdfPattern? GetPattern(in PdfColor color)
The colour.
null for a colour that is not a pattern, the initial Pattern colour (which paints
nothing) and an object that is not a pattern.
ISO 32000-2 §8.7.3 and §8.7.4.1. Map pattern space with GetPatternSpace(in PdfColor): the pattern matrix followed by the matrix of the stream that selected the pattern (PatternMatrix), never the CTM at the paint (§8.7.2). A shading pattern gives its Shading, Background and ExtGState; a tiling pattern's cell runs with RunPatternCell(in PdfColor, ContentProcessor).