Represents the "BG2" entry of the graphics state parameter dictionary object.

It is an optional entry defined as part of the PDF 1.3 specification.

This property may contain one of two different types:.

1) A string representing a PDF name object.

If provided, this item must always take the value "Default".

2) A FunctionElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 58, page 129.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 57, page 163.

BG2 supersedes BG in PDF 1.3 and later. It specifies the black-generation function using the same semantics as BG but is recognised by conforming readers that support the updated color processing model.

When both BG and BG2 are present in a graphics state parameter dictionary, BG2 takes precedence for conforming readers that support it.