Represents the "OPI" entry of the form XObject dictionary object.

It is an optional entry defined as part of the PDF 1.2 specification. It was deprecated in PDF 2.0.

It contains an OpiVersionElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 95, page 219.

Adobe Supplement to the ISO 32000, BaseVersion: 1.7, ExtensionLevel: 3; Table: 4.45, page 27.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 93, page 270.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 363, page 632.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 399, page 812.

The OPI dictionary carries Open Prepress Interface metadata for the form, used when the form serves as a low-resolution proxy for high-resolution external artwork. At output time, OPI processing replaces the proxy with the full-resolution version.